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Creatine Supplementation during Resistance Training in Older Adults—A Meta-analysis
Abstract
Age-related sarcopenia and dynapenia have negative effects on strength and the ability to perform activities of daily living. Resistance training (RT) increases muscle mass and strength in older adults and is an established countermeasure for sarcopenia and dynapenia and creatine may enhance this effect. We aimed to determine whether the addition of Cr to RT increased gains in muscle mass, strength and function in older adults over RT alone by conducting a systematic review and meta-analysis.
Pubmed and Healthstar databases were searched. Randomized, placebo (PL) controlled trials that involved older adults supplemented with Cr and including RT regimes (>6wk) were included. Data were analyzed using fixed or random (if data were heterogeneous) effects meta-analysis using RevMan 5.
The meta-analysis comprised 357 older adults (avg ± SD Cr: 63.6 ± 5.9, Pl: 64.2 ± 5.4) with 12.6 ± 4.9 wk of RT. Cr+RT increased total body mass (P = 0.004) and fat free mass (P < 0.0001) with no effect on fat mass as compared with RT alone. Cr+RT increased chest press (P = 0.004) and leg press (P = 0.02)1RM to a greater extent than RT alone, with no difference in effect on knee extension or biceps curl 1RM, isokinetic or isometric knee extension peak torque. Cr+RT had a greater effect than RT alone on the 30s chair stand test (P = 0.03).
Retention of muscle mass and strength is integral to healthy aging. The results from this meta-analysis are encouraging in supporting a role for Cr supplementation during RT in healthful aging by enhancing muscle mass gain, strength and functional performance; however, the limited number of studies indicates further work is needed.
... The effects of creatine on muscle mass have been previously reviewed (8,11,14,15). The results of a meta-analysis by Branch (8) showed that, in adults younger than 48 years, the percentage change in LBM from creatine (2.2 6 0.7%) was significantly greater than a placebo (0.6 6 0.2%). ...
... Meta-analyses in adults over 45 years showed that creatine supplementation with RT significantly increased fat-free mass compared with RT with a placebo (mean difference 5 1.33 kg; 95% CI 0.79-1.89) (15) and LBM (mean difference 5 1.37 kg; 95% CI 0.97-1.76) (11) compared with RT without creatine supplementation. ...
... We identified one study during citation tracking (1), resulting in 12 studies (see Table 1, Supplemental Digital Content 1, http://links.lww. com/JSCR/A514) being included in the review and meta-analysis (1,3,10,12,15,23,31,35,38,45,47,50). The number of subjects randomized was 362: 48 female subjects (13.3%) and 329 male subjects (86.7%). ...
Desai, I, Wewege, MA, Jones, MD, Clifford, BK, Pandit, A, Kaakoush, NO, Simar, D, and Hagstrom, AD. The effect of creatine supplementation on resistance training-based changes to body composition: A systematic review and meta-analysis. J Strength Cond Res XX(X): 000–000, 2024—The purpose of this review was to determine the added effect of creatine supplementation on changes in body composition with resistance training in adults younger than 50 years. The review protocol was preregistered on the Open Science Framework (osf.io/x48a6/). Our primary outcome was lean body mass (LBM); secondary outcomes were body fat percentage (%) and body fat mass (kg). We performed a random-effects meta-analysis in R using the metafor package. Subgroup analyses were conducted to examine the effects of training status and use of a carbohydrate drink with creatine. We conducted a meta-regression to examine the moderating effect of total training volume. Statistical significance was set at p < 0.05. One thousand six hundred ninety-four records were screened, and 67 full-text articles were assessed for eligibility. Twelve studies were included in the meta-analysis. Fifty-two percentages of the studies had low risk, 41% some concerns, and 7% high risk of bias. Compared with resistance training (RT) alone, creatine supplementation increased LBM by 1.14 kg (95% CI 0.69 to 1.59), and reduced body fat percentage by −0.88% (95% CI −1.66 to −0.11) and body fat mass by −0.73 kg (95% CI −1.34 to −0.11). There were no differences between training status or carbohydrate subgroups. Training volume was not associated with effect size in all outcomes; 7 g or 0.3 g/kg of body mass of creatine per day is likely to increase LBM by 1 kg and reduce fat mass by 0.7 kg more than RT alone. Concurrent carbohydrate ingestion did not enhance the hypertrophy benefits of creatine.
... [31][32][33][34] In previous metaanalyses, creatine in combination with resistance training improves lean body mass and muscle strength in the older population, making it highly plausible that it may be effective in improving physical function in those at risk of functional disability. [35][36][37][38] This systematic review and meta-analysis will update and build on this previous work by including populations with chronic disease and studies that do not use resistance training. We investigated the effect of creatine supplementation on physical function in populations at risk of functional disability, namely the older population and those with chronic disease, using outcomes that are patient centered and relevant to normal daily activities. ...
... 19 Our findings support those of two previous meta-analyses of older adults demonstrating creatine supplementation in conjunction with resistance training resulted in greater improvements in STS performance than that of resistance training and placebo. 37,38 This must be interpreted cautiously because wide confidence intervals and a low posterior probability suggest some uncertainty regarding the true effect size. Our additional inclusion of studies using creatine supplementation as a sole intervention investigating a heterogeneous population with chronic disease enhances the clinical relevance of creatine use. ...
... 84 Previous meta-analyses have consistently found that the combination of creatine supplementation and resistance training augments lean tissue mass (0.9-1.3 kg) and upper-body strength in older adults when compared with the placebo and resistance training. [35][36][37]85 The effect on lower body strength is more heterogeneous. We found no difference between the groups in lower body strength, similar to a previous meta-analysis of older adults. ...
Background
The efficacy of creatine replacement through supplementation for the optimization of physical function in the population at risk of functional disability is unclear.
Methods
We conducted a systematic literature search of MEDLINE, EMBASE, the Cochrane Library, and CINAHL from inception to November 2022. Studies included were randomized controlled trials (RCTs) comparing creatine supplementation with placebos in older adults and adults with chronic disease. The primary outcome was physical function measured by the sit‐to‐stand test after pooling data using random‐effects modeling. We also performed a Bayesian meta‐analysis to describe the treatment effect in probability terms. Secondary outcomes included other measures of physical function, muscle function, and body composition. The risk of bias was assessed using the Cochrane risk‐of‐bias tool.
Results
We identified 33 RCTs, comprising 1076 participants. From six trials reporting the primary outcome, the pooled standardized mean difference (SMD) was 0.51 (95% confidence interval [CI]: 0.01–1.00; I ² = 62%; P = 0.04); using weakly informative priors, the posterior probability that creatine supplementation improves physical function was 66.7%. Upper‐body muscle strength (SMD: 0.25; 95% CI: 0.06–0.44; I ² = 0%; P = 0.01), handgrip strength (SMD 0.23; 95% CI: 0.01–0.45; I ² = 0%; P = 0.04), and lean tissue mass (MD 1.08 kg; 95% CI: 0.77–1.38; I ² = 26%; P < 0.01) improved with creatine supplementation. The quality of evidence for all outcomes was low or very low because of a high risk of bias.
Conclusion
Creatine supplementation improves sit‐to‐stand performance, muscle function, and lean tissue mass. It is crucial to conduct high‐quality prospective RCTs to confirm these hypotheses (PROSPERO number, CRD42023354929).
... Studies indicate that creatine supplementation may have the capacity to enhance MPS and reduce MPB [17]. Current evidence suggests that supplementing with creatine combined with resistance training can increase skeletal muscle mass [18][19][20][21] and could moderate sarcopenia and skeletal muscle atrophy [17]. Additionally, there is accumulating evidence suggesting that creatine supplementation may evoke anti-inflammatory and anticatabolic effects [22] which would be beneficial in mitigating the cascade of events during and following surgery that leads to the loss of skeletal muscle mass. ...
... Aside from supplementing with creatine post-surgery, it may also be beneficial presurgery. Creatine is well recognized for its ability to increase muscle mass [18][19][20][21] and could therefore be postulated as beneficial during a prehabilitation program to optimize muscle mass prior to surgery. Recently it has been identified that a subset of individuals experience inflammatory dysregulation following anterior cruciate ligament (ACL) rupture which could increase the risk of developing osteoarthritis [31]. ...
Background: Orthopedic surgery and the corresponding events (i.e., immobilization and muscle disuse) result in a cascade of biological events to promote healing but can come with the loss of skeletal muscle mass and strength. A good nutritional status of patients is associated with positive post-surgical outcomes, with macronutrients receiving the majority of emphasis in the research literature. However, beyond the surgical literature, there are other nutrients and nutritional supplements that have been established or postulated to improve skeletal muscle mass and strength. Objective: The purpose of this narrative review is to provide evidence for the utility of using creatine, vitamin D, omega-3 fatty acids, glutamine, essential amino acids-branched chain amino acids (EAA-BCAA) and beta-hydroxy-beta-methylbutyrate (HMB) supplementation and the role they may play in minimizing muscle atrophy and strength loss following orthopedic surgery. The review will also highlight areas of future research to support a better understanding of the efficacy of supplementing with these substances pre- and/or post-surgery.
... 13,14 Creatine supplementation has been demonstrated to consistently yield superior improvements in LM, muscle strength and physical function outcomes relative to resistance exercise alone in older adults. 15 These adaptations may vary as a result of baseline levels of intramuscular creatine, and dietary habits (whereby individuals with a vegan/vegetarian diet may benefit more from supplementation). 16 Nevertheless, given the accelerated decline of lean mass, strength and physical function that is commonly observed with ADT in prostate cancer, 3,17,18 there is a clear and strong rationale for the investigation of therapeutic strategies to offset these declines. ...
... This dosing protocol has been previously demonstrated to be safe and efficacious in older adults. 15,23 Patients in the PLA group followed the same dosing protocol but with dextrose, a type of sugar that is commonly used as a placebo. 23,24 Patients were asked to dissolve the supplements in 200-300 mL of juice (orange or apple) to mask the solubility of Cr and taste of dextrose. ...
... Although speculative, th very small reduction in body fat percentage from creatine could be attributable to change in lean mass and/or muscle accretion over time. For example, several meta-analyses hav been performed collectively showing that the combination of creatine supplementation and resistance exercise increases measures of whole-body lean tissue mass by ~1.37 kg (a measured by dual-energy X-ray absorptiometry, air-displacement plethysmography, hy drodensitometry, and bioelectrical impedance analysis) compared to placebo and re sistance exercise [28][29][30][31][32]. Furthermore, Burke et al. [33] performed a systematic review and meta-analysis involving 10 studies and found significant improvements in direc measures of limb muscle hypertrophy (0.10-0.16 cm; as measured using ultrasound and peripheral quantitative computed tomography {pQCT}) in the upper-and lower-body from creatine supplementation and resistance exercise compared to resistance exercis and placebo. ...
... Although speculative, the very small reduction in body fat percentage from creatine could be attributable to changes in lean mass and/or muscle accretion over time. For example, several meta-analyses have been performed collectively showing that the combination of creatine supplementation and resistance exercise increases measures of whole-body lean tissue mass by~1.37 kg (as measured by dual-energy X-ray absorptiometry, air-displacement plethysmography, hydrodensitometry, and bioelectrical impedance analysis) compared to placebo and resistance exercise [28][29][30][31][32]. Furthermore, Burke et al. [33] performed a systematic review and meta-analysis involving 10 studies and found significant improvements in direct measures of limb muscle hypertrophy (0.10-0.16 cm; as measured using ultrasound and peripheral quantitative computed tomography {pQCT}) in the upper-and lower-body from creatine supplementation and resistance exercise compared to resistance exercise and placebo. ...
The combination of resistance exercise and creatine supplementation has been shown to decrease body fat percentage in adults ≥ 50 years of age. However, the effect on adults < 50 years of age is currently unknown. To address this limitation, we systematically reviewed the literature and performed several meta-analyses comparing studies that included resistance exercise and creatine supplementation to resistance exercise and placebo on fat mass and body fat percentage Twelve studies were included, involving 266 participants. Adults (<50 years of age) who supplemented with creatine and performed resistance exercise experienced a very small, yet significant reduction in body fat percentage (−1.19%, p = 0.006); however, no difference was found in absolute fat mass (−0.18 kg, p = 0.76). Collectively, in adults < 50 years of age, the combination of resistance exercise and creatine supplementation produces a very small reduction in body fat percentage without a corresponding decrease in absolute fat mass.
... Several meta-analyses have investigated the combined effects of creatine supplementation and RT, operationally defined as "a form of physical activity that is designed to improve muscular fitness by exercising a muscle or a muscle group against external resistance" [8], on changes in whole-body lean mass, as assessed by methods such as dual-energy X-ray absorptiometry (DXA), hydrodensitometry, whole-body air displacement plethysmography, and bioelectrical impedance analyses [2,[9][10][11]. Collectively, a combination of creatine supplementation and RT results in greater gains in lean mass compared to RT and a placebo. However, lean mass is an imprecise proxy surrogate for skeletal muscle mass as it comprises all non-fat tissue, including body water. ...
... However, compared to a placebo, the magnitude of this effect was trivial to small (ES = 0.11), with a fairly narrow 95% CrI (−0.02, 0.25); as such, the practical significance and implications of this on an individual level are likely small. Previous metaanalyses performed on creatine supplementation and RT have shown significant increases in whole-body lean mass over time (1.1 to 1.4 kg) [2,[9][10][11], with larger standardized mean differences (SMD range: 0.24-0.42). These larger SMDs may be associated with creatine's effect on increasing total body water; as such, it is possible that a portion of the observed increases in the lean mass may reflect the accumulation of extracellular fluid, as opposed to muscle hypertrophy. ...
The purpose of this paper was to carry out a systematic review with a meta-analysis of randomized controlled trials that examined the combined effects of resistance training (RT) and creatine supplementation on regional changes in muscle mass, with direct imaging measures of hypertrophy. Moreover, we performed regression analyses to determine the potential influence of covariates. We included trials that had a duration of at least 6 weeks and examined the combined effects of creatine supplementation and RT on site-specific direct measures of hypertrophy (magnetic resonance imaging (MRI), computed tomography (CT), or ultrasound) in healthy adults. A total of 44 outcomes were analyzed across 10 studies that met the inclusion criteria. A univariate analysis of all the standardized outcomes showed a pooled mean estimate of 0.11 (95% Credible Interval (CrI): −0.02 to 0.25), providing evidence for a very small effect favoring creatine supplementation when combined with RT compared to RT and a placebo. Multivariate analyses found similar small benefits for the combination of creatine supplementation and RT on changes in the upper and lower body muscle thickness (0.10–0.16 cm). Analyses of the moderating effects indicated a small superior benefit for creatine supplementation in younger compared to older adults (0.17 (95%CrI: −0.09 to 0.45)). In conclusion, the results suggest that creatine supplementation combined with RT promotes a small increase in the direct measures of skeletal muscle hypertrophy in both the upper and lower body.
... This increase in Cr allows for greater PCr resynthesis and enhanced performance in high-intensity, repetitive exercise bouts (Harris et al., 1992). Over time, this performance enhancement has been shown to lead to greater gains in muscular strength, lean body mass (LBM), and muscular endurance after a period of resistance training and other high-intensity exercise in both young and older adults (Branch, 2003;Devries & Phillips, 2014). ...
... We did not observe any changes to LBM as measured by dualenergy X-ray absorptiometry in any groups. While Cr supplementation is known to enhance the training-induced gain in LBM (Branch, 2003;Devries & Phillips, 2014), most demonstrating this effect employ a longer duration of supplementation (i.e., >8 weeks) in combination with a progressive resistance training program. One study reports a significant increase in fat-free mass following 3 days of loading and 7 days of maintenance supplementation at a dose of 20 and 5 g/day, respectively (Safdar et al., 2008). ...
Creatine (Cr) supplementation is a well-established strategy to enhance gains in strength, lean body mass, and power from a period of resistance training. However, the effectiveness of creatyl-L-leucine (CLL), a purported Cr amide, is unknown. Therefore, the purpose of this study was to assess the effects of CLL on muscle Cr content. Twenty-nine healthy men ( n = 17) and women ( n = 12) consumed 5 g/day of either Cr monohydrate ( n = 8; 28.5 ± 7.3 years, 172.1 ± 11.0 cm, 76.6 ± 10.7 kg), CLL ( n = 11; 29.2 ± 9.3 years, 170.3 ± 10.5 cm, 71.9 ± 14.5 kg), or placebo ( n = 10; 30.3 ± 6.9 years, 167.8 ± 9.9 cm, 69.9 ± 11.1 kg) for 14 days in a randomized, double-blind design. Participants completed three bouts of supervised resistance exercise per week. Muscle biopsies were collected before and after the intervention for quantification of muscle Cr. Cr monohydrate supplementation which significantly increased muscle Cr content with 14 days of supplementation. No changes in muscle Cr were observed for the placebo or CLL groups. Cr monohydrate supplementation is an effective strategy to augment muscle Cr content while CLL is not.
... Creatine is a dietary supplement intensively used in sports to enhance endurance and strength in athletes. [1][2][3][4][5] It is available in the diet through the consumption of milk, red and white meat, fish, molluscs and crustaceans (Table 1). On average, a 70-kg man has a creatine pool of 120-140 g (1.7-2 g kg À1 ). ...
... 30,77,78 When comparing studies, it does not seem that the effects of creatine supplementation on lean muscle mass are strictly dose-dependent. 1,3 In addition, when creatine is supplemented, methionine, arginine and leucine, required for creatine synthesis, could subsequently be used for protein synthesis and growth. 12,78 Due to the high creatine content in fish muscle, this sparing effect might be significant. ...
Creatine is an amino acid derivate commonly found in vertebrate muscle tissue. Creatine facilitates the recycling of adenosine triphosphate and thus contributes to the energy supply of the muscles as well as the brain. Creatine is used as a supplement for several reasons and its effects in humans, particularly in sports medicine, have been studied excessively. Also, creatine supplementation has been studied for its functions and benefits in terrestrial farm animals. Up to date, little is known about the use of creatine as a supplement in fish nutrition. Yet, due to its many physiological functions, creatine may serve as a valuable supplement in aquafeeds of farmed aquaculture species. Indeed, creatine plays a pivotal role in the fish's muscle and may help to enhance performance of fish reared in aquaculture systems. With regard to swimming exercise, creatine may even amplify its metabolic effects. Upon supplementation, creatine stimulates muscle growth increasing body mass and it has the potential to improve feed utilisation particularly of plant‐based diets. Also, creatine plays a part in osmoregulation when fish adapt to changes in salinity. Furthermore, it may improve product quality upon slaughter. Here, we compile what is known about the many functions of creatine as well as its physiological effects in fish in comparison to mammals. We also highlight its potential beneficial effects as a supplement in aquaculture and infer why creatine can help increase the sustainability of fish feeds.
... These have typically been undertaken as two assessments -the value of creatine in combination with resistance training, or as a supplement alone. Firstly, creatine supplementation in combination with resistance exercise training has been shown to be beneficial for muscle mass and functional performance in older adults [39,41,42]. A recent meta-analysis performed in 2021 by Forbes and colleagues [43] suggested that any dose of creatine in combination with resistance exercise training increased lean mass, chest-press and leg-press strength compared with resistance training alone. ...
Sarcopenia is characterised by progressive and generalised decline in muscle strength, function, and muscle mass. Now recognised as a muscle disease, it is highly prevalent in older adults, with estimates of up to 30% in some populations. Sarcopenia has a complex multifactorial aetiology, including cellular and molecular changes, chronic disease, lower physical activity as well as nutritional deficiency. Sarcopenia is associated with a range of adverse physical and metabolic outcomes leading to disability, morbidity, impaired quality of life and mortality. Given the demographic shifts in the population, there is an urgent need to improve skeletal muscle health in older adults. Unfortunately, there are no pharmacologic therapies suitable for widespread use currently. In this short review, we discuss the existing literature reporting the benefits of various options for nutritional supplementation in older sarcopenic participants or healthy older adults. Several systematic reviews have been undertaken on this topic with some key findings. In general, supplementation is more effective in combination with resistance exercise. The research literature supports protein and vitamin D supplementation in individuals who are insufficient. There is also evidence in support of supplementation with creatine, leucine with vitamin D, whey supplements and combinations of creatine, whey and leucine. Probiotics may also be beneficial. Further well conducted and standardised research trials are required.
... Supplementation therefore acts to saturate muscle creatine, with suggested loading patterns of four 5 g doses every day for approximately a week. Creatine stores can be maintained by ingesting between 3 and 10 g daily depending on the size of the athlete [4,5]. ...
The use of creatine as a dietary supplement is widespread. However, its reported performance benefit has been largely demonstrated in male populations. The aim was to evaluate the effectiveness of creatine supplementation in improving exercise performance in active females. A secondary aim was to appraise the quality of research in this area. Five databases were searched from the earliest record to July 2024. Eligible studies used supplemental creatine as an intervention with physically active female participants and reported an exercise performance-related outcome. Study quality was appraised using the Critical Appraisal Skills Program randomised controlled trials checklist with four additional items related to methodological considerations for research with active females. Performance outcomes were categorised as strength/power, anaerobic, or aerobic. Of the 10,563 records identified, 27 studies were included. Participant calibre ranged from recreationally active to elite. Creatine interventions ranged from five days to 12 weeks and included a range of dosage strategies. Compared to placebo, 3/11 studies showed an improvement in strength/power outcomes, 4/17 showed an improvement in anaerobic outcomes, and 1/5 showed an improvement in aerobic outcomes. Study quality varied, but methodological considerations for research with female athletes were poorly addressed by most studies. Although some benefits were reported, most studies showed no improvement in performance compared to placebo. The heterogeneity in participant characteristics, performance tests, creatine intervention, insufficient consideration of the unique physiological characteristics of females, and an overall small evidence base limits our understanding of how creatine supplementation influences physical performance in active females.
... Muscle creatine levels are lower in vegetarians [17]. resistance training to increase muscle mass [7]. Athletes often implement a loading phase of 5-6 g doses four times a day for 5-6 days before a daily 2-5 g/d maintenance dose is used of creatine throughout the remainder of supplementation [17]. ...
This research paper provides a comprehensive review of the effects of creatine supplementation on memory function. Creatine, a compound traditionally associated with muscle energy metabolism, has garnered attention for its potential cognitive benefits. The paper synthesizes findings from various studies exploring creatine’s impact on different types of memory, including short-term, long-term, and working memory, in healthy individuals and those with cognitive impairments. The review aims to clarify the conditions under which creatine supplementation may enhance memory performance by analyzing experimental designs, dosage variations, and participant demographics. Additionally, the paper discusses the underlying mechanisms, such as creatine’s role in cellular energy production and neuroprotection, which may contribute to its cognitive effects. The review concludes with recommendations for future research directions, highlighting the need for standardized protocols and long-term studies to fully understand creatine’s potential as a cognitive enhancer.
... Collectively, creatine has the capacity to increase anabolic processes and to attenuate catabolic processes [30,37]. From a muscle or lean tissue mass perspective, a large body of evidence has demonstrated that creatine supplementation combined with strength training enhances adaptations [6,9,19,31,32,38,39]. The evidence is strong that to achieve gains in muscle mass, creatine must be combined with strength training [32], thus the primary driver of anabolism and hypertrophy is strength training. ...
Aging is associated with numerous physiological, musculoskeletal, and neurological impairments including a loss of muscle, strength, function, bone mineral, and cognition. Strength training is an effective intervention to counter these age-associated declines. In addition, creatine supplementation is purported to enhance strength training gains in lean tissue mass, muscular strength, and function. There is emerging evidence that creatine combined with strength training can alter bone geometry and cognitive performance. The purpose of this review is to update previous meta-analyses examining creatine combined with strength training on lean tissue mass and bone density compared to strength training and placebo. A secondary purpose was to explore the effects of creatine and strength training on cognition. Updated meta-analyses revealed that creatine enhances lean tissue mass (mean difference [MD]: 1.18 kg, 95 % CI: 0.70–1.67; p<0.00001) and upper body muscular strength (standard mean difference [SMD]: 0.24, 95 % CI: 0.05–0.43; p=0.02) compared to strength training and placebo. Creatine combined with strength training had no greater effects compared to strength training and placebo on lower body muscular strength (SMD: 0.17, 95 % CI: −0.03–0.38; p=0.09), whole-body (MD: −0.00 g cm⁻²; 95 % CI: −0.01–0.00, p=0.32), femoral neck (MD: −0.00 g cm⁻²; 95 % CI: −0.01–0.00, p=1.00), or lumbar bone mineral density (MD: 0.00 g cm⁻², 95 % CI: −0.01–0.01; p=045). There is preliminary evidence that combining strength training and creatine is an effective strategy to improve bone geometry in postmenopausal females and cognitive function in older adults. Overall, the combination of creatine and strength training has favorable effects on lean tissue mass and upper body strength. In contrast, creatine combined with strength training does not enhance lower-body strength or bone mineral.
... This points to possible synergistic effects of the two in augmenting the MIS formulation in the current study. Creatine alone has been shown to enhance increases in muscle mass and strength (45)(46)(47)(48), as well as reduce leucine oxidation and urinary 3MH excretion (48,49), offering both an anabolic and anticatabolic benefit to users. With training, creatine has also shown greater enhancements in SC content and myonuclear concentration in skeletal muscle fibers (19). ...
Introduction
Skeletal muscle satellite cells (SC) contribute to the adaptive process of resistance exercise training (RET) and may be influenced by nutritional supplementation. However, little research exists on the impact of multi-ingredient supplementation on the SC response to RET.
Purpose
We tested the effect of a multi-ingredient supplement (MIS) including whey protein, creatine, leucine, calcium citrate, and vitamin D on SC content and activity as well as myonuclear accretion, SC and myonuclear domain compared with a collagen control (COL) throughout a 10-wk RET program.
Methods
Twenty-six participants underwent a 10-wk linear RET program while consuming either the MIS or COL supplement twice daily. Muscle biopsies were taken from the vastus lateralis at baseline and 48 h after a bout of damaging exercise, before and after RET. Muscle tissue was analyzed for SC and myonuclear content, domain, acute SC activation, and fiber cross-sectional area (fCSA).
Results
MIS resulted in a greater increase in type II fCSA following 10 wk of RET (effect size (ES) = 0.89) but not myonuclear accretion or SC content. Change in myonuclei per fiber was positively correlated with type I and II and total fiber hypertrophy in the COL group only, indicating a robust independent effect of MIS on fCSA. Myonuclear domain increased similarly in both groups, whereas SC domain remained unchanged following RET. SC activation was similar between groups for all fiber types in the untrained state but showed a trend toward greater increases with MIS after RET (ES = 0.70).
Conclusions
SC responses to acute damaging exercise and long-term RET are predominantly similar in MIS and COL groups. However, MIS can induce greater increases in type II fCSA with RET and potentially SC activation following damage in the trained state.
... Notably, creatine was shown to improve sit-to-stand performance in older adults, which has great clinical significance, since it is a predictor of reduced risk of falls [98,99]. Nevertheless, the results of studies investigating the effect of creatine on bone health are unambiguous [97,100]. ...
... Studies have shown that skeletal muscle contraction stimulates intramyocellular uptake of creatine, and that a combination of creatine supplementation and resistance training may maximize its accretion [76]. As results, creatine supplementation combined with resistance training increases LBM and muscle strength [75,[77][78][79][80]. However, there is no evidence to suggest that creatine supplementation independent of resistance training can increase muscle strength. ...
Maintaining skeletal muscle mass is important for improving muscle strength and function. Hence, maximizing lean body mass (LBM) is the primary goal for both elite athletes and fitness enthusiasts. The use of amino acids as dietary supplements is widespread among athletes and physically active individuals. Extensive literature analysis reveals that branched-chain amino acids (BCAA), creatine, glutamine and β-alanine may be beneficial in regulating skeletal muscle metabolism, enhancing LBM and mitigating exercise-induced muscle damage. This review details the mechanisms of these amino acids, offering insights into their efficacy as supplements. Recommended dosage and potential side effects are then outlined to aid athletes in making informed choices and safeguard their health. Lastly, limitations within the current literature are addressed, highlighting opportunities for future research.
... Here participants will be instructed to consume five grams of supplementation four times daily, with each dose consumed with 16 fluid ounces of a carbohydratecontaining beverage. The loading phase is established with demonstrated safety in apparently healthy and clinical populations [30,38,43,44], including data from our group which demonstrates safety among men living with mCSPC on ADT (NCT03987217). Weeks 2-52 is considered the maintenance phase. ...
Background
Muscle mass is important for metastatic prostate cancer survival and quality of life (QoL). The backbone of treatment for men with metastatic castration sensitive prostate cancer (mCSPC) is androgen deprivation therapy (ADT) with an androgen signaling inhibitor. ADT is an effective cancer treatment, but it facilitates significant declines in muscle mass and adverse health outcomes important to mCSPC survivors, such as fatigue, and reductions in physical function, independence, insulin sensitivity, and QoL. In non-metastatic CSPC survivors, resistance training (RT) preserves muscle mass and improves these related health outcomes, but the biggest barrier to RT in CSPC survivors of all stages is fatigue. Creatine monohydrate supplementation coupled with RT (Cr + RT) may address this barrier since creatine plays a critical role in energy metabolism. Cr + RT in cancer-free older adults and other clinical populations improves muscle mass and related health outcomes. Evidence also suggests that creatine supplementation can complement cancer treatment. Thus, Cr + RT is a strategy that addresses gaps in survivorship needs of people with mCSPC. The purpose of this parallel, double-blind randomized controlled trial is to test the effects of 52-weeks of Cr + RT compared with placebo (PLA) and RT (PLA + RT) on muscle mass, other related health outcomes, and markers of cancer progression.
Methods
We will carry out this trial with our team’s established, effective, home-based, telehealth RT program in 200 mCSPC survivors receiving ADT, and evaluate outcomes at baseline, 24-, and 52-weeks. RT will occur twice weekly with elastic resistance bands, and an established creatine supplementation protocol will be used for supplementation delivery. Our approach addresses a major facilitator to RT in mCSPC survivors, a home-based RT program, while utilizing a supervised model for safety.
Discussion
Findings will improve delivery of comprehensive survivorship care by providing a multicomponent, patient-centered lifestyle strategy to preserve muscle mass, improve health outcomes, and complement cancer treatment (NCT06112990).
... En algunos estudios (Mujika et al., 2000;Cox et al., 2002;Ostojic, 2004) se observó que la evidencia es beneficiosa para el desarrollo en el fútbol. Aún existen limitaciones en las recomendaciones de aplicación en el fútbol, específicamente en lo relacionado a la cantidad de gramos utilizados en la suplementación dietética, sin embargo, aún hay controversias en torno a la dosis recomendada, por ejemplo, Devries & Phillips (2014) mencionan en su metaanálisis dosis que van desde los 0,07 g/kg de peso hasta 5 g/d para obtener resultados positivos a partir del entrenamiento de resistencia para aumentar la masa magra. Igualmente se ha visto que la dosis más efectiva de creatina es de 0,3 g/kg/d durante cinco días (fase carga), seguido de un consumo de 0,03 g/kg/d durante al menos 14-21 días adicionales (fase mantenimiento) para lograr una mayor reserva de creatina en el músculo esquelético (Jurado-Castro et al., 2020). ...
El futbol es un deporte colectivo, uno de los deportes más populares a lo largo del mundo. Por lo cual, se requiere el aporte de estrategias nutricionales para el óptimo rendimiento del deportista. El objetivo de esta revisión sistemática es analizar y describir a través de la literatura científica los efectos del consumo de creatina en futbolistas. A través de las bases de datos Scopus, WoS, Pubmed y SciELO, se identificaron un total de 6 artículos científicos, que fueron encontrados mediante el uso de las palabras claves “Soccer” OR “Football”, AND “Creatine” AND" physical condition" OR "performance". Se encontraron resultados relacionados con “Dosis de creatina y periodo de intervención”, “Efectos en las vías respiratorias y volumen respiratorio”, “Altura de salto”, “Resistencia aeróbica”, “Potencia anaeróbica”, “Habilidad deportiva”, y “Velocidad y cambios de dirección”. Finalmente, la efectividad del consumo de creatina se encuentra orientado a la presencia de una fase de mantenimiento o a una fase de carga adicionado a una de mantenimiento, permitiendo mejoras en las vías respiratorias, potencia muscular, la velocidad y el rendimiento físico en los futbolistas. Palabras claves: Fútbol; Creatina; Rendimiento; Condición física Abstract. Soccer is a collective sport, one of the most popular sports throughout the world. Therefore, the contribution of nutritional strategies is required for the optimal performance of the athlete. The objective of this systematic review is to analyze and describe through the scientific literature the effects of creatine consumption in soccer players. Through the Scopus, WoS, Pubmed and SciELO databases, a total of 6 scientific articles were identified, which were found using the keywords "Soccer" OR "Football", AND "Creatine" AND "physical condition". " OR "performance". Results related to "Creatine dose and intervention period", "Effects on the respiratory tract and respiratory volume", "Jump height", "Aerobic resistance", "Anaerobic power", "Sportsmanship", and "Speed" were found. and address changes. Finally, the effectiveness of creatine consumption depends on the inclusion of a maintenance phase or not, allowing improvements in muscle power, speed and physical performance in soccer players. Keywords: Soccer; Creatine; Performance; Physical condition
... Creatine monohydrate consumption has been reported to provide multiple bene ts including increasing muscle size, strength, and power [6], improving performance during short bursts of high-extension exercises [7], and increasing post-exercise recovery [8]. In the literature, there are some studies examining the effects of creatine intake on increasing the performance level and body composition in some sports branches [6, 9,10]. Some of these studies have shown an increase in lean body mass [6,11] and type II muscle ber area [12,13] in addition to performance. ...
Background
Different training methods and ergogenic aids has been used to increase athletic performance. In this study, to understand the effect of the combination of the six-week high intensity interval training (HIIT) and creatine supplementation on body composition, leg strength, and anaerobic power in physically active male adults was purposed.
Methods
In this six-week study a total of fifteen physically active men with the mean age of 21.13 ± 1.68 years were divided into two groups as Wingate based HIIT training group (HIIT) and Wingate based HIIT training + Creatine supplementation group (C-HIIT). Both groups performed a total of six weeks three days a week of HIIT training, the scope of which increased in the second three-week period and organized based on Wingate. In addition to these trainings, the C-HIIT group took a total of 10 g of creatine each training day, 5 grams 30 minutes before the load and 5 grams immediately after the load. Their body composition, leg strength, anaerobic power measurements were taken three days before the study started and three days after it ended.
Results
According to the findings, although there was no significant difference in body composition values between the two groups, it was observed that leg strength (p < 0.05) and anaerobic power parameters such as peak power, average power, and minimum power improved significantly in the C-HIIT group (p < 0.01).
Conclusions
Comparative effectiveness of additive of 10 gram of creatine monohydrate to HIIT appears to be efficient in improving leg strength and anaerobic power in physically active adult men.
Trial registration
This research was registered retrospectively on August 7, 2023 with the number NCT05981820.
... Therefore, an athlete could gain 1.08% of weight gain after a protocol of 5g/day during 28 days of CrM supplementation or ~1.89% of bodyweight gains after 20g/day for seven days followed by 5g/day for 21 days. The bodyweight gain may be linked to the physicochemical properties of CrM and its pharmacokinetic characteristics [36], which we will further discuss in the next section. ...
Creatine monohydrate (CrM) supplementation is not recommended for athletes with weight-gain restriction due to its significant water retention adverse effect. Because of this CrM limitation, creatine hydrochloride (CrHCl) was presented in the market. Compared to CrM, CrHCl possesses a different pharmacokinetic and, in theory, could not promote weight gain similar to CrM. However, several aspects related to the stability and efficiency of this new CrHCl molecule need to be investigated and compared to the traditional CrM. This article reviewed the experimental articles that evaluated both weight and body water gain after CrM or CrHCl supplementation. Also, we discuss the possible limitation on performance enhancement of CrM in physical activities where bodyweight influences performance. We will propose CrHCl as an alternative creatine supplement source for the athlete’s population, which has weight-gain restrictions. Finally, we will indicate several research questions that must be answered before the CrHCl recommendation for the population of athletes with weight gain restrictions.
... Since dynapenia impacts older adults' health and is associated with negative outcomes, determining the prevalence of dynapenia may help health systems minimize its consequences using proper interventions [22][23][24] . In this context, the Brazilian Longitudinal Study of Aging (ELSI-Brazil) revealed a high prevalence of dynapenia (17.2%) in older adults in Brazil 12 . ...
Objective:
This study aims to investigate handgrip strength and dynapenia prevalence among older adults stratified by Brazilian macroregions. Additionally, we aim to evaluate the overlap between dynapenia and Instrumental Activities of Daily Living (IADL) disability, depression, and executive dysfunction on a national basis and by each Brazilian macroregion.
Methods:
This cross-sectional analysis was based on data from the Brazilian Longitudinal Study of Aging (ELSI-Brazil). A multistage cluster sample design was used, with a representative population-based study of non-institutionalized community-dwelling Brazilians aged ≥ 50 years from 70 municipalities across all five macroregions of the country. The outcome variable was dynapenia. Covariables were IADL disability, depression, and executive dysfunction. The Brazilian macroregions were used for stratification. In addition, the following additional variables were included: age group, gender, education level, macroregions (North, Northeast, Southeast, South, and Midwest), self-reported health, multimorbidity, and falls.
Results:
A total of 8,849 (94%) of the sample provided complete information for the handgrip strength assessment and were included in this analysis. Dynapenia prevalence was higher in North and Northeast regions (28.5% and 35.1%, respectively). We identified statistically significant differences between different macroregions for dynapenia, IADL disability, and verbal fluency, with worse values in the North and Northeast regions. In the North and Northeast macroregions, nearly half of the subjects that presented executive dysfunction and IADL disability also had dynapenia. There was a more significant overlap in the prevalence of all four conditions in the North and Northeast regions (4.8% and 5.5%, respectively), whereas the overlap was smaller in the South (2.3%). There was also a smaller overlap in the prevalence of dynapenia and depression in the South (5.8%) compared with other macroregions.
Conclusions:
Macroregions in Brazil exhibit marked differences in the prevalence of dynapenia and in its overlap with IADL disability, depression, and executive dysfunction.
... Creatine transport into skeletal muscle is elevated if muscle contractions (i.e., resistance exercise) are performed [128]. Several meta-analyses show that the combination of creatine supplementation and resistance exercise improves measures of muscle strength [129][130][131] and functional ability in older adults [132] compared to resistance exercise training alone. Mechanistically, creatine supplementation may influence high-energy phosphate metabolism, calcium kinetics, glycogen content, muscle protein kinetics, inflammation, and oxidative stress [129,132,133]. ...
Aims:
Sarcopenia generally refers to the age-related reduction in muscle strength, functional ability, and muscle mass. Sarcopenia is a multifactorial condition associated with poor glucose disposal, insulin resistance, and subsequently type 2 diabetes (T2D). The pathophysiological connection between sarcopenia and T2D is complex but likely involves glycemic control, inflammation, oxidative stress, and adiposity.
Methods and results:
Resistance exercise and aerobic training are two lifestyle interventions that may improve glycemic control in older adults with T2D and counteract sarcopenia. Further, there is evidence that dietary protein, Omega-3 fatty acids, creatine monohydrate, and Vitamin D hold potential to augment some of these benefits from exercise.
Conclusions:
The purpose of this narrative review is: (1) discuss the pathophysiological link between age-related sarcopenia and T2D, and (2) discuss lifestyle interventions involving physical activity and nutrition that may counteract sarcopenia and T2D.
... A recent meta-analysis showed that creatine supplementation induced greater increases in fat-free mass, upper and lower-body strength, and physical function compared with placebo in older adults engaged in resistance training [166]. Studies investigating the effect of creatine supplementation on muscle-related parameters in nonexercising older adults yielded mixed results [167][168][169][170]. ...
Sarcopenia is a geriatric condition characterized by a progressive loss of skeletal muscle mass and strength, with an increased risk of adverse health outcomes (e.g., falls, disability, institutionalization, reduced quality of life, mortality). Pharmacological remedies are currently unavailable for preventing the development of sarcopenia, halting its progression, or impeding its negative health outcomes. The most effective strategies to contrast sarcopenia rely on the adoption of healthier lifestyle behaviors, including adherence to high-quality diets and regular physical activity. In this review, the role of nutrition in the prevention and management of sarcopenia is summarized. Special attention is given to current "blockbuster" dietary regimes and agents used to counteract age-related muscle wasting, together with their putative mechanisms of action. Issues related to the design and implementation of effective nutritional strategies are discussed, with a focus on unanswered questions on the most appropriate timing of nutritional interventions to preserve muscle health and function into old age. A brief description is also provided on new technologies that can facilitate the development and implementation of personalized nutrition plans to contrast sarcopenia.
... Beyond these potential direct mechanisms, creatine supplementation may indirectly have a favorable effect on fat mass through its positive effect on lean tissue mass and muscle accretion. Several meta-analyses have been performed collectively showing that the combination of creatine supplementation and resistance exercise increases measures of whole-body lean tissue mass by ~1.37 kg compared to placebo and resistance exercise [35][36][37][38][39]. Furthermore, Burke et al. [40] performed a systematic review and meta-analysis involving 10 studies and found significant improvements in direct measures of limb muscle hypertrophy (0.10-0.16 cm; as measured using ultrasound and peripheral quantitative computed tomography [pQCT]) in the upper-and lower-body from creatine supplementation and resistance exercise compared to resistance exercise and placebo. ...
Adiposity is associated with adverse health conditions such as obesity, cardiovascular disease and type 2 diabetes. The combination of resistance exercise and creatine supplementation has been shown to decrease body fat % in adults ≥ 50 years of age. However, the effects in adults < 50 years of age is unknown. To address this limitation, we systematically reviewed the literature and performed several meta-analyses comparing studies that included resistance exercise and creatine supplementation to resistance exercise and placebo. Twelve studies were included involving 266 participants. Adults (< 50 years of age) that supplemented with creatine and performed resistance exercise experienced a significant reduction in body fat % (-1.19%, p=0.006) and a non-significant reduction in absolute fat mass (-0.09 kg, p=0.88). Collectively, the combination of resistance exercise and creatine supplementation produces a very small reduction in body fat % in adults < 50 years of age.
... It has been shown that this might be due to energy and mechanical optimization of the cells, which results in the prevention of protein degradation, an activation of satellite cells and an increase in glycogen synthesis [101]. Three meta-analyses have been performed to determine the efficacy of creatine (≥ 3 g/day) vs. placebo during a resistance training program (≥ 7 weeks) on measures of muscle accretion and strength [102][103][104]. Collectively, these meta-analyses showed that the combination of creatine and resistance training augmented muscle accretion (≈1.2 kg), and upper-and lower-body strength, more than placebo and resistance training alone in older adults [99]. ...
Muscle wasting is one of the main causes for exercise intolerance and ventilatory inefficiency in patients with heart failure and a strong predictor of frailty and reduced survival. The prevalence of sarcopenia is at least 20% in patients with heart failure. Patients with heart failure often have subclinical systemic inflammation, which may exert sustained effects on skeletal muscle. Besides exercise, nutrition should also be carefully evaluated, as an appropriate diet with selected nutraceuticals may be able to stimulate muscle anabolism and inhibit muscle catabolism. This review summarizes the epidemiological and clinical trial evidence supporting the recommendations for the use of nutraceuticals with anti-inflammatory properties in heart failure and provides an overview of the state of the evidence for nutraceutical supplementation to prevent and/or mitigate heart failure muscle wasting.
... Micronutrient intake, however, is dependent on source, as some micronutrients are derived strictly from animal-based products, which places plantbased dieters at higher risk of micronutrient deficiency if unaware [12,19,36,37]. The organic compound creatine is found at higher levels in the blood of non-plant-based dieters when compared to plant-based-dieters on average, which ultimately may affect strength and power of athletes regardless of age; notwithstanding, creatine supplementation has been shown to be beneficial to plant-based athletes to compensate for power creatine levels [4,20,84]. These findings may imply that though diets contain varying levels of energy-and power-providing materials, ultimately these differences can be negated with supplemental intake or the differences may be clinically irrelevant. ...
Purpose
Plant-based diets have become increasingly popular in Western culture. Although studies have examined physiologic health improvements of plant-based diets, there is little data on plant-based diets as it relates to sports performance.
Methods
Clinical review of systematic reviews, randomized trials, prospective and retrospective cohort studies available in English on PubMed and Google Scholar databases utilizing combinations of the search terms “athlete, sport, nutrition, diet, vegan, vegetarian, strength, endurance, health, performance, and exercise.”
Results
There are no significant differences in athletic performance in participants maintaining plant-based diets compared to those consuming omnivorous diets specifically related to strength, power, and endurance. Plant-based diets are at higher risk of predisposing individuals to certain micronutrient deficiencies, reduced protein intake, and lower serum creatine and sex testosterone levels, though supplementation may effectively replace the lacking components. Non-plant-based diets are associated with a higher risk of obesity, type II diabetes mellitus, certain malignancies, and cardiovascular disease, though several studies demonstrate that a particular meat- and fish-filled diet may reduce body weight, blood pressure, fat composition, and all-cause mortality.
Conclusion
Though plant-based and mixed omnivorous eaters may vary in their macronutrient and micronutrient intake, disease propensities, and oxygen consumption during exertion, a plant-based diet does not translate into a significantly different physical performance compared to a non-plant-based diet across measures of strength, power, and aerobic/anaerobic performance. For athletes, trainers, nutritionists and dieticians, and physicians, the most important recommendation is to maintain a nutritionally sufficient diet that provides the appropriate levels of vital nutrients and vitamins.
... The authors of the 5,507 records were analyzed, and 1,019 nodes and 3,517 links were obtained ( (10), protein supplementation on muscle protein synthesis (11-15) and muscle strength (16) in sarcopenia. PHILLIPS SM mainly focuses on nutritional supplements in support of resistance exercise to sarcopenia (17)(18)(19)(20). EMANUELE MARZETTI not only focused on physical activity and exercise (21), but also analyzed biomarkers of frailty and sarcopenia to provide a reference for the diagnosis and detection of sarcopenia (22)(23)(24). ...
Exercise is an effective method for the prevention and treatment of sarcopenia, which can improve skeletal muscle mass, strength and physical function in individuals with sarcopenia to varying degrees. Moreover, exercise has an important role in improving ability to perform daily activities and quality of life on sarcopenia. In this study, articles and review articles on exercise interventions for sarcopenia from January 2003 to July 2022 were retrieved from the Web of Science core collection. Then, the number of annual publications, journal/cited journal, country, institution, author/cited author, references and keywords were analyzed using CiteSpace 6.1.R2. A total of 5,507 publications were collected and the number of publications increasing each year. Experimental Gerontology was the most productive journal and the most cited journal was J GERONTOL A-BIOL. The United States of America was the most influential country with the largest number of publications and centrality. Maastricht University in the Netherlands is the most productive institution. The author VAN LOON LJC has the highest ranking in terms of publications and CRUZ-JENTOFT A is ranked first in terms of cited authors. The most frequently occurring keywords in the field of exercise interventions for sarcopenia are “skeletal muscle,” “exercise,” “body composition,” “strength,” and “older adult”; the keyword “elderly men” showed the strongest explosive intensity. The keywords formed 6 clusters, namely “skeletal muscle,” “muscle strength,” “heart failure,” “muscle protein synthesis,” “insulin resistance” and “high-intensity interval training.” In conclusion, this study demonstrates a new perspective on the current state of research and trends in exercise interventions for sarcopenia over the past 20 years via the visualization software CiteSpace. It may help researchers to identify potential collaborators and partner institutions, hotspots and research frontiers in the field of exercise interventions for sarcopenia.
... Exercise further promotes the body's metabolic process, improves lipid metabolism, and increases energy consumption [41,42]. In several meta-analyses and review articles related to creatine supplementation, creatine supplementation was found to be readily and positively associated with muscle endurance and exercise performance [43][44][45][46][47]. It was also possible that creatine supplements increase calcium reuptake by the sarcoplasmic reticulum, which would lead to faster actin-myosin cross-bridge cycling during repeated muscle contractions [48]. ...
The present study aimed to assess the changes in muscle strength and plasma metabolites in athletes with β-glucan supplementation. A total of 29 athletes who met the inclusion criteria were recruited for this study (ChiCTR2200058091) and were randomly divided into a placebo group (n = 14) and β-glucan group (n = 15). During the trial, the experimental group received β-glucan supplementation (2 g/d β-glucan) for 4 weeks and the control group received an equal dose of placebo supplementation (0 g/d β-glucan), with both groups maintaining their regular diet and exercise habits during the trial. The athletes’ exercise performance, muscle strength, and plasma metabolome changes were analyzed after 4 weeks of β-glucan supplementation. The results showed a significant increase in mean grip strength (kg), right hand grip strength (kg), left triceps strength (kg), and upper limb muscle mass (kg) in the experimental group after the 4-week intervention compared to the preintervention period (p < 0.05). A comparison of the difference between the two groups after the intervention showed that there were significant differences between the control group and the experimental group in mean grip strength (kg) and right-hand grip strength (kg) (p < 0.05). Athletes in the experimental group showed significant improvements in 1 min double rocking jump (pcs), VO2max (ml/kg-min) (p < 0.05). The β-glucan intake increased the creatine-related pathway metabolites in plasma. Overall, these results suggest that 4 weeks of β-glucan supplementation can improve muscle strength in athletes, with the potential to increase aerobic endurance and enhance immune function, possibly by affecting creatine-related pathways.
... A recent researches show that the Cr doses are ranging from 0.03 g/kg/day up to 5 g/d. [25,26] There is also a tendency, mostly among the athletes, to implement a loading dose of creatine before the introduction of a daily maintenance dose. A widely accepted loading dose ranges from 20 to 25 g/day, in 4 doses for a period of 5 to 7 days. ...
Creatine is one of the most often used supplements nowadays. Its popularity can be attributed to a wide variety of clinical implications. The intent of this paper was to evaluate and review the latest publications about the usage and potential clinical effects on the human body of creatine supplementation and to bring attention to new findings in this subject. Authors explored PubMed, CrossRef and Google Scholar using keywords: creatine, supplements, ergogenic aids, neuroprotection, bioenergetics. Furthermore, the references of selected articles were manually investigated for additional relevant articles. The bibliography focused mainly on systematic reviews, randomized controlled trials (RCTs) and case reports. The selection of individual articles was carried out in accordance with the determinants of general medicine readership. There is still a lot to learn about creatine supplementation and its potentially beneficial effects. Further evidence-based studies are required, as the amount of reliable data and information is still not sufficient and lots of them have yet to be examined.
... These contrasting findings may be associated with methodological differences between studies, including participant characteristics (age, training and health status), training program duration, frequency and design, and creatine ingestion strategy. Further, it is important to note that the group who consumed creatine experienced a ~ 1.2 kg increase in lean tissue mass over time which aligns with an average increase (~ 1.2 kg) found in three meta-analyses involving creatine supplementation and resistance training in older adults (17,22,25,28). ...
The purpose was to investigate the effects of progressive resistance training (PRT) and creatine supplementation in stroke survivors. Participants were randomized to one of two groups: creatine (n = 5; 51 ± 16y) or placebo (n = 3; 73 ± 8y) during 10 weeks of supervised PRT. Prior to and following PRT and supplementation, assessments were made for body composition (lean tissue and fat mass), muscle thickness, muscle strength (1-repetition maximum), functional exercise capacity (6-minute walk test, Berg Balance Scale; BBS), cognition (Montreal Cognitive Assessment; MoCA), and symptoms of anxiety (Generalized Anxiety Disorder Assessment-7; GAD-7) and depression (Center for Epidemiological Studies Depression Scale; CES-D). There were time main effects for leg press strength (increased; p = 0.001), chest press strength (increased; p = 0.003), elbow flexor muscle thickness (increased; p = 0.007), BBS (increased; p = 0.002), MoCA (increased; p = 0.031) and CES-D (decreased; p = 0.045). There was a group x time interaction for the 6 minute walk test (p = 0.039). The creatine group significantly increased walking distance over time (p = 0.002) with no change in the placebo group (p = 0.120). Ten weeks of PRT had some positive effects on measures of muscle strength and size, balance, cognition and depression. The addition of creatine to PRT significantly improved walking performance in stroke survivors.
Introdução: A aptidão física relacionada à saúde envolve cinco componentes, entre eles a composição corporal, que é importante para a uma boa qualidade de vida e para a prevenção de doenças crônicas. O aumento da massa magra tem impacto direto na redução do risco de patologias, como diabetes e osteoporose, sendo essencial para a manutenção da funcionalidade, especialmente em mulheres a partir dos 30 anos, quando se inicia a perda muscular. Objetivo: Investigar o efeito da suplementação de creatina sobre o aumento de massa magra em mulheres adultas, buscando esclarecer seus benefícios e identificar lacunas na literatura atual. Metodologia: Foi realizada uma revisão integrativa de literatura, com buscas nas bases de dados SciELO, PubMed, Google Acadêmico e EFDeportes, considerando publicações entre 2011 e 2024. Os critérios de inclusão abrangeram estudos sobre suplementação de creatina em mulheres adultas, focando no ganho de massa magra, com estudos experimentais e revisões de literatura. Foram excluídos artigos que não abordassem diretamente o efeito da creatina na composição corporal feminina. Resultados: A análise demonstrou que a suplementação de creatina promove aumento significativo de massa magra e força em mulheres adultas, especialmente quando associada ao treinamento resistido. Estudos indicam que protocolos de suplementação com creatina são benéficos para a hipertrofia muscular de mulheres, variando em eficácia, com doses de 3 a 5 g/dia sendo recomendadas para manutenção. Conclusão: A suplementação de creatina é uma estratégia eficaz para melhorar a composição corporal feminina, embora mais estudos sejam necessários para aprofundar o entendimento sobre seus efeitos a longo prazo em diferentes faixas etárias e contextos.
Bir aminoasit olan kreatin, en sık kullanılan ergojenik desteklerden birisidir ve doping sayılmamaktadır. Kreatin tip-2 hızlı kasılan liflerde depo edilir ve kaslarda depolanma formu olan fosfokreatinin (PCr) kas hücrelerindeki biyolojik oluşumu arttıran kreatin yüklemesi ile kas performasındaki artış çeşitli mekanizmalarla açıklanmaktadır. Uygun dozda kullanımında yan etki gözlemlenmese de ozmotik etkisinden dolayı dehidratasyon riski bulunmaktadır ve bu sebeple bol sıvı tüketimi önerilmektedir. Sporcular üzerine birçok olumlu etkisi olduğu iddia edilmektedir. Özellikle kısa süreli, yüksek şiddetli egzersizler ve anaerobik egzersizler için performansı arttırmak için önerilmektedir. Farklı spor dallarında, farklı takviye protokollerine göre, kreatinin sporcu üzerindeki elde edilen sonuçları farklılık gösterebilmektedir. Başlangıçtaki kreatin depolarının durumu, takviye sonrası gerçekleşecek kas kreatin artışını etkilemektedir. Kreatin takviyesi ile ilgili genellikle kırk yaş üzeri olan ve düzenli egzersiz yapan veteran sporcular üzerine yapılan çalışmalarda çelişkili sonuçlar bulunmaktadır. Kreatin takviyesi yapılan çalışmalarda hem yağsız vücut kütlesini hemde yağ kütlesinde artışlar olduğunu gösteren sonuçlar bulunmaktadır. Kreatin takviyesi üzerine yapılan çalışmalarda kısa süreli etkilerine dair sonuçlar elde edilmiş olsa da, uzun dönemde gerçekleşecek sonuçlar belirsizliğini korumaktadır.
In this opinion article, we advocate for the combination of creatine monohydrate supplementation and resistance training as a safe and effective non-pharmacological strategy to prevent and treat sarcopenia that should be internationally recognized by health practitioners and public health organizations.
Purpose of Review
Sarcopenia, generally characterized by the age-related reduction in muscle strength, lean/muscle mass and functional ability, is also associated with reduced bone mass and strength and impaired brain health and function. One potential intervention which has received much ‘hype’ over the past few decades to countermeasure these negative consequences of biological aging is creatine monohydrate supplementation.
Recent Findings
From a skeletal muscle perspective, the combination of creatine monohydrate supplementation and resistance training provides ‘hope’ for older adults as it improves measures of lean mass, regional (limb) muscle thickness, upper- and lower-body muscle strength and functional ability. Further, there is some evidence that creatine (supplementation or habitual diet) provides a ray of ‘hope’ for improving some aspects of cognitive function. The majority of research suggests that creatine is more ‘hype’ than ‘hope’ for improving measures of bone mass in older adults.
Summary
Creatine monohydrate supplementation provides some anti-sarcopenic benefits for older adults.
Sarcopenia is characterized by a decline in muscle strength, generalized loss of skeletal muscle mass, and impaired physical performance, which are common outcomes used to screen, diagnose, and determine severity of sarcopenia in older adults. These outcomes are associated with poor quality of life, increased risk of falls, hospitalization, and mortality in this population. The development of sarcopenia is underpinned by aging, but other factors can lead to sarcopenia, such as chronic diseases, physical inactivity, inadequate dietary energy intake, and reduced protein intake (nutrition‐related sarcopenia), leading to an imbalance between muscle protein synthesis and muscle protein breakdown. Protein digestion and absorption are also modified with age, as well as the reduced capacity of metabolizing protein, hindering older adults from achieving ideal protein consumption (i.e., 1–1.5 g/kg/day). Nutritional supplement strategies, like animal (i.e., whey protein) and plant‐based protein, leucine, and creatine have been shown to play a significant role in improving outcomes related to sarcopenia. However, the impact of other supplements (e.g., branched‐chain amino acids, isolated amino acids, and omega‐3) on sarcopenia and related outcomes remain unclear. This narrative review will discuss the evidence of the impact of these nutritional strategies on sarcopenia outcomes in older adults.
Background/Objectives: Firefighters, tactical police officers, and warriors often engage in periodic, intermittent, high-intensity physical work in austere environmental conditions and have a heightened risk of premature mortality. In addition, tough decision-making challenges, routine sleep deprivation, and trauma exacerbate this risk. Therefore, identifying strategies to bolster these personnel’s health and occupational performance is critical. Creatine monohydrate (CrM) supplementation may offer several benefits to firefighters and tactical athletes (e.g., police, security, and soldiers) due to its efficacy regarding physical performance, muscle, cardiovascular health, mental health, and cognitive performance. Methods: We conducted a narrative review of the literature with a focus on the benefits and application of creatine monohydrate among firefighters. Results: Recent evidence demonstrates that CrM can improve anaerobic exercise capacity and muscular fitness performance outcomes and aid in thermoregulation, decision-making, sleep, recovery from traumatic brain injuries (TBIs), and mental health. Emerging evidence also suggests that CrM may confer an antioxidant/anti-inflammatory effect, which may be particularly important for firefighters and those performing tactical occupations exposed to oxidative and physiological stress, which can elicit systemic inflammation and increase the risk of chronic diseases. Conclusions: This narrative review highlights the potential applications of CrM for related tactical occupations, with a particular focus on firefighters, and calls for further research into these populations.
Background
Despite the robust evidence demonstrating positive effects from creatine supplementation (primarily when associated with resistance training) on measures of body composition, there is a lack of a comprehensive evaluation regarding the influence of creatine protocol parameters (including dose and form) on body mass and estimates of fat-free and fat mass.
Methods
Randomized controlled trials (RCTs) evaluating the effect of creatine supplementation on body composition were included. Electronic databases, including PubMed, Web of Science, and Scopus were searched up to July 2023. Heterogeneity tests were performed. Random effect models were assessed based on the heterogeneity tests, and pooled data were examined to determine the weighted mean difference (WMD) with a 95% confidence interval (CI).
Results
From 4831 initial records, a total of 143 studies met the inclusion criteria. Creatine supplementation increased body mass (WMD: 0.86 kg; 95% CI: 0.76 to 0.96, I² = 0%) and fat-free mass (WMD: 0.82 kg; 95% CI: 0.57 to 1.06, I² = 0%) while reducing body fat percentage (WMD: −0.28 %; 95% CI: −0.47 to −0.09; I² = 0%). Studies that incorporated a maintenance dose of creatine or performed resistance training in conjunction with supplementation had greater effects on body composition.
Conclusion
Creatine supplementation has a small effect on body mass and estimates of fat-free mass and body fat percentage. These findings were more robust when combined with resistance training.
As a result of advances in medical treatments and associated policy over the last century, life expectancy has risen substantially and continues to increase globally. However, the disconnect between lifespan and ‘health span’ (the length of time spent in a healthy, disease-free state) has also increased, with skeletal muscle being a substantial contributor to this. Biological ageing is accompanied by declines in both skeletal muscle mass and function, termed sarcopenia. The mechanisms underpinning sarcopenia are multifactorial and are known to include marked alterations in muscle protein turnover and adaptations to the neural input to muscle. However, to date, the relative contribution of each factor remains largely unexplored. Specifically, muscle protein synthetic responses to key anabolic stimuli are blunted with advancing age, whilst alterations to neural components, spanning from the motor cortex and motoneuron excitability to the neuromuscular junction, may explain the greater magnitude of function losses when compared with mass. The consequences of these losses can be devastating for individuals, their support networks, and healthcare services; with clear detrimental impacts on both clinical (e.g., mortality, frailty, and post-treatment complications) and societal (e.g., independence maintenance) outcomes. Whether declines in muscle quantity and quality are an inevitable component of ageing remains to be completely understood. Nevertheless, strategies to mitigate these declines are of vital importance to improve the health span of older adults. This review aims to provide an overview of the declines in skeletal muscle mass and function with advancing age, describes the wide-ranging implications of these declines, and finally suggests strategies to mitigate them, including the merits of emerging pharmaceutical agents.
Sarcopenia is a progressive and generalized loss of skeletal muscle and functions associated with ageing with currently no definitive treatment. Alterations in gut microbial composition have emerged as a significant contributor to the pathophysiology of multiple diseases. Recently, its association with muscle health has pointed to its potential role in mediating sarcopenia. The current review focuses on the association of gut microbiota and mediators of muscle health, connecting the dots between the influence of gut microbiota and their metabolites on biomarkers of sarcopenia. It further delineates the mechanism by which the gut microbiota affects muscle health with progressing age, aiding the formulation of a multi-modal treatment plan involving nutritional supplements and pharmacological interventions along with lifestyle changes compiled in the review. Nutritional supplements containing proteins, vitamin D, omega-3 fatty acids, creatine, curcumin, kefir, and ursolic acid positively impact the gut microbiome. Dietary fibres foster a conducive environment for the growth of beneficial microbes such as Bifidobacterium, Faecalibacterium, Ruminococcus, and Lactobacillus. Probiotics and prebiotics act by protecting against reactive oxygen species (ROS) and inflammatory cytokines. They also increase the production of gut microbiota metabolites like short-chain fatty acids (SCFAs), which aid in improving muscle health. Foods rich in polyphenols are anti-inflammatory and have an antioxidant effect, contributing to a healthier gut. Pharmacological interventions like faecal microbiota transplantation (FMT), non-steroidal anti-inflammatory drugs (NSAIDs), ghrelin mimetics, angiotensin-converting enzyme inhibitors (ACEIs), and butyrate precursors lead to the production of anti-inflammatory fatty acids and regulate appetite, gut motility, and microbial impact on gut health. Further research is warranted to deepen our understanding of the interaction between gut microbiota and muscle health for developing therapeutic strategies for ameliorating sarcopenic muscle loss.
Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disease that is associated with significant morbidity, mortality, and healthcare costs. The burden of respiratory symptoms and airflow limitation can translate to reduced physical activity, in turn contributing to poor exercise capacity, muscle dysfunction, and body composition abnormalities. These extrapulmonary features of the disease are targeted during pulmonary rehabilitation, which provides patients with tailored therapies to improve the physical and emotional status. Patients with COPD can be divided into metabolic phenotypes, including cachectic, sarcopenic, normal weight, obese, and sarcopenic with hidden obesity. To date, there have been many studies performed investigating the individual effects of exercise training programs as well as nutritional and pharmacological treatments to improve exercise capacity and body composition in patients with COPD. However, little research is available investigating the combined effect of exercise training with nutritional or pharmacological treatments on these outcomes. Therefore, this review focuses on exploring the potential additional beneficial effects of combinations of exercise training and nutritional or pharmacological treatments to target exercise capacity and body composition in patients with COPD with different metabolic phenotypes.
Background
The efficacy of creatine replacement through supplementation for the optimisation of physical function in the population at risk of functional disability is unclear.
Methods
We conducted a systematic literature search of MEDLINE, EMBASE, Cochrane Library and CINAHL until November 2022. Studies included were randomised controlled trials comparing the use of creatine supplementation with placebo in older adults and adults with chronic disease. The primary outcome was physical function measured by the sit-to-stand test after pooling data using random effects modelling. We also performed a Bayesian meta-analysis to describe the treatment effect in probability terms. Secondary outcomes included other measures of physical function, muscle function and body composition. The risk of bias was assessed using the Cochrane risk-of-bias tool.
Results
We identified 33 RCTs, comprising 1076 participants. From 6 trials reporting the primary outcome, the pooled standardised mean difference was 0.51 (95% CI 0.01 to 1.00; I2=62%; p=0.04); using weakly informative priors, the posterior probability that creatine supplementation improves physical function was 66.7%. Upper body muscle strength (SMD 0.25, 95% CI 0.06 to 0.44; I2=0%; p=0.01), handgrip strength (SMD 0.23, 95% CI 0.01 to 0.45; I2=0%; p=0.04) and lean tissue mass (MD 1.08kg; 95% CI 0.77 to 1.38; I2=26%; p<0.01) improved with creatine supplementation. The quality of evidence for all outcomes was low or very low due to a high risk of bias.
Conclusion
Creatine supplementation improves sit-to-stand performance, muscle function and lean tissue mass. It is crucial to conduct high-quality prospective RCTs to confirm these hypotheses (Prospero number, CRD42023354929).
Consuming adequate calories, protein, and micronutrients is vital for supporting muscle mass, muscle strength, and physical function as we age. Without sufficient nutrition, older people put themselves at an increased risk of developing sarcopenia. Therefore, in addition to weight-bearing exercise, nutritional supplementation may be important to ensure older individuals have good physical health. This review discusses the role of nutritional supplementation in maintaining muscle health in older people.
Purpose:
Our purpose was to examine the effects of 2 years of creatine monohydrate supplementation and exercise on bone health in postmenopausal women.
Methods:
237 postmenopausal women (mean age 59y) were randomized to receive creatine (0.14 g·kg -1·day -1) or placebo during a resistance training (3d/wk) and walking (6d/wk) program for 2 years. Our primary outcome was femoral neck bone mineral density (BMD), with lumbar spine BMD, and proximal femur geometric properties as secondary outcomes.
Results:
Compared to placebo, creatine supplementation had no effect on BMD of the femoral neck (creatine: 0.725 ± 0.110 to 0.712 ± 0.100; placebo: 0.721 ± 0.102 to 0.706 ± 0.097 g/cm2), total hip (creatine: 0.879 ± 0.118 to 0.872 ± 0.114; placebo: 0.881 ± 0.111 to 0.873 ± 0.109 g/cm2), or lumbar spine (creatine: 0.932 ± 0.133 to 0.925 ± 0.131; placebo: 0.923 ± 0.145 to 0.915 ± 0.143 g/cm2). Creatine significantly maintained section modulus (1.35 ± 0.29 to 1.34 ± 0.26 vs. placebo 1.34 ± 0.25 to 1.28 ± 0.23 cm3, p = 0.0011), predictive of bone bending strength, and buckling ratio (10.8 ± 2.6 to 11.1 ± 2.2 vs. placebo 11.0 ± 2.6 to 11.6 ± 2.7; p = 0.011), predictive of reduced cortical bending under compressive loads, at the narrow part of the femoral neck. Creatine reduced walking time over 80 meters (48.6 ± 5.6 to 47.1 ± 5.4 vs. placebo 48.3 ± 4.5 to 48.2 ± 4.9 s; p = 0.0008), but had no effect on muscular strength (i.e., 1RM) during the bench press (32.1 ± 12.7 to 42.6 ± 14.1 vs. placebo 30.6 ± 10.9 to 41.4 ± 14 kg) and hack squat (57.6 ± 21.6 to 84.4 ± 28.1 vs. placebo 56.6 ± 24.0 to 82.7 ± 25.0 kg). In sub-analysis of valid completers, creatine increased lean tissue mass compared to placebo (40.8 ± 5.7 to 43.1 ± 5.9 vs. placebo 40.4 ± 5.3 to 42.0 ± 5.2 kg; p = 0.046).
Conclusions:
Two years of creatine supplementation and exercise in postmenopausal women had no effect on bone mineral density, yet improved some bone geometric properties at the proximal femur.
Introdução: O envelhecimento é um processo comumente associado aos últimos anos de vida, no entanto é uma condição inerente a todos, até mesmo os mais jovens estão em processo de envelhecimento, processo este que causa alterações negativas na composição corporal ao passar dos anos, chamamos essa alteração de sarcopenia, assim é necessário intervenções físicas e farmacológicas que auxiliarão na promoção de qualidade de vida. Objetivos: Mensurar a capacidade de promoção de ganho de força e hipertrofia de tecido muscular em indivíduos idosos sarcopênicos através da abordagem do exercício resistido (ER) e uso de suplementos nutricionais e fármacos como coadjuvantes a proposta de treinamento. Metodologia: O presente estudo trata-se de uma revisão de literatura sendo incluída a pesquisa de artigos e livros para complementação das informações. Resultados: Observou-se aumento significativo da força e da massa muscular esquelética nessa pesquisa mediante protocolos de ER e utilização coadjuvante de esteroides anabólicos e/ou suplementos nutricionais. Conclusão: Esta revisão sugere que com a abordagem de estratégias geradoras de stress mecânico e químico através do ER é possível inibir a ação da sarcopenia, sendo observado que a ministração de suplementos alimentares e esteroides anabolizantes potencializaram as adaptações hipertróficas, bem como promoveram significativa melhora na qualidade de vida e Atividades de Vida Diária.
The aim of this narrative review is to discuss the evidence on exercise for fall, fracture and sarcopenia prevention, including evidence that aligns with the specificity and progressive overload principles used in exercise physiology, implementation strategies and future research priorities. We also provide a brief discussion of the influence of protein intake and creatine supplementation as potential effect modifiers. We prioritized evidence from randomized controlled trials and systematic reviews. Resistance training can improve muscle mass, muscle strength and a variety of physical performance measures in older adults. Resistance training may also prevent bone loss or increase bone mass, although whether it needs to be done in combination with impact exercise to be effective is less clear, because many studies use combination interventions. Exercise programs prevent falls, and subgroup and network meta-analyses suggest an emphasis on balance and functional training, or specifically, anticipatory control, dynamic stability, functional stability limits, reactive control and flexibility, to maximize efficacy. Resistance training for major muscle groups at a 6–12 repetitions maximum intensity, and challenging balance exercises should be performed at least twice weekly. Choose resistance training exercises aligned with patient goals or movements done during daily activities (task specificity), alongside balance exercises tailored to ability and aspects of balance that need improvement. Progress the volume, level of difficulty or other aspects to see continuous improvement (progressive overload). A critical future priority will be to address implementation barriers and facilitators to enhance uptake and adherence.
Context
Conjugated linoleic acid (CLA) has been reported to have anti-obesity and antidiabetic effects. However, the benefits of CLA combined with exercise remain unclear, and studies report conflicting results.
Objective
A systematic review and meta-analysis were performed to investigate the synergistic effect of CLA and exercise on body composition, exercise-related indices, insulin resistance, and lipid profiles; and of the safety of CLA supplements.
Data sources
In October 2021, the PubMed, Embase, and Cochrane Library databases were searched for reports on clinical trials of the combined intervention of CLA and exercise.
Data extraction
A total of 18 randomized controlled trials and 2 crossover trials were included. The methodological quality assessment was performed using the revised Cochrane risk-of-bias tool. Pooled effect sizes were reported as standardized mean difference (SMD) for continuous data and risk ratio for dichotomous data with their corresponding 95% confidence intervals (CIs). Heterogeneity was tested using the I2 statistic.
Data analysis
The combination of CLA and exercise resulted in significantly decreased body fat (SMD, –0.42 [95%CI, –0.70, –0.14]; P = 0.003; I2 = 65) and insulin resistance (SMD, –0.25 [95%CI, –0.44, –0.06]; P = 0.01; I2 = 0) than did exercise alone. In subgroup analysis, the following factors were associated with significant outcomes: (1) body mass index ≥25 kg/m2; (2) female sex; (3) follow-up time >4 weeks; and (4) intervention duration >4 weeks. Nevertheless, supplementation with CLA during exercise programs was not effective for body-weight control, exercise performance enhancement, or lipid-profile improvement. CLA in combination with exercise did not result in a higher risk of adverse events (risk ratio, 1.32 [95%CI, 0.94–1.84]; P > 0.05; I2 = 0).
Conclusion
CLA combined with exercise is generally safe and can lower body fat and insulin resistance but does not reduce body weight, enhance exercise performance, or improve lipid profiles.
Age-related loss of muscle mass, strength, and performance, commonly referred to as sarcopenia, has wide-ranging detrimental effects on human health, the ramifications of which can have serious implications for both morbidity and mortality. Various interventional strategies have been proposed to counteract sarcopenia, with a particular emphasis on those employing a combination of exercise and nutrition. However, the efficacy of these interventions can be confounded by an age-related blunting of the muscle protein synthesis response to a given dose of protein/amino acids, which has been termed “anabolic resistance.” While the pathophysiology of sarcopenia is undoubtedly complex, anabolic resistance is implicated in the progression of age-related muscle loss and its underlying complications. Several mechanisms have been proposed as underlying age-related impairments in the anabolic response to protein consumption. These include decreased anabolic molecular signaling activity, reduced insulin-mediated capillary recruitment (thus, reduced amino acid delivery), and increased splanchnic retention of amino acids (thus, reduced availability for muscular uptake). Obesity and sedentarism can exacerbate, or at least facilitate, anabolic resistance, mediated in part by insulin resistance and systemic inflammation. This narrative review addresses the key factors and contextual elements involved in reduction of the acute muscle protein synthesis response associated with aging and its varied consequences. Practical interventions focused on dietary protein manipulation are proposed to prevent the onset of anabolic resistance and mitigate its progression.
This study examined the effects of long-term creatine supplementation combined with resistance training (RT) on the one-repetition maximum (1RM) strength, motor functional performance (e.g., 30-s chair stand, arm curl, and getting up from lying on the floor tests) and body composition (e.g., fat-free mass, muscle mass, and % body fat using DEXA scans) in older women. Eighteen healthy women (64.9 ± 5.0 yr) were randomly assigned in a double-blind fashion to either a creatine (CR, N = 9) or placebo (PL, N = 9) group. Both groups underwent a 12-wk RT program (3 d∙wk-1), consuming an equivalent amount of either creatine (5.0 g∙d-1) or placebo (maltodextrin). After 12 wk, the CR group experienced a greater (P < 0.05) increase (Δ%) in training volume (+ 164,2), and 1RM bench press (+ 5.1), knee extension (+ 3.9) and biceps curl (+ 8.8) performance than the PL group. Furthermore, CR group gained significantly more fat-free mass (+ 3.2) and muscle mass (+ 2.8) and were more efficient in performing submaximal-strength functional tests than the PL group. No changes (P > 0.05) in body mass or % body fat were observed from pre- to post-test in either group. These results indicate that long-term creatine supplementation combined with RT improves the ability to perform submaximal-strength functional tasks and promotes a greater increase in maximal strength, fat-free mass and muscle mass in older women.
This study compares the effects of 6 months resistance-type exercise training (three times per week) between healthy elderly women (n = 24; 71±1 years) and men (n = 29; 70±1 years). Muscle mass (dual-energy x-ray absorptiometry-computed tomography), strength (one-repetition maximum), functional capacity (sit-to-stand time), muscle fiber characteristics (muscle biopsies), and metabolic profile (blood samples) were assessed. Leg lean mass (3% ± 1%) and quadriceps cross-sectional area (9% ± 1%) increased similarly in both groups. One-repetition maximum leg extension strength increased by 42% ± 3% (women) and 43% ± 3% (men). Following training, type II muscle fiber size had increased, and a type II muscle fiber specific increase in myonuclear and satellite cell content was observed with no differences between genders. Sit-to-stand time decreased similarly in both groups. Glycemic control and blood lipid profiles improved to a similar extent in both women and men. A generic resistance-type exercise training program can be applied for both women and men to effectively counteract the loss of muscle mass and strength with aging. © 2012 © The Author 2012. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: [email protected]
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Funnel plots, and tests for funnel plot asymmetry, have been widely used to examine bias in the results of meta-analyses. Funnel plot asymmetry should not be equated with publication bias, because it has a number of other possible causes. This article describes how to interpret funnel plot asymmetry, recommends appropriate tests, and explains the implications for choice of meta-analysis modelThe 1997 paper describing the test for funnel plot asymmetry proposed by Egger et al 1 is one of the most cited articles in the history of BMJ.1 Despite the recommendations contained in this and subsequent papers,2 3 funnel plot asymmetry is often, wrongly, equated with publication or other reporting biases. The use and appropriate interpretation of funnel plots and tests for funnel plot asymmetry have been controversial because of questions about statistical validity,4 disputes over appropriate interpretation,3 5 6 and low power of the tests.2This article recommends how to examine and interpret funnel plot asymmetry (also known as small study effects2) in meta-analyses of randomised controlled trials. The recommendations are based on a detailed MEDLINE review of literature published up to 2007 and discussions among methodologists, who extended and adapted guidance previously summarised in the Cochrane Handbook for Systematic Reviews of Interventions.7What is a funnel plot?A funnel plot is a scatter plot of the effect estimates from individual studies against some measure of each study’s size or precision. The standard error of the effect estimate is often chosen as the measure of study size and plotted on the vertical axis8 with a reversed scale that places the larger, most powerful studies towards the top. The effect estimates from smaller studies should scatter more widely at the bottom, with the spread narrowing among larger studies.9 In the absence of bias and between study heterogeneity, the scatter will be due to sampling variation alone and the plot will resemble a symmetrical inverted funnel (fig 1⇓). A triangle centred on a fixed effect summary estimate and extending 1.96 standard errors either side will include about 95% of studies if no bias is present and the fixed effect assumption (that the true treatment effect is the same in each study) is valid. The appendix on bmj.com discusses choice of axis in funnel plots.View larger version:In a new windowDownload as PowerPoint SlideFig 1 Example of symmetrical funnel plot. The outer dashed lines indicate the triangular region within which 95% of studies are expected to lie in the absence of both biases and heterogeneity (fixed effect summary log odds ratio±1.96×standard error of summary log odds ratio). The solid vertical line corresponds to no intervention effectImplications of heterogeneity, reporting bias, and chance Heterogeneity, reporting bias, and chance may all lead to asymmetry or other shapes in funnel plots (box). Funnel plot asymmetry may also be an artefact of the choice of statistics being plotted (see appendix). The presence of any shape in a funnel plot is contingent on the studies having a range of standard errors, since otherwise they would lie on a horizontal line.Box 1: Possible sources of asymmetry in funnel plots (adapted from Egger et al1)Reporting biasesPublication bias: Delayed publication (also known as time lag or pipeline) bias Location biases (eg, language bias, citation bias, multiple publication bias)Selective outcome reportingSelective analysis reportingPoor methodological quality leading to spuriously inflated effects in smaller studiesPoor methodological designInadequate analysisFraudTrue heterogeneitySize of effect differs according to study size (eg, because of differences in the intensity of interventions or in underlying risk between studies of different sizes)ArtefactualIn some circumstances, sampling variation can lead to an association between the intervention effect and its standard errorChanceAsymmetry may occur by chance, which motivates the use of asymmetry testsHeterogeneityStatistical heterogeneity refers to differences between study results beyond those attributable to chance. It may arise because of clinical differences between studies (for example, setting, types of participants, or implementation of the intervention) or methodological differences (such as extent of control over bias). A random effects model is often used to incorporate heterogeneity in meta-analyses. If the heterogeneity fits with the assumptions of this model, a funnel plot will be symmetrical but with additional horizontal scatter. If heterogeneity is large it may overwhelm the sampling error, so that the plot appears cylindrical.Heterogeneity will lead to funnel plot asymmetry if it induces a correlation between study sizes and intervention effects.5 For example, substantial benefit may be seen only in high risk patients, and these may be preferentially included in early, small studies.10 Or the intervention may have been implemented less thoroughly in larger studies, resulting in smaller effect estimates compared with smaller studies.11Figure 2⇓ shows funnel plot asymmetry arising from heterogeneity that is due entirely to there being three distinct subgroups of studies, each with a different intervention effect.12 The separate funnels for each subgroup are symmetrical. Unfortunately, in practice, important sources of heterogeneity are often unknown.View larger version:In a new windowDownload as PowerPoint SlideFig 2 Illustration of funnel plot asymmetry due to heterogeneity, in the form of three distinct subgroups of studies. Funnel plot including all studies (top left) shows clear asymmetry (P<0.001 from Egger test for funnel plot asymmetry). P values for each subgroup are all >0.49.Differences in methodological quality may also cause heterogeneity and lead to funnel plot asymmetry. Smaller studies tend to be conducted and analysed with less methodological rigour than larger studies,13 and trials of lower quality also tend to show larger intervention effects.14 15Reporting biasReporting biases arise when the dissemination of research findings is influenced by the nature and direction of results. Statistically significant “positive” results are more likely to be published, published rapidly, published in English, published more than once, published in high impact journals, and cited by others.16 17 18 19 Data that would lead to negative results may be filtered, manipulated, or presented in such a way that they become positive.14 20 Reporting biases can have three types of consequence for a meta-analysis:A systematic review may fail to locate an eligible study because all information about it is suppressed or hard to find (publication bias) A located study may not provide usable data for the outcome of interest because the study authors did not consider the result sufficiently interesting (selective outcome reporting) A located study may provide biased results for some outcome—for example, by presenting the result with the smallest P value or largest effect estimate after trying several analysis methods (selective analysis reporting).These biases may cause funnel plot asymmetry if statistically significant results suggesting a beneficial effect are more likely to be published than non-significant results. Such asymmetry may be exaggerated if there is a further tendency for smaller studies to be more prone to selective suppression of results than larger studies. This is often assumed to be the case for randomised trials. For instance, it is probably more difficult to make a large study disappear without trace, while a small study can easily be lost in a file drawer.21 The same may apply to specific outcomes—for example, it is difficult not to report on mortality or myocardial infarction if these are outcomes of a large study. Smaller studies have more sampling error in their effect estimates. Thus even though the risk of a false positive significant finding is the same, multiple analyses are more likely to yield a large effect estimate that may seem worth publishing. However, biases may not act this way in real life; funnel plots could be symmetrical even in the presence of publication bias or selective outcome reporting19 22—for example, if the published findings point to effects in different directions but unreported results indicate neither direction. Alternatively, bias may have affected few studies and therefore not cause glaring asymmetry.ChanceThe role of chance is critical for interpretation of funnel plots because most meta-analyses of randomised trials in healthcare contain few studies.2 Investigations of relations across studies in a meta-analysis are seriously prone to false positive findings when there is a small number of studies and heterogeneity across studies,23 and this may affect funnel plot symmetry.Interpreting funnel plot asymmetryAuthors of systematic reviews should distinguish between possible reasons for funnel plot asymmetry (box 1). Knowledge of the intervention, and the circumstances in which it was implemented in different studies, can help identify causes of asymmetry in funnel plots, which should also be interpreted in the context of susceptibility to biases of research in the field of interest. Potential conflicts of interest, whether outcomes and analyses have been standardised, and extent of trial registration may need to be considered. For example, studies of antidepressants generate substantial conflicts of interest because the drugs generate vast sales revenues. Furthermore, there are hundreds of outcome scales, analyses can be very flexible, and trial registration was uncommon until recently.24 Conversely, in a prospective meta-analysis where all data are included and all analyses fully standardised and conducted according to a predetermined protocol, publication or reporting biases cannot exist. Reporting bias is therefore more likely to be a cause of an asymmetric plot in the first situation than in the second.Terrin et al found that researchers were poor at identifying publication bias from funnel plots.5 Including contour lines corresponding to perceived milestones of statistical significance (P=0.01, 0.05, 0.1, etc) may aid visual interpretation.25 If studies seem to be missing in areas of non-significance (fig 3⇓, top) then asymmetry may be due to reporting bias, although other explanations should still be considered. If the supposed missing studies are in areas of higher significance or in a direction likely to be considered desirable to their authors (fig 3⇓, bottom), asymmetry is probably due to factors other than reporting bias. View larger version:In a new windowDownload as PowerPoint SlideFig 3 Contour enhanced funnel plots. In the top diagram there is a suggestion of missing studies in the middle and right of the plot, broadly in the white area of non-significance, making publication bias plausible. In the bottom diagram there is a suggestion of missing studies on the bottom left hand side of the plot. Since most of this area contains regions of high significance, publication bias is unlikely to be the underlying cause of asymmetryStatistical tests for funnel plot asymmetryA test for funnel plot asymmetry (sometimes referred to as a test for small study effects) examines whether the association between estimated intervention effects and a measure of study size is greater than might be expected to occur by chance. These tests typically have low power, so even when a test does not provide evidence of asymmetry, bias cannot be excluded. For outcomes measured on a continuous scale a test based on a weighted linear regression of the effect estimates on their standard errors is straightforward.1 When outcomes are dichotomous and intervention effects are expressed as odds ratios, this corresponds to an inverse variance weighted linear regression of the log odds ratio on its standard error.2 Unfortunately, there are statistical problems because the standard error of the log odds ratio is mathematically linked to the size of the odds ratio, even in the absence of small study effects.2 4 Many authors have therefore proposed alternative tests (see appendix on bmj.com).4 26 27 28Because it is impossible to know the precise mechanism(s) leading to funnel plot asymmetry, simulation studies (in which tests are evaluated on large numbers of computer generated datasets) are required to evaluate test characteristics. Most have examined a range of assumptions about the extent of reporting bias by selectively removing studies from simulated datasets.26 27 28 After reviewing the results of these studies, and based on theoretical considerations, we formulated recommendations on testing for funnel plot asymmetry (box 2). The appendix describes the proposed tests, explains the reasons that some were not recommended, and discusses funnel plots for intervention effects measured as risk ratios, risk differences, and standardised mean differences. Our recommendations imply that tests for funnel plot asymmetry should be used in only a minority of meta-analyses.29Box 2: Recommendations on testing for funnel plot asymmetryAll types of outcomeAs a rule of thumb, tests for funnel plot asymmetry should not be used when there are fewer than 10 studies in the meta-analysis because test power is usually too low to distinguish chance from real asymmetry. (The lower the power of a test, the higher the proportion of “statistically significant” results in which there is in reality no association between study size and intervention effects). In some situations—for example, when there is substantial heterogeneity—the minimum number of studies may be substantially more than 10Test results should be interpreted in the context of visual inspection of funnel plots— for example, are there studies with markedly different intervention effect estimates or studies that are highly influential in the asymmetry test? Even if an asymmetry test is statistically significant, publication bias can probably be excluded if small studies tend to lead to lower estimates of benefit than larger studies or if there are no studies with significant resultsWhen there is evidence of funnel plot asymmetry, publication bias is only one possible explanation (see box 1)As far as possible, testing strategy should be specified in advance: choice of test may depend on the degree of heterogeneity observed. Applying and reporting many tests is discouraged: if more than one test is used, all test results should be reported Tests for funnel plot asymmetry should not be used if the standard errors of the intervention effect estimates are all similar (the studies are of similar sizes)Continuous outcomes with intervention effects measured as mean differencesThe test proposed by Egger et al may be used to test for funnel plot asymmetry.1 There is no reason to prefer more recently proposed tests, although their relative advantages and disadvantages have not been formally examined. General considerations suggest that the power will be greater than for dichotomous outcomes but that use of the test with substantially fewer than 10 studies would be unwiseDichotomous outcomes with intervention effects measured as odds ratiosThe tests proposed by Harbord et al26 and Peters et al27 avoid the mathematical association between the log odds ratio and its standard error when there is a substantial intervention effect while retaining power compared with alternative tests. However, false positive results may still occur if there is substantial between study heterogeneityIf there is substantial between study heterogeneity (the estimated heterogeneity variance of log odds ratios, τ2, is >0.1) only the arcsine test including random effects, proposed by Rücker et al, has been shown to work reasonably well.28 However, it is slightly conservative in the absence of heterogeneity and its interpretation is less familiar than for other tests because it is based on an arcsine transformation.When τ2 is <0.1, one of the tests proposed by Harbord et al,26 Peters et al,27 or Rücker et al28 can be used. Test performance generally deteriorates as τ2 increases.Funnel plots and meta-analysis modelsFixed and random effects modelsFunnel plots can help guide choice of meta-analysis method. Random effects meta-analyses weight studies relatively more equally than fixed effect analyses by incorporating the between study variance into the denominator of each weight. If effect estimates are related to standard errors (funnel plot asymmetry), the random effects estimate will be pulled more towards findings from smaller studies than the fixed effect estimate will be. Random effects models can thus have undesirable consequences and are not always conservative.30The trials of intravenous magnesium after myocardial infarction provide an extreme example of the differences between fixed and random effects analyses that can arise in the presence of funnel plot asymmetry.31 Beneficial effects on mortality, found in a meta-analysis of small studies,32 were subsequently contradicted when the very large ISIS-4 study found no evidence of benefit.33 A contour enhanced funnel plot (fig 4⇓) gives a clear visual impression of asymmetry, which is confirmed by small P values from the Harbord and Peters tests (P<0.001 and P=0.002 respectively).View larger version:In a new windowDownload as PowerPoint SlideFig 4 Contour enhanced funnel plot for trials of the effect of intravenous magnesium on mortality after myocardial infarctionFigure 5⇓ shows that in a fixed effect analysis ISIS-4 receives 90% of the weight, and there is no evidence of a beneficial effect. However, there is clear evidence of between study heterogeneity (P<0.001, I2=68%), and in a random effects analysis the small studies dominate so that intervention appears beneficial. To interpret the accumulated evidence, it is necessary to make a judgment about the validity or relevance of the combined evidence from the smaller studies compared with that from ISIS-4. The contour enhanced funnel plot suggests that publication bias does not completely explain the asymmetry, since many of the beneficial effects reported from smaller studies were not significant. Plausible explanations for these results are that methodological flaws in the smaller studies, or changes in the standard of care (widespread adoption of treatments such as aspirin, heparin, and thrombolysis), led to apparent beneficial effects of magnesium. This belief was reinforced by the subsequent publication of the MAGIC trial, in which magnesium added to these treatments which also found no evidence of benefit on mortality (odds ratio 1.0, 95% confidence interval 0.8 to 1.1).34View larger version:In a new windowDownload as PowerPoint SlideFig 5 Comparison of fixed and random effects meta-analytical estimates of the effect of intravenous magnesium on mortality after myocardial infarctionWe recommend that when review authors are concerned about funnel plot asymmetry in a meta-analysis with evidence of between study heterogeneity, they should compare the fixed and random effects estimates of the intervention effect. If the random effects estimate is more beneficial, authors should consider whether it is plausible that the intervention is more effective in smaller studies. Formal investigations of heterogeneity of effects may reveal explanations for funnel plot asymmetry, in which case presentation of results should focus on these. If larger studies tend to be methodologically superior to smaller studies, or were conducted in circumstances more typical of the use of the intervention in practice, it may be appropriate to include only larger studies in the meta-analysis.Extrapolation of a funnel plot regression lineAn assumed relation between susceptibility to bias and study size can be exploited by extrapolating within a funnel plot. When funnel plot asymmetry is due to bias rather than substantive heterogeneity, it is usually assumed that results from larger studies are more believable than those from smaller studies because they are less susceptible to methodological flaws or reporting biases. Extrapolating a regression line on a funnel plot to minimum bias (maximum sample size) produces a meta-analytical estimate that can be regarded as corrected for such biases.35 36 37 However, because it is difficult to distinguish between asymmetry due to bias and asymmetry due to heterogeneity or chance, the broad applicability of such approaches is uncertain. Further approaches to adjusting for publication bias are described and discussed in the appendix.DiscussionReporting biases are one of a number of possible explanations for the associations between study size and effect size that are displayed in asymmetric funnel plots. Examining and testing for funnel plot asymmetry, when appropriate, is an important means of addressing bias in meta-analyses, but the multiple causes of asymmetry and limited power of asymmetry tests mean that other ways to address reporting biases are also of importance. Searches of online trial registries can identify unpublished trials, although they do not currently guarantee access to trial protocols and results. When there are no registered but unpublished trials, and the outcome of interest is reported by all trials, restricting meta-analyses to registered trials should preclude publication bias. Recent comparisons of results of published trials with those submitted for regulatory approval have also provided clear evidence of reporting bias.38 39 Methods for dealing with selective reporting of outcomes have been described elsewhere. 40Our recommendations apply to meta-analyses of randomised trials, and their applicability in other contexts such as meta-analyses of epidemiological or diagnostic test studies is unclear.41 The performance of tests for funnel plot asymmetry in these contexts is likely to differ from that in meta-analyses of randomised trials. Further factors, such as confounding and precision of measurements, may cause a relation between study size and effect estimates in observational studies. For example, large studies based on routinely collected data might not fully control confounding compared with smaller, purpose designed studies that collected a wide range of potential confounding variables. Alternatively, larger studies might use self reported exposure levels, which are more error prone, while smaller studies used precise measuring instruments. However, simulation studies have usually not considered such situations. An exception is for diagnostic studies, where large imbalances in group sizes and substantial odds ratios lead to poor performance of some tests: that proposed by Deeks et al was designed for use in this context.4Summary points Inferences on the presence of bias or heterogeneity should consider different causes of funnel plot asymmetry and should not be based on visual inspection of funnel plots aloneThey should be informed by contextual factors, including the plausibility of publication bias as an explanation for the asymmetryTesting for funnel plot asymmetry should follow the recommendations detailed in this articleThe fixed and random effects estimates of the intervention effect should be compared when funnel plot asymmetry exists in a meta-analysis with between study heterogeneityNotesCite this as: BMJ 2011;342:d4002FootnotesContributors: All authors contributed to the drafting and editing of the manuscript. DA, JC, JD, RMH, JPTH, JPAI, DRJ, DM, JP, GR, JACS, AJS and JT contributed to the chapter in the Cochrane Handbook for Systematic Reviews of Interventions on which our recommendations on testing for funnel plot asymmetry are based. JACS will act as guarantor.Funding: Funded in part by the Cochrane Collaboration Bias Methods Group, which receives infrastructure funding as part of a commitment by the Canadian Institutes of Health Research (CIHR) and the Canadian Agency for Drugs and Technologies in Health (CADTH) to fund Canadian based Cochrane entities. This supports dissemination activities, web hosting, travel, training, workshops and a full time coordinator position. JPTH was funded by MRC Grant U.1052.00.011. DGA is supported by Cancer Research UK. GR was supported by a grant from Deutsche Forschungsgemeinschaft (FOR 534 Schw 821/2-2).Competing interests. JC, JJD, SD, RMH, JPAI, DRJ, PM, JP, GR, GS, JACS and AJS are all authors on papers proposing tests for funnel plot asymmetry, but have no commercial interests in the use of these tests. All authors have completed the ICJME unified disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that they have no financial or non-financial interests that may be relevant to the submitted work.Provenance and peer review: Not commissioned; externally peer reviewed.References↵Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ1997;315:629-34.OpenUrlFREE Full Text↵Sterne JAC, Gavaghan D, Egger M. Publication and related bias in meta-analysis: power of statistical tests and prevalence in the literature. J Clin Epidemiol2000;53:1119-29.OpenUrlCrossRefMedlineWeb of Science↵Lau J, Ioannidis JP, Terrin N, Schmid CH, Olkin I. The case of the misleading funnel plot. 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Objective: To investigate the effect of oral creatine supplementation in conjunction with an exercise programme on physical fitness in patients with coronary artery disease or chronic heart failure.
Design: Single centre double-blind randomized placebo controlled trial.
Setting: Cardiac rehabilitation centre.
Subjects and intervention: 70 (4 women) cardiac patients (age 57.5 (8.4) years) were randomized to a placebo (n = 37) or creatine (n = 33) treatment for three months. Combined aerobic endurance and resistance training (three sessions/ week) was performed during supplementation.
Main Measures: Aerobic power was determined during graded bicycle testing, knee extensor peak isometric and isokinetic strength, endurance and recovery were assessed by an isokinetic dynamometer, and health related quality of life was evaluated with the SF-36 and MacNew Heart Disease questionnaires. In addition, blood samples were taken after an overnight fast and 24 hour urinary collection was performed.
Results: At baseline there were no significant differences between both groups. We observed main time effects for aerobic power, muscle performance, health related quality of life, high density lipoprotein cholesterol and triglycerides (pre vs post; P<0.05 for all). However, changes after training were similar between placebo group and creatine group (P>0.05). Further, no detrimental effect on renal or liver function was observed nor were there any reports of side effects.
Conclusion: Oral creatine supplementation in combination with exercise training does not exert any additional effect on the improvement in physical performance, health related quality of life, lipid profile in patients with coronary artery disease or chronic heart failure than exercise training alone.
We aimed to determine whether women consuming fat-free milk versus isoenergetic carbohydrate after resistance exercise would see augmented gains in lean mass and reductions in fat mass similar to what we observed in young men.
Young women were randomized to drink either fat-free milk (MILK: n = 10; age (mean +/- SD) = 23.2 +/- 2.8 yr; BMI = 26.2 +/- 4.2 kg x m(-2)) or isoenergetic carbohydrate (CON: n = 10; age = 22.4 +/- 2.4 yr; BMI = 25.2 +/- 3.8 kg x m(-2)) immediately after and 1 h after exercise (2 x 500 mL). Subjects exercised 5 d x wk(-1) for 12 wk. Body composition changes were measured by dual-energy x-ray absorptiometry, and subjects' strength and fasting blood were measured before and after training.
CON gained weight after training (CON: +0.86 +/- 0.4 kg, P < 0.05; MILK: +0.50 +/- 0.4 kg, P = 0.29). Lean mass increased with training in both groups (P < 0.01), with a greater net gain in MILK versus CON (1.9 +/- 0.2 vs 1.1 +/- 0.2 kg, respectively, P < 0.01). Fat mass decreased with training in MILK only (-1.6 +/- 0.4 kg, P < 0.01; CON: -0.3 +/- 0.3 kg, P = 0.41). Isotonic strength increased more in MILK than CON (P < 0.05) for some exercises. Serum 25-hydroxyvitamin D increased in both groups but to a greater extent in MILK than CON (+6.5 +/- 1.1 vs +2.8 +/- 1.3 nM, respectively, P < 0.05), and parathyroid hormone decreased only in MILK (-1.2 +/- 0.2 pM, P < 0.01).
Heavy, whole-body resistance exercise with the consumption of milk versus carbohydrate in the early postexercise period resulted in greater muscle mass accretion, strength gains, fat mass loss, and a possible reduction in bone turnover in women after 12 wk. Our results, similar to those in men, highlight that milk is an effective drink to support favorable body composition changes in women with resistance training.
The purpose of this study was to determine whether growth hormone (GH) administration enhances the muscle anabolism associated with heavy-resistance exercise. Sixteen men (21-34 yr) were assigned randomly to a resistance training plus GH group (n = 7) or to a resistance training plus placebo group (n = 9). For 12 wk, both groups trained all major muscle groups in an identical fashion while receiving 40 micrograms recombinant human GH.kg-1.day-1 or placebo. Fat-free mass (FFM) and total body water increased (P less than 0.05) in both groups but more (P less than 0.01) in the GH recipients. Whole body protein synthesis rate increased more (P less than 0.03), and whole body protein balance was greater (P = 0.01) in the GH-treated group, but quadriceps muscle protein synthesis rate, torso and limb circumferences, and muscle strength did not increase more in the GH-treated group. In the young men studied, resistance exercise with or without GH resulted in similar increments in muscle size, strength, and muscle protein synthesis, indicating that 1) the larger increase in FFM with GH treatment was probably due to an increase in lean tissue other than skeletal muscle and 2) resistance training supplemented with GH did not further enhance muscle anabolism and function.
The purpose of this study was to determine whether growth hormone (GH) administration enhances the muscle protein anabolism associated with heavy-resistance exercise training in older men. Twenty-three healthy, sedentary men (67 +/- 1 yr) with low serum insulin-like growth factor I levels followed a 16-wk progressive resistance exercise program (75-90% max strength, 4 days/wk) after random assignment to either a GH (12.5-24 micrograms.kg-1.day-1; n = 8) or placebo (n = 15) group. Fat-free mass (FFM) and total body water increased more in the GH group. Whole body protein synthesis and breakdown rates increased in the GH group after treatment. However, increments in vastus lateralis muscle protein synthesis rate, urinary creatinine excretion, and training-specific isotonic and isokinetic muscle strength were similar in both groups, while 24-h urinary 3-methylhistidine excretion was unchanged after treatment. These observations suggest that resistance exercise training improved muscle strength and anabolism in older men, but these improvements were not enhanced when exercise was combined with daily GH administration. The greater increase in FFM with GH treatment may have been due to an increase in noncontractile protein and fluid retention.
Body composition and the components of energy metabolism were examined in 12 men and women, aged 56-80 y, before and after 12 wk of resistance training. Subjects were randomly assigned to groups that consumed diets that providing either 0.8 or 1.6 g protein.kg-1.d-1 and adequate total energy to maintain baseline body weight. Fat mass decreased 1.8 +/- 0.4 kg (P < 0.001) and fat-free mass (FFM) increased 1.4 +/- 0.4 kg (P < 0.01) in these weight-stable subjects. The increase in FFM was associated with a 1.6 +/- 0.4 kg increase in total body water (P < 0.01) but no significant change in either protein plus mineral mass or body cell mass. With resistance training, the mean energy intake required for body weight maintenance increased by approximately 15%. Increased energy expenditure included increased resting metabolic rate (P < 0.02) and the energy cost of resistance exercise. Dietary protein intake did not influence these results. Resistance training is an effective way to increase energy requirements, decrease body-fat mass, and maintain metabolically active tissue mass in healthy older people and may be useful as an adjunct to weight-control programs for older adults.
It has been suggested that the quality of clinical trials should be assessed by blinded raters to limit the risk of introducing bias into meta-analyses and systematic reviews, and into the peer-review process. There is very little evidence in the literature to substantiate this. This study describes the development of an instrument to assess the quality of reports of randomized clinical trials (RCTs) in pain research and its use to determine the effect of rater blinding on the assessments of quality. A multidisciplinary panel of six judges produced an initial version of the instrument. Fourteen raters from three different backgrounds assessed the quality of 36 research reports in pain research, selected from three different samples. Seven were allocated randomly to perform the assessments under blind conditions. The final version of the instrument included three items. These items were scored consistently by all the raters regardless of background and could discriminate between reports from the different samples. Blind assessments produced significantly lower and more consistent scores than open assessments. The implications of this finding for systematic reviews, meta-analytic research and the peer-review process are discussed.
To investigate the effects of an oral creatine supplementation in older adults, 32 elderly subjects (67-80 years; 16 females, 16 males) were randomly assigned to four equivalent subgroups (control-creatine; control-placebo; trained-creatine; trained-placebo) based on whether or not they took part in an 8-week strength training programme and an 8-week oral creatine monohydrate creatine supplementation programme. The strength training programme consisted of three sets of eight repetitions at 80% of one-repetition maximum, for leg press, leg extension and chest press, 3 days a week. The 52-day supplementation programme consisted of 20 g of creatine monohydrate (or glucose) and 8 g of glucose per day for the initial 5 days followed by 3 g of creatine monohydrate (or glucose), and 2 g of glucose per day. Prior to and after the training and supplementation periods, body mass, body fat, lower limb muscular volume, 1-, 12-repetitions maxima and isometric intermittent endurance tests for leg press, leg extension and chest press were determined. In all groups, no significant changes in anthropometric parameters were observed. For all movements, the increases in 1- and 12-repetitions maxima were greater (P < 0.02) in trained than control subjects. No significant interactions (supplementation/training/time) were observed for the 1-, 12-repetitions maxima, and the isometric intermittent endurance, whatever the movement considered. We conclude that oral creatine supplementation does not provide additional benefits for body composition, maximal dynamical strength, and dynamical and isometric endurances of healthy elderly subjects, whether or not it is associated with an effective strength training.
Creatine monohydrate (CrM) supplementation during resistance exercise training results in a greater increase in strength and fat-free mass than placebo. Whether this is solely due to an increase in intracellular water or whether there may be alterations in protein turnover is not clear at this point. We examined the effects of CrM supplementation on indexes of protein metabolism in young healthy men (n = 13) and women (n = 14). Subjects were randomly allocated to CrM (20 g/day for 5 days followed by 5 g/day for 3-4 days) or placebo (glucose polymers) and tested before and after the supplementation period under rigorous dietary and exercise controls. Muscle phosphocreatine, creatine, and total creatine were measured before and after supplementation. A primed-continuous intravenous infusion of L-[1-(13)C]leucine and mass spectrometry were used to measure mixed-muscle protein fractional synthetic rate and indexes of whole body leucine metabolism (nonoxidative leucine disposal), leucine oxidation, and plasma leucine rate of appearance. CrM supplementation increased muscle total creatine (+13.1%, P < 0.05) with a trend toward an increase in phosphocreatine (+8.8%, P = 0.09). CrM supplementation did not increase muscle fractional synthetic rate but reduced leucine oxidation (-19.6%) and plasma leucine rate of appearance (-7.5%, P < 0.05) in men, but not in women. CrM did not increase total body mass or fat-free mass. We conclude that short-term CrM supplementation may have anticatabolic actions in some proteins (in men), but CrM does not increase whole body or mixed-muscle protein synthesis.
The purpose of this study was to quantify which dietary supplements augment lean mass and strength gains during resistance training. Peer-reviewed studies between the years 1967 and 2001 were included in the analysis if they met a predetermined set of experimental criteria, among which were at least 3-wk duration and resistance-training 2 or more times a week. Lean mass and strength were normalized for meta-analysis by conversion to percent change per week and by calculating the effect size for each variable. Of the 250 supplements examined, only 6 had more than 2 studies that met the criteria for inclusion in the meta-analysis. Creatine and beta-hydroxy-beta-methylbutyrate (HMB) were found to significantly increase net lean mass gains of 0.36 and 0.28%/wk and strength gains of 1.09 and 1.40%/wk (P < 0.05), respectively. Chromium, dehydroepiandrosterone, androstenedione, and protein did not significantly affect lean gain or strength. In conclusion, two supplements, creatine and HMB, have data supporting their use to augment lean mass and strength gains with resistance training.
effect of oral creatine supplementation (CR; 5 g/day) in conjunction with exercise training on physical fitness was investigated in men between 55 and 75 yr of age (n = 46). A double-blind randomized placebo-controlled (PL) trial was performed over a 6-mo period. Furthermore, a subgroup (n = 20) completed a 1-yr follow-up. The training program consisted of cardiorespiratory endurance training as well as moderate resistance training (2-3 sessions/wk). Endurance capacity was evaluated during a maximal incremental bicycle ergometer test, maximal isometric strength of the knee-extensor muscles was assessed by an isokinetic dynamometer, and body composition was assessed by hydrostatic weighing. Furthermore, in a subgroup (PL: n = 13; CR: n = 12) biopsies were taken from m. vastus lateralis to determine total creatine (TCr) content. In PL, 6 mo of training increased peak oxygen uptake rate (+16%; P < 0.05). Fat-free mass slightly increased (+0.3 kg; P < 0.05), whereas percent body fat slightly decreased (-1.2%; P < 0.05). The training intervention did not significantly change either maximal isometric strength or body weight. The responses were independent of CR. Still, compared with PL, TCr was increased by approximately 5% in CR, and this increase was closely correlated with initial muscle creatine content (r = -0.78; P < 0.05). After a 1-yr follow-up, muscle TCr was not higher in CR than in PL. Furthermore, the other measurements were not affected by CR. It is concluded that long-term creatine intake (5 g/day) in conjunction with exercise training does not beneficially impact physical fitness in men between 55 and 75 yr of age.
Creatine supplementation (CS) has been reported to increase body mass and improve performance in high-intensity, short-duration exercise tasks. Research on CS, most of which has come into existence since 1994, has been the focus of several qualitative reviews, but only one meta-analysis, which was conducted with a limited number of studies.
This study compared the effects of CS on effect size (ES) for body composition (BC) variables (mass and lean body mass), duration and intensity (< or = 30 s, [ATP-PCr = A]; 30-150 s [glycolysis = G]; >150 s, [oxidative phosphorylation = O]) of the exercise task, type of exercise task (single, repetitive, laboratory, field, upper-body, lower-body), CS duration (loading, maintenance), and subject characteristics (gender, training status).
A search of MEDLINE and SPORTDiscus using the phrase "creatine supplementation" revealed 96 English-language, peer-reviewed papers (100 studies), which included randomized group formation, a placebo control, and human subjects who were blinded to treatments. ES was calculated for each body composition and performance variable.
Small, but significant (ES > 0, p < or = .05) ES were reported for BC (n=163, mean +/- SE=0.17 +/- 0.03), ATP-PCr (n=17, 0.24 +/- 0.02), G (n=135, 0.19 +/- 0.05), and O (n=69, 0.20 +/- 0.07). ES was greater for change in BC following a loading-only CS regimen (0.26 +/- 0.03, p=.0003) compared to a maintenance regimen (0.04 +/- 0.05), for repetitive-bout (0.25 +/- 0.03,p=.028) compared to single-bout (0.18 +/- 0.02) exercise, and for upper-body exercise (0.42 +/- 0.07, p<.0001) compared to lower (0.21 +/- 0.02) and total body (0.13 +/- 0.04) exercise. ES for laboratory-based tasks (e.g., isometric/isotonic/isokinetic exercise, 0.25 +/- 0.02) were greater (p=.014) than those observed for field-based tasks (e.g., running, swimming, 0.14 +/- 0.04). There were no differences in BC or performance ES between males and females or between trained and untrained subjects.
ES was greater for changes in lean body mass following short-term CS, repetitive-bout laboratory-based exercise tasks < or = 30 s (e.g., isometric, isokinetic, and isotonic resistance exercise), and upper-body exercise. CS does not appear to be effective in improving running and swimming performance. There is no evidence in the literature of an effect of gender or training status on ES following CS.
Using an integrative approach, this review highlights the benefits of resistance training toward improvements in functional status, health and quality of life among older adults. Sarcopenia (i.e. muscle atrophy) and loss of strength are known to occur with age. While its aetiology is poorly understood, the multifactorial sequelae of sarcopenia are well documented and present a major public health concern to our aging population, as both the quality of life and the likelihood of age-associated declines in health status are influenced. These age-related declines in health include decreased energy expenditure at rest and during exercise, and increased body fat and its accompanying increased dyslipidaemia and reduced insulin sensitivity. Quality of life is affected by reduced strength and endurance and increased difficulty in being physically active. Strength and muscle mass are increased following resistance training in older adults through a poorly understood series of events that appears to involve the recruitment of satellite cells to support hypertrophy of mature myofibres. Muscle quality (strength relative to muscle mass) also increases with resistance training in older adults possibly for a number of reasons, including increased ability to neurally activate motor units and increased high-energy phosphate availability. Resistance training in older adults also increases power, reduces the difficulty of performing daily tasks, enhances energy expenditure and body composition, and promotes participation in spontaneous physical activity. Impairment in strength development may result when aerobic training is added to resistance training but can be avoided with training limited to 3 days/week.
This study examined the effects of 14 days of creatine supplementation on the physical working capacity at fatigue threshold (PWCFT), maximal isometric grip strength (GRIP), sit-to-stand (STS), and body weight (BW) in elderly men and women.
Using a double blind cross-over design, fifteen men (n = 7) and women (n = 8) (age +/- SD = 74.5 +/- 6.4 yrs) were randomly assigned to either the creatine (CR) (20g.d-1 during week 1 decreasing to 10g.d-1 at week 2) or Placebo (PL) group. After a 4 to 6 week washout period, the subjects were assigned the other treatment. Before (pre) and after (post) the supplementation period, participants performed a discontinuous, cycle ergometry test to determine the PWCFT. In addition, subjects performed STS, GRIP, BW test prior to and post treatment.
Southeastern part of the United States.
Significant increases in GRIP (6.7%) and PWCFT (15.6%) from pre- to post-supplementation were found for the CR (p < 0.05) treatment, but no change for the PL treatment was observed. However, no significant change (p superior 0.05) was noted for STS or BW for either treatment.
These findings suggest that 14 days of CR supplementation may increase upper body grip strength and increase physical working capacity by delaying neuromuscular fatigue in the elderly men and women in this study. While more research is needed, CR supplementation may improve upper body grip strength and lower body muscle endurance which may be important for maintaining health and independent living in elderly men and women.
Skeletal muscle strength and bulk are reduced in patients with chronic obstructive pulmonary disease (COPD) and influence quality of life, survival, and utilization of health care resources. Exercise training during pulmonary rehabilitation (PR) can reverse some of these effects. In athletes and healthy elderly individuals, dietary creatine supplementation (CrS) has been shown to augment high-intensity exercise training, thereby increasing muscle mass.
This article examines the effect of CrS on functional exercise capacity and muscle performance in people with COPD.
One hundred subjects with COPD (mean [SD] age, 68.2 [8.2] yr; FEV(1), 44.0 [19.6] %predicted) were randomized to a double-blind, placebo-controlled, parallel group trial of CrS during 7 weeks of PR encompassing aerobic and resistance exercises. Subjects ingested creatine (22 g/d loading for 5 d; maintenance, 3.76 g/d throughout PR) or placebo. Baseline, postloading, and postrehabilitation measurements included pulmonary function, body composition, peripheral muscle strength, and functional performance (shuttle walking tests). A volunteer subgroup (n = 44) had pre- and postloading quadriceps muscle biopsies.
Eighty subjects completed the trial (38 creatine, 42 placebo). All outcome measures significantly improved after PR. There were no significant differences between groups post-PR (mean [SD] change in incremental shuttle walk distance, 84 [79] m in the creatine group vs. 83.8 [60] m in the placebo group; P = 1.0; knee extensor work, 19.2 [16] Nm [Newton meters] in the creatine group vs. 19.5 [17] Nm in the placebo group; P = 0.9). Muscle biopsies showed evidence of creatine uptake.
This adequately powered, randomized, placebo-controlled trial shows that CrS does not augment the substantial training effect of multidisciplinary PR for patients with COPD. Clinical trial registered with https://portal.nihr.ac.uk/Pages/NRRArchiveSearch.aspx (NO123138126).
We conducted a 12-wk resistance training program in elderly women [mean age 69 +/- 1.0 (SE) yr] to determine whether increases in muscle strength are associated with changes in cross-sectional fiber area of the vastus lateralis muscle. Twenty-seven healthy women were randomly assigned to either a control or exercise group. The program was satisfactorily completed and adequate biopsy material obtained from 6 controls and 13 exercisers. After initial testing of baseline maximal strength, exercisers began a training regimen consisting of seven exercises that stressed primary muscle groups of the lower extremities. No active intervention was prescribed for the controls. Increases in muscle strength of the exercising subjects were significant compared with baseline values (28-115%) in all muscle groups. No significant strength changes were observed in the controls. Cross-sectional area of type II muscle fibers significantly increased in the exercisers (20.1 +/- 6.8%, P = 0.02) compared with baseline. In contrast, no significant change in type II fiber area was observed in the controls. No significant changes in type I fiber area were found in either group. We conclude that a program of resistance exercise can be safely carried out by elderly women, such a program significantly increases muscle strength, and such gains are due, at least in part, to muscle hypertrophy.
OBJECTIVES Oral creatine is the most widely used nutritional supplement among athletes. Our purpose was to investigate whether creatine supplementation increases maximal strength and power in healthy adults. STUDY DESIGN Meta-analysis of existing literature. DATA SOURCES We searched MEDLINE (1966-2000) and the Cochrane Controlled Trials Register (through June 200 1) to locate relevant articles. We reviewed conference proceedings and bibliographies of identified studies. An expert in the field was contacted for sources of unpublished data. Randomized or matched placebo controlled trials comparing creatine supplementation with placebo in healthy adults were considered. OUTCOMES MEASURED Presupplementation and postsupplementation change in maximal weight lifted, cycle ergometry sprint peak power, and isokinetic dynamometer peak torque were measured. RESULTS Sixteen studies were identified for inclusion. The summary difference in maximum weight lifted was 6.85 kg (95% confidence interval [CI], 5.24-8.47) greater after creatine than placebo for bench press and 9.76 kg (95% CI, 3-37-16.15) greater for squats; there was no difference for arm curls. In 7 of 10 studies evaluating maximal weight lifted, subjects were young men (younger than 36 years) engaged in resistance training. There was no difference in cycle ergometer or isokinetic dynamometer performance. CONCLUSIONS Oral creatine supplementation combined with resistance training increases maximal weight lifted in young men. There is no evidence for improved performance in older individuals or women or for other types of strength and power exercises. Also, the safety of creatine remains unproven. Therefore, until these issues are addressed, its use cannot be universally recommenced.
Purpose:
To study the effect of creatine (Cr) supplementation combined with resistance training on muscular performance and body composition in older men.
Methods:
Thirty men were randomized to receive creatine supplementation (CRE, N = 16, age = 70.4 +/- 1.6 yr) or placebo (PLA, N = 14, age = 71.1 +/- 1.8 yr), using a double blind procedure. Cr supplementation consisted of 0.3-g Cr.kg(-1) body weight for the first 5 d (loading phase) and 0.07-g Cr.kg(-1) body weight thereafter. Both groups participated in resistance training (36 sessions, 3 times per week, 3 sets of 10 repetitions, 12 exercises). Muscular strength was assessed by 1-repetition maximum (1-RM) for leg press (LP), knee extension (KE), and bench press (BP). Muscular endurance was assessed by the maximum number of repetitions over 3 sets (separated by 1-min rest intervals) at an intensity corresponding to 70% baseline 1-RM for BP and 80% baseline 1-RM for the KE and LP. Average power (AP) was assessed using a Biodex isokinetic knee extension/flexion exercise (3 sets of 10 repetitions at 60 degrees.s(-1) separated by 1-min rest). Lean tissue (LTM) and fat mass were assessed using dual energy x-ray absorptiometry.
Results:
Compared with PLA, the CRE group had significantly greater increases in LTM (CRE, +3.3 kg; PLA, +1.3 kg), LP 1-RM (CRE, +50.1 kg; PLA +31.3 kg), KE 1-RM (CRE, +14.9 kg; PLA, +10.7 kg), LP endurance (CRE, +47 reps; PLA, +32 reps), KE endurance (CRE, +21 reps; PLA +14 reps), and AP (CRE, +26.7 W; PLA, +18 W). Changes in fat mass, fat percentage, BP 1-RM, and BP endurance were similar between groups.
Conclusion:
Creatine supplementation, when combined with resistance training, increases lean tissue mass and improves leg strength, endurance, and average power in men of mean age 70 yr.
Background: Protein ingestion after a single bout of resistance-type exercise stimulates net muscle protein accretion during acute postexercise recovery. Consequently, it is generally accepted that protein supplementation is required to maximize the adaptive response of the skeletal muscle to prolonged resistance-type exercise training. However, there is much discrepancy in the literature regarding the proposed benefits of protein supplementation during prolonged resistance-type exercise training in younger and older populations.
Objective: The objective of the study was to define the efficacy of protein supplementation to augment the adaptive response of the skeletal muscle to prolonged resistance-type exercise training in younger and older populations.
Design: A systematic review of interventional evidence was performed through the use of a random-effects meta-analysis model. Data from the outcome variables fat-free mass (FFM), fat mass, type I and II muscle fiber cross-sectional area, and 1 repetition maximum (1-RM) leg press strength were collected from randomized controlled trials (RCTs) investigating the effect of dietary protein supplementation during prolonged (>6 wk) resistance-type exercise training.
Results: Data were included from 22 RCTs that included 680 subjects. Protein supplementation showed a positive effect for FFM (weighted mean difference: 0.69 kg; 95% CI: 0.47, 0.91 kg; P < 0.00001) and 1-RM leg press strength (weighted mean difference: 13.5 kg; 95% CI: 6.4, 20.7 kg; P < 0.005) compared with a placebo after prolonged resistance-type exercise training in younger and older subjects.
Conclusion: Protein supplementation increases muscle mass and strength gains during prolonged resistance-type exercise training in both younger and older subjects.
The underlying cause of sarcopenia and dynapenia (age-related strength loss) are not fully elucidated, but may be the result, or combination, of alterations in lifestyle or inflammatory and endocrine profiles. What is clear is function ability is limited and mortality risk is elevated. Mechanistically, muscle atrophy is the result of the prolonged periods of net negative muscle protein balance, brought about by the imbalance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). Contractile loading of skeletal muscle, through resistive-type exercise and amino acid ingestion both act as a strong stimulus for MPS and, when combined, can induce a net positive protein balance and muscle hypertrophy. Given that MPS in older muscles display a blunted response to anabolic stimuli compared with the young, the combined effect and manipulation of contractile and nutrient interventions to optimize muscle anabolism could be extremely important for counteracting sarcopenia. Specifically, the dose, absorption kinetics, leucine content, but less-so the timing of ingestion, are important determinants of the mRNA translational signalling response regulating MPS. In addition, resistance exercise-induced rates of MPS and hypertrophy appear to be dependent on exercise volume (to achieve maximal muscle fibre recruitment), as opposed to the absolute load that is lifted. A number of recent studies in young adults lend weight to this notion by showing that contraction can be manipulated; allowing low-load weight lifting to effectively stimulate rates of MPS to a level comparable to traditional high-loads - a finding with important implications for older adults interested in undertaking resistance exercise.
We have reported that the acute postexercise increases in muscle protein synthesis rates, with differing nutritional support, are predictive of longer-term training-induced muscle hypertrophy. Here, we aimed to test whether the same was true with acute exercise-mediated changes in muscle protein synthesis. Eighteen men (21 ± 1 yr, 22.6 ± 2.1 kg/m(2); means ± SE) had their legs randomly assigned to two of three training conditions that differed in contraction intensity [% of maximal strength (1 repetition maximum)] or contraction volume (1 or 3 sets of repetitions): 30%-3, 80%-1, and 80%-3. Subjects trained each leg with their assigned regime for a period of 10 wk, 3 times/wk. We made pre- and posttraining measures of strength, muscle volume by magnetic resonance (MR) scans, as well as pre- and posttraining biopsies of the vastus lateralis, and a single postexercise (1 h) biopsy following the first bout of exercise, to measure signaling proteins. Training-induced increases in MR-measured muscle volume were significant (P < 0.01), with no difference between groups: 30%-3 = 6.8 ± 1.8%, 80%-1 = 3.2 ± 0.8%, and 80%-3= 7.2 ± 1.9%, P = 0.18. Isotonic maximal strength gains were not different between 80%-1 and 80%-3, but were greater than 30%-3 (P = 0.04), whereas training-induced isometric strength gains were significant but not different between conditions (P = 0.92). Biopsies taken 1 h following the initial resistance exercise bout showed increased phosphorylation (P < 0.05) of p70S6K only in the 80%-1 and 80%-3 conditions. There was no correlation between phosphorylation of any signaling protein and hypertrophy. In accordance with our previous acute measurements of muscle protein synthetic rates a lower load lifted to failure resulted in similar hypertrophy as a heavy load lifted to failure.
Feeding stimulates robust increases in muscle protein synthesis (MPS); however, ageing may alter the anabolic response to protein ingestion and the subsequent aminoacidaemia. With this as background, we aimed to determine in the present study the dose-response of MPS with the ingestion of isolated whey protein, with and without prior resistance exercise, in the elderly. For the purpose of this study, thirty-seven elderly men (age 71 (sd 4) years) completed a bout of unilateral leg-based resistance exercise before ingesting 0, 10, 20 or 40 g of whey protein isolate (W0-W40, respectively). Infusion of l-[1-13C]leucine and l-[ring-13C6]phenylalanine with bilateral vastus lateralis muscle biopsies were used to ascertain whole-body leucine oxidation and 4 h post-protein consumption of MPS in the fed-state of non-exercised and exercised leg muscles. It was determined that whole-body leucine oxidation increased in a stepwise, dose-dependent manner. MPS increased above basal, fasting values by approximately 65 and 90 % for W20 and W40, respectively (P < 0·05), but not with lower doses of whey. While resistance exercise was generally effective at stimulating MPS, W20 and W40 ingestion post-exercise increased MPS above W0 and W10 exercised values (P < 0·05) and W40 was greater than W20 (P < 0·05). Based on the study, the following conclusions were drawn. At rest, the optimal whey protein dose for non-frail older adults to consume, to increase myofibrillar MPS above fasting rates, was 20 g. Resistance exercise increases MPS in the elderly at all protein doses, but to a greater extent with 40 g of whey ingestion. These data suggest that, in contrast to younger adults, in whom post-exercise rates of MPS are saturated with 20 g of protein, exercised muscles of older adults respond to higher protein doses.
The ingestion of the dietary supplement creatine (about 20 g/day for 5 days or about 2 g/day for 30 days) results in increased skeletal muscle creatine and phosphocreatine. Subsequently, the performance of high-intensity exercise tasks, which rely heavily on the creatine-phosphocreatine energy system, is enhanced. The well documented benefits of creatine supplementation in young adults, including increased lean body mass, increased strength, and enhanced fatigue resistance are particularly important to older adults. With aging and reduced physical activity, there are decreases in muscle creatine, muscle mass, bone density, and strength. However, there is evidence that creatine ingestion may reverse these changes, and subsequently improve activities of daily living. Several groups have demonstrated that in older adults, short-term high-dose creatine supplementation, independent of exercise training, increases body mass, enhances fatigue resistance, increases muscle strength, and improves the performance of activities of daily living. Similarly, in older adults, concurrent creatine supplementation and resistance training increase lean body mass, enhance fatigue resistance, increase muscle strength, and improve performance of activities of daily living to a greater extent than resistance training alone. Additionally, creatine supplementation plus resistance training results in a greater increase in bone mineral density than resistance training alone. Higher brain creatine is associated with improved neuropsychological performance, and recently, creatine supplementation has been shown to increase brain creatine and phosphocreatine. Subsequent studies have demonstrated that cognitive processing, that is either experimentally (following sleep deprivation) or naturally (due to aging) impaired, can be improved with creatine supplementation. Creatine is an inexpensive and safe dietary supplement that has both peripheral and central effects. The benefits afforded to older adults through creatine ingestion are substantial, can improve quality of life, and ultimately may reduce the disease burden associated with sarcopenia and cognitive dysfunction.
The aim of this study was to investigate the efficacy of creatine (CR) supplementation combined with strengthening exercises in knee osteoarthritis (OA).
A randomized, double-blind, placebo-controlled trial was performed. Postmenopausal women with knee OA were allocated to receive either CR (20 g·d(-1) for 1 wk and 5 g·d(-1) thereafter) or placebo (PL) and were enrolled in a lower limb resistance training program. They were assessed at baseline (PRE) and after 12 wk (POST). The primary outcome was the physical function as measured by the timed-stands test. Secondary outcomes included lean mass, quality of life, pain, stiffness, and muscle strength.
Physical function was significantly improved only in the CR group (P = 0.006). In addition, a significant between-group difference was observed (CR: PRE = 15.7 ± 1.4, POST = 18.1 ± 1.8; PL: PRE = 15.0 ± 1.8, POST = 15.2 ± 1.2; P = 0.004). The CR group also presented improvements in physical function and stiffness subscales as evaluated by the Western Ontario and McMaster Universities Osteoarthritis Index (P = 0.005 and P = 0.024, respectively), whereas the PL group did not show any significant changes in these parameters (P > 0.05). In addition, only the CR group presented a significant improvement in lower limb lean mass (P = 0.04) as well as in quality of life (P = 0.01). Both CR and PL groups demonstrated significant reductions in pain (P < 0.05). Similarly, a main effect for time revealed an increase in leg-press one-repetition maximum (P = 0.005) with no significant differences between groups (P = 0.81).
CR supplementation improves physical function, lower limb lean mass, and quality of life in postmenopausal women with knee OA undergoing strengthening exercises.
Creatine and protein supplementation can enhance the training outcomes of young subjects, but it is not clear if there are benefits for older individuals. Therefore, the purpose of this study was to determine the effects of creatine and protein supplementation on strength gains following a traditional resistance training program for middle-aged and older men.
This study assessed changes in strength of men aged 48-72 years following 14 weeks of resistance training supplemented with creatine and/or protein. A double-blind, randomized, placebo-controlled design placed 42 males into one of four groups: Resistance Trained Placebo (RTP, n=10); Resistance Trained Creatine (RTCr, 5g Cr, n=10); Resistance Trained Protein (RTPr, 35g whey Pr, n=11); or Resistance Trained Creatine and Protein (RTCrPr, 5g Cr and 35g Pr, n=11).
All groups trained 3 days per week for 14 weeks. The resistance training program was based on progressive overload. Training loads corresponded to 80% 1 RM (one repetition maximum strength), 3 sets of 8 repetitions for the following exercises: knee extension/knee flexion; bicep curl/tricep extension; military press; lat pull down; seated leg press; and bench press.
1 RM for each exercise and measures of lean body mass were assessed prior to and following the 14 week program.
Each group significantly (p < 0.05) increased strength and lean body mass, however, there were no significant group effects or group X trial interactions.
Resistance training in middle-aged and older men significantly increased muscular strength and added muscle mass with no additional benefits from creatine and/or protein supplementation.
The anabolic effect of resistance exercise is enhanced by the provision of dietary protein.
We aimed to determine the ingested protein dose response of muscle (MPS) and albumin protein synthesis (APS) after resistance exercise. In addition, we measured the phosphorylation of candidate signaling proteins thought to regulate acute changes in MPS.
Six healthy young men reported to the laboratory on 5 separate occasions to perform an intense bout of leg-based resistance exercise. After exercise, participants consumed, in a randomized order, drinks containing 0, 5, 10, 20, or 40 g whole egg protein. Protein synthesis and whole-body leucine oxidation were measured over 4 h after exercise by a primed constant infusion of [1-(13)C]leucine.
MPS displayed a dose response to dietary protein ingestion and was maximally stimulated at 20 g. The phosphorylation of ribosomal protein S6 kinase (Thr(389)), ribosomal protein S6 (Ser(240/244)), and the epsilon-subunit of eukaryotic initiation factor 2B (Ser(539)) were unaffected by protein ingestion. APS increased in a dose-dependent manner and also reached a plateau at 20 g ingested protein. Leucine oxidation was significantly increased after 20 and 40 g protein were ingested.
Ingestion of 20 g intact protein is sufficient to maximally stimulate MPS and APS after resistance exercise. Phosphorylation of candidate signaling proteins was not enhanced with any dose of protein ingested, which suggested that the stimulation of MPS after resistance exercise may be related to amino acid availability. Finally, dietary protein consumed after exercise in excess of the rate at which it can be incorporated into tissue protein stimulates irreversible oxidation.
To determine whether low-dose creatine and protein supplementation during resistance training (RT; 3 d x wk(-1); 10 wk) in older men (59-77 yr) is effective for improving strength and muscle mass without producing potentially cytotoxic metabolites (formaldehyde).
Older men were randomized (double-blind) to receive 0.1 g x kg(-1) creatine + 0.3 g x kg(-1) protein (CP; n = 10), creatine (C; n = 13), or placebo (PLA; n = 12) on training days. Measurements before and after RT included lean tissue mass (air-displacement plethysmography), muscle thickness (ultrasound) of elbow, knee, and ankle flexors and extensors, leg and bench press strength, and urinary indicators of cytotoxicity (formaldehyde), myofibrillar protein degradation [3-methylhistidine (3-MH)],and bone resorption [cross-linked N-telopeptides of type I collagen (NTx)].
Subjects in C and CP groups combined experienced greater increases in body mass and total muscle thickness than PLA (P < 0.05). Subjects who received CP increased lean tissue mass (+5.6%) more than C (+2.2%) or PLA (+1.0%; P < 0.05) and increased bench press strength (+25%) to a greater extent than C and PLA combined (+12.5%; P < 0.05). CP and C did not differ from PLA for changes in formaldehyde production (+24% each). Subjects receiving creatine (C and CP) experienced a decrease in 3-MH by 40% compared with an increase of 29% for PLA (P < 0.05) and a reduction in NTx (-27%) versus PLA (+13%; P = 0.05).
Low-dose creatine combined with protein supplementation increases lean tissue mass and results in a greater relative increase in bench press but not leg press strength. Low-dose creatine reduces muscle protein degradation and bone resorption without increasing formaldehyde production.
We conducted a 12-wk resistance training program in elderly women [mean age 69 +/- 1.0 (SE) yr] to determine whether increases in muscle strength are associated with changes in cross-sectional fiber area of the vastus lateralis muscle. Twenty-seven healthy women were randomly assigned to either a control or exercise group. The program was satisfactorily completed and adequate biopsy material obtained from 6 controls and 13 exercisers. After initial testing of baseline maximal strength, exercisers began a training regimen consisting of seven exercises that stressed primary muscle groups of the lower extremities. No active intervention was prescribed for the controls. Increases in muscle strength of the exercising subjects were significant compared with baseline values (28-115%) in all muscle groups. No significant strength changes were observed in the controls. Cross-sectional area of type II muscle fibers significantly increased in the exercisers (20.1 +/- 6.8%, P = 0.02) compared with baseline. In contrast, no significant change in type II fiber area was observed in the controls. No significant changes in type I fiber area were found in either group. We conclude that a program of resistance exercise can be safely carried out by elderly women, such a program significantly increases muscle strength, and such gains are due, at least in part, to muscle hypertrophy.
This study investigated the effect of carbohydrate (CHO) ingestion on skeletal muscle creatine (Cr) accumulation during Cr supplementation in humans. Muscle biopsy, urine, and plasma samples were obtained from 24 males before and after ingesting 5 g Cr in solution (group A) or 5 g Cr followed, 30 min later, by 93 g simple CHO in solution (group B) four times each day for 5 days. Supplementation resulted in an increase in muscle phosphocreatine (PCr), Cr, and total creatine (TCr; sum of PCr and Cr) concentration in groups A and B, but the increase in TCr in group B was 60% greater than in group A (P < 0.01). There was also a corresponding decrease in urinary Cr excretion in group B (P < 0.001). Creatine supplementation had no effect on serum insulin concentration, but Cr and CHO ingestion dramatically elevated insulin concentration (P < 0.001). These findings demonstrate that CHO ingestion substantially augments muscle Cr accumulation during Cr feeding in humans, which appears to be insulin mediated.
In this investigation we evaluated the effects of oral creatine (Cr) supplementation on body composition, strength of the elbow flexors, and fatigue of the knee extensors in 20 males aged 60-82 years who were randomly administered Cr or placebo (P) in a double-blind fashion. Subjects ingested either 20 g of Cr or P for 10 days, followed by either 4 g of Cr or P, respectively, for 20 days. Tests were conducted pre-supplementation and following 10 and 30 days of supplementation. Leg fatigue was determined using an isokinetic dynamometer; subjects performed 5 sets of 30 maximal voluntary contractions at 180 degrees x s(-1), with 1 min of recovery between sets. The strength of the elbow flexors was assessed using a modified preacher bench attached to a strain gauge. There was a significant interaction (P < 0.05; group x time) in leg fatigue following supplementation. However, this interaction appears to have resulted from a combination of the improved fatigue score by the Cr-supplemented group and the decreased fatigue score by the P-supplemented group, because when the simple main effects were analyzed for the groups individually, there was no significant difference over time for either of the groups. There were no significant differences in body mass, body density, or fat-free mass as assessed by hydrostatic weighing, or strength between the Cr-supplemented or P-supplemented groups. These data suggest that 30 days of Cr-supplementation may have a beneficial effect on reducing muscle fatigue in men over the age of 60 years, but it does not affect body composition or strength.
The hypothesis of this study was that short term creatine (Cr) ingestion in older individuals would increase body mass and exercise performance, as has been shown in younger subjects. Seventeen males 60-78 years old were randomly placed into two groups, Cr and placebo (P), and supplemented in double-blind fashion for 5 days. Subjects ingested either 5 g of Cr plus 1 g of sucrose 4x per day or 6 g of a sucrose placebo 4x per day. Isometric strength of the elbow flexors was assessed using a modified preacher bench attached to a strain gauge. Isokinetic exercise performance was assessed using an intermittent fatigue test of the knee extensors. Subjects performed 3 sets of 30 repetitions with 60 sec rest between sets. There was a small (0.5 kg) but statistically significant increase in body mass (p < 0.05) in the Cr group after supplementation. There was a significant overall interaction between groups in isokinetic performance from pre to post supplementation (group x time x set, p < 0.05). However, analysis of the groups separately revealed that the subjects in the Cr group demonstrated a small non-significant increase in isokinetic performance while subjects in the P group demonstrated a small non-significant performance decrement. There was no significant difference in isometric strength between groups from pre to post supplementation. These data suggest that acute oral Cr supplementation does not increase isometric strength and only produces small increases in isokinetic performance and body mass in men over the age of 60.
The purpose of this study was to investigate the effects of creatine (Cr) supplementation in 12 older (65-82 years) men. The subjects were randomly assigned to a Cr or a placebo (P) group. Seven men were supplemented with 5 g of Cr and 5 g maltodextrin four times a day for 5 days (Cr), and 5 men consumed 5 g of maltodextrin four times a day for 5 days (P). Following this treatment body mass increased significantly in the Cr group (1 kg), but did not change in the P group, and measurements of arm anthropometry were not affected in either group. Prior to and following supplementation maximal isometric voluntary force (MVC), muscle activation, contractile properties and surface electromyography (EMG) were measured in the elbow flexor muscles at baseline, during a fatiguing task and over 10 min of recovery. The fatigue protocol involved both voluntary and contractile stimulated. Stimulated contractile properties, MVC, and muscle activation were not affected by Cr supplementation. Furthermore, there were no changes in time to fatigue, decline in MVC force, muscle activation, EMG or contractile properties during the fatigue protocol. The rates of recovery of voluntary force, and stimulated contractile force did not change following Cr supplementation. These results indicate that short-term Cr supplementation in older men does not influence isometric performance of the elbow flexor muscles.
To study the effect of creatine (Cr) supplementation combined with resistance training on muscular performance and body composition in older men.
Thirty men were randomized to receive creatine supplementation (CRE, N = 16, age = 70.4 +/- 1.6 yr) or placebo (PLA, N = 14, age = 71.1 +/- 1.8 yr), using a double blind procedure. Cr supplementation consisted of 0.3-g Cr.kg(-1) body weight for the first 5 d (loading phase) and 0.07-g Cr.kg(-1) body weight thereafter. Both groups participated in resistance training (36 sessions, 3 times per week, 3 sets of 10 repetitions, 12 exercises). Muscular strength was assessed by 1-repetition maximum (1-RM) for leg press (LP), knee extension (KE), and bench press (BP). Muscular endurance was assessed by the maximum number of repetitions over 3 sets (separated by 1-min rest intervals) at an intensity corresponding to 70% baseline 1-RM for BP and 80% baseline 1-RM for the KE and LP. Average power (AP) was assessed using a Biodex isokinetic knee extension/flexion exercise (3 sets of 10 repetitions at 60 degrees.s(-1) separated by 1-min rest). Lean tissue (LTM) and fat mass were assessed using dual energy x-ray absorptiometry.
Compared with PLA, the CRE group had significantly greater increases in LTM (CRE, +3.3 kg; PLA, +1.3 kg), LP 1-RM (CRE, +50.1 kg; PLA +31.3 kg), KE 1-RM (CRE, +14.9 kg; PLA, +10.7 kg), LP endurance (CRE, +47 reps; PLA, +32 reps), KE endurance (CRE, +21 reps; PLA +14 reps), and AP (CRE, +26.7 W; PLA, +18 W). Changes in fat mass, fat percentage, BP 1-RM, and BP endurance were similar between groups.
Creatine supplementation, when combined with resistance training, increases lean tissue mass and improves leg strength, endurance, and average power in men of mean age 70 yr.
Creatine supplementation has been shown to enhance muscle strength and power after only 5-7 d in young adults. Creatine supplementation could therefore benefit older individuals because aging is associated with a decrease in muscle strength and explosive power.
We examined the effects of 7 d of creatine supplementation in normally active older men (59-72 yr) by using a double-blind, placebo-controlled design with repeated measures. After a 3-wk familiarization period to minimize learning effects, a battery of tests was completed on three occasions separated by 7 d (T1, T2, and T3). After T1, subjects were matched and randomly assigned into creatine (N = 10) and placebo (N = 8) groups. After T2, subjects consumed supplements (0.3 g x kg(-1) x d(-1)) for 7 d until T3. All subjects were tested for maximal dynamic strength (one-repetition maximum leg press and bench press), maximal isometric strength (knee extension/flexion), upper- and lower-body explosive power (6 x 10-s sprints on a cycle ergometer), and lower-extremity functional ability (timed sit-stand test and tandem gait test). Body composition was assessed via hydrostatic weighing, and blood samples were obtained to assess renal and hepatic responses and muscle creatine concentrations.
No significant increases in any performance measures were observed from T1 to T2 with the exception of isometric right-knee flexion in the placebo group indicating stability in the testing protocols. Significant group-by -time interactions indicated the responses from T2 to T3 were significantly greater (P <or= 0.05) in the creatine compared with the placebo group, respectively, for body mass (1.86 and -1.01 kg), fat-free mass (2.22 and 0.00 kg), maximal dynamic strength (7-8 and 1-2%), maximal isometric strength (9-15 and -6 to 1%), lower-body mean power (11 and 0%), and lower-extremity functional capacity (6-9 and 1-2%). No adverse side effects were observed.
These data indicate that 7 d of creatine supplementation is effective at increasing several indices of muscle performance, including functional tests in older men without adverse side effects. Creatine supplementation may be a useful therapeutic strategy for older adults to attenuate loss in muscle strength and performance of functional living tasks.
Oral creatine is the most widely used nutritional supplement among athletes. Our purpose was to investigate whether creatine supplementation increases maximal strength and power in healthy adults.
Meta-analysis of existing literature.
We searched MEDLINE (1966-2000) and the Cochrane Controlled Trials Register (through June 2001) to locate relevant articles. We reviewed conference proceedings and bibliographies of identified studies. An expert in the field was contacted for sources of unpublished data. Randomized or matched placebo controlled trials comparing creatine supplementation with placebo in healthy adults were considered.
Presupplementation and postsupplementation change in maximal weight lifted, cycle ergometry sprint peak power, and isokinetic dynamometer peak torque were measured.
Sixteen studies were identified for inclusion. The summary difference in maximum weight lifted was 6.85 kg (95% confidence interval [CI], 5.24-8.47) greater after creatine than placebo for bench press and 9.76 kg (95% CI, 3.37-16.15) greater for squats; there was no difference for arm curls. In 7 of 10 studies evaluating maximal weight lifted, subjects were young men (younger than 36 years) engaged in resistance training. There was no difference in cycle ergometer or isokinetic dynamometer performance.
Oral creatine supplementation combined with resistance training increases maximal weight lifted in young men. There is no evidence for improved performance in older individuals or women or for other types of strength and power exercises. Also, the safety of creatine remains unproven. Therefore, until these issues are addressed, its use cannot be universally recommended.
We sought to determine whether creatine monohydrate (CrM) supplementation would enhance the increases in strength and fat-free mass that develop during resistance exercise training in older adults. Twenty-eight healthy men and women over the age of 65 years participated in a whole-body resistance exercise program 3 days per week for 14 weeks. The study participants were randomly allocated, in a double-blind fashion, to receive either CrM (5 g/d + 2 g of dextrose; n = 14) or placebo (7 g of dextrose; n = 14). The primary outcome measurements included the following: total body mass, fat-free mass, one-repetition maximum strength for each body part, isometric knee extension, handgrip, and dorsiflexion strength, chair stand performance, 30-m walk test, 14-stair climb performance, muscle fiber type and area, and intramuscular total creatine. Fourteen weeks of resistance exercise training resulted in significant increases in all measurements of strength and functional tasks and muscle fiber area for both groups (p <.05). CrM supplementation resulted in significantly greater increases in fat-free mass and total body mass, as compared with placebo (p <.05). The CrM group also showed a greater increase in isometric knee extension strength in men and women, as compared with placebo (p <.05), and also greater gains in isometric dorsiflexion strength (p <.05), but in men only. There was a significant increase in intramuscular total creatine in the CrM group (p <.05). Finally, there were no significant side effects of treatment or exercise training. This study confirms that supervised heavy resistance exercise training can safely increase muscle strength and functional capacity in older adults. The addition of CrM supplementation to the exercise stimulus enhanced the increase in total and fat-free mass, and gains in several indices of isometric muscle strength.
The purposes of this investigation were first to determine the impact of 3 different creatine (Cr) loading procedures on skeletal muscle total Cr (TCr) accumulation and, second, to evaluate the effectiveness of 2 maintenance regimes on retaining intramuscular TCr stores, in the 6 weeks following a 5-day Cr loading program (20 g x day(-1). Eighteen physically active male subjects were divided into 3 equal groups and administered either: (a) Cr (4 x 5 g x day(-1) x 5 days), (b) Glucose+Cr (1 g x (-1) of body mass twice per day), or (c) Cr in conjunction with 60 min of daily muscular (repeated-sprint) exercise. Following the 5-day loading period, subjects were reassigned to 3 maintenance groups and ingested either 0 g x day(-1), 2 g. day(-1) or 5 g x day(-1) of Cr for a period of 6 weeks. Muscle biopsy samples (vastus lateralis) were taken pre- and post-loading as well as post-maintenance and analyzed for skeletal muscle ATP, phosphocreatine (PCr), Cr, and TCr concentrations. Twenty-four hour urine samples were collected for each of the loading days and last 2 maintenance days, and used to determine whole body Cr retention. Post-loading TCr stores were significantly (p <.05) increased in all treatment conditions. The Glucose+Cr condition produced a greater elevation (p <.05) in TCr concentrations (25%) than the Cr Only (16%) or Exercise+Cr (18%) groups. Following the maintenance period, muscle TCr stores were still similar to post-loading values for both the 2 g x day(-1) and 5 g x day(-1) conditions. Intramuscular TCr values for the 0 g x day(-1) condition were significantly lower than the other conditions after the 6-week period. Although not significantly different from pre-loading concentrations, muscle TCr for the 0 g x day(-1) group had not fully returned to baseline levels at 6 weeks post-loading. The data suggests that Glucose+Cr (but with a much smaller glucose intake than currently accepted) is potentially the most effective means of elevating TCr accumulation in human skeletal muscle. Furthermore, after 5 days of Cr loading, elevated muscle TCr concentrations can be maintained by the ingestion of small daily Cr doses (2-5 g) for a period of 6 weeks and that TCr concentrations may take longer than currently accepted to return to baseline values after such a Cr loading regime.
Isotonic strength training can result in neuromuscular improvements evidenced in other forms of muscular effort, ie, isokinetic or isometric, especially in young subjects; however, it is unclear if older muscle maintains this same adaptive ability. Additionally, it is not known if the benefits of resistance training can be augmented by creatine and protein supplementation in older men. Therefore, the purpose of this study was to assess changes in isokinetic parameters at varying speeds in men aged 48 to 72 years (mean=57+/-2.1) following 16 weeks of isotonic resistance training and creatine and/or protein supplementation.
Forty-two male subjects were randomly assigned to 1 of 4 training groups: (1) resistance training placebo (n=10), (2) resistance trained creatine supplemented (n=10), (3) resistance trained protein supplemented (n=11), and (4) resistance trained creatine and protein supplemented (n=11). The program consisted of progressive overload resistance training (3 d/wk) and supplement consumption following the workout.
There were significant time effects (P>.05) for peak torque (PT), time to PT, and average power for both the knee extensors and flexors at all velocities. However, no significant group or group by time interactions were noted, indicating that the supplementation protocols had no added benefits.
Men aged 48 to 72 years maintained their ability to improve isokinetic muscle function following isotonic training, however, supplementation did not enhance muscle adaptability.
This study assessed age and sex effects on muscle fibre adaptations to heavy-resistance strength training (ST). Twenty-two young men and women (20-30 years old) and 18 older men and women (65-75 years old) completed 9 weeks of heavy-resistance knee extension exercises with the dominant leg 3 days week(-1); the non-dominant leg served as a within-subject, untrained control. Bilateral vastus lateralis muscle biopsies were obtained before and after ST for analysis of type I, IIa and IIx muscle fibre cross-sectional area (CSA) and fibre type distribution. One-repetition maximum (1-RM) strength was also assessed before and after ST. ST resulted in increased CSA of type I, IIa and IIx muscle fibres in the trained leg of young men, type I and IIa fibres in young women, type IIa fibres in older men, and type IIx fibres in older women (all P<0.05). Analysis of fibre type distribution revealed a significant increase in the percentage of type I fibres (P<0.05) along with a decrease in type IIx fibres (P=0.054) after ST only in young women. There were no significant changes in muscle fibre CSA or fibre type distribution in the untrained leg for any group. All groups displayed significant increases in 1-RM (27-39%; all P<0.01). In summary, ST led to significant increases in 1-RM and type II fibre CSA in all groups; however, age and sex influence specific muscle fibre subtype responses to ST.
Acute consumption of fat-free fluid milk after resistance exercise promotes a greater positive protein balance than does soy protein.
We aimed to determine the long-term consequences of milk or soy protein or equivalent energy consumption on training-induced lean mass accretion.
We recruited 56 healthy young men who trained 5 d/wk for 12 wk on a rotating split-body resistance exercise program in a parallel 3-group longitudinal design. Subjects were randomly assigned to consume drinks immediately and again 1 h after exercise: fat-free milk (Milk; n = 18); fat-free soy protein (Soy; n = 19) that was isoenergetic, isonitrogenous, and macronutrient ratio matched to Milk; or maltodextrin that was isoenergetic with Milk and Soy (control group; n = 19).
Muscle fiber size, maximal strength, and body composition by dual-energy X-ray absorptiometry (DXA) were measured before and after training. No between-group differences were seen in strength. Type II muscle fiber area increased in all groups with training, but with greater increases in the Milk group than in both the Soy and control groups (P < 0.05). Type I muscle fiber area increased after training only in the Milk and Soy groups, with the increase in the Milk group being greater than that in the control group (P < 0.05). DXA-measured fat- and bone-free mass increased in all groups, with a greater increase in the Milk group than in both the Soy and control groups (P < 0.05).
We conclude that chronic postexercise consumption of milk promotes greater hypertrophy during the early stages of resistance training in novice weightlifters when compared with isoenergetic soy or carbohydrate consumption.
Muscle power and strength decrease with age leading to reduced independence and increased health risk from falls. Creatine supplementation can increase muscle power and strength. The purpose of this study was to examine the effects of 7 days of creatine supplementation on body composition, muscular strength, and lower-body motor functional performance in older women. Thirty 58-71 year old women performed three test sessions (T1-T3) each separated by one week. Each session consisted of one repetition maximum tests for bench press and leg press, and isometric hand-grip, tandem gait, upper-body ergometer, and lower-body ergometer tests. Following T2, subjects were assigned to a creatine monohydrate (0.3 g kg body mass(-1) for 7 days) (CR: 63.31 +/- 1.22 year, 160.00 +/- 1.58 cm, 67.11 +/- 4.38 kg) or a placebo (PL: 62.98 +/- 1.11 year, 162.25 +/- 2.09 cm, 67.84 +/- 3.90 kg) supplementation group. CR significantly (P < 0.05) increased bench press (1.7 +/- 0.4 kg), leg press (5.2 +/- 1.8 kg), body mass (0.49 +/- 0.04 kg) and fat free mass (0.52 +/- 0.05) and decreased completion time on the functional tandem gait tests from T2-T3. No significant changes were found for PL on any of the measured variables. No adverse side-effects were reported by either group. Short-term creatine supplementation resulted in an increase in strength, power, and lower-body motor functional performance in older women without any adverse side effects.
Creatine and whey protein are supplements believed to have an ergogenic effect. Very little is known regarding the effects of these dietary supplements in older men. The purpose of this study was to determine the effect of creatine and whey protein supplements, consumed independently and in combination, on total and regional body composition in middle-aged men during a resistance-training program.
Forty-two men were randomly assigned to four groups to receive supplements according to a double-blind protocol. Groups consumed their supplements three times per week immediately following their resistance training sessions. The groups were: 1) placebo (480 ml of Gatorade); 2) creatine (480 ml of Gatorade plus 5 grams of creatine); 3) whey protein (480 ml of Gatorade plus 35 grams of whey protein powder); and 4) whey protein/creatine (480 ml of Gatorade plus 5 grams of creatine and 35 grams of whey protein powder). All groups participated in resistance training 3 times per week for 14 weeks.
At the beginning and end of the study, total and regional measures of body composition (DXA) and total (TBW), intracellular (ICW), and extracellular (ECW) body water (Multifrequency BIA) were measured and 3-day diet records were completed. Results: There were significant training effects for regional arm fat (decrease), regional arm bone free-fat free mass (BF-FFM - increase), total body BF-FFM (increase), ICW (increase), and ECW (increase) but no significant group effects and only one significant group by training interaction (ECW). There were no significant changes for total calorie, carbohydrate, fat or protein intake for any of the groups from prestudy to post-study testing.
The results from this study suggest that supplementation with creatine, whey protein, or a combination of creatine and whey protein, when combined with resistance training in middle-aged men, have no added benefit to changes that occur to body composition due to resistance training alone.
Effect of growth hormone and resistance exercise on muscle growth and strength in older men.
- Yaraskeski