Article

Whey Protein Does Not Enhance the Adaptations to Elbow Flexor Resistance Training

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Abstract

It is unclear whether protein supplementation augments the gains in muscle strength and size observed after resistance training (RT) because limitations to previous studies include small cohorts, imprecise measures of muscle size and strength, and no control of prior exercise or habitual protein intake. We aimed to determine whether whey protein supplementation affected RT-induced changes in elbow flexor muscle strength and size. We pair-matched 33 previously untrained, healthy young men for their habitual protein intake and strength response to 3-wk RT without nutritional supplementation (followed by 6 wk of no training) and then randomly assigned them to protein (PRO, n = 17) or placebo (PLA, n = 16) groups. Participants subsequently performed elbow flexor RT 3 d · wk(-1) for 12 wk and consumed PRO or PLA immediately before and after each training session. We assessed elbow flexor muscle strength (unilateral 1-repetition maximum and isometric maximum voluntary force) and size (total volume and maximum anatomical cross-sectional area determined with magnetic resonance imaging) before and after the 12-wk RT. PRO and PLA demonstrated similar increases in muscle volume (PRO 17.0% ± 7.1% vs PLA 14.9% ± 4.6%, P = 0.32), anatomical cross-sectional area (PRO 16.2% ± 7.1% vs PLA 15.6% ± 4.4%, P = 0.80), 1-repetition maximum (PRO 41.8% ± 21.2% vs PLA 41.4% ± 19.9%, P = 0.97), and maximum voluntary force (PRO 12.0% ± 9.9% vs PLA 14.5% ± 8.3%, P = 0.43). In the context of this study, protein supplementation did not augment elbow flexor muscle strength and size changes that occurred after 12 wk of RT.

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... For example, in untrained individuals, Antonio et al. [70] found no effects of protein supplementation on measures of muscle mass and strength following a 6-week combined aerobic and resistance training program. Similarly, Erskine et al. [71] reported no effect of protein supplementation following 12 weeks of resistance training of the elbow flexors. In contrast, an early study by Fern et al. [72] reported greater gains in muscle mass following 4 weeks of resistance training for those participants consuming an additional 2 gÁkg -1 of protein powder daily. ...
... It is unclear whether the sensitivity analyses conducted by Amann et al. [124] for cycling time-trial and time-to-exhaustion tests have been performed for measures of muscle strength using isokinetic, isometric or 1 RM techniques. Since many investigations incorporated more than one method to evaluate changes in muscle strength and reported consistent [71,81,87] or inconsistent [73,74,89,102,104] findings for the same or different muscle groups, sensitivity of these various test metrics may not be similar. Other factors such as specificity of adaptation to the training velocity of contraction may explain disparate findings reported with slow versus fast isokinetic tests of muscle strength [74], which speaks to the advantage of using 1 RM tests for exercises performed during the training programs to evaluate changes in muscle strength with supplements [75, 76, 81, 82, 92-94, 96, 102-107, 111]. ...
... Likewise, the sensitivity and accuracy of the various methods used by studies to estimate muscle or lean mass is noteworthy. The use of magnetic resonance imaging provides the most accurate estimate of muscle mass [125] but this methodology is expensive and was usually not used in the studies reviewed [69,71,73,75]. Dual X-ray absorbance technology was consequently used [77, 82, 85, 89, 92-94, 103-109, 111, 112] but this method can overestimate muscle mass due to its inclusion of organ tissue mass and body water [125]. ...
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Background: Protein supplements are frequently consumed by athletes and recreationally active adults to achieve greater gains in muscle mass and strength and improve physical performance. Objective: This review provides a systematic and comprehensive analysis of the literature that tested the hypothesis that protein supplements accelerate gains in muscle mass and strength resulting in improvements in aerobic and anaerobic power. Evidence statements were created based on an accepted strength of recommendation taxonomy. Data sources: English language articles were searched through PubMed and Google Scholar using protein and supplements together with performance, exercise, strength, and muscle, alone or in combination as keywords. Additional articles were retrieved from reference lists found in these papers. Study selection: Studies recruiting healthy adults between 18 and 50 years of age that evaluated the effects of protein supplements alone or in combination with carbohydrate on a performance metric (e.g., one repetition maximum or isometric or isokinetic muscle strength), metrics of body composition, or measures of aerobic or anaerobic power were included in this review. The literature search identified 32 articles which incorporated test metrics that dealt exclusively with changes in muscle mass and strength, 5 articles that implemented combined resistance and aerobic training or followed participants during their normal sport training programs, and 1 article that evaluated changes in muscle oxidative enzymes and maximal aerobic power. Study appraisal and synthesis methods: All papers were read in detail, and examined for experimental design confounders such as dietary monitoring, history of physical training (i.e., trained and untrained), and the number of participants studied. Studies were also evaluated based on the intensity, frequency, and duration of training, the type and timing of protein supplementation, and the sensitivity of the test metrics. Results: For untrained individuals, consuming supplemental protein likely has no impact on lean mass and muscle strength during the initial weeks of resistance training. However, as the duration, frequency, and volume of resistance training increase, protein supplementation may promote muscle hypertrophy and enhance gains in muscle strength in both untrained and trained individuals. Evidence also suggests that protein supplementation may accelerate gains in both aerobic and anaerobic power. Limitations: To demonstrate measureable gains in strength and performance with exercise training and protein supplementation, many of the studies reviewed recruited untrained participants. Since skeletal muscle responses to exercise and protein supplementation differ between trained and untrained individuals, findings are not easily generalized for all consumers who may be considering the use of protein supplements. Conclusions: This review suggests that protein supplementation may enhance muscle mass and performance when the training stimulus is adequate (e.g., frequency, volume, duration), and dietary intake is consistent with recommendations for physically active individuals.
... Some of the muscle response data reported here have been published in a previous report investigating the effects of protein supplementation on the gains in muscle size, strength and architecture with rt (Erskine et al. 2012). As no differences between protein and placebo supplementation groups were observed regarding any of the training adaptations, the data have been collapsed across groups for the purpose of answering the current (long-standing and previously unresolved) research question, i.e., what is the contribution of muscle hypertrophy to strength changes following rt? ...
... As no differences between protein and placebo supplementation groups were observed regarding any of the training adaptations, the data have been collapsed across groups for the purpose of answering the current (long-standing and previously unresolved) research question, i.e., what is the contribution of muscle hypertrophy to strength changes following rt? In addition to the previously reported data, stabilizer surface EMg (sEMg) and explosive force data 1 3 have been included here to provide a more comprehensive account of the neuromuscular adaptations to chronic rt. the rt protocol and some of the pre and post-training measurements have been described in detail in the previously published study (Erskine et al. 2012). therefore, they will be described briefly here. ...
... which is in agreement with previous reports (Kanehisa et al. 1994;Bamman et al. 2000;Fukunaga et al. 2001), it is perhaps surprising that we did not find stronger relationships between the changes in muscle size and strength with rt. Despite strenuous efforts to minimize the test-retest variability of our measurements, resulting in high reproducibility (Erskine et al. 2012), any errors in the measurements of muscle strength and size, or discrepancies in the measurement of these variables, could confound their relationship. In addition, assessing the changes that occur with rt involves measurements at two time points, which is likely to lead to a greater accumulation of measurement errors than cross-sectional assessments that rely on a single measurement. ...
Article
Whilst skeletal muscle hypertrophy is considered an important adaptation to resistance training (RT), it has not previously been found to explain the inter-individual changes in strength after RT. This study investigated the contribution of hypertrophy to individual gains in isometric, isoinertial and explosive strength after 12 weeks of elbow flexor RT. Thirty-three previously untrained, healthy men (18-30 years) completed an initial 3-week period of elbow flexor RT (to facilitate neurological responses) followed by 6-week no training, and then 12-week elbow flexor RT. Unilateral elbow flexor muscle strength [isometric maximum voluntary force (iMVF), single repetition maximum (1-RM) and explosive force], muscle volume (V m), muscle fascicle pennation angle (θ p) and normalized agonist, antagonist and stabilizer sEMG were assessed pre and post 12-week RT. Percentage gains in V m correlated with percentage changes in iMVF (r = 0.527; P = 0.002) and 1-RM (r = 0.482; P = 0.005) but not in explosive force (r ≤ 0.243; P ≥ 0.175). Percentage changes in iMVF, 1-RM, and explosive force did not correlate with percentage changes in agonist, antagonist or stabilizer sEMG (all P > 0.05). Percentage gains in θ p inversely correlated with percentage changes in normalized explosive force at 150 ms after force onset (r = 0.362; P = 0.038). We have shown for the first time that muscle hypertrophy explains a significant proportion of the inter-individual variability in isometric and isoinertial strength gains following 12-week elbow flexor RT in healthy young men.
... Notwithstanding the potential inaccuracy of self-reported diet data, this finding is somewhat unexpected both in the context of the general body of literature (15,16) and when considering our hypothesis that increasing MyoPS would be associated with greater gains in muscle size. Yet, evidence exists that protein-and/or amino acid-based supplements do not augment increases in whole muscle volume or CSA during RET using single-limb models (69) or isolated muscle groups (70). Although these previous reports may be attributable to low contraction volume [i.e., 18-30 repetitions/training session (69)] or a suboptimal quantity of additional protein [i.e., $10 g/day (70)], our similar findings arose despite our unilateral training model using 150 repetitions per session and our intervention providing 38 g of additional daily protein. ...
... Yet, evidence exists that protein-and/or amino acid-based supplements do not augment increases in whole muscle volume or CSA during RET using single-limb models (69) or isolated muscle groups (70). Although these previous reports may be attributable to low contraction volume [i.e., 18-30 repetitions/training session (69)] or a suboptimal quantity of additional protein [i.e., $10 g/day (70)], our similar findings arose despite our unilateral training model using 150 repetitions per session and our intervention providing 38 g of additional daily protein. Moreover, the absence of a difference in posttraining muscle volume and CSA remains consistent with our posttraining measures of function, peak torques, and MyoPS. ...
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Factors underpinning the time-course of resistance-type exercise training (RET) adaptations are not fully understood. The present study hypothesized that consuming a twice-daily protein-polyphenol beverage (PPB; n=15; age, 24 ± 1 years; BMI, 22.3 ± 0.7 kg·m ⁻² ) previously shown to accelerate recovery from muscle damage and increase daily myofibrillar protein synthesis (MyoPS) rates would accelerate early (10 sessions) improvements in muscle function and potentiate quadriceps volume and muscle fiber cross-sectional area (fCSA) following 30 unilateral RET sessions in healthy, recreationally active, adults. Versus isocaloric placebo (PLA; n=14; age, 25 ± 2 years; BMI, 23.9 ± 1.0 kg·m ⁻² ), PPB increased 48 h MyoPS rates after the first RET session measured using deuterated water (2.01 ± 0.15 %·d ⁻¹ vs. 1.51 ± 0.16 , respectively; P<0.05). Additionally, PPB increased isokinetic muscle function over 10 sessions of training relative to the untrained control leg (%U) from 99.9 ± 1.8 pre-training to 107.2 ± 2.4 %U at session 10 (versus 102.6 ± 3.9 to 100.8 ± 2.4 %U at session 10 in PLA; interaction P<0.05). Pre-to-post-training, PPB increased type II fCSA (PLA: 120.8 ± 8.2 to 109.5 ± 8.6 %U; PPB: 92.8 ± 6.2 to 108.4 ± 9.7 %U; interaction P<0.05), but the gain in quadriceps muscle volume was similar between groups. Similarly, PPB did not further increase peak isometric torque, muscle function or MyoPS measured post-training. This suggests that although PPB increases MyoPS and early adaptation, it may not influence longer term adaptations to unilateral RET.
... Protein supplements, essential amino acids, and leucine increase MPS rates while decreasing muscle protein degradation and possibly enhancing recovery after exercise [Jäger et al., 2017], although whether protein supplementation promotes hypertrophy and increases muscle strength gain remains unclear [Erskine et al., 2012] because studies have limitations, including small sample size, inaccurate measures of muscle size and strength, lack of control over previous training programs or regular protein intake, and issues with the study period or number of study variables [Nogiec & Ka- sif, 2013]. Furthermore, the individual response to strength training may vary between subjects [Erskine et al., 2010], and this effect may be reduced by the increased experimental control of physical activity and protein intake [Erskine et al., 2012]. ...
... Protein supplements, essential amino acids, and leucine increase MPS rates while decreasing muscle protein degradation and possibly enhancing recovery after exercise [Jäger et al., 2017], although whether protein supplementation promotes hypertrophy and increases muscle strength gain remains unclear [Erskine et al., 2012] because studies have limitations, including small sample size, inaccurate measures of muscle size and strength, lack of control over previous training programs or regular protein intake, and issues with the study period or number of study variables [Nogiec & Ka- sif, 2013]. Furthermore, the individual response to strength training may vary between subjects [Erskine et al., 2010], and this effect may be reduced by the increased experimental control of physical activity and protein intake [Erskine et al., 2012]. The lack of studies measuring MPS also prevents the establishment of an RDA of protein during the muscle recovery period [Areta et al., 2013]. ...
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The inactivation and sublethal injury of two strains of Listeria innocua (one collection strain and one wild strain isolated from beetroot juice) suspended in beetroot juice and in model solutions, after high hydrostatic pressure (HHP) were investigated. Changes within the population assessed by plating count methods of both L. innocua strains suspended in a buffer pH 4.0 were more noticeable than in the natural beetroot juice environment. In beetroot juice the lethal effect was reported after 1 min of pressure treatment at 400 MPa for the collection strain. In the case of the wild type strain, exposure to the maximal parameters of the compression process (400 MPa, 10 min) decreased the population number below 1 log (CFU/mL) but did not cause complete injury. The collection strain of L. innocua was easier to inactivate in beetroot juice than the strain isolated from this environment. The maximum level of sublethal injury was observed when the cells were suspended in a buffer pH 7.0. Structural damage in cell membranes after HHP processing was observed using a transmission electron microscope (TEM). © Copyright by Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences
... Protein supplements, essential amino acids, and leucine increase MPS rates while decreasing muscle protein degradation and possibly enhancing recovery after exercise [Jäger et al., 2017], although whether protein supplementation promotes hypertrophy and increases muscle strength gain remains unclear [Erskine et al., 2012] because studies have limitations, including small sample size, inaccurate measures of muscle size and strength, lack of control over previous training programs or regular protein intake, and issues with the study period or number of study variables [Nogiec & Kasif, 2013]. Furthermore, the individual response to strength training may vary between subjects [Erskine et al., 2010], and this effect may be reduced by the increased experimental control of physical activity and protein intake [Erskine et al., 2012]. ...
... Protein supplements, essential amino acids, and leucine increase MPS rates while decreasing muscle protein degradation and possibly enhancing recovery after exercise [Jäger et al., 2017], although whether protein supplementation promotes hypertrophy and increases muscle strength gain remains unclear [Erskine et al., 2012] because studies have limitations, including small sample size, inaccurate measures of muscle size and strength, lack of control over previous training programs or regular protein intake, and issues with the study period or number of study variables [Nogiec & Kasif, 2013]. Furthermore, the individual response to strength training may vary between subjects [Erskine et al., 2010], and this effect may be reduced by the increased experimental control of physical activity and protein intake [Erskine et al., 2012]. The lack of studies measuring MPS also prevents the establishment of an RDA of protein during the muscle recovery period [Areta et al., 2013]. ...
Article
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Whey protein (WP) is a highly nutritious, commercially available alternative food source that is used primarily as a food supplement by athletes and physically active individuals to provide them with essential amino acids and bioactive peptides, and additional benefits have been attributed to WP consumption. In this context, the objective of this review was to explore current evidence regarding the consumption of different WP supplements in sports nutrition to elucidate their efficiency in affecting muscle hypertrophy, physical performance, response to muscle injury, weight loss, and body composition changes. Furthermore, these effects were assessed by comparing whey protein hydrolysate (WPH), whey protein concentrate (WPC), and whey protein isolate (WPI) supplementation. Supplementation with WPI or WPC was related to increased muscle protein synthesis (MPS), and WPH caused muscle hypertrophy and improved physical performance. Compared to WPC and WPI, WPH improved peak torque associated with strength training without reducing the creatine kinase (CK) and tumor necrosis factor alpha (TNF-α) levels in this type of physical activity, and the decreases in CK and lactate dehydrogenase (LDH) associated with aerobic exercise were significant. Supplementation with WPC resulted in weight loss, satiety, and improved body composition, without compromising whole-body lean mass loss. WPH was more effective than WPC and WPI regarding improved peak torque and muscle hypertrophy associated with strength training, and WPH reduced muscle damage associated with aerobic exercise via decreased CK levels. © Copyright by Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences.
... Therefore, the amplification of the anabolic environment within the muscle seen with the combination of both amino acid/protein ingestion and resistance exercise ( Biolo et al., 1997;Tipton et al., 1999) suggests that RT with protein supplementation should confer greater gains in skeletal muscle size and strength than RT alone. However, the evidence for protein supplementation enhancing the increases in muscle size and strength following longer term RT programs in young ( Erskine, Fletcher, Hanson, Folland, 2012;Hartman et al., 2007) and older ( Candow et al., 2008;Verdijk et al., 2009b) individuals is equivocal. The controversy surrounding the longer-term RT studies could be due to methodological differences/limitations between studies. ...
... Different measures of muscle hypertrophy may also compound this discrepancy. For example, some studies have determined muscle thickness using ultrasonography ( Candow et al., 2008;Vieillevoye, Poortmans, Duchateau, Carpentier, 2010) or whole body fat-free mass assessed via dual-energy X-ray absorptiometry ( Hartman et al., 2007), while others have used magnetic resonance imaging to provide a more precise assessment of muscle size, but still found no effect of protein supplementation on muscle hypertrophy following RT ( Coburn et al., 2006;Erskine et al., 2012;Holm et al., 2008;Hulmi et al., 2009). There are, however, circumstances where protein supplementation may have a beneficial effect on muscle hypertrophy and strength gains. ...
... For example, one study examining the correlation between exercise-induced changes in muscle size and strength [1] was actually designed to compare different contraction types [15]. Another similar study assessing this correlation [2] was originally designed to assess the importance of whey protein supplementation combined with resistance training [16]. Therefore, these studies testing correlations between exercise-induced changes in muscle size and strength [1,2] were simply an afterthought using data that were already collected from studies not designed to answer this question [15,16]. ...
... Another similar study assessing this correlation [2] was originally designed to assess the importance of whey protein supplementation combined with resistance training [16]. Therefore, these studies testing correlations between exercise-induced changes in muscle size and strength [1,2] were simply an afterthought using data that were already collected from studies not designed to answer this question [15,16]. If one considers the previous paper from our laboratory, a within-subject correlational analysis performed on the group performing traditional sets of resistance exercise would yield a large correlation (b = 51.9, ...
Article
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It is well known that resistance exercise results in increased muscle strength, but the cause of the improvement is not well understood. It is generally thought that initial increases in strength are caused by neurological factors, before being predominantly driven by increases in muscle size. Despite this hypothesis, there is currently no direct evidence that training-induced increases in muscle size contribute to training-induced increases in muscle strength. The evidence used to support this hypothesis is exclusively correlational analyses and these are often an afterthought using data collected to answer a different question of interest. Not only do these studies not infer causality, but they have inherent limitations associated with measurement error and limited inter-individual variability. To answer the question as to whether training-induced increases in muscle size lead to training-induced increases in strength requires a study designed to produce differential effects on muscle size based on group membership (i.e., one group increases muscle size and one does not) and observe how this impacts muscle strength. We have performed studies in our laboratory in which muscle strength increases similarly independent of whether muscle growth is or is not present, illustrating that the increases in muscle strength are not likely driven by increases in muscle size. The hypothesis that training-induced increases in muscle size contribute to training-induced increases in muscle strength requires more appropriately designed studies, and until such studies are completed, this statement should not be made as there are no data to support this hypothesis.
... Given these findings, it is no surprise that only one study on protein supplementation showed an enhancement of strength, although myofiber CSA was not different with protein supplementation (9). The remainder of the studies demonstrate identical increases in strength with protein supplementation compared with carbohydrate placebo (2,6,10,12,13,19,(21)(22)(23)(31)(32)(33), similar to our observations, in part. Indeed, in examination of the literature, we have previously highlighted that~40 to 500 participants (depending on the clinical trial) would be needed to find a statistical effect of protein supplementation on myofiber CSA (39). ...
... 10). There was no significant effect in the change of PRO over MDP in all fibers pooled (P = 0.746), MHC I (P = 0.880), or MHC II (P = 0.379) myofibers.Correlational analysis. ...
Article
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Purpose: To determine the efficacy of protein supplementation (and the type of protein) during traditional resistance training on myofiber cross-sectional-area, satellite cell content and myonuclear addition. Methods: Healthy young men participated in supervised whole body progressive resistance training 3d/wk for 12 weeks. Participants were randomized to one of three groups ingesting a daily 22g macronutrient dose of soy-dairy protein blend (PB, N=22), whey protein isolate (WP, N=15) or an isocaloric maltodextrin placebo (MDP, N=17). Lean mass, vastus lateralis myofiber-type-specific cross-sectional-area, satellite cell content and myonuclear addition were assessed pre and post resistance training. Results: PB and the pooled protein treatments (PB+WP=PRO) exhibited a greater whole body lean mass %change compared to MDP (p=0.057 for PB) and (P=0.050 for PRO), respectively. All treatments demonstrated similar leg muscle hypertrophy and vastus lateralis myofiber-type-specific cross-sectional-area (P<0.05). Increases in myosin heavy chain I and II myofiber satellite cell content and myonuclei content were also detected following exercise training (P<0.05). Conclusion: Protein supplementation during resistance training has a modest effect on whole body lean mass as compared to exercise training without protein supplementation and there was no effect on any outcome between protein supplement types (Blend vs Whey). However, protein supplementation did not enhance resistance exercise-induced increases in myofiber hypertrophy, satellite cell content or myonuclear addition in young healthy men. We propose that as long as protein intake is adequate during muscle overload the adaptations in muscle growth and function will not be influenced by protein supplementation.
... Creatine supplementation has been universally accepted to enhance performance with multiple short-term work bouts, improve recovery and long-term adaptation to training (Vandenberghe,et al. [59,60,43,65,49] The 'muscle full theory' indicates that there is a finite level of protein that is required to elicit MPS, and that leucine is the prominent AA that triggers the response. However, it is interesting to note that only two studies used >40g of protein per-day. ...
Article
The generally accepted modus operandi for stimulating muscle strength adaptation is high-magnitude resistance training which is facilitated by protein and with the addition of augmented exogenous protein intake this outcome is potentiated. The aforementioned protocol has been observed in many studies over time periods (up to 12 weeks) however; very few longitudinal studies have examined the temporal dynamics of muscle strength adaptation throughout the entire period. These data could prove vital in constructing training and rehabilitation programs for both athletes and non-athletes. The objective of this review was to establish whether high-magnitude training with the addition of nutritional supplementation results in enhanced temporal adaptation dynamics and at what point these adaptations are significant. The searches were achieved utilising PubMed, Google Scholar, Medline, ScienceDirect, Wiley Online and SPORTS. Discuss databases. Of the inclusion criteria a total 362 participants from 11 studies were included in the review and concluded that the mean time point for muscle adaption was ~6.7-weeks. With the results indicating that adaptation to high-magnitude resistance training occurred at each time-point (up to and including 10, 12 and 24-weeks) for the training only groups of each study (placebo), this was equivalent to the supplement intervention group. While, both groups evidenced adaptation only ~27% showed significance between the placebo and intervention groups. These findings are contrary to the known paradigm that supplements enhance muscle protein synthesis thus recovery and subsequent adaptation. However, there are considerations regarding the protocols used in the studies reviewed including dietary standardization that may have impacted the results. Notwithstanding, the results do indicate that supplements may enhance the effects of high-magnitude training and that this could have an impact on temporal adaptation dynamics leading to augmented muscle strength increases at an earlier stage in a training cycle than the current paradigm dictates. This could pose problems for other associated tissues such as tendinous tissue, as a differential in adaptation between muscles and tendons could cause non-uniformities within the muscle-tendon-unit and potentially lead to tendinopathy. Consequently, it may be prudent to investigate the temporal dynamics of muscle and tendon adaptation with a supplement intervention.
... However, the literature is contradictory in relation to the biological effects of these ergogenic resources on physical performance, with some studies reporting performance improvements in users of these substances (Coombes and Hamilton, 2000), while others have failed to demonstrate any benefit (Balsom et al., 1993;Jentjens et al., 2001;Erskine et al., 2012). Therefore, given the growing demand for these products, the supplement industry has been looking for new compounds, particularly those that can consistently be shown to increase athletic performance. ...
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Background The Erythroxylaceae family is known worldwide for its species that contain compounds with a marked positive effect on physical performance, such as ephedrine and coca. E. mucronatum is a species of this family found in several parts of South America, mainly in the northern and northeastern regions of Brazil, used by natives to improve strength and physical performance. Purpose We set out to investigate, for the first time, in a series of experiments whether the ethanolic extract of E. mucronatum (EEM) had any effect on performance and strength of rats undergoing resistance training. Methods We promoted a supplementation with EEM and searched it increased strength, muscular endurance and reduced body fat in the rodents. Results we registered a significant reduction in lipid peroxidation and an increase in superoxide dismutase in the exercised muscles. EEM supplementation did not alter the effect of exercise on blood pressure and heart rate. Additionally, we noticed a significant reduction in two markers of muscle damage, CK and LDH, but no alterations were observed in the levels of ALT and AST. Conclusions The results showed that EEM was able to improve the physical performance of the rats without any remarkable adverse effects on hemodynamic variables, so it should be further investigated to examine whether it also has potential as an effective dietary supplement in humans to improve performance in resistance exercise cycles.
... Collectively, these observations suggest that factors related to fatigue development can constitute drivers of myofibrillar protein accretion. In support of this notion, we previously found that 6 wk of arm flexor LLRE and BFRRE (both conducted to volitional failure at 40% of dynamic strength) produced almost identical muscle growth (18), with increases approaching those reported after much longer periods of arm flexor HLRE (19). It is noteworthy that for the BFRRE arm, this was accomplished with only approximately one third of the total work performed with the LLRE arm (18). ...
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Low-load blood flow restricted resistance exercise (BFRRE) can stimulate whole-muscle growth and improve muscle function. However, limited knowledge exists on the effects at the myocellular level. We hypothesize that BFRRE possesses the ability to produce concurrent skeletal muscle myofibrillar, mitochondrial, and microvascular adaptations, thus offering an alternative strategy to counteract decay in skeletal muscle health and function in clinical populations.
... Taking each of these variables into consideration, the effects of supplemental protein consumption has on maximal strength enhancement are varied, with a majority of the investigations reporting no benefit [15][16][17][18][19][20][21][22][23][24][25] and a few reporting improvements in maximal strength [26][27][28][29]. With limited exceptions [16,18,23,27], most of the studies utilized young, healthy, untrained males as participants. ...
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Position statement The International Society of Sports Nutrition (ISSN) provides an objective and critical review related to the intake of protein for healthy, exercising individuals. Based on the current available literature, the position of the Society is as follows: 1) An acute exercise stimulus, particularly resistance exercise, and protein ingestion both stimulate muscle protein synthesis (MPS) and are synergistic when protein consumption occurs before or after resistance exercise. 2) For building muscle mass and for maintaining muscle mass through a positive muscle protein balance, an overall daily protein intake in the range of 1.4–2.0 g protein/kg body weight/day (g/kg/d) is sufficient for most exercising individuals, a value that falls in line within the Acceptable Macronutrient Distribution Range published by the Institute of Medicine for protein. 3) There is novel evidence that suggests higher protein intakes (>3.0 g/kg/d) may have positive effects on body composition in resistance-trained individuals (i.e., promote loss of fat mass). 4) Recommendations regarding the optimal protein intake per serving for athletes to maximize MPS are mixed and are dependent upon age and recent resistance exercise stimuli. General recommendations are 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g. 5) Acute protein doses should strive to contain 700–3000 mg of leucine and/or a higher relative leucine content, in addition to a balanced array of the essential amino acids (EAAs). 6) These protein doses should ideally be evenly distributed, every 3–4 h, across the day. 7) The optimal time period during which to ingest protein is likely a matter of individual tolerance, since benefits are derived from pre- or post-workout ingestion; however, the anabolic effect of exercise is long-lasting (at least 24 h), but likely diminishes with increasing time post-exercise. 8) While it is possible for physically active individuals to obtain their daily protein requirements through the consumption of whole foods, supplementation is a practical way of ensuring intake of adequate protein quality and quantity, while minimizing caloric intake, particularly for athletes who typically complete high volumes of training. 9) Rapidly digested proteins that contain high proportions of essential amino acids (EAAs) and adequate leucine, are most effective in stimulating MPS. 10) Different types and quality of protein can affect amino acid bioavailability following protein supplementation. 11) Athletes should consider focusing on whole food sources of protein that contain all of the EAAs (i.e., it is the EAAs that are required to stimulate MPS). 12) Endurance athletes should focus on achieving adequate carbohydrate intake to promote optimal performance; the addition of protein may help to offset muscle damage and promote recovery. 13) Pre-sleep casein protein intake (30–40 g) provides increases in overnight MPS and metabolic rate without influencing lipolysis.
... Although the group mean for the change in lean mass in our WP group, ;2.3 kg, is almost identical to the amount shown via meta-analysis of RET and WP supplementation (37), our WP treatment did not differ significantly from placebo (0.46 kg; 95% CI: 20.63, 1.55 kg; P = 0.57), which, in itself, is not an uncommon finding (21,38,39). These findings are not the result of low compliance to the WP treatment; correlation analysis between treatment compliance and primary outcomes in this group indicated no relation (see Results). ...
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Background: To our knowledge the efficacy of soy-dairy protein blend (PB) supplementation with resistance exercise training (RET) has not been evaluated in a longitudinal study. Objective: Our aim was to determine the effect of PB supplementation during RET on muscle adaptation. Methods: In this double-blind randomized clinical trial, healthy young men [18-30 y; BMI (in kg/m(2)): 25 ± 0.5] participated in supervised whole-body RET at 60-80% 1-repetition maximum (1-RM) for 3 d/wk for 12 wk with random assignment to daily receive 22 g PB (n = 23), whey protein (WP) isolate (n = 22), or an isocaloric maltodextrin (carbohydrate) placebo [(MDP) n = 23]. Serum testosterone, muscle strength, thigh muscle thickness (MT), myofiber cross-sectional area (mCSA), and lean body mass (LBM) were assessed before and after 6 and 12 wk of RET. Results: All treatments increased LBM (P < 0.001). ANCOVA did not identify an overall treatment effect at 12 wk (P = 0.11). There tended to be a greater change in LBM from baseline to 12 wk in the PB group than in the MDP group (0.92 kg; 95% CI: -0.12, 1.95 kg; P = 0.09); however, changes in the WP and MDP groups did not differ. Pooling data from combined PB and WP treatments showed a trend for greater change in LBM from baseline to 12 wk compared with MDP treatment (0.69 kg; 95% CI: -0.08, 1.46 kg; P = 0.08). Muscle strength, mCSA, and MT increased (P < 0.05) similarly for all treatments and were not different (P > 0.10) between treatments. Testosterone was not altered. Conclusions: PB supplementation during 3 mo of RET tended to slightly enhance gains in whole-body and arm LBM, but not leg muscle mass, compared with RET without protein supplementation. Although protein supplementation minimally enhanced gains in LBM of healthy young men, there was no enhancement of gains in strength. This trial was registered at clinicaltrials.gov as NCT01749189.
... Studies using MRI are uncommon in nutritional intervention studies due to the cost and availability to researchers. Four notable studies have examined body composition changes using an MRI device, Coburn et al. (2006) and Erskine (2012) both found no significant changes with training and supplementation whereas Esmark et al. (2001) and Humli et al. (2009) found statistical alterations with supplementation. The MRI may provide excellent data for researchers regarding changes in muscle over the course of a training study but due to the cost and lack of availability this measurement tool may be unsuitable for all researchers to use in nutritional intervention studies. ...
Thesis
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The purposes of this dissertation were to examine the effect of a protein and carbohydrate recovery beverage versus a placebo on weightlifting performance, its effect on muscle morphological changes and specific muscle protein accretion. The following are major finding from the dissertation: 1) Protein and carbohydrate recovery supplementation does not appear to have influence on performance measure in trained weightlifters. This finding may be associated with the short-term nature of this study and the trained population used. 2) Compared with placebo, a protein and carbohydrate beverage provided greater benefits on cross sectional area of type I and type II muscle fibers. Additionally, the block periodization protocol incorporating phase potentiation improved cross sectional area of both groups compared to baseline. 3) Finally, protein and carbohydrate supplementation provided greater benefits on total mTOR and myosin heavy chains 6 & 7. These findings indicate that a protein and carbohydrate beverage provide greater benefits compared with a placebo on cellular signaling, myosin heavy gene expression and muscle fiber increases in trained weightlifters. Improved cross sectional area and increased myosin heavy chains indicate positive adaptations to resistance training combined with supplementation and may indicate improved skeletal muscle qualities necessary for increased power output. The mTOR pathway is the master regulator of cellular growth and increases in total mTOR indicate a greater proclivity for cellular growth and greater activity resulting from resistance training may increase synthesis and accretion of muscle contractile proteins. This dissertation highlighted several benefits of recovery supplementation, however further longitudinal studies utilizing block periodization and well-trained athletes are necessary to fully elucidate benefits for strength and power athletes.
... Although a number of studies have shown no effect of added protein/AA supplementation (169,(178)(179)(180)(181)(182)(183)(184)(185)(186)(187)(188)(189)(190)(191), other studies with a high-quality protein supplement during RET occasionally showed improved lean mass and, more infrequently, strength compared with no protein supplementation (182,(192)(193)(194)(195)(196)(197)(198). The reasons for the confusion in the literature have been suggested to stem from differences in study design, choice and measurement of outcomes, target populations, exercise protocols and timing, and the type and amount of the protein supplement or placebo given. ...
Article
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The goal of this critical review is to comprehensively assess the evidence for the molecular, physiologic, and phenotypic skeletal muscle responses to resistance exercise (RE) combined with the nutritional intervention of protein and/or amino acid (AA) ingestion in young adults. We gathered the literature regarding the translational response in human skeletal muscle to acute exposure to RE and protein/AA supplements and the literature describing the phenotypic skeletal muscle adaptation to RE and nutritional interventions. Supplementation of protein/AAs with RE exhibited clear protein dose-dependent effects on translational regulation (protein synthesis) through mammalian target of rapamycin complex 1 (mTORC1) signaling, which was most apparent through increases in p70 ribosomal protein S6 kinase 1 (S6K1) phosphorylation, compared with postexercise recovery in the fasted or carbohydrate-fed state. These acute findings were critically tested via long-term exposure to RE training (RET) and protein/AA supplementation, and it was determined that a diminishing protein/AA supplement effect occurs over a prolonged exposure stimulus after exercise training. Furthermore, we found that protein/AA supplements, combined with RET, produced a positive, albeit minor, effect on the promotion of lean mass growth (when assessed in >20 participants/treatment); a negligible effect on muscle mass; and a negligible to no additional effect on strength. A potential concern we discovered was that the majority of the exercise training studies were underpowered in their ability to discern effects of protein/AA supplementation. Regardless, even when using optimal methodology and large sample sizes, it is clear that the effect size for protein/AA supplementation is low and likely limited to a subset of individuals because the individual variability is high. With regard to nutritional intakes, total protein intake per day, rather than protein timing or quality, appears to be more of a factor on this effect during long-term exercise interventions. There were no differences in strength or mass/muscle mass on RET outcomes between protein types when a leucine threshold (>2 g/dose) was reached. Future research with larger sample sizes and more homogeneity in design is necessary to understand the underlying adaptations and to better evaluate the individual variability in the muscle-adaptive response to protein/AA supplementation during RET.
... The reason for a lack of change may be due to small differences in muscle size and also the fact that increased muscle strength during the first months of RT is achieved through not just increased muscle size, but especially through neural adaptations [23] that may be less responsive to nutrition. This may have occurred, even though we had a 4-week preparatory RT period to accommodate the influence of neural adaptations on muscle strength as has been suggested [9,36]. Thus, neural and possibly other confounding factors and high individual variation on muscle strength adaptation [37] may be the reason why the effects of postexercise nutrient supplementation have been less consistent for muscle strength adaptation than for muscle hypertrophy [9]. ...
Article
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Background Nutrition intake in the context of a resistance training (RT) bout may affect body composition and muscle strength. However, the individual and combined effects of whey protein and carbohydrates on long-term resistance training adaptations are poorly understood. Methods A four-week preparatory RT period was conducted in previously untrained males to standardize the training background of the subjects. Thereafter, the subjects were randomized into three groups: 30 g of whey proteins (n = 22), isocaloric carbohydrates (maltodextrin, n = 21), or protein + carbohydrates (n = 25). Within these groups, the subjects were further randomized into two whole-body 12-week RT regimens aiming either for muscle hypertrophy and maximal strength or muscle strength, hypertrophy and power. The post-exercise drink was always ingested immediately after the exercise bout, 2–3 times per week depending on the training period. Body composition (by DXA), quadriceps femoris muscle cross-sectional area (by panoramic ultrasound), maximal strength (by dynamic and isometric leg press) and serum lipids as basic markers of cardiovascular health, were analysed before and after the intervention. Results Twelve-week RT led to increased fat-free mass, muscle size and strength independent of post-exercise nutrient intake (P < 0.05). However, the whey protein group reduced more total and abdominal area fat when compared to the carbohydrate group independent of the type of RT (P < 0.05). Thus, a larger relative increase (per kg bodyweight) in fat-free mass was observed in the protein vs. carbohydrate group (P < 0.05) without significant differences to the combined group. No systematic effects of the interventions were found for serum lipids. The RT type did not have an effect on the adaptations in response to different supplementation paradigms. Conclusions Post-exercise supplementation with whey proteins when compared to carbohydrates or combination of proteins and carbohydrates did not have a major effect on muscle size or strength when ingested two to three times a week. However, whey proteins may increase abdominal fat loss and relative fat-free mass adaptations in response to resistance training when compared to fast-acting carbohydrates.
... The data from the present study support such findings, as we demonstrate that provided performed to volitional fatigue, both BFR and low-load TRT produce substantial and equal size muscle growth. Furthermore, with only 6 weeks of training to fatigue, the magnitude of muscle hypertrophy are comparable with previously reported magnitudes of hypertrophy achieved with upper body heavy load resistance training (approximately 15%), typically requiring 10-12 weeks of training (Erskine et al., 2012). ...
Article
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This study investigated the hypertrophic potential of load-matched blood-flow restricted resistance training (BFR) vs free-flow traditional resistance training (low-load TRT) performed to fatigue. Ten healthy young subjects performed unilateral BFR and contralateral low-load TRT elbow flexor dumbbell curl with 40% of one repetition maximum until volitional concentric failure 3 days per week for 6 weeks. Prior to and at 3 (post-3) and 10 (post-10) days post-training, magnetic resonance imaging (MRI) was used to estimate elbow flexor muscle volume and muscle water content accumulation through training. Acute changes in muscle thickness following an early vs a late exercise bout were measured with ultrasound to determine muscle swelling during the immediate 0-48 h post-exercise. Total work was threefold lower for BFR compared with low-load TRT (P < 0.001). Both BRF and low-load TRT increased muscle volume by approximately 12% at post-3 and post-10 (P < 0.01) with no changes in MRI-determined water content. Training increased muscle thickness during the immediate 48 h post-exercise (P < 0.001) and to greater extent with BRF (P < 0.05) in the early training phase. In conclusion, BFR and low-load TRT, when performed to fatigue, produce equal muscle hypertrophy, which may partly rely on transient exercise-induced increases in muscle water content. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
... The authors attributed this lack of effect to an adequate total daily protein intake. Recently, a 12-week trial by Erksine et al. [89] reported a lack of effect of 20 g protein taken pre-and post-exercise compared to placebo. ...
Article
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The popularity of natural bodybuilding is increasing; however, evidence-based recommendations for it are lacking. This paper reviewed the scientific literature relevant to competition preparation on nutrition and supplementation, resulting in the following recommendations. Caloric intake should be set at a level that results in bodyweight losses of approximately 0.5 to 1%/wk to maximize muscle retention. Within this caloric intake, most but not all bodybuilders will respond best to consuming 2.3-3.1 g/kg of lean body mass per day of protein, 15-30% of calories from fat, and the reminder of calories from carbohydrate. Eating three to six meals per day with a meal containing 0.4-0.5 g/kg bodyweight of protein prior and subsequent to resistance training likely maximizes any theoretical benefits of nutrient timing and frequency. However, alterations in nutrient timing and frequency appear to have little effect on fat loss or lean mass retention. Among popular supplements, creatine monohydrate, caffeine and beta-alanine appear to have beneficial effects relevant to contest preparation, however others do not or warrant further study. The practice of dehydration and electrolyte manipulation in the final days and hours prior to competition can be dangerous, and may not improve appearance. Increasing carbohydrate intake at the end of preparation has a theoretical rationale to improve appearance, however it is understudied. Thus, if carbohydrate loading is pursued it should be practiced prior to competition and its benefit assessed individually. Finally, competitors should be aware of the increased risk of developing eating and body image disorders in aesthetic sport and therefore should have access to the appropriate mental health professionals.
... In agreement with our findings, whey protein has shown no effect on strength gains after 12 weeks of high-intensity resistance exercise training in healthy young men. 40 We found that the increases in muscle strength after 4 weeks of CET did not influence BP and arterial function. Our CET included endurance training, a modality that has consistently shown reductions in BP and PWV. ...
Article
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Obesity and reduced muscle strength are associated with increased blood pressure (BP). We examined the impact of milk proteins and combined exercise training (CET) on BP, arterial function, and muscle strength (one-repetition maximum (1-RM)). Thirty-three obese sedentary women (age = 30±1 years; body mass index = 35.2±0.9kg/m(2); systolic BP (SBP) = 129±2mm Hg) were randomized to control carbohydrate (n = 11), whey (n = 11), and casein (n = 11) supplementation for 4 weeks. All participants performed moderate-intensity CET 3 days/week. Brachial and aortic SBP, augmentation index adjusted for 75 beats/minute (AIx@75), arterial stiffness (brachial-ankle pulse wave velocity (baPWV)), and 1-RM were measured before and after the interventions. There were significant (P < 0.05) time-by-group interactions for brachial SBP (bSBP), aortic SBP (aSBP), AIx@75, and baPWV. Whey and casein supplementation significantly (P < 0.05) decreased bSBP (approximately 5mm Hg for both), aSBP (approximately 7mm Hg and approximately 6mm Hg, respectively), AIx@75 (approximately 9.2% and approximately 8.1%, respectively) and baPWV (approximately 57cm/s and approximately 53cm/s, respectively) compared with no changes in the control group. Upper- (approximately 22.2%) and lower-body 1-RM (approximately 44.0%) increased similarly in all groups. Changes in arterial function and 1-RM were not correlated. Milk protein supplementation with CET reduced SBP, wave reflection, and arterial stiffness in young obese women with prehypertension and hypertension. Because CET did not affect arterial function, milk proteins may have an antihypertensive effect by improving arterial function, as shown by reduced AIx@75 and baPWV. Muscle strength improvements after CET did not affect BP and arterial function. ClinicalTrial.gov Registration NCT01830946.
... Participants were randomly assigned to receive protein or placebo before and after each exercise session. 113 However, in neither the Hoffman et al 112 nor Erskine et al 113 studies was nutrient consumption controlled after the exercise training sessions. In summary, most investigations demonstrate that supplementation that ensures appropriate nutrient levels within the first 45 minutes postexercise results in the greatest adaptive response to endurance as well as resistance exercise training. ...
Article
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As the incidence rate of lifestyle-related chronic conditions such as cardiovascular disease, obesity, and type 2 diabetes continues to increase, the importance of regular exercise and a healthy diet for improving or maintaining good health is critical. Exercise training is known to improve fitness and many health risk factors, as well as to improve the performance of competitive athletes. It has become increasingly clear, however, that nutrient intake before, during, and after exercise sessions has a powerful influence on the adaptive response to the exercise stimuli. In this review, the science behind nutrient timing will be discussed as it relates to exercise performance, recovery, and training adaptation. Evidence will be provided that validates intake of appropriate nutrients before, during, and immediately after exercise not only to improve exercise performance but also to maximize the training response. Ultimately, the combined response to exercise and proper nutrient intake leads to not only better performance in athletes but also greater health benefits for all exercisers.
... In contrast, as the number of weekly training sessions increases or the duration of the training program extends beyond 8 wk, some positive effects of supplementation on changes in body composition and muscle strength have been reported in naive participants (98)(99)(100)(101)(102)(103), a view that is consistent with findings from a recent meta-analysis (104). The exception was 1 study that reported no effect of protein supplementation after 12 wk of training 3 times weekly (105). Even with experienced resistance-trained participants, protein supplements had little or no effect on measures of strength and body composition when programs lasted #4 wk (106)(107)(108), whereas positive effects of protein supplements were observed on changes in lean mass and/or muscle strength when training was longer than 8 wk (109)(110)(111)(112)(113)(114). ...
Article
Protein supplement use is common among athletes, active adults, and military personnel. This review provides a summary of the evidence base that either supports or refutes the ergogenic effects associated with different mechanisms that have been proposed to support protein supplementation. It was clear that if carbohydrate delivery was optimal either during or after an acute bout of exercise that additional protein will not increase exercise capacity. Evidence was also weak to substantiate use of protein supplements to slow the increase in brain serotonin and onset of central fatigue. It was also evident that additional research is warranted to test whether the benefits of protein supplements for enhancing recovery of fluid balance after exercise will affect subsequent work in the heat. In contrast, with repeated exercise, use of protein supplementation was associated with reductions in muscle soreness and often a faster recovery of muscle function due to reductions in protein degradation. There was also good supportive evidence for long-term benefits of protein supplementation for gains in muscle mass and strength through accelerated rates of protein synthesis, as long as the training stimulus was of sufficient intensity, frequency, and duration. However, studies have not examined the impact of protein supplements under the combined stress of a military environment that includes repeated bouts of exercise with little opportunity for feeding and recovery, lack of sleep, and exposure to extreme environments. Both additional laboratory and field research is warranted to help provide evidence-based guidance for the choice of protein supplements to enhance soldier performance.
... Modified from [55] with permiesion. ' muscle hypertrophy following RT [92,99,101)02]. There are, however, circumstances where protein supplementation may have a beneficial effect on muscle hypertrophy and strength gains. ...
Chapter
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Skeletal muscle is able to grow, or hypertrophy, in response to a variety of anabolic stimuli, which include resistance exercise, amino acid ingestion, and an increase in IGF-I expression. All these stimuli are able to activate the mTORC1 signaling pathway, which stimulates MPS and inhibits MPD. When the rate of MPS exceeds MPD, there is a positive net protein balance (NPB) and an accretion of contractile material occurs, leading to muscle hypertrophy and an increase in strength. Inducing muscle hypertrophy can have beneficial effects on individuals suffering from cachectic conditions, such as cancer, AIDS, and sarcopenia, where muscle atrophy can have devastating effects on an individual’s quality of life. Muscle atrophy occurs when there is a negative NPB, i.e., when the rate of MPD is greater than that of MPS. There are a number of stimuli that have been associated with muscle atrophy, including chronically elevated levels of proinflammatory cytokines (e.g., IL-1, IL-6 and TNF-α), a reduction in IGF-I and increased expression of myostatin. Furthermore, strenuous unaccustomed exercise cancause mechanical damage to the muscle, which activates MPD systems, including calpain, inflammation and the ubiquitin�proteasome protein degradation pathway. Damaged proteins within the muscle fiber are broken down, resulting in an increased intracellular amino acid concentration, which in turn activates mTORC1 and increases MPS, thus helping to repair the muscle. Elevated local IGF-I and MRF expression facilitates the repair process by activating satellite cells and enabling fusion with existing fibers. Many of the molecular signaling pathways associated with muscle hypertrophy, atrophy and repair have been identified. However, there is still much to be learned about these pathways, and understanding them may help us to prevent or reverse muscle atrophy associated with a host of muscle wasting conditions.
... This additive effect has also been shown during longitudinal training studies [124][125][126][127]. Although long term training adaptations are mainly due to accumulation of the individual responses to each exercise session [128,129], other longitudinal training studies have shown that protein supplementation together with resistance exercise does not result in any extra gains in muscle mass [130][131][132][133][134]. Therefore, clear conclusions from single studies should be interpreted with caution. ...
Article
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Ingestion of protein is crucial for maintenance of a variety of body functions and within the scope of this review we will specifically focus on the regulation of skeletal muscle mass. A quantitative limitation exists as to how much muscle protein the body can synthesize in response to protein intake. Ingestion of excess protein exerts an unwanted load to the body and therefore, it is important to find the least amount of protein that provides the maximal hypertrophic stimulus. Hence, research has focused on revealing the relationship between protein intake (dose) and its resulting stimulation of muscle protein synthesis (response). In addition to the protein amount, the protein digestibility and, hence, the availability of its constituent amino acids is decisive for the response. In this regard, recent studies have provided in-depth knowledge about the time-course of the muscle protein synthetic response dependent on the characteristics of the protein ingested. The effect of protein intake on muscle protein accretion can further be stimulated by prior exercise training. In the ageing population, physical training may counteract the development of "anabolic resistance" and restore the beneficial effect of protein feeding. Presently, our knowledge is based on measures obtained in standardized experimental settings or during long-term intervention periods. However, to improve coherence between these types of data and to further improve our knowledge of the effects of protein ingestion, other investigative approaches than those presently used are requested.
... In agreement with our findings, whey protein has shown no effect on strength gains after 12 weeks of high-intensity resistance exercise training in healthy young men. 40 We found that the increases in muscle strength after 4 weeks of CET did not influence BP and arterial function. Our CET included endurance training, a modality that has consistently shown reductions in BP and PWV. ...
Article
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Background: Obesity and aging are associated with increased arterial stiffness as indicated by an increased pulse-wave velocity (PWV). We evaluated the independent and combined effects on PWV and body composition of a hypocaloric diet and low-intensity resistance exercise training (LIRET) with slow movement. Methods: Forty-one postmenopausal women (mean age, 54±6 years; body mass index (BMI), 33.8±0.5kg/m(2)) were randomly assigned to LIRET (n = 14), diet (n = 13), or diet + LIRET (n = 14) for 12 weeks. The women's PWV, mean arterial pressure (MAP), body composition by dual-en ergy x-ray absorptiometry (DXA), and plasma adipokine and insulin levels were measured before and after the interventions. Results: Body weight (P = 0.0001), trunk-fat mass (FM, P = 0.0001), and the serum concentration of leptin (P = 0.02 and P = 0.004) decreased similarly with diet and diet + LIRET, but not with LIRET alone. Leg lean mass (LM) decreased (P = 0.02) with diet, but did not change with diet + LIRET or with LIRET alone. Leg muscle strength increased similarly with LIRET (P = 0.001) and diet + LIRET (P = 0.0001), but did not change with diet alone. Brachial-ankle PWV (baPWV) decreased with diet (P = 0.04) and diet + LIRET (P = 0.01), whereas femoral-ankle PWV (legPWV) decreased only with diet (P = 0.01). Mean arterial pressure (MAP) decreased after LIRET (P = 0.03), diet (P = 0.04), and diet + LIRET (P = 0.004). Carotid-femoral PWV, serum adiponectin concentration, and insulin were not significantly affected by the interventions examined in the study. The reductions in baPWV and legPWV were correlated with one another (r = 0.73, P = 0.0001), and the reductions in legPWV and trunk FM were also correlated with one another (r = 0.36, P = 0.03). Conclusions: A hypocaloric diet decreases baPWV mainly by reducing legPWV, and this reduction is related to the loss of truncal fat. Although LIRET alone does not affect PWV or body composition, LIRET combined with diet improves baPWV and muscle strength while preventing loss of lean body mass in obese postmenopausal women.
... Most recently, Erskine et al. [75] failed to show a hypertrophic benefit from post-workout nutrient timing. Subjects were 33 untrained young males, pair-matched for habitual protein intake and strength response to a 3week pre-study resistance training program. ...
Article
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Nutrient timing is a popular nutritional strategy involves the consumption of combinations of nutrients--primarily protein and carbohydrate--in and around an exercise session. Some have claimed that this approach can produce dramatic improvements in body composition. It has even been postulated that the timing of nutritional consumption may be more important than the absolute daily intake of nutrients. The post-exercise period is widely considered the most critical part of nutrient timing. Theoretically, consuming the proper ratio of nutrients during this time not only initiates the rebuilding of damaged muscle tissue and restoration of energy reserves, but it does so in a supercompensated fashion that enhances both body composition and exercise performance. Several researchers have made reference to an anabolic "window of opportunity" whereby a limited time exists after training to optimize training-related muscular adaptations. However, the importance - and even the existence - of a post-exercise 'window' can vary according to a number of factors. Not only is nutrient timing research open to question in terms of applicability, but recent evidence has directly challenged the classical view of the relevance of post-exercise nutritional intake with respect to anabolism. Therefore, the purpose of this paper will be twofold: 1) to review the existing literature on the effects of nutrient timing with respect to post-exercise muscular adaptations, and; 2) to draw relevant conclusions that allow practical, evidence-based nutritional recommendations to be made for maximizing the anabolic response to exercise.
Article
Aim: Bioactive collagen peptides (CP) have been suggested to augment the functional, structural (size and architecture) and contractile adaptations of skeletal muscle to resistance training (RT), but with limited evidence. This study aimed to determine if CP vs placebo (PLA) supplementation enhanced the functional and underpinning structural, and contractile adaptations after 15 weeks of lower body RT. Methods: Young healthy males were randomized to consume either 15 g of CP (n=19) or PLA (n=20) once every day during a standardized program of progressive knee extensor, knee flexor and hip extensor RT 3 times/wk. Measurements pre and post RT included: knee extensor and flexor isometric strength; quadriceps, hamstrings and gluteus maximus volume with MRI; evoked twitch contractions, 1RM lifting strength and architecture (with ultrasound) of the quadriceps. Results: Percentage changes in maximum strength (isometric or 1RM) did not differ between groups (0.684≤P≤0.929). Increases in muscle volume were greater (quadriceps 15.2 vs. 10.3%; vastus medialis (VM) 15.6 vs. 9.7%; total muscle volume 15.7 vs. 11.4%; [all] P≤0.032) or tended to be greater (hamstring 16.4 vs. 12.5%; gluteus maximus 16.6 vs. 12.9%; 0.089≤P≤0.091) for CP vs. PLA. There were also greater increases in twitch peak torque (22.3 vs. 12.3%; P=0.038) and angle of pennation of the VM (16.8 vs. 5.8%, P=0.046), but not other muscles, for CP vs. PLA. Conclusions: CP supplementation produced a cluster of consistent effects indicating greater skeletal muscle remodelling with RT compared to PLA. Notably, CP supplementation amplified the quadriceps and total muscle volume increases induced by RT.
Article
Objective. High-density surface electromyography (HD-sEMG) allows the reliable identification of individual motor unit (MU) action potentials. Despite the accuracy in decomposition, there is a large variability in the number of identified MUs across individuals and exerted forces. Here we present a systematic investigation of the anatomical and neural factors that determine this variability. Approach. We investigated factors of influence on HD-sEMG decomposition, such as synchronization of MU discharges, distribution of MU territories, muscle-electrode distance (MED - subcutaneous adipose tissue thickness), maximum anatomical cross-sectional area (ACSA max ), and fiber CSA. For this purpose, we recorded HD-sEMG signals, ultrasound and, magnetic resonance images, and took a muscle biopsy from the biceps brachii muscle from 30 male participants drawn from two groups to ensure variability within the factors – untrained-controls (UT=14) and strength-trained individuals (ST=16). Participants performed isometric ramp contractions with elbow flexors (at 15, 35, 50 and 70% maximum voluntary torque - MVT). We assessed the correlation between the number of accurately detected MUs by HD-sEMG decomposition and each measured parameter, for each target force level. Multiple regression analysis was then applied. Main results. ST subjects showed lower MED (UT=5.1±1.4 mm; ST=3.8±0.8 mm) and a greater number of identified motor units (UT:21.3±10.2 vs ST:29.2±11.8 MUs/subject across all force levels). The entire cohort showed a negative correlation between MED and the number of identified MUs at low forces (r= -0.6, p=0.002 at 15%MVT). Moreover, the number of identified MUs was positively correlated to the distribution of MU territories (r=0.56, p=0.01) and ACSA max (r=0.48, p=0.03) at 15%MVT. By accounting for all anatomical parameters, we were able to partly predict the number of decomposed MUs at low but not at high forces. Significance. Our results confirmed the influence of subcutaneous tissue on the quality of HD-sEMG signals and demonstrated that MU spatial distribution and ACSA max are also relevant parameters of influence for current decomposition algorithms.
Article
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Objectives This systematic review, meta-analysis, and meta-regression aimed to determine if increasing daily protein ingestion contributes to gaining lean mass (LM), muscle strength, and physical/functional test performance in healthy persons. Methods The present review was registered on PROSPERO - CRD42020159001. A systematic search in Medline, Embase, CINAHL, and Web of Sciences databases was undertaken. Randomized controlled trials (RCT) including healthy and non-obese adult participants increasing daily protein intake were selected. Subgroup analysis, splitting the studies by participation in resistance exercise training (RE), age (< 65 or ≥ 65 y), and daily protein ingestion were also performed. Results 74 RCT fit our inclusion criteria. The age range of the participants was 19 to 85 y, and study protocols in the trials lasted from 6 to 108 wks (76% of the studies between 8 and 12 wks). In ∼80% of the studies, baseline protein ingestion was at least 1.2 g of protein/kg/d. Increasing daily protein ingestion may lead to small gains in LM in subjects enrolled in RE (SMD [standardized mean difference] = 0.22, CI95% [95% confidence interval] 0.14:0.30, P < 0.01, 62 studies, moderate level of evidence). Also, ≥ 65 y subjects ingesting 1.2–1.59 g of protein/kg/d and younger subjects (< 65 y) increasing their ingestion to ≥ 1.6 g of protein/kg/d during RE showed a higher LM gain. Lower-body strength gain was slightly higher at ≥ 1.6 g of protein/kg/d during RE (SMD = 0.40, CI95% 0.09:0.35, P < 0.01, 19 studies, low level of evidence). Bench press strength was slightly increased by ingesting more protein in < 65 y subjects during RE (SMD = 0.18, CI95% 0.03:0.33, P = 0.01, 32 studies, low level of evidence). Effects on handgrip strength are unclear and only marginal for performance in physical function tests. Conclusions The number of studies increasing daily protein ingestion alone was too low (n = 6) to conduct a meta-analysis. The current evidence shows that increasing protein ingestion by consuming supplements or food, resulted in small additional gain in LM, and lower body muscle strength in healthy adults enrolled in RE. Effects on bench press strength and performance in physical function tests are minimal. The effect on handgrip strength was unclear. Funding Sources This research received a grant from the International Life Science Institute (Europe) and CNPq.
Article
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Abstract We performed a systematic review, meta‐analysis, and meta‐regression to determine if increasing daily protein ingestion contributes to gaining lean body mass (LBM), muscle strength, and physical/functional test performance in healthy subjects. A protocol for the present study was registered (PROSPERO, CRD42020159001), and a systematic search of Medline, Embase, CINAHL, and Web of Sciences databases was undertaken. Only randomized controlled trials (RCT) where participants increased their daily protein intake and were healthy and non‐obese adults were included. Research questions focused on the main effects on the outcomes of interest and subgroup analysis, splitting the studies by participation in a resistance exercise (RE), age (
Preprint
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Objective High-density surface electromyography (HD-sEMG) allows the reliable identification of individual motor unit (MU) action potentials. Despite the accuracy in decomposition, there is a large variability in the number of identified MUs across individuals and exerted forces. Here we present a systematic investigation of the anatomical and neural factors that determine this variability. Approach We investigated factors of influence on HD-sEMG decomposition, such as synchronization of MU discharges, distribution of MU territories, muscle-electrode distance (MED - subcutaneous fat thickness), maximum anatomical cross-sectional area (ACSA max ), and fiber CSA. For this purpose, we recorded HD-sEMG signals, ultrasound, magnetic resonance imaging, and muscle biopsy of the biceps brachii muscle from two groups of participants – untrained-controls (UT=14) and strength-trained (>3 years of training, ST=16) – while they performed isometric ramp contractions with elbow flexors (at 15, 35, 50 and 70% maximum voluntary torque - MVT). We assessed the correlation between the number of accurately detected MUs by HD-sEMG decomposition and each measured parameter, for each target force level. Multiple regression analysis was then applied. Main results ST subjects showed lower MED (UT: 4.8 ± 1.4 vs. ST: 3.7 ± 0.8 mm) associated to a greater number of identified motor units (UT: 21.3 ± 10.2 vs. ST: 29.2 ± 11.8 MUs/subject). Both groups showed a negative correlation between MED and the number of identified MUs at low forces (r= −0.6, p=0.002 at 15% MVT). Moreover, the number of identified MUs was positively correlated to the distribution of MU territories (r=0.56, p=0.01) and ACSA max (r=0.48, p=0.03) at 15% MVT. By accounting for all anatomical parameters, we were able to partly predict the number of decomposed MUs at low but not at high forces. Significance Our results confirmed the influence of subcutaneous tissue on the quality of HD-sEMG signals and demonstrated that MU spatial distribution and ACSA max are also relevant parameters of influence for current decomposition algorithms.
Article
Neural and morphological adaptations combine to underpin the enhanced muscle strength following prolonged exposure to strength training, although their relative importance remains unclear. We investigated the contribution of motor unit (MU) behaviour and muscle size to submaximal force production in chronically strength-trained athletes (ST) vs. untrained controls (UT). Sixteen ST (age, 22.9±3.5 yr; training experience, 5.9±3.5 yr) and fourteen UT (age, 20.4±2.3 yr) performed maximal voluntary isometric force (MViF) and ramp contractions (at 15, 35, 50, 70%MViF) with elbow flexors, whilst high-density surface EMG (HDsEMG) was recorded from the biceps brachii (BB). Recruitment thresholds (RT) and discharge rates (DR) of MUs identified from the submaximal contractions were assessed. The neural drive-to-muscle gain was estimated from the relation between changes in force (ΔFORCE, i.e. muscle output) relative to changes in MU DR (ΔDR, i.e. neural input). BB maximum anatomical cross-sectional area (ACSA MAX ) was also assessed by MRI. MViF (+64.8% vs. UT, P<0.001) and BB ACSA MAX (+71.9%, P<0.001) were higher in ST. Absolute MU RT was higher in ST (+62.6%, P<0.001), but occurred at similar normalized forces. MU DR did not differ between groups at the same normalized forces. The absolute slope of the ΔFORCE-ΔDR relationship was higher in ST (+66.9%, P=0.002), whereas it did not differ for normalized values. We observed similar MU behaviour between ST athletes and UT controls. The greater absolute force-generating capacity of ST for the same neural input, demonstrates that morphological, rather than neural, factors are the predominant mechanism for their enhanced force generation during submaximal efforts.
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This study compared elbow flexor (EF; Experiment 1) and knee extensor (KE; Experiment 2) maximal compound action potential (M max ) amplitude between long-term resistance trained (LTRT; n=15 and n=14, 6±3 and 4±1 years of training) and untrained (UT; n=14 and n=49) men; and examined the effect of normalising electromyography (EMG) during maximal voluntary torque (MVT) production to M max amplitude on differences between LTRT and UT. EMG was recorded from multiple sites and muscles of EF and KE, M max was evoked with percutaneous nerve stimulation, and muscle size was assessed with ultrasonography (thickness, EF) and magnetic resonance imaging (cross-sectional area, KE). Muscle-electrode distance (MED) was measured to account for the effect of adipose tissue on EMG and M max . LTRT displayed greater MVT (+66-71%, p<0.001), muscle size (+54-56%, p<0.001), and M max amplitudes (+29-60%, p≤0.010) even when corrected for MED (p≤0.045). M max was associated with the size of both muscle groups (r≥0.466, p≤0.011). Compared to UT, LTRT had higher absolute voluntary EMG amplitude for the KE (p<0.001), but not the EF (p=0.195), and these differences/similarities were maintained after correction for MED; however, M max normalisation resulted in no differences between LTRT and UT for any muscle and/or muscle group (p≥0.652). The positive association between M max and muscle size, and no differences when accounting for peripheral electrophysiological properties (EMG/M max ), indicates the greater absolute voluntary EMG amplitude of LTRT might be confounded by muscle morphology, rather than provide a discrete measure of central neural activity. This study therefore suggests limited agonist neural adaptation after LTRT.
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This study evaluates the effect of whey protein (WP) supplementation with resistance training (RT) on body mass and muscular strength reported by randomized controlled trials (RCTs). Literature survey was conducted in electronic databases and study selection was based on précised eligibility criteria. Meta-analyses of mean differences (MD) in lean/fat mass or standardized MD (SMD) in muscular strength between WP supplementation during RT sessions (WP-RT) and placebo-RT groups were conducted along with sensitivity and subgroup analyses. Data were taken from 22 RCTs in which 837 participants attended 13.08 weeks [95% CI 10.47, 15.69] of RT. In comparison with placebo-RT group, WP-RT significantly improved lean mass (MD 0.46 kg [0.10, 0.81]; p=0.01), fat mass (MD −0.86 [−1.20, −0.51]; p˂0.00001) and muscular strength (SMD 0.34 [0.11, 0.58]; p=0.005) in younger (˂40 years) individuals only. Moreover, in comparison with placebo-RT group, WP-RT improved lean mass (0.38 [−0.03, 0.79]; p=0.07), fat mass (MD −0.75 [−1.09, −0.42]; p˂0.00001) and muscular strength (SMD 0.29 [0.07, 0.51]; p=0.01) only in healthy individuals but not in individuals with a pathological condition. WP-RT improves lean mass, fat mass and muscular only in healthy individuals under age 40.
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Introducción. El número de estudios relacionados con la fuerza muscular y la funcionalidad invitan al análisis en profundidad de sus resultados antes de su aplicación profesional. Objetivo. Desarrollar una revisión sistemática para la construcción de programas de actividad física centrados en el entrenamiento de fuerza muscular y la capacidad funcional de sedentarios entre los 19 y 79 años. Materiales y métodos. Se emplearon los parámetros PRISMA, Chocrane y de la Universidad de York para el diseño y ejecución de revisiones sistemáticas. Además, se garantizaron criterios de calidad y especificidad estrictos que permitieron identificar 14 categorías de análisis, de las cuales emergieron las pautas de programación que se informan en la revisión sistemática. Resultados. 49 estudios con nivel de evidencia 1+ (24%), 1- (33%), 2++ (4%), 2+ (29%) y 2- (10%) cumplieron con los criterios de selección establecidos y permitieron alimentar las 14 categorías propuestas y hacer una síntesis de contenido. Conclusión. Es posible elevar el efecto de los programas de actividad física sobre la fuerza muscular y la funcionalidad a partir de la identificación y consideración de unas variables de programación (categoría) básicas que se sustentan en la calidad de evidencia científica circulante.
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Objective To examine the effects of whey protein supplementation in association with resistance training on additional muscle strength gain in older adults. News Data concerning the effect of dietary interventions are emerging in the literature as a promising co-adjuvant intervention to potentiate muscle mass and strength gains. Whey protein concentrate may represent an ideal protein source to promote muscle anabolism in older individuals undergoing resistance exercise However, randomized controlled trials (RCTs) show contradictory results. Systematic review or meta-analysis has never been performed to investigate the effects of whey protein supplementation in additional muscle strength gain in elderly engaged in resistance exercise training. Prospects and projects Future investigations in effects of whey protein supplementation on muscle strength in older adults are needed to support the findings presented in the current review. Conclusions Whey protein supplementation in association with resistance exercise training did not contribute to additional gain of muscle strength in the older adults.
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Objective We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength. Data sources A systematic search of Medline, Embase, CINAHL and SportDiscus. Eligibility criteria Only randomised controlled trials with RET ≥6 weeks in duration and dietary protein supplementation. Design Random-effects meta-analyses and meta-regressions with four a priori determined covariates. Two-phase break point analysis was used to determine the relationship between total protein intake and changes in fat-free mass (FFM). Results Data from 49 studies with 1863 participants showed that dietary protein supplementation significantly (all p<0.05) increased changes (means (95% CI)) in: strength—one-repetition-maximum (2.49 kg (0.64, 4.33)), FFM (0.30 kg (0.09, 0.52)) and muscle size—muscle fibre cross-sectional area (CSA; 310 µm² (51, 570)) and mid-femur CSA (7.2 mm² (0.20, 14.30)) during periods of prolonged RET. The impact of protein supplementation on gains in FFM was reduced with increasing age (−0.01 kg (−0.02,–0.00), p=0.002) and was more effective in resistance-trained individuals (0.75 kg (0.09, 1.40), p=0.03). Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM. Summary/conclusion Dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults. Increasing age reduces and training experience increases the efficacy of protein supplementation during RET. With protein supplementation, protein intakes at amounts greater than ~1.6 g/kg/day do not further contribute RET-induced gains in FFM.
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Introducción: Los suplementos de proteína y aminoácidos de cadena ramificada (BCAAs) son consumidos por la población buscando una serie de efectos fisiológicos y metabólicos sobre el rendimiento y recuperación, entre otros. Objetivos: Revisión de las publicaciones más recientes que estudien los efectos del consumo de suplementos de proteína y BCAAs en entrenamiento de fuerza en diferentes parámetros fisiológicos y metabólicos. Material y métodos: Estudio descriptivo de revisión bibliográfica. Se realizó una búsqueda específica de palabras clave en la base de datos PubMed y estrategia de bola de nieve. Criterios de inclusión: estudios realizados en humanos de ≥ 18 años sin patología, metaanálisis, revisiones sistemáticas y ensayos clínicos controlados aleatorizados en inglés y español relacionados con el consumo de suplementos de proteína y/o BCAAs en entrenamiento de fuerza y sus efectos sobre el daño muscular, respuesta anabólica en la recuperación muscular, ganancia de masa muscular y fuerza, composición corporal y fatiga. Resultados: 64 estudios identificados mediante la ecuación de búsqueda, 20 cumplieron con los criterios de inclusión. La media aritmética de los sujetos participantes fue igual a (30,59 ± 24,47). Conclusiones: Los suplementos de proteína podrían tener un efecto positivo en el aumento del rendimiento y la masa muscular, pero hacen falta más estudios para esclarecer su posible beneficio sobre la composición corporal, la fatiga, la atenuación y reducción del dolor y daño muscular. La leucina tiene efecto en el aumento de la masa muscular y su función en población de edad avanzada. Los BCAAs podrían actuar sobre la atenuación de la fatiga central y en la mejora del rendimiento.
Article
The present investigation examined the effects of chocolate cow's and goat's milk on endocrine responses and isometric mid-thigh pull performance post back squat exercise. Twelve college-aged males volunteered to participate and reported to the lab on four occasions. The first visit included anthropometric measurement, one-repetition back squat (1RM), and familiarization with the isometric mid-thigh pull assessment (IMTP). During the subsequent three visits, five sets of eight repetitions of the back squat exercise at 80% of 1RM were performed. For these trials, the participants performed an IMTP and gave a saliva sample prior to, immediately after, 1 hr and 2 hr post exercise. After exercise, a treatment of low-fat chocolate goat's milk (355 ml, 225 kcal), low-fat chocolate cow's milk (355 ml, 225 kcal), or control (water 355 ml, 0 kcal) was given in a counterbalanced order. Saliva samples were analyzed for testosterone, cortisol, and dehydroepiandrosterone (DHEA). Cortisol and DHEA hormone were unaffected by exercise; however, testosterone values did increase significantly post exercise. For IMTP, there was a significant main effect for time (F = 8.41, p = .007) but no treatment or interactions effects. N changes were noted post supplementation for cortisol or DHEA, but testosterone was found to be significantly reduced in both diary treatments compared to control (F = 4.27, p = .022). Based upon these data, it appears that a single treatment of chocolate goat's or cow's milk results in similar endocrine alterations but both fail to enhance postexercise isometric strength following resistance exercise.
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Protein consumption is unquestionably required for skeletal muscle maintenance and growth. However, debate persists over whether or not the timing of ingestion matters. Some argue immediately after exercise is best, whereas others disagree. This article will discuss the importance of timing of postexercise protein ingestion. © National Strength and Conditioning Association.
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Protein timing is a popular dietary strategy designed to optimize the adaptive response to exercise. The strategy involves consuming protein in and around a training session in an effort to facilitate muscular repair and remodeling, and thereby enhance post-exercise strength- and hypertrophy-related adaptations. Despite the apparent biological plausibility of the strategy, however, the effectiveness of protein timing in chronic training studies has been decidedly mixed. The purpose of this paper therefore was to conduct a multi-level meta-regression of randomized controlled trials to determine whether protein timing is a viable strategy for enhancing post-exercise muscular adaptations. The strength analysis comprised 478 subjects and 96 ESs, nested within 41 treatment or control groups and 20 studies. The hypertrophy analysis comprised 525 subjects and 132 ESs, nested with 47 treatment or control groups and 23 studies. A simple pooled analysis of protein timing without controlling for covariates showed a small to moderate effect on muscle hypertrophy with no significant effect found on muscle strength. In the full meta-regression model controlling for all covariates, however, no significant differences were found between treatment and control for strength or hypertrophy. The reduced model was not significantly different from the full model for either strength or hypertrophy. With respect to hypertrophy, total protein intake was the strongest predictor of ES magnitude. These results refute the commonly held belief that the timing of protein intake in and around a training session is critical to muscular adaptations and indicate that consuming adequate protein in combination with resistance exercise is the key factor for maximizing muscle protein accretion.
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In a comparative study, we investigated the effects of maximal eccentric or concentric resistance training combined with whey protein or placebo on muscle and tendon hypertrophy. 22 subjects were allocated into either a high-leucine whey protein hydrolysate + carbohydrate group (WHD) or a carbohydrate group (PLA). Subjects completed 12 weeks maximal knee extensor training with one leg using eccentric contractions and the other using concentric contractions. Before and after training cross-sectional area (CSA) of m. quadriceps and patellar tendon CSA was quantified with magnetic resonance imaging and a isometric strength test was used to assess maximal voluntary contraction (MVC) and rate of force development (RFD). Quadriceps CSA increased by 7.3 ± 1.0% (P < 0.001) in WHD and 3.4 ± 0.8% (P < 0.01) in PLA, with a greater increase in WHD compared to PLA (P < 0.01). Proximal patellar tendon CSA increased by 14.9 ± 3.1% (P < 0.001) and 8.1 ± 3.2% (P = 0.054) for WHD and PLA, respectively, with a greater increase in WHD compared to PLA (P < 0.05), with no effect of contraction mode. MVC and RFD increased by 15.6 ± 3.5% (P < 0.001) and 12-63% (P < 0.05), respectively, with no group or contraction mode effects. In conclusion, high-leucine whey protein hydrolysate augments muscle and tendon hypertrophy following 12 weeks of resistance training - irrespective of contraction mode.
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The effects of timed ingestion of high-quality protein before and after resistance exercise are not well known. In this study, young men were randomized to protein (n = 11), placebo (n = 10) and control (n = 10) groups. Muscle cross-sectional area by MRI and muscle forces were analyzed before and after 21 weeks of either heavy resistance training (RT) or control period. Muscle biopsies were taken before, and 1 and 48 h after 5 x 10 repetition leg press exercise (RE) as well as 21 weeks after RT. Protein (15 g of whey both before and after exercise) or non-energetic placebo were provided to subjects in the context of both single RE bout (acute responses) as well as each RE workout twice a week throughout the 21-week-RT. Protein intake increased (P < or = 0.05) RT-induced muscle cross-sectional area enlargement and cell-cycle kinase cdk2 mRNA expression in the vastus lateralis muscle suggesting higher proliferating cell activation response with protein supplementation. Moreover, protein intake seemed to prevent 1 h post-RE decrease in myostatin and myogenin mRNA expression but did not affect activin receptor IIb, p21, FLRG, MAFbx or MyoD expression. In conclusion, protein intake close to resistance exercise workout may alter mRNA expression in a manner advantageous for muscle hypertrophy.
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We aimed to determine whether an exercise-mediated enhancement of muscle protein synthesis to feeding persisted 24 h after resistance exercise. We also determined the impact of different exercise intensities (90% or 30% maximal strength) or contraction volume (work-matched or to failure) on the response at 24 h of recovery. Fifteen men (21 ± 1 y, BMI = 24.1 ± 0.8 kg · m(-2)) received a primed, constant infusion of l-[ring-(13)C(6)]phenylalanine to measure muscle protein synthesis after protein feeding at rest (FED; 15 g whey protein) and 24 h after resistance exercise (EX-FED). Participants performed unilateral leg exercises: 1) 4 sets at 90% of maximal strength to failure (90FAIL); 2) 30% work-matched to 90FAIL (30WM); or 3) 30% to failure (30FAIL). Regardless of condition, rates of mixed muscle protein and sarcoplasmic protein synthesis were similarly stimulated at FED and EX-FED. In contrast, protein ingestion stimulated rates of myofibrillar protein synthesis above fasting rates by 0.016 ± 0.002%/h and the response was enhanced 24 h after resistance exercise, but only in the 90FAIL and 30FAIL conditions, by 0.038 ± 0.012 and 0.041 ± 0.010, respectively. Phosphorylation of protein kinase B on Ser473 was greater than FED at EX-FED only in 90FAIL, whereas phosphorylation of mammalian target of rapamycin on Ser2448 was significantly increased at EX-FED above FED only in the 30FAIL condition. Our results suggest that resistance exercise performed until failure confers a sensitizing effect on human skeletal muscle for at least 24 h that is specific to the myofibrillar protein fraction.
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Considerable variation exists between people in the muscle response to resistance training, but there are numerous ways muscle might adapt to overload that might explain this variable response. Therefore, the aim of this study was to quantify the range of responses concerning the training-induced change in maximum voluntary contraction (MVC) knee joint torque, quadriceps femoris (QF) maximum muscle force (F), physiological cross-sectional area (PCSA) and specific tension (F/PCSA). It was hypothesized that the variable change in QF specific tension between individuals would be less than that of MVC. Fifty-three untrained young men performed progressive leg-extension training three times a week for 9 weeks. F was determined from MVC torque, voluntary muscle activation level, antagonist muscle co-activation and patellar tendon moment arm. QF specific tension was established by dividing F by QF PCSA, which was calculated from the ratio of QF muscle volume to muscle fascicle length. MVC torque increased by 26 ± 11% (P < 0.0001; range -1 to 52%), while F increased by 22 ± 11% (P < 0.0001; range -1 to 44%). PCSA increased by 6 ± 4% (P < 0.001; range -3 to 18%) and specific tension increased by 17 ± 11% (P < 0.0001; range -5 to 39%). In conclusion, training-induced changes in F and PCSA varied substantially between individuals, giving rise to greater inter-individual variability in the specific tension response compared to that of MVC. Furthermore, it appears that the change in specific tension is responsible for the variable change in MVC.
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The aim of our study was to determine whether resistance exercise-induced elevations in endogenous hormones enhance muscle strength and hypertrophy with training. Twelve healthy young men (21.8 +/- 1.2 yr, body mass index = 23.1 +/- 0.6 kg/m(2)) trained their elbow flexors independently for 15 wk on separate days and under different hormonal milieu. In one training condition, participants performed isolated arm curl exercise designed to maintain basal hormone concentrations (low hormone, LH); in the other training condition, participants performed identical arm exercise to the LH condition followed immediately by a high volume of leg resistance exercise to elicit a large increase in endogenous hormones (high hormone, HH). There was no elevation in serum growth hormone (GH), insulin-like growth factor (IGF-1), or testosterone after the LH protocol but significant (P < 0.001) elevations in these hormones immediately and 15 and 30 min after the HH protocol. The hormone responses elicited by each respective exercise protocol late in the training period were similar to the response elicited early in the training period, indicating that a divergent postexercise hormone response was maintained over the training period. Muscle cross-sectional area (CSA) increased by 12% in LH and 10% in HH (P < 0.001) with no difference between conditions (condition x training interaction, P = 0.25). Similarly, type I (P < 0.01) and type II (P < 0.001) muscle fiber CSA increased with training with no effect of hormone elevation in the HH condition. Strength increased in both arms, but the increase was not different between the LH and HH conditions. We conclude that exposure of loaded muscle to acute exercise-induced elevations in endogenous anabolic hormones enhances neither muscle hypertrophy nor strength with resistance training in young men.
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To determine the 3D location of the intramuscular motor nerve endings of the biceps brachii and brachialis, we identified from 56 fresh cadaveric arms the regions where the intramuscular branches were most densely located in relation to a reference line connecting the medial epicondyle of humerus and the coracoid process. For the biceps, these points were most densely distributed at a length from 64.6 to 70.3% point of the reference line with the coracoid process as starting point, at a width of 21.6-32.6 mm lateral to the reference line. For the brachialis muscle, these points were located at a length of 75.4% point and width of 27.1-35.4 mm lateral to the reference line. At these points, the biceps was located at a depth of the upper two-third portion and the brachialis at the lower one-third portion of the upper arm, from skin to humeral bone.
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We aimed to determine whether exercise-induced elevations in systemic concentration of testosterone, growth hormone (GH) and insulin-like growth factor-1 (IGF-1) enhanced post-exercise myofibrillar protein synthesis (MPS) and phosphorylation of signalling proteins important in regulating mRNA translation. Eight young men (20 +/- 1.1 years, BMI = 26 +/- 3.5 kg m(-2)) completed two exercise protocols designed to maintain basal hormone concentrations (low hormone, LH) or elicit increases in endogenous hormones (high hormone, HH). In the LH protocol, participants performed a bout of unilateral resistance exercise with the elbow flexors. The HH protocol consisted of the same elbow flexor exercise with the contralateral arm followed immediately by high-volume leg resistance exercise. Participants consumed 25 g of protein after arm exercise to maximize MPS. Muscle biopsies and blood samples were taken as appropriate. There were no changes in serum testosterone, GH or IGF-1 after the LH protocol, whereas there were marked elevations after HH (testosterone, P < 0.001; GH, P < 0.001; IGF-1, P < 0.05). Exercise stimulated a rise in MPS in the biceps brachii (rest = 0.040 +/- 0.007, LH = 0.071 +/- 0.008, HH = 0.064 +/- 0.014% h(-1); P < 0.05) with no effect of elevated hormones (P = 0.72). Phosphorylation of the 70 kDa S6 protein kinase (p70S6K) also increased post-exercise (P < 0.05) with no differences between conditions. We conclude that the transient increases in endogenous purportedly anabolic hormones do not enhance fed-state anabolic signalling or MPS following resistance exercise. Local mechanisms are likely to be of predominant importance for the post-exercise increase in MPS.
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This study was designed to compare the acute response of mixed muscle protein synthesis (MPS) to rapidly (i.e., whey hydrolysate and soy) and slowly (i.e., micellar casein) digested proteins both at rest and after resistance exercise. Three groups of healthy young men (n = 6 per group) performed a bout of unilateral leg resistance exercise followed by the consumption of a drink containing an equivalent content of essential amino acids (10 g) as either whey hydrolysate, micellar casein, or soy protein isolate. Mixed MPS was determined by a primed constant infusion of l-[ring-(13)C(6)]phenylalanine. Ingestion of whey protein resulted in a larger increase in blood essential amino acid, branched-chain amino acid, and leucine concentrations than either casein or soy (P < 0.05). Mixed MPS at rest (determined in the nonexercised leg) was higher with ingestion of faster proteins (whey = 0.091 +/- 0.015, soy = 0.078 +/- 0.014, casein = 0.047 +/- 0.008%/h); MPS after consumption of whey was approximately 93% greater than casein (P < 0.01) and approximately 18% greater than soy (P = 0.067). A similar result was observed after exercise (whey > soy > casein); MPS following whey consumption was approximately 122% greater than casein (P < 0.01) and 31% greater than soy (P < 0.05). MPS was also greater with soy consumption at rest (64%) and following resistance exercise (69%) compared with casein (both P < 0.01). We conclude that the feeding-induced simulation of MPS in young men is greater after whey hydrolysate or soy protein consumption than casein both at rest and after resistance exercise; moreover, despite both being fast proteins, whey hydrolysate stimulated MPS to a greater degree than soy after resistance exercise. These differences may be related to how quickly the proteins are digested (i.e., fast vs. slow) or possibly to small differences in leucine content of each protein.
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It is not known to what extent the inter-individual variation in human muscle strength is explicable by differences in specific tension. To investigate this, a comprehensive approach was used to determine in vivo specific tension of the quadriceps femoris (QF) muscle (Method 1). Since this is a protracted technique, a simpler procedure was also developed to accurately estimate QF specific tension (Method 2). Method 1 comprised calculating patellar tendon force (F t) in 27 young, untrained males, by correcting maximum voluntary contraction (MVC) for antagonist co-activation, voluntary activation and moment arm length. For each component muscle, the physiological cross-sectional area (PCSA) was calculated as volume divided by fascicle length during MVC. Dividing F t by the sum of the four PCSAs (each multiplied by the cosine of its pennation angle during MVC) provided QF specific tension. Method 2 was a simplification of Method 1, where QF specific tension was estimated from a single anatomical CSA and vastus lateralis muscle geometry. Using Method 1, the variability in MVC (18%) and specific tension (16%) was similar. Specific tension from Method 1 (30 ± 5 N cm−2) was similar to and correlated with that of Method 2 (29 ± 5 N cm−2; R 2 = 0.67; P < 0.05). In conclusion, most of the inter-individual variability in MVC torque remains largely unexplained. Furthermore, a simple method of estimating QF specific tension provided similar values to the comprehensive approach, thereby enabling accurate estimations of QF specific tension where time and resources are limited.
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Considerable discrepancy exists in the literature on the proposed benefits of protein supplementation on the adaptive response of skeletal muscle to resistance-type exercise training in the elderly. The objective was to assess the benefits of timed protein supplementation on the increase in muscle mass and strength during prolonged resistance-type exercise training in healthy elderly men who habitually consume adequate amounts of dietary protein. Healthy elderly men (n = 26) aged 72 +/- 2 y were randomly assigned to a progressive, 12-wk resistance-type exercise training program with (protein group) or without (placebo group) protein provided before and immediately after each exercise session (3 sessions/wk, 20 g protein/session). One-repetition maximum (1RM) tests were performed regularly to ensure a progressive workload during the intervention. Muscle hypertrophy was assessed at the whole-body (dual-energy X-ray absorptiometry), limb (computed tomography), and muscle fiber (biopsy) level. The 1RM strength increased approximately 25-35% in both groups (P < 0.001). Dual-energy X-ray absorptiometry and computed tomography scans showed similar increases in leg muscle mass (6 +/- 1% in both groups; P < 0.001) and in the quadriceps (9 +/- 1% in both groups), from 75.9 +/- 3.7 and 73.8 +/- 3.2 to 82.4 +/- 3.9 and 80.0 +/- 3.0 cm2 in the placebo and protein groups, respectively (P < 0.001). Muscle fiber hypertrophy was greater in type II (placebo: 28 +/- 6%; protein: 29 +/- 4%) than in type I (placebo: 5 +/- 4%; protein: 13 +/- 6%) fibers, but the difference between groups was not significant. Timed protein supplementation immediately before and after exercise does not further augment the increase in skeletal muscle mass and strength after prolonged resistance-type exercise training in healthy elderly men who habitually consume adequate amounts of dietary protein. This trial was registered at clinicaltrials.gov as NCT00744094.
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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.
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It is widely believed that women experience less skeletal muscle hypertrophy consequent to heavy-resistance training than men. The purpose of this study was to test this hypothesis using both traditional indirect indicators as well as a direct measure of muscle size. Seven male experimental (ME), 8 female experimental (FE), and 7 control subjects were studied before and after a 16-wk weight training program, in which ME and FE trained 3 days.wk-1 at 70 to 90% of maximum voluntary contraction using exercise designed to produce hypertrophy of the upper arm and thigh. Strength increased significantly (P less than 0.05) in ME and FE, respectively, on elbow flexion (36.2 and 59.2%), elbow extension (32.6 and 41.7%), knee flexion (12.8 and 24.4%), and knee extension (28.8 and 33.9%) tests. Absolute changes were significantly greater in ME than FE in 2 of the 4 tests, whereas percentage changes were not significantly different. Substantial muscle hypertrophy occurred in the upper arms of both ME and FE as evidenced by significant increases in upper arm circumference (7.9 and 7.9%), bone-plus-muscle (B+M) cross-sectional area (CSA) estimated by anthropometry (17.5 and 20.4%), and muscle CSA determined from computed tomography scanning (15.9 and 22.8%). Changes by ME and FE were not significantly different, except for the absolute increase in estimated B+M CSA, which was significantly greater in ME (11.2 vs 7.4 cm2). No muscle hypertrophy occurred in the thigh of either ME and FE as evidenced by non-significant changes in thigh circumference (1.7 and 2.3%), B+M CSA (4.9 and 6.1%), and muscle CSA (2.9 and 2.9%). Changes by ME and FE in body weight, fat-free weight, and fat weight were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)
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This study examined 10 wks of resistance training and the ingestion of supplemental protein and amino acids on muscle performance and markers of muscle anabolism. Nineteen untrained males were randomly assigned to supplement groups containing either 20 g protein (14 g whey and casein protein, 6 g free amino acids) or 20 g dextrose placebo ingested 1 h before and after exercise for a total of 40 g/d. Participants exercised 4 times/wk using 3 sets of 6-8 repetitions at 85-90% of the one repetition maximum. Data were analyzed with two-way ANOVA (p < 0.05). The protein supplement resulted in greater increases in total body mass, fat-free mass, thigh mass, muscle strength, serum IGF-1, IGF-1 mRNA, MHC I and IIa expression, and myofibrillar protein. Ten-wks of resistance training with 20 g protein and amino acids ingested 1 h before and after exercise is more effective than carbohydrate placebo in up-regulating markers of muscle protein synthesis and anabolism along with subsequent improvements in muscle performance.
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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.
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The construct validity and the test-retest reliability of a self-administered questionnaire about habitual physical activity were investigated in young males (n = 139) and females (n = 167) in three age groups (20 to 22, 25 to 27, and 30 to 32 yr) in a Dutch population. By principal components analysis three conceptually meaningful factors were distinguished. They were interpreted as: 1) physical activity at work; 2) sport during leisure time; and 3) physical activity during leisure time excluding sport. Test-retest showed that the reliability of the three indices constructed from these factors was adequate. Further, it was found that level of education was inversely related to the work index, and positively related to the leisure-time index in both sexes. The subjective experience of work load was not related to the work index, but was inversely related to the sport index, and the leisure-time index in both sexes. The lean body mass was positively related to the work index, and the sport index in males, but was not related to the leisure-time index in either sex. These differences in the relationships support the subdivision of habitual physical activity into the three components mentioned above.
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Muscle mass declines with aging. Amino acids alone stimulate muscle protein synthesis in the elderly. However, mixed nutritional supplementation failed to improve muscle mass. We hypothesized that the failure of nutritional supplements is due to altered responsiveness of muscle protein anabolism to increased amino acid availability associated with endogenous hyperinsulinemia. We measured muscle protein synthesis and breakdown, and amino acid transport in healthy young (30 +/- 3 yr) and elderly (72 +/- 1 yr) volunteers in the basal postabsorptive state and during the administration of an amino acid-glucose mixture, using L-[ring-(2)H(5)]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Basal muscle amino acid turnover was similar in young and elderly subjects. The mixture increased phenylalanine leg delivery and transport into the muscle in both groups. Phenylalanine net balance increased in both groups (young, -27 +/- 8 to 64 +/- 17; elderly, -16 +/- 4 to 29 +/- 7 nmol/(min.100 mL); P: < 0.0001, basal vs. mixture), but the increase was significantly blunted in the elderly (P: = 0.030 vs. young). Muscle protein synthesis increased in the young, but remained unchanged in the elderly [young, 61 +/- 17 to 133 +/- 30 (P: = 0. 005); elderly, 62 +/- 9 to 70 +/- 14 nmol/(min.100 mL) (P: = NS)]. In both groups, protein breakdown decreased (P: = 0.012) and leg glucose uptake increased (P: = 0.0258) with the mixture. We conclude that the response of muscle protein anabolism to hyperaminoacidemia with endogenous hyperinsulinemia is impaired in healthy elderly due to the unresponsiveness of protein synthesis.
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High-resistance strength training (HRST) is one of the most widely practiced forms of physical activity, which is used to enhance athletic performance, augment musculo-skeletal health and alter body aesthetics. Chronic exposure to this type of activity produces marked increases in muscular strength, which are attributed to a range of neurological and morphological adaptations. This review assesses the evidence for these adaptations, their interplay and contribution to enhanced strength and the methodologies employed. The primary morphological adaptations involve an increase in the cross-sectional area of the whole muscle and individual muscle fibres, which is due to an increase in myofibrillar size and number. Satellite cells are activated in the very early stages of training; their proliferation and later fusion with existing fibres appears to be intimately involved in the hypertrophy response. Other possible morphological adaptations include hyperplasia, changes in fibre type, muscle architecture, myofilament density and the structure of connective tissue and tendons. Indirect evidence for neurological adaptations, which encompasses learning and coordination, comes from the specificity of the training adaptation, transfer of unilateral training to the contralateral limb and imagined contractions. The apparent rise in whole-muscle specific tension has been primarily used as evidence for neurological adaptations; however, morphological factors (e.g. preferential hypertrophy of type 2 fibres, increased angle of fibre pennation, increase in radiological density) are also likely to contribute to this phenomenon. Changes in inter-muscular coordination appear critical. Adaptations in agonist muscle activation, as assessed by electromyography, tetanic stimulation and the twitch interpolation technique, suggest small, but significant increases. Enhanced firing frequency and spinal reflexes most likely explain this improvement, although there is contrary evidence suggesting no change in cortical or corticospinal excitability. The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors. Whilst the neurological factors may make their greatest contribution during the early stages of a training programme, hypertrophic processes also commence at the onset of training.
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J Physiol 2001 August 15: 535(1): 301–11(1) Age-associated loss of skeletal muscle mass and strength can partly be counteracted by resistance training, causing a net synthesis of muscular proteins. Protein synthesis is influenced synergistically by post-exercise amino acid supplementation, but the importance of the timing of protein intake remains unresolved. (2) The study investigated the importance of immediate (P0) or delayed (P2) intake of an oral protein supplement upon muscle hypertrophy and strength over a period of resistance training in elderly males. (3) Thirteen men (age 74 ± 1 years; body mass index (BMI), 25 ± 1 kg m- 2 (means ± SEM)) completed a 12-week resistance training program (three times per week) receiving oral protein in liquid form (10 g protein, 7 g carbohydrate, 3 g fat) immediately after (P0) or 2 h after (P2) each training session. Muscle hypertrophy was evaluated by magnetic resonance imaging (MRI) and from muscle biopsies and muscle strength was determined using dynamic and isokinetic strength measurements. Body composition was determined from dual-energy X-ray absorptiometry (DEXA) and food records were obtained over 4 days. The plasma insulin response to protein supplementation was also determined. (4) In response to training, the cross-sectional area of m. quadriceps femoris (54.6 ± 0.5–58.3 ± 0.5 cm2) and mean fiber area (4047 ± 320–5019 ± 615 μ m2) increased in the P0 group, whereas no significant increase was observed in P2. For P0 both dynamic and isokinetic strength increased, by 46 and 15%, respectively (P P
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Electromyograms (EMGs) need to be normalized if comparisons are sought between trials when electrodes are reapplied, as well as between different muscles and individuals. The methods used to normalize EMGs recorded from healthy individuals have been appraised for more than a quarter of a century. Eight methods were identified and reviewed based on criteria relating to their ability to facilitate the comparison of EMGs. Such criteria included the magnitude and pattern of the normalized EMG, reliability, and inter-individual variability. If the aim is to reduce inter-individual variability, then the peak or mean EMG from the task under investigation should be used as the normalization reference value. However, the ability of such normalization methods to facilitate comparisons of EMGs is questionable. EMGs from MVCs can be as reliable as those from submaximal contractions, and do not appear to be affected by contraction mode or joint kinematics, particularly for the elbow flexors. Thus, the EMG from an isometric MVC is endorsed as a normalization reference value. Alternatively the EMG from a dynamic MVC can be used, although it is recognized that neither method is guaranteed to be able to reveal how active a muscle is in relation to its maximal activation capacity.
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Increase in myofibrillar protein accretion can occur in the very early post-exercise period and can be potentiated by ingestion of essential amino acid (EAA). Furthermore, strength exercise induces important disturbances in protein turnover, especially in novice athletes. The purpose of this investigation was to evaluate the effects of an EAA supplementation on muscle mass, architecture and strength in the early stages of a heavy-load training programme. 29 young males trained during 12 weeks. They were divided into a placebo (PLA) (n = 14) group and an EAA group (n = 15). At baseline, daily food intake and nitrogenous balance were assessed with a food questionnaire over 7 days and two 24-h urine collections. The effect of training on muscle mass was assessed by anthropometric techniques. Muscle thickness and pennation angle were recorded by ultrasonography of the gastrocnemius medialis (GM). Maximal strength during squat and bench press exercises were tested on an isokinetic ergometer. Training resulted in significant increase in muscle mass and strength in both PLA and EAA groups. Positive linear regressions were found between nitrogen balance and increase in muscle mass in the PLA group (P < 0.01, r2 = 0.63) and between the initial strength and the increase in muscle strength in the EAA group (P <0.05, r2 = 0.29). EAA ingestion resulted in greater changes in GM muscle architecture. These data indicate that EAA supplementation has a positive effect on muscle hypertrophy and architecture and that such a nutritional intervention seems to be more effective in subject having lower nitrogen balance and/or lower initial strength.
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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.
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The time course of strength gain with respect to the contributions of neural factors and hypertrophy was studied in seven young males and eight females during the course of an 8 week regimen of isotonic strength training. The results indicated that neural factors accounted for the larger proportion of the initial strength increment and thereafter both neural factors and hypertrophy took part in the further increase in strength, with hypertrophy becoming the dominant factor after the first 3 to 5 weeks. Our data regarding the untrained contralateral arm flexors provide further support for the concept of cross education. It was suggested that the nature of this cross education effect may entirely rest on the neural factors presumably acting at various levels of the nervous system which could result in increasing the maximal level of muscle activation.
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In studies of the effects of different training programmes, one muscle--most commonly the vastus lateralis--is used for the experiment while the contralateral muscle serves as a control, at the same time as muscle biopsies are taken from both sides. In order to increase the reliability of such studies, the sources and the magnitude of the sampling errors in the biopsy techniques need to be assessed in detail. In this study, cross-sections of whole right and left vastus lateralis muscle from six young sedentary right-handed men were prepared, and the total number and size of fibres and the proportion of the different fibre types were calculated. A significant difference (P less than 0.05-P less than 0.001) between the right and the left muscle was found for at least one of the three variables in each of the six men, but there was no systematic difference and, therefore, no significant right-left difference for the whole group. The maximum difference between the right and the left side for the mean fibre size was 25% and for the fibre type proportion 5%; these differences are much smaller than the known variation within individual muscles. In conclusion, any study involving biopsies from both the right and the left vastus lateralis may use either muscle for the experiment while the contralateral muscle serves as a control without leading to systematic sampling error, whereas the errors involved in taking small samples from each muscle are much more important to control and to reduce.
The central changes associated with a period of strength training have been investigated in a group of 32 young healthy volunteers. Subjects participated in one of three 12 week training programmes, which required different degrees of skill and coordination. Study 1 consisted of unilateral isometric training of the quadriceps with the contralateral leg acting as a control, the apparatus providing firm back support and a lap strap. In Study 2 training consisted of unilateral concentric leg-extension with back support and hand-grips. In Study 3 subjects performed bilateral leg-extension with no back support. Measurements of maximum voluntary isometric strength were made at 2-3 week intervals and a continual record was kept of the weights lifted in Studies 2 and 3. The largest increase in isometric force was seen for the trained leg in Study 1 (approximately 40%). There was no significant change in strength in the contralateral untrained leg. In Studies 2 and 3 there was a large increase in training weights (about 200%) associated with smaller increase in isometric force (15-20%). It is concluded that a large part of the improvement in the ability to lift weights was due to an increased ability to coordinate other muscle groups involved in the movement such as those used to stabilise the body. The importance of these findings for athletic training and rehabilitation is discussed.
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1. Skinfold thicknesses at four sites – biceps, triceps, subscapular and supra-iliac – and total body density (by underwater weighing) were measured on 209 males and 272 females aged from 16 to 72 years. The fat content varied from 5 to 50% of body-weight in the men and from 10 to 61% in the women.2. When the results were plotted it was found necessary to use the logarithm of skinfold measurements in order to achieve a linear relationship with body density.3. Linear regression equations were calculated for the estimation of body density, and hence body fat, using single skinfolds and all possible sums of two or more skinfolds. Separate equations for the different age-groupings are given. A table is derived where percentage body fat can be read off corresponding to differing values for the total of the four standard skinfolds. This table is subdivided for sex and for age.4. The possible reasons for the altered position of the regression lines with sex and age, and the validation of the use of body density measurements, are discussed.
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The construct validity and the test-retest reliability of a self-administered questionnaire about habitual physical activity were investigated in young males (n = 139) and females (n = 167) in three age groups (20 to 22, 25 to 27, and 30 to 32 yr) in a Dutch population. By principal components analysis three conceptually meaningful factors were distinguished. They were interpreted as: 1) physical activity at work; 2) sport during leisure time; and 3) physical activity during leisure time excluding sport. Test-retest showed that the reliability of the three indices constructed from these factors was adequate. Further, it was found that level of education was inversely related to the work index, and positively related to the leisure-time index in both sexes. The subjective experience of work load was not related to the work index, but was inversely related to the sport index, and the leisure-time index in both sexes. The lean body mass was positively related the the work index, and the sport index in males, but was not related to the leisure-time index in either sex. These differences in the relationships support the subdivision of habitual physical activity into the three components mentioned above.