Effect of in-season creatine supplementation on body composition and performance in rugby union football players
Applied Physiology Nutrition and Metabolism
Abstract
Rugby union football requires muscular strength and endurance, as well as aerobic endurance. Creatine supplementation may enhance muscular performance, but it is unclear if it would interfere with aerobic endurance during running because of increased body mass. The purpose of this study was to determine if creatine supplementation during 8weeks of a season of rugby union football can increase muscular performance, without negatively affecting aerobic endurance. Rugby union football players were randomized to receive 0.1gkg¹d¹ creatine monohydrate (n = 9) or placebo (n = 9) during 8weeks of the rugby season. Players practiced twice per week for approximately 2h per session and played one 80 min game per week. Before and after the 8weeks, players were measured for body composition (air displacement plethysmography), muscular endurance (number of repetitions at 75% of one repetition maximum (1 RM) for bench press and leg press), and aerobic endurance (Leger shuttle-run test with 1min stages of progressively increasing speed). There were time main effects for body mass (0.7 0.4kgp = 0.05), fat mass (1.9 0.8kgp<0.05), and a trend for an increase in lean tissue mass (+1.2 0.5kgp = 0.07), with no differences between groups. The group receiving creatine supplementation had a greater increase in the number of repetitions for combined bench press and leg press tests compared with the placebo group (+5.8 1.4 vs.+0.9 2.0 repetitionsp<0.05). There were no changes in either group for aerobic endurance. Creatine supplementation during a rugby union football season is effective for increasing muscular endurance, but has no effect on body composition or aerobic endurance.
... Creatine is one of the most widely used ergogenic aids in sports nutrition among athletes [46][47][48]. The most common use of creatine for athletes is to increase intracellular creatine within the muscles, thus increasing creatine phosphate (PCr) availability in the muscles to increase an individual's capacity for acute exercise in pursuit of increases in training adaptations [49][50][51][52][53][54][55][56]. It has been chiefly used by power or strength athletes for optimal adaptations to training and recovery from PCr exhaustive endeavors [57]. ...
... In addition, Mills et al. demonstrated that a creatine-supplemented group experienced a more significant increase in leg press, chest press, and total body strength and leg press endurance versus a placebo [64]. Furthermore, creatine supplementation can increase regional muscle thickness [55], enhance muscular endurance in rugby players [53], and increase muscular strength [51,52] and power [50]. ...
... Chilibeck PD et al., 2007 [53] 8-week supplementation of creatine 5 g or placebo Increased repetitions for both bench press and leg press in the creatine group Creatine helps increase muscle endurance in rugby players. ...
Background/Objectives: Sports supplements have become popular among fitness enthusiasts for enhancing the adaptive response to exercise. This review analyzes five of the most effective ergogenic aids: creatine, beta-alanine, nitrates, caffeine, and protein. Methods: We conducted a narrative review of the literature with a focus on the sport supplements with the most robust evidence for efficacy and safety. Results: Creatine, one of the most studied ergogenic aids, increases phosphocreatine stores in skeletal muscles, improving ATP production during high-intensity exercises like sprinting and weightlifting. Studies show creatine supplementation enhances skeletal muscle mass, strength/power, and muscular endurance. The typical dosage is 3–5 g per day and is safe for long-term use. Beta-alanine, when combined with the amino acid histidine, elevates intramuscular carnosine, which acts as a buffer in skeletal muscles and delays fatigue during high-intensity exercise by neutralizing hydrogen ions. Individuals usually take 2–6 g daily in divided doses to minimize paresthesia. Research shows significant performance improvements in activities lasting 1–4 min. Nitrates, found in beetroot juice, enhance aerobic performance by increasing oxygen delivery to muscles, enhancing endurance, and reducing oxygen cost during exercise. The recommended dosage is approximately 500 milligrams taken 2–3 h before exercise. Caffeine, a central nervous system stimulant, reduces perceived pain while enhancing focus and alertness. Effective doses range from 3 to 6 milligrams per kilogram of body weight, typically consumed an hour before exercise. Protein supplementation supports muscle repair, growth, and recovery, especially after resistance training. The recommended intake for exercise-trained men and women varies depending on their specific goals. Concluions: In summary, creatine, beta-alanine, nitrates, caffeine, and protein are the best ergogenic aids, with strong evidence supporting their efficacy and safety.
... Consequently, 41 eligible studies were included for the fulltext screening. Finally, 13 articles were considered to be included in this SRMA, involving 277 participants [37][38][39][40][41][42][43][44][45][46][47][48][49]. Figure 1 displays the information concerning the PRISMA flow diagram. ...
... All relevant information regarding studies meeting the inclusion criteria is summarized in Table 1. Nine studies reported a loading supplementation protocol [37-39, 41, 44-48], while six studies reported a maintenance supplementation protocol [40,42,43,45,48,49]. Two studies started with a loading protocol and continued with the maintenance protocol [45,48]. ...
... Concerning the body mass change, five studies showed a significant body mass increase after CrM supplementation [39,40,[43][44][45], while three studies observed no change in body mass after a period of CrM ingestion [37,42,48]. Five studies included in this SRMA did not provide data regarding body mass change [38,41,46,47,49]. ...
Background
There is robust evidence that creatine monohydrate supplementation can enhance short-term high-intensity exercise in athletes. However, the effect of creatine monohydrate supplementation on aerobic performance and its role during aerobic activities is still controversial.
Objective
The purpose of this systematic review and meta-analysis was to evaluate the supplementation effects of creatine monohydrate on endurance performance in a trained population.
Methods
The search strategy in this systematic review and meta-analysis was designed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and PubMed/MEDLINE, Web of Science, and Scopus databases were explored from inception until 19 May, 2022. Only human experimental trials, controlled with a placebo group, evaluating the effects of creatine monohydrate supplementation on endurance performance in a trained population were analyzed in this systematic review and meta-analysis. The methodological quality of included studies was evaluated using the Physiotherapy Evidence Database (PEDro) scale.
Results
A total of 13 studies satisfied all the eligibility criteria and were included in this systematic review and meta-analysis. The results for the pooled meta-analysis showed a non-significant change in endurance performance after creatine monohydrate supplementation in a trained population (p = 0.47), with a trivial negative effect (pooled standardized mean difference = − 0.07 [95% confidence interval − 0.32 to 0.18]; I² = 34.75%). Further, after excluding the studies not evenly distributed around the base of the funnel plot, the results were similar (pooled standardized mean difference = − 0.07 [95% confidence interval − 0.27 to 0.13]; I² = 0%; p = 0.49).
Conclusions
Creatine monohydrate supplementation was shown to be ineffective on endurance performance in a trained population.
Clinical Trial Registration
The study protocol was registered in the Prospective Register of Systematic Review (PROSPERO) with the following registration number: CRD42022327368.
... El análisis detallado de los estudios revela que la dosis estándar de 0,1gr/Kg/día (ya ampliamente difundida como principal indicación de uso) (24,25) por períodos superiores a los 30 días genera aumentos significativos en la masa magra, asociados también a una disminución notable en el porcentaje de grasa corporal. Esos datos respaldan hallazgos anteriores (26,27,28) y refuerzan la idea de que la creatina monohidratada puede ser un aliado eficaz en la modulación de la composición corporal, ofreciendo beneficios importantes para deportistas profesionales. Es importante destacar que se presenta una marcada variabilidad en los resultados cuando se aplica la suplementación a poblaciones de individuos clasificados como deportistas recreativos. ...
Background: Considering the growing awareness of the population regarding the importance of engaging in physical activity, the utilization of supplements, such as creatine monohydrate, is also expanding in search of the attributed benefits of these substances. This study describes and analyzes the relationship between supplementation with creatine monohydrate and the improvement in the athletic performance of athletes from various disciplines and training levels, as well as non-athletes. Material and methods: A systematic review of clinical trials that address the use of creatine monohydrate in various sports contexts was conducted, followed by an analysis of the results based on body composition, jump capacity, and strength performance to determine points of correlation between the data presented in each publication. Results: A significant improvement in body composition, jump capacity, and strength performance was observed among participants who used supplementation, although in many cases, the results were heterogeneous. Conclusion: Creatine monohydrate supplementation positively influences body composition and physical performance, but further research is needed to understand its effects in specific populations.
... Prior studies indicate that CrM loading (i.e., 4 × 5 g/day for 5-7 days) or low-dose longterm intake (e.g., 3-6 g/day for 4-12 weeks) increases muscle creatine retention typically by 20-40% depending on initial creatine content in the muscle [12,22,[68][69][70][71]] and brain creatine content by 5-15% [72][73][74][75][76][77]. CrM supplementation has been reported to improve acute exercise performance particularly in intermittent high-intensity exercise bouts as well as enhance training adaptations in adolescents [78][79][80][81][82], young adults [29,55,[83][84][85][86][87][88][89][90][91][92], and older individuals [8,77,[93][94][95][96][97][98][99][100][101]. High-intensity exercise performance is generally increased by 10-20% with greater improvements seen in individuals starting the supplementation protocol with lower muscle creatine and PCr content [102]. ...
In 2011, we published a paper providing an overview about the bioavailability, efficacy, and regulatory status of creatine monohydrate (CrM), as well as other “novel forms” of creatine that were being marketed at the time. This paper concluded that no other purported form of creatine had been shown to be a more effective source of creatine than CrM, and that CrM was recognized by international regulatory authorities as safe for use in dietary supplements. Moreover, that most purported “forms” of creatine that were being marketed at the time were either less bioavailable, less effective, more expensive, and/or not sufficiently studied in terms of safety and/or efficacy. We also provided examples of several “forms” of creatine that were being marketed that were not bioavailable sources of creatine or less effective than CrM in comparative effectiveness trials. We had hoped that this paper would encourage supplement manufacturers to use CrM in dietary supplements given the overwhelming efficacy and safety profile. Alternatively, encourage them to conduct research to show their purported “form” of creatine was a bioavailable, effective, and safe source of creatine before making unsubstantiated claims of greater efficacy and/or safety than CrM. Unfortunately, unsupported misrepresentations about the effectiveness and safety of various “forms” of creatine have continued. The purpose of this critical review is to: (1) provide an overview of the physiochemical properties, bioavailability, and safety of CrM; (2) describe the data needed to substantiate claims that a “novel form” of creatine is a bioavailable, effective, and safe source of creatine; (3) examine whether other marketed sources of creatine are more effective sources of creatine than CrM; (4) provide an update about the regulatory status of CrM and other purported sources of creatine sold as dietary supplements; and (5) provide guidance regarding the type of research needed to validate that a purported “new form” of creatine is a bioavailable, effective and safe source of creatine for dietary supplements. Based on this analysis, we categorized forms of creatine that are being sold as dietary supplements as either having strong, some, or no evidence of bioavailability and safety. As will be seen, CrM continues to be the only source of creatine that has substantial evidence to support bioavailability, efficacy, and safety. Additionally, CrM is the source of creatine recommended explicitly by professional societies and organizations and approved for use in global markets as a dietary ingredient or food additive.
... Chappell et al. reported that~48 % of males and~51 % of females supplemented with creatine during their contest preparation [2]. Creatine has been shown to improve body composition (i.e. increase lean body mass, decrease fat mass) [127,128] and increase intracellular hydration status [129,130]. Ziegenfuss et al. [129] demonstrated that a three day creatine loading phase increased intracellular fluid volume by~3 % without impacting extracellular fluid. ...
Bodybuilding is a competitive endeavor where a combination of muscle size, symmetry, “conditioning” (low body fat levels), and stage presentation are judged. Success in bodybuilding requires that competitors achieve their peak physique during the day of competition. To this end, competitors have been reported to employ various peaking interventions during the final days leading to competition. Commonly reported peaking strategies include altering exercise and nutritional regimens, including manipulation of macronutrient, water, and electrolyte intake, as well as consumption of various dietary supplements. The primary goals for these interventions are to maximize muscle glycogen content, minimize subcutaneous water, and reduce the risk abdominal bloating to bring about a more aesthetically pleasing physique. Unfortunately, there is a dearth of evidence to support the commonly reported practices employed by bodybuilders during peak week. Hence, the purpose of this article is to critically review the current literature as to the scientific support for pre-contest peaking protocols most commonly employed by bodybuilders and provide evidence-based recommendations as safe and effective strategies on the topic.
Background
Despite the robust evidence demonstrating positive effects from creatine supplementation (primarily when associated with resistance training) on measures of body composition, there is a lack of a comprehensive evaluation regarding the influence of creatine protocol parameters (including dose and form) on body mass and estimates of fat-free and fat mass.
Methods
Randomized controlled trials (RCTs) evaluating the effect of creatine supplementation on body composition were included. Electronic databases, including PubMed, Web of Science, and Scopus were searched up to July 2023. Heterogeneity tests were performed. Random effect models were assessed based on the heterogeneity tests, and pooled data were examined to determine the weighted mean difference (WMD) with a 95% confidence interval (CI).
Results
From 4831 initial records, a total of 143 studies met the inclusion criteria. Creatine supplementation increased body mass (WMD: 0.86 kg; 95% CI: 0.76 to 0.96, I² = 0%) and fat-free mass (WMD: 0.82 kg; 95% CI: 0.57 to 1.06, I² = 0%) while reducing body fat percentage (WMD: −0.28 %; 95% CI: −0.47 to −0.09; I² = 0%). Studies that incorporated a maintenance dose of creatine or performed resistance training in conjunction with supplementation had greater effects on body composition.
Conclusion
Creatine supplementation has a small effect on body mass and estimates of fat-free mass and body fat percentage. These findings were more robust when combined with resistance training.
The maximal number of repetitions that can be completed at various percentages of the one repetition maximum (1RM) [REPS ~ %1RM relationship] is foundational knowledge in resistance exercise programming. The current REPS ~ %1RM relationship is based on few studies and has not incorporated uncertainty into estimations or accounted for between-individuals variation. Therefore, we conducted a meta-regression to estimate the mean and between-individuals standard deviation of the number of repetitions that can be completed at various percentages of 1RM. We also explored if the REPS ~ %1RM relationship is moderated by sex, age, training status, and/or exercise. A total of 952 repetitions-to-failure tests, completed by 7289 individuals in 452 groups from 269 studies, were identified. Study groups were predominantly male (66%), healthy (97%), < 59 years of age (92%), and resistance trained (60%). The bench press (42%) and leg press (14%) were the most commonly studied exercises. The REPS ~ %1RM relationship for mean repetitions and standard deviation of repetitions were best described using natural cubic splines and a linear model, respectively, with mean and standard deviation for repetitions decreasing with increasing %1RM. More repetitions were evident in the leg press than bench press across the loading spectrum , thus separate REPS ~ %1RM tables were developed for these two exercises. Analysis of moderators suggested little influences of sex, age, or training status on the REPS ~ %1RM relationship, thus the general main model REPS ~ %1RM table can be applied to all individuals and to all exercises other than the bench press and leg press. More data are needed to develop REPS ~ %1RM tables for other exercises.
Creatine supplementation has been shown to increase measures of lean body mass (LBM), however there is often high heterogeneity across individual studies. Therefore, we systematically reviewed and meta-analyzed randomized controlled trials (RCTs) investigating creatine supplementation on LBM. Sub-analyses were performed based on age, sex, and type of exercise. Based on PRISMA guidelines, we searched the following databases: Pubmed, SPORTDiscus, Web of Science, and Scopus (PROSPERO register: CRD42020207122) until May 2022. RCTs that investigated creatine supplementation on LBM were included. Animal studies and studies on individuals with specific diseases were excluded. Thirty-five studies were included, totaling 1192 participants. Overall (i.e., inclusion of all studies with and without exercise training interventions) revealed that creatine increased LBM by 0.68 kg (CI95%: 0.26, 1.11). Sub-analyses revealed greater gains in LBM when creatine was combined with resistance training [mean difference (MD): 1.10 kg; CI95%: 0.56, 1.65], regardless of age. There was no statistically significant effect of creatine on LBM when combined with mixed exercise (MD: 0.74 kg; CI95%: -3.89, 5.36) or without exercise (MD: 0.03 kg; CI95%: -0.65, 0.70). Further sub-analyses found that males on creatine increased LBM by 1.46 kg (CI95%: 0.47, 2.46), compared to a non-significant increase of 0.29 kg (CI95%: -0.43, 1.01) for females. In conclusion, the addition of creatine supplementation to a resistance training program increases LBM. During a resistance training program, males on creatine respond more favorably compared to females.
Vücut geliştirme sporunun popülaritesi gün geçtikçe artmaktadır fakat buna karşılık literatüre bakıldığında kanıta dayalı beslenme önerilerinin sayısının oldukça az olduğu görülmektedir. Bu çalışmada literatürde geçen, vücut ge- liştirme sporcuları için verilen kanıta dayalı güncel beslenme önerileri derlenmiştir. Vücut geliştirme sporuyla ilgilenen bireylerde enerji ihtiyacının doğru hesaplanması, vücut ağırlığında azalma sağlamak için temel hedef olmalıdır. Vücut geliştirme sporcularında kas kaybını önlemek için haftalık en fazla %1’lik vücut ağırlığında azalma önerilmektedir. Vücut geliştirme sporcusu için gerekli enerji hesaplaması yapıldıktan sonra, vücut ağırlığında kilogram başına en az 2.3 g/kg/gün protein alımı önerilmektedir. Aynı zamanda her öğünün 0.4-0.5 g/kg protein içermesi önerilmektedir. Günlük enerji gereksiniminin %15-30’unun yağlardan, %20’sinin proteinlerden ve geri kalanın ise karbonhidratlardan gelecek şekilde beslenme programı düzenlenmelidir. Vücut geliştirme sporcuları için ideal öğün sayısında ise özellikle dayanıklılık egzersizleri süresince günlük 3 ile 6 öğün tercih edilmelidir. Yapılan araştırma sonuçlarına göre öğün saatleri ve sıklığının vücut ağırlığında azalma veya yağsız kütleyi korumak için belirgin bir pozitif etkisinin olmadığı görülmüştür. Müsabakalardan birkaç gün önce uygulanan dehidrasyon programı, elektrolit imbalansına sebep olabileceğinden dikkatli olunması gerekmektedir. Müsabakalara hazırlanılan son dönemlerde karbonhidrat alımındaki artışın olumlu etkileri olabilir, bu sebeple karbonhidrat yüklemesi sporcuya uygun olarak yapılmalıdır. Vücut geliştirme sporcularında supleman kullanımıyla ilgili de farklı tartışmalar bulunmaktadır. Kreatin monohidrat, kafein ve beta alanin alımının müsabakalara hazırlanma süresince olumlu etkileri olduğu görülmüştür. Diğer suplemanlarla ilgili daha fazla çalışmaya ihtiyaç olduğu, güncel literatür verileri dahilinde düşünülmektedir. Son olarak, estetik bir spor çeşidi olan vücut geliştirme sporcularında yeme bozuklukları ve vücut algısı bozukluklarının sık görüldüğü unutulmamalıdır.
Creatine monohydrate (CrM) is one of the most widely used nutritional supplements among active individuals and athletes to improve high-intensity exercise performance and training adaptations. However, research suggests that CrM supplementation may also serve as a therapeutic tool in the management of some chronic and traumatic diseases. Creatine supplementation has been reported to improve high-energy phosphate availability as well as have antioxidative, neuroprotective, anti-lactatic, and calcium-homoeostatic effects. These characteristics may have a direct impact on mitochondrion’s survival and health particularly during stressful conditions such as ischemia and injury. This narrative review discusses current scientific evidence for use or supplemental CrM as a therapeutic agent during conditions associated with mitochondrial dysfunction. Based on this analysis, it appears that CrM supplementation may have a role in improving cellular bioenergetics in several mitochondrial dysfunction-related diseases, ischemic conditions, and injury pathology and thereby could provide therapeutic benefit in the management of these conditions. However, larger clinical trials are needed to explore these potential therapeutic applications before definitive conclusions can be drawn.
Thirty-five healthy men were matched and randomly assigned to one of four training groups that performed high-intensity strength and endurance training (C; n = 9), upper body only high-intensity strength and endurance training (UC; n = 9), high-intensity endurance training (E; n = 8), or high-intensity strength training (ST; n = 9). The C and ST groups significantly increased one-repetition maximum strength for all exercises (P < 0.05). Only the C, UC, and E groups demonstrated significant increases in treadmill maximal oxygen consumption. The ST group showed significant increases in power output. Hormonal responses to treadmill exercise demonstrated a differential response to the different training programs, indicating that the underlying physiological milieu differed with the training program. Significant changes in muscle fiber areas were as follows: types I, IIa, and IIc increased in the ST group; types I and IIc decreased in the E group; type IIa increased in the C group; and there were no changes in the UC group. Significant shifts in percentage from type IIb to type IIa were observed in all training groups, with the greatest shift in the groups in which resistance trained the thigh musculature. This investigation indicates that the combination of strength and endurance training results in an attenuation of the performance improvements and physiological adaptations typical of single-mode training.
Anthropometric measurements were collected from a group of Australian Rules footballers at the start and end of the competitive season. Eighty-nine players were studied, drawn from a top level professional league team, a second level association team and an A-grade amateur association team. Changes in the physical profile of these players during the season were observed. A small but significant gain in fat-free body mass in the top level players was observed (0.9 kg, p less than 0.01), but no change in body fat. The intermediate level players showed no significant change in body mass and a tendency toward a slight loss in body fat, while the lower level players showed a significant loss in body fat during the season (1.8 kg, p less than 0.001) without significant change in fat-free body mass.
In order to validate a maximal multistage 20-m shuttle run test for the prediction of VO2 max, 91 adults (32 females and 59 males, aged 27.3 +/- 9.2 and 24.8 +/- 5.5 year respectively and with mean VO2 max (+/- SD) of 39.3 +/- 8.3 and 51.6 +/- 7.8 ml . kg-1 . min-1 respectively) performed the test and had VO2 max estimated by the retroextrapolation method (extrapolation to time zero of recovery of the exponential least squares regression of the first four 20-s recovery VO2 values). Starting at 8 km . h-1 and increasing by 0.5 km . h-1 every 2 min, the 20-m shuttle run test enabled prediction of the VO2 max (y, ml . kg-1 . min-1) from the maximal speed (x, km . h-1) by means of the following regression equation: y = 5.857x - 19.458; r = 0.84 and SEE = 5.4. Later, the multistage protocol was slightly modified to its final version, in which the test started at stage 7 Met and continued with a 1 Met (3.5 ml O2 . kg-1 . min-1) increment every 2 min. Twenty-five of the 91 subjects performed the 20-m shuttle test twice, once on a hard, low-friction surface (vinyl-asbestos tiles) and another time on a rubber floor, as well as a walking maximal multistage test on an inclined treadmill. There was no difference between the means of these tests or between the slopes of the VO2max - maximal speed regressions for the two types of surfaces. The 20-m shuttle run test and another maximal multistage field test involving continuous track running gave comparable results (r = 0.92, SEE = 2.6 ml O2 . kg-1 . min-1, n = 70). Finally, test and retest of the 20-m shuttle run test also yielded comparable results (r = 0.975, SEE = 2.0 ml O2 . kg-1 . min-1, n = 50). It is concluded that the 20-m shuttle run test is valid and reliable test for the prediction of the VO2 max of male and female adults, individually or in groups, on most gymnasium surfaces.
Purpose:
To study the effect of creatine (Cr) supplementation combined with resistance training on muscular performance and body composition in older men.
Methods:
Thirty men were randomized to receive creatine supplementation (CRE, N = 16, age = 70.4 +/- 1.6 yr) or placebo (PLA, N = 14, age = 71.1 +/- 1.8 yr), using a double blind procedure. Cr supplementation consisted of 0.3-g Cr.kg(-1) body weight for the first 5 d (loading phase) and 0.07-g Cr.kg(-1) body weight thereafter. Both groups participated in resistance training (36 sessions, 3 times per week, 3 sets of 10 repetitions, 12 exercises). Muscular strength was assessed by 1-repetition maximum (1-RM) for leg press (LP), knee extension (KE), and bench press (BP). Muscular endurance was assessed by the maximum number of repetitions over 3 sets (separated by 1-min rest intervals) at an intensity corresponding to 70% baseline 1-RM for BP and 80% baseline 1-RM for the KE and LP. Average power (AP) was assessed using a Biodex isokinetic knee extension/flexion exercise (3 sets of 10 repetitions at 60 degrees.s(-1) separated by 1-min rest). Lean tissue (LTM) and fat mass were assessed using dual energy x-ray absorptiometry.
Results:
Compared with PLA, the CRE group had significantly greater increases in LTM (CRE, +3.3 kg; PLA, +1.3 kg), LP 1-RM (CRE, +50.1 kg; PLA +31.3 kg), KE 1-RM (CRE, +14.9 kg; PLA, +10.7 kg), LP endurance (CRE, +47 reps; PLA, +32 reps), KE endurance (CRE, +21 reps; PLA +14 reps), and AP (CRE, +26.7 W; PLA, +18 W). Changes in fat mass, fat percentage, BP 1-RM, and BP endurance were similar between groups.
Conclusion:
Creatine supplementation, when combined with resistance training, increases lean tissue mass and improves leg strength, endurance, and average power in men of mean age 70 yr.
Previous measures of physical activity for epidemiologic studies were considered Inadequate to meet the needs of a community-based health education trial. Therefore, new methods of quantifying the physical activity habits of communities were developed which are practical for large health surveys, provide Information on the distribution of activity habits in the population, can detect changes in activity over time, and can be compared with other epidemiologic studies of physical activity. Independent sell-reports of vigorous activity (at least 6 metabolic equivalents (METs)), moderate activity (3–5 METs), and total energy expenditure (kilocalories per day) are described, and the physical activity practices of samples of California cities are presented. Relationships between physical activity measures and age, education, occupation, ethnicity, marital status, and body mass index are analyzed, and the reliabilities of the three activity indices are reported. The new assessment procedure is contrasted with nine other measures of physical activity used in community surveys.
The purpose of this investigation was to determine the short-term reproducibility of measurements of whole-body and subregion bone mass and density, as well as body composition, made by dual energy x-ray absorptiometry. Bone mineral content, bone mineral density and body composition were measured on two occasions, 1 to 2 weeks apart, in 21 women (average age, 20.9 [standard deviation 1.6] years). The method errors of the duplicate measurements, expressed as a percentage of the combined mean values from the two sets of measurements (i.e., as a coefficient of variation), for whole-body bone mineral content, bone mineral density, lean tissue mass and fat mass were 1.6%, 1.1%, 1.4% and 1.8% respectively. The method errors for bone mineral density in the hip were 2.2%, 1.1% and 2.5% for the neck, trochanter and Ward's triangle respectively. On the basis of the method errors and the expected treatment effects, the sample sizes needed for intervention trials (e.g., exercise training) were calculated. All of the whole-body and most of the subregion bone mineral density and lean tissue mass measurements made by dual-energy x-ray absorptiometry were sufficient for detecting the small changes (about 2%) expected in trials with 20 subjects, whereas measurements of subregion bone mineral content and fat mass were less precise.
A new air displacement plethysmograph, the BOD POD (BP), was evaluated in comparison to hydrostatic weighing (HW). Sixty-eight adult subjects (26 F, 42 M) varying widely in age (range 20-56 yr), ethnicity, and fatness participated in this study. Same-day test-retest reliability was assessed in a subsample of 16 subjects (9 F, 7 M) and validity was assessed in all subjects (N = 68). The test-retest coefficients of variation (CV) for %FAT measured by BP (%FATBP) and HW (%FATHW) were not significantly different (1.7% +/- 1.1% and 2.3% +/- 1.9% for BP and HW, respectively (mean +/- SD)), indicating excellent reliability for both methods. Validity of percent fat measured by the BP (%FATBP) was also excellent. The mean difference in %FAT (BP - HW) was -0.3 +/- 0.2 (SEM), with a 95% confidence interval of -0.6 to 0 %FAT. The regression equation (%FATHW = 1.86 + 0.94 %FATBP; r2 = 0.93, SEE = 1.81) was not significantly different from the line of identity (%FATHW = %FATBP), and did not differ by gender. These findings indicate that the BOD POD is a highly reliable and valid method for determining %FAT in adult humans in comparison to HW. This new method has several advantages over HW in that it is quick, relatively simple to operate and may be able to accommodate special populations such as the obese, elderly, and disabled.