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Building muscle: Nutrition to maximize bulk and strength adaptations to resistance exercise training
European Journal of Sport Science
Abstract
Several nutritional strategies can optimize muscle bulk and strength adaptations and enhance recovery from heavy training sessions. Adequate energy intake to meet the needs of training and carbohydrate intake sufficient to maintain glycogen stores (>7 g carbohydrate·kg·day for women; >8 g carbohydrate·kg·day for men) are important. Dietary protein intake for top sport athletes should include some foods with high biological value, with a maximum requirement of approximately 1.7 g·kg·day being easily met with an energy sufficient diet. The early provision of carbohydrate (>1 g·kg) and protein (>10 g) early after an exercise session will enhance protein balance and optimize glycogen repletion. Creatine monohydrate supplementation over several days increases body mass through water retention and can increase high-intensity repetitive ergometer performance. Creatine supplementation can enhance total body and lean fat free mass gains during resistance exercise training; however, strength gains do not appear to be enhanced versus an optimal nutritional strategy (immediate post-exercise protein and carbohydrate). Some studies have suggested that β-OH-methyl butyric acid (β-HMB) can enhance gains made through resistance exercise training; however, it has not been compared “head to head” with optimal nutritional practices. Overall, the most effective way to increase strength and bulk is to perform sport-specific resistance exercise training with the provision of adequate energy, carbohydrate, and protein. Creatine monohydrate and β-HMB supplementation may enhance the strength gains made through training by a small margin but the trade-off is likely to be greater bulk, which may be ergolytic for any athlete participating in a weight-supported activity.
... Berikut ini adalah tanda-tanda klinis yang mengindikasikan bahwa seseorang mengalami kekurangan zat gizi. (Houston, 1999;Kloby Nielsen et al., 2020;Tarnopolsky, 2008;Tipton & Ferrando, 2008). Rekomendasi umum untuk asupan protein dalam meningkatkan massa otot adalah 1,6-2,2 g/kgBB/hari. ...
... Contoh pilihan protein dalam pangan yang bisa dikonsumsi adalah telur (bagian putihnya) dan susu. Protein tersebut memiliki kemampuan absorpsi dan utilisasi yang lebih efisien di dalam tubuh dibandingkan dengan protein nabati (Tarnopolsky, 2008). ...
... Rekomendasi 7 g/kgBB/ hari untuk perempuan dan 8 g/kgBB/hari untuk laki-laki dapat diterapkan selama latihan yang intensif. Sumber karbohidrat yang diajurkan adalah bijibijian utuh, buah-buahan, sayuran, dan produk susu (Baranauskas et al., 2023;Kloby Nielsen et al., 2020;Tarnopolsky, 2008). ...
Buku Dasar Gizi Olahraga adalah panduan komprehensif yang dirancang untuk memberikan pemahaman mendalam tentang peran penting gizi dalam mendukung performa atlet dan kebugaran tubuh. Gizi olahraga adalah salah satu terapan ilmu gizi kepada atlet agar mampu mencapai prestasi yang optimal. Ilmu gizi olahraga adalah ilmu yang mempelajari hubungan antara pengelolaan makanan dengan kinerja fisik yang bermanfaat bagi kesehatan, kebugaran, pertumbuhan dan pembinaan prestasi olahraga bagi atlet secara khusus. Dalam buku ini, pembaca diajak untuk mengeksplorasi hubungan antara kebutuhan gizi dengan aktivitas fisik. Keunggulan buku ini adalah pendekatannya yang praktis, dengan dilengkapi studi kasus, tabel gizi, dan rekomendasi pola makan berdasarkan tingkat aktivitas fisik. Buku ini terdiri dari enam belas bab yang mencakup berbagai aspek gizi olahraga yang tersusun secara sistematis: (1) Dasar Ilmu Gizi, (2) Gizi Olahraga, Jenis dan Klasifikasinya, (3) Kebutuhan Zat Gizi Makro, (4) Kebutuhan Zat Gizi Mikro, (5) Kebutuhan Cairan dan Elektrolit, (6) Zat Ergogenik Gizi, (7) Gizi Sebelum, Saat dan Sesudah Olahraga, (8) Gizi pada Olahraga Daya Tahan (Endurance), (9) Gizi pada Olahraga Kekuatan (Strengh Training), (10) Gizi Atlet untuk Remaja dan Anak-Anak, (11) Gizi untuk Atlet Wanita, (12) Pengukuran dan Penilaian Status Gizi, (13) Manajemen Berat Badan Atlet, (14) Penggunaan Suplemen dan Doping dalam Olahraga, (15)Gangguan dan Penyakit Gizi pada Atlet, (16) Mitos Makanan dan Minuman untuk Atlet.
... 2,4 Some studies also suggest to the possibility of an even higher intake. 9 The majority of dietary carbohydrate should come from complex carbohydrates with a low to moderate glycemic index (named "slow carbs"). Appropriate sources are whole grains, fruit, vegetables, legumes, etc. ...
... It is advisable to consume a carbohydrate-rich meal with a low glycemic index approximately 1-2 hours before training . 4,9 Athletes should not exclude simple carbohydrates with high glycemic index (absorbed more quickly and faster) from their diet. These should be taken immediately after awakening and within two hours after training. ...
... Research over the last decade has indicated that athletes engaged in intense training need to ingest about two times the usual recommended daily allowance (RDA) of protein in their diet to maintain protein balance. 4,9 An insufficient amount of protein in the diet leads to the negative nitrogen balance, which can increase protein catabolism and can slow post-workout recovery. This may lead to muscle wasting, training intolerance and, certainly, overtraining. ...
The scientific literature contains an abundance of information on the nutritional demands of athletes. However, designing the most suitable sports diet is very difficult.The principal aim of this article is to summarize knowledge about sports nutrition, especially the intake of macronutrients and dietary supplements.
... Another factor contributing to the changes observed in body weight and body composition over time is the use of improved nutritional intake. This is especially true as it relates to adequate carbohydrate and protein intake during training (53). Numerous studies have demonstrated the importance of adequate carbohydrate and protein intake during training for the purpose of increasing body weight and muscle mass (53). ...
... This is especially true as it relates to adequate carbohydrate and protein intake during training (53). Numerous studies have demonstrated the importance of adequate carbohydrate and protein intake during training for the purpose of increasing body weight and muscle mass (53). Furthermore, an appropriate macronutrient intake is especially important during periods of heavy training when attempting to increase muscle mass (53). ...
... Numerous studies have demonstrated the importance of adequate carbohydrate and protein intake during training for the purpose of increasing body weight and muscle mass (53). Furthermore, an appropriate macronutrient intake is especially important during periods of heavy training when attempting to increase muscle mass (53). ...
The purpose of this study was to document changes in height (cm), body weight (kg) and body composition (%fat) of American football players from 1942 to 2011. Published articles were identified from data bases and cross referencing of bibliographies. Studies selected met the requirements of: 1) having two of three dependent (height, body weight, and body composition) variables reported in the results; 2) containing a skill level of college or professional; 3) providing measured, not self-reported data; and 4) published studies in English-language journals. The data were categorized into groups based on skill level (college and professional). The player positions were grouped into three categories: mixed linemen (offensive and defensive linemen, tight ends, and linebackers), mixed offensive backs (quarterback, and running backs), and mixed skilled positions (defensive backs and wide receivers). Linear regression was used to provide slope estimates and 95% confidence intervals. Unpaired t-tests were used to determine whether an individual regression slope was significantly different from zero. Statistical significance was set at p < 0.017. College level players in all position groups have significantly increased body weight over time (95% CI mixed lineman .338-.900 kg/yr; mixed offensive backs .089-.298 kg/yr; mixed skilled .078-.334 kg/yr). The college level mixed linemen showed a significant increase over time for height (95% CI .034-.188 cm/yr) and body composition (.046-.275 %fat/year). Significant increases in body weight over time were found for professional level mixed lineman (95% CI .098-.756 kg/yr) and mixed offensive backs (95% CI .180-.545 kg/yr). There were no other significant changes at the professional level. These data demonstrate that body weight of all college players and professional mixed lineman have significantly increased from 1942 to 2011.
... Likewise, our data show temporal gains in 1RM bench press ranging from 7.3 to 36.2 kg depending on position from those reported by Shields et al. (26). These improvements in strength may be because of players and strength and conditioning specialists becoming more knowledgeable about nutrition strategies focusing on macronutrient content and timing (31), nutraceutical and anabolic steroid use (15), year-round physical training (8), and the prevalence of professionally educated and trained strength and conditioning specialists. ...
... Beyond body composition and performance, several publications have observed high BM indexes in football players (particularly linemen) suggesting obesity and consequently increased cardiometabolic disease risk (14,15,30,31,32). It is important to note that BM index cannot distinguish between lean mass and fat mass, especially in athletes, limiting utility in correlating disease risk in this population (20). ...
The purpose of this study was to document the physical profiles of players on the 2011 New York Giants team (NYG) and to make comparisons with the historical literature on previous NFL player profiles. In this study height, body mass (BM), body fat percentage (BF%) using skin fold measurements, and several predicted one repetition maximal strength and power measures in 30 returning players from the 2011 NYG team, who recently won the Super Bowl, were collected. Players were grouped by position: running back (RB), quarterback (QB), wide receiver (WR), tight end (TE), offensive lineman (OL), defensive lineman (DL), linebacker (LB), and defensive back (DB). Pooled and weighted mean differences (NYG - NFL) and effect sizes were used to evaluate height, BM, and BF% comparisons of NYG to previous NFL studies from 1998-2009. The characteristics of the players as a group were: age, height, BM, BF% = 26±2 years, 183.8±9.0 cm, 144.9±20.8 kg, 14.3±5.5%, respectively. Comparisons highlight distinct position specific dissimilarity in strength measures, BM, and BF% which reflect current strength training, conditioning, and team play strategy. As expected, NYG positional differences were found for height (p≤0.05), BM (p≤0.037), BF% (p≤0.048), bench press (p≤0.048), inclined bench press (p≤0.013) and squat (p≤0.026). Anthropometrics profiles did not significantly differ from previously published trends in NFL players indicating equity in physical characteristics over the past 13 years. However, NYG linebackers, defensive and offensive linemen, quarterbacks and wide receivers trended toward less BF% but generally similar BM compared to NFL players, suggesting greater lean body mass in these positions. This study adds new players' data to prototypical position specific databases that may be used as templates for comparison of players for draft selection or physical training.
... Since many athletes consume Cr supplements during intense training periods as well as before major competitions [3]. Cr monohydrate (CrM) (a-methyl guandino-acetic acid), a naturally occurring nitrogenous compound is both synthesized endogenously mainly in the liver as well as in pancreas and kidney from three amino acids; glycine, arginine, methionine; and provided through normal dietary intake for body [4,5]. However, there is anecdotal information about of Cr supplementation effects on various aspects of athlete's health [6][7][8][9][10]. ...
... Despite a large number of publications on the ergogenic effects of Cr [5,9,12,17], there are limited, anecdotal reports on the possible adverse effects of this supplement [6][7][8][9]12]. Hence, this study was done to clarify the effects of CrM loading on some serum indirect markers of cellular damage in young soccer players who participated in one week circuit weight training. ...
In recent years, creatine (Cr) supplementation has received great attention in both popular and scientific media. Nevertheless, there is anecdotal information on the side effects of this supplement. Hence, we hypothesized that Cr monohydrate (CrM) loading would induce increase in serum enzymes activity as indirect markers of cellular damage. Therefore, the present study was conducted to identify the effect of short-term Cr supplementation on serum lactate dehydrogenase (LDH), creatine phosphokinase (CK), and myocardial CK isoform (CKMB) in young male soccer players.
... The recommendations for protein intake in athletes are described with a maximum requirement of approximately 1.7 g per kg body mass (11). Dietary surveys show that the dietary patterns of athletes provide protein intakes of 1.2-2.0 ...
... However, recent reviews discussing this aspect conclude that it still seems unclear if there is a real benefi t for athletes following this strategy (8,12). Even if studies show different fi ndings, a protein-carbohydrate snack or meal after strenuous workout seems to be a possible choice for muscle repair, adaptation to training and to provide carbohydrate fuel to restore muscle glycogen levels (11). Nevertheless, in general this does not make a carbohydrate-protein bar, drink or powder necessary, it can be provided by a food based snack or meal. ...
Multiple components of the immune systems in athletes exhibit transient dysfunction after prolonged, heavy exertion. During this "open window" of impaired immunity, pathogens may gain a foothold, increasing infection risk. Nutritional supplements have been studied as countermeasures to exercise-induced immune changes and infection risk. This review focuses on findings from recent exercise-based studies with macro- and micronutrient supplements, and "advanced" immunonutrition supplements including beta-glucan, curcumin, and quercetin. Results from these studies indicate that immunonutrition supplements have the potential to lessen the magnitude of exercise-induced perturbations in immune function and to reduce the risk of upper respiratory tract infections.
... Carbohydrate intakes greater than 7.0 g · kg -1 day -1 for women and greater than 8.0 g kg -1 · day -1 for men is probably sufficient for the maintenance of carbohydrate store during repetitive training sessions (Burke, Loucks & Board, 2006). The sport-specific and periodization training, optimal nutrition intake, genetic factors, and equipment are the main determinants of athletic performance ( (Tarnopolsky, 2008). ...
Background Introduction and theme actuality: this study is part of a larger work, which involves increasing sporting
performance by applying mental training techniques, special techniques of neuro-linguistic programming.
Objectives Purpose of study and hypothesis is if ideomotor representations of athletes are completed with multiple sensations
of all sensory sub modalities such as visual, auditory, kinaesthetic, olfactory and gustatory, the possibility of applying the techniques
of NLP (neurolinguistic programming) will have more effective results. We have studied the relationship between sensory sub
modalities, in accordance with the Bandler & Thomson, (2012) and application of Jacobson, (2011).
Methods and material two records were made by using two tests, test 1 and test 2, on master students of the ―Babeș-Bolyai‖
University Cluj-Napoca, from the Faculty of Physical Education and Sport. The statistical indicators were calculated on elements of
descriptive statistics and the data is presented using indicators of centrality, location and distribution. Statistical analysis of nonparametric
Wilcoxon test was used for sample pairs.
Results. Discussions and findings to pinpoint the correlation between the two variables, we used the Spearman rank
correlation coefficient (ρ). Statistical analysis was performed using the correlation coefficients Colton‘s rule. No statistically
significant differences were found (p> 0.05) in the statistical analysis because the short timeframe, but there are many good and very
good correlations at both tests, between the values of the items studied.
Conclusions and recommendations: we want to continue with this study because the time difference between T1 and T2 was
three months and we want to extend this study to a minimum of six months. All sensory sub modalities are particularly important in
achieving ideomotor representations underlying mental training.
... The first is that Tsitsimpikou et al. [47] found that crea¬ tine supplementation was more prevalent in power than endurance AWD. The second reason is that the physical qualities sought by power athletes, such as strength, power, speed and repeated sprint ability, are more commonly assessed variables in studies involving creatine supplementation in able-bodied athletes [54] and other chronic condition groups [55]. However, sig¬ nificant increases in strength have been reported to occur from creatine supplementation in humans with neuromuscular conditions in one study [56]. ...
This chapter reviews the literature for the benefits of exercise and nutrition in improving physical performance for individuals with a disability, in particular spinal cord injuries or amputation. The ways in which spinal cord injury or amputation can negatively affect muscle, fat and bone mass are discussed in light of the potentially questionable validity of many common body composition techniques for use with individuals with these disabilities. While resistance training significantly increased muscular strength and power and even aerobic fitness in recreationally active individuals with a disability, very few studies were conducted on athletes with a disability (AWD). The relatively modest literature on dietary habits of AWD suggests that, as a group, they meet most macronutrient and micronutrient RDAs, but that individual AWD dietary records reveal many may still not meet RDAs on several important micronutrients. The small number of studies on carbohydrate and creatine monohydrate supplementation is somewhat equivocal but does suggest some performance benefits can be gained in different situations.
... Although it was not measured in this study, it can be speculated that the increases in body mass over time can be attributed to the changing demands of the game (28), training (15), and nutritional intervention (33). Drugs, in particular anabolic steroids, have also been attributed to the increases in body mass (18). ...
This study compared changes in the body size and physical characteristics of South African u20 rugby union players over a 13-year period. A total of 453 South African u20 players, (Forwards; n = 256 and Backs; n = 197), underwent measurements of body mass, stature, muscular strength, endurance and 10 m and 40 m sprint times. A two-way analysis of variance was used to determine significance differences for the main effects of position (Forwards vs. Backs) and time (1998-2010). The pooled data showed that Forwards were significantly heavier (22%), taller (5%) and stronger (18%) than the Backs. However, when 1 RM strength scores were adjusted for body mass, Backs were stronger per kg body mass. Stature did not change over the 13-year period for both groups. There were however significant increases in muscular strength (50%), body mass (20%), muscular endurance (50%). Furthermore, an improvement in sprint times over 40 m (4%) and 10 m (7%) was evident over the period of the study. In conclusion, the players became heavier, stronger, taller and improved their upper body muscular endurance over the 13 years of the study. Furthermore, sprint times over 10 m and 40 m improved over the same time period despite the increase in body mass. It can be speculated that the changes in physical characteristics of the players over time are possibly a consequence of; 1) adaptations to the changing demands of the game, and 2) advancements in training methods.
... The collective agreement among reviewers is that a protein intake of 1.2-2.2 g/kg is sufficient to allow adaptation to training for athletes whom are at or above their energy needs [23][24][25][26][27][28][35][36][37][38]. However, bodybuilders during their contest preparation period typically perform resistance and cardiovascular training, restrict calories and achieve very lean conditions [2][3][4][5][6][17][18][19][20][21]. ...
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.
... It is important to note that studies have indicated that exercising in a carbohydrate-depleted state causes the body to adapt to such conditions [50, 51] by increasing mitochondria density, which allows for greater oxidation of fatty acids for energy production [50, 51]. Also, studies have shown that when carbohydrate intake is low, dietary protein oxidation occurs at a greater rate, allowing for sustained energy production [52, 53]. This allows working muscle to continue working at a higher level when consuming a low-carbohydrate diet. ...
Background: Mixed Martial Arts (MMA) is a growing sport that places competitors into specific weight classes to level the competition field. Athletes “cut weight” to compete in a weight class lower than their “walk around” weight. Techniques for cutting weight include dehydration, starvation and exercise in hot environments jeopardizing health and performance. Higher-protein diets (HPD) have been shown to improve weight loss by increasing satiety, thermogenesis, decreasing total energy intake, and maintain lean mass during periods of energy deficiency, such as weight loss. Research regarding the impact of HPD on performance is limited and conflicting. Specific Aims: The central hypothesis for this study was: HPD diets will elicit greater weight loss and enhance body composition compare to tradition low-fat diets in non-obese, active individuals. The three specific aims of this study are: 1) examine the effects of HPD on weight loss, 2) evaluate the impact of HPD of athletic performance, and 3) determine the effectiveness of HPD for accelerated weight loss. Methods: Military personnel participating in the Combatives program were recruited. Participants were assigned a HPD (40% CHO, 30% PRO, 30% fat), traditional low-fat, high-carbohydrate diet (65% CHO, 15% PRO, 20% fat), or an ad libitum diet for 12-day to 6-weeks depending on their training program. Fields tests for pre- and post-intervention measures of performance included: vertical jump and leg power index to measure explosive power, 600 meter shuttle run for anaerobic capacity and 1.5 mile run for aerobic capacity. Pre- and post-intervention of weight and body composition were determined using dual energy x-ray absorptiometry. Diet analysis software was used to determine nutrient intakes during the study. SPSS statistical software was used to determine descriptive statistics, paired t-tests, Pearson’s Correlations and one-way ANOVA. Results & Conclusions: Due to the unanticipated high rate of dropout, statistical significance was difficult to determine, however, there was a trend for the HPD to elicit fat-free mass retention and it not negatively impact performance. Discrepancies in energy and nutrient intake made dietary comparison difficult. Future studies with larger samples and greater dietary control are needed to further evaluate the research goals of this study. Doctor of Philosophy Doctoral Department of Human Nutrition Mark D. Haub
OvERvIEw As discussed in the last issue, attempting to train strength-and endurance-related qualities concurrently within the same programme appears to produce an interference effect which compromises gains in muscular strength. This article aims to provide recommendations for the strength and conditioning (S&C) coach to minimise the negative effects associated with concurrent training, based on an understanding of the mechanisms (presented in Part I) which are likely to be responsible.
This study examined how exercise goals predicted body image concerns and the use of supplements in a sample of Lithuanian fitness center exercisers of both genders. Fitness exercisers (N=238) completed questionnaires measuring exercising goals, body image (BI), social physique anxiety (SPA) and the use of muscle gain (MGS) and weight loss (WLS) supplements. Regression analyses showed that appearance goals of exercising were associated with higher BI concerns and SPA. Relatively intrinsic exercise goals (interest/enjoyment, fitness, and competence) were not associated or negatively associated with BI and SPA. Relatively intrinsic social interaction goals were associated with higher BI and SPA. No differences in BI and SPA between MGS and WLS users versus nonusers were found. Women WLS users demonstrated higher overweight preoccupation. Relatively intrinsic fitness goals were associated with lower MGS use. Competence goals were associated with higher MGS use. Results highlight the importance of understanding the motives of goals and fostering self-determined motivation when preventing body image concerns among exercisers.
THIS REVIEW EXAMINES THE LITERATURE ON PROTEIN REQUIREMENTS FOR STRENGTH TRAINING AND PROVIDES PRACTICAL SUGGESTIONS WITH REGARDS TO THE AMOUNT AND TIMING OF PROTEIN INTAKE. BY ANALYZING THE EFFECTS OF RESISTANCE EXERCISE ON PROTEIN METABOLISM, EXCESSIVELY HIGH PROTEIN REQUIREMENTS FOR STRENGTH TRAINING MAY BE EXPELLED. FURTHERMORE, AN EXAMINATION INTO THE RELIABILITY OF PROTEIN TURNOVER MEASUREMENT MODELS, INCLUDING THE NITROGEN BALANCE METHOD AND TRACER METHODS, UNDERLINES THE LACK OF SCIENTIFIC EVIDENCE FOR THE HABITUAL HIGH PROTEIN INTAKE CURRENTLY ESTABLISHED WITHIN THOSE WHO UNDERTAKE STRENGTH TRAINING.
Sports nutrition is a constantly evolving field with many of research papers published annually. However, designing the most suitable sports diet is very difficult. It must be given to the type of training, its duration and intensity, the age and sex of the athlete and also for overall health. The aim of this article is to summarize knowledges about sports nutrition, especially intake of carbohydrates, proteins, fats and dietary supplements and their influence on the performance and recovery of the athlete.doi:10.5219/126
Designing the most suitable diet for an athlete requires an intimate knowledge of the relevant scientific literature, the training and competition demands of the sport, the individual athlete's preferences and social situation. The scientific literature contains an abundance of information on nutritional demands of athletes undertaking endurance or strength training programmes, but much less information is available on sprint/power sports, team, racquet, weight-making, aesthetic (diving, gymnastics), and skill-based events. Furthermore, most research has been undertaken on adult males, with the assumption that females and adolescent athletes follow the same patterns of fuel usage and requirements. Consequently, assessing the optimal composition of an athlete's diet relies at best on an informed interpretation of the scientific data, plus individually collected observations. The aims of this article are to provide an overview of the current evidence on macronutrient requirements for day-to-day training for a range of different athletes, provide some recommendations regarding formulating an athlete's diet, and highlight areas where more research is required.
Background: Resistance exercise leads to net muscle protein accretion through a synergistic interaction of exercise and feeding. Proteins from different sources may differ in their ability to support muscle protein accretion because of different patterns of postprandial hyperaminoacidemia.
Objective: We examined the effect of consuming isonitrogenous, isoenergetic, and macronutrient-matched soy or milk beverages (18 g protein, 750 kJ) on protein kinetics and net muscle protein balance after resistance exercise in healthy young men. Our hypothesis was that soy ingestion would result in larger but transient hyperaminoacidemia compared with milk and that milk would promote a greater net balance because of lower but prolonged hyperaminoacidemia.
Design: Arterial-venous amino acid balance and muscle fractional synthesis rates were measured in young men who consumed fluid milk or a soy-protein beverage in a crossover design after a bout of resistance exercise.
Results: Ingestion of both soy and milk resulted in a positive net protein balance. Analysis of area under the net balance curves indicated an overall greater net balance after milk ingestion (P < 0.05). The fractional synthesis rate in muscle was also greater after milk consumption (0.10 ± 0.01%/h) than after soy consumption (0.07 ± 0.01%/h; P = 0.05).
Conclusions: Milk-based proteins promote muscle protein accretion to a greater extent than do soy-based proteins when consumed after resistance exercise. The consumption of either milk or soy protein with resistance training promotes muscle mass maintenance and gains, but chronic consumption of milk proteins after resistance exercise likely supports a more rapid lean mass accrual.
The speed of absorption of dietary amino acids by the gut varies according to the type of ingested dietary protein. This could
affect postprandial protein synthesis, breakdown, and deposition. To test this hypothesis, two intrinsically 13C-leucine-labeled milk proteins, casein (CAS) and whey protein (WP), of different physicochemical properties were ingested
as one single meal by healthy adults. Postprandial whole body leucine kinetics were assessed by using a dual tracer methodology.
WP induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia,
probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not
after WP ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with
the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 ± 91 μmol⋅kg−1) than with WP (373 ± 56 μmol⋅kg−1). Leucine intake was identical in both meals (380 μmol⋅kg−1). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP (P < 0.05, WP vs. CAS). In conclusion, the speed of protein digestion and amino acid absorption from the gut has a major effect
on whole body protein anabolism after one single meal. By analogy with carbohydrate metabolism, slow and fast proteins modulate
the postprandial metabolic response, a concept to be applied to wasting situations.
The purpose of this study was to investigate the magnitude and time course for changes in muscle protein synthesis (MPS) after a single bout of resistance exercise. Two groups of six male subjects performed heavy resistance exercise with the elbow flexors of one arm while the opposite arm served as a control. MPS from exercised (ex) and control (con) biceps brachii was assessed 4 (group A) and 24 h (group B) postexercise by the increment in L-[1-13C]leucine incorporation into muscle biopsy samples. In addition, RNA capacity and RNA activity were determined to assess whether transcriptional and/or translational processes affected MPS. MPS was significantly elevated in biceps of the ex compared with the con arms of both groups (group A, ex 0.1007 +/- 0.0330 vs. con 0.067 +/- 0.0204%/h; group B ex 0.0944 +/- 0.0363 vs. con 0.0452 +/- 0.0126%/h). RNA capacity was unchanged in the ex biceps of both groups relative to the con biceps, whereas RNA activity was significantly elevated in the ex biceps of both groups (group A, ex 0.19 +/- 0.10 vs. con 0.12 +/- 0.05 micrograms protein.h-1.microgram-1 total RNA; group B, ex 0.18 +/- 0.06 vs. con 0.08 +/- 0.02 micrograms protein.h-1.microgram-1 total RNA). The results indicate that a single bout of heavy resistance exercise can increase biceps MPS for up to 24 h postexercise. In addition, these increases appear to be due to changes in posttranscriptional events.
This randomized double-blind cross-over study assessed protein (PRO) requirements during the early stages of intensive bodybuilding training and determined whether supplemental PRO intake (PROIN) enhanced muscle mass/strength gains. Twelve men [22.4 +/- 2.4 (SD) yr] received an isoenergetic PRO (total PROIN 2.62 g.kg-1.day-1) or carbohydrate (CHO; total PROIN 1.35 g.kg-1.day-1) supplement for 1 mo each during intensive (1.5 h/day, 6 days/wk) weight training. On the basis of 3-day nitrogen balance (NBAL) measurements after 3.5 wk on each treatment (8.9 +/- 4.2 and -3.4 +/- 1.9 g N/day, respectively), the PROIN necessary for zero NBAL (requirement) was 1.4-1.5 g.kg-1.day-1. The recommended intake (requirement + 2 SD) was 1.6-1.7 g.kg-1.day-1. However, strength (voluntary and electrically evoked) and muscle mass [density, creatinine excretion, muscle area (computer axial tomography scan), and biceps N content] gains were not different between diet treatments. These data indicate that, during the early stages of intensive bodybuilding training, PRO needs are approximately 100% greater than current recommendations but that PROIN increases from 1.35 to 2.62 g.kg-1.day-1 do not enhance muscle mass/strength gains, at least during the 1st mo of training. Whether differential gains would occur with longer training remains to be determined.
Eight highly trained cyclists were studied during exercise after glycogen depletion (test A) and during carbohydrate (CHO) loading (test B). In test B subjects were able to complete 2 h of exercise at 70-75% maximal workload (Wmax), whereas the initial intensity of 70% Wmax had to be reduced to 50% in test A. Plasma ammonia increased more rapidly, and plasma alanine, glutamate, and glutamine were lower in test A. Exercise caused a 3.6-fold increase in the proportion of active branched-chain 2-oxoacid dehydrogenase (BC) complex in muscle in test A. No activation occurred in test B. There was an inverse correlation between the activity of the BC complex and the glycogen content of the postexercise biopsies. Exercise did not cause changes in the muscle content of ATP, ADP, AMP, IMP, hypoxanthine, and lactate. It is concluded that CHO loading abolishes increases in branched-chain amino acid (BCAA) oxidation during exercise and that part of the ammonia production during prolonged exercise originates from deamination of amino acids. The data appear to confirm the hypothesis (A.J. M. Wagenmakers, J.H. Coakley, and R.H.T. Edwards. Int. J. Sports Med. 11: S101-S113, 1990) that acceleration of the BCAA aminotransferase reaction may drain the tricarboxylic acid cycle and that glycogen is a carbon chain precursor of tricarboxylic acid cycle intermediates and glutamine.
The kinetics of urea metabolism were measured in children recovering from severe malnutrition. For a period of up to 10 d they received one of four diets which provided 711 kJ (170 kcal)/kg per d. Two groups received a diet with a high protein:energy (P:E) ratio of 10-6% (HP), enriched with either fat (HP/F) or maize starch and sucrose (HP/C). Two groups received a diet with a low P:E ratio of 8.8% (LP), enriched with either fat (LP/F) or maize starch and sucrose (LP/C). The rate of weight gain on the HP diets was significantly greater than on the LP diets. There was no difference in urea production between any of the four diets: HP/F 1.23 (SE 0.12), HP/C 1.37 (SE 0.14), LP/F 1.64 (SE 0.22), LP/C 1.15 (SE 0.15) mmol nitrogen/kg per h. On the HP diets urea excretion was 0.77 (SE 0.07) mmol N/kg per h, 61% of production. There was significantly less urea excreted in the urine on diet LP/C than on LP/F (0.36 (SE 0.05) and 0.64 (SE 0.04) mmol N/kg per h respectively). A significantly greater percentage of the urea production was hydrolysed on the LP diets (61%) compared with the HP diets (39%), with the consequence that 50% of urea-N produced was available for synthetic activity on the LP diets compared with 30% on the HP diets. The increase in the urea hydrolysed on the LP diets was equivalent in magnitude to the decreased intake of N, so that overall intake plus hydrolysis did not differ between the LP and the HP diets. Crude N balance was similar on diets HP/F, HP/C and LP/C, but was significantly reduced on diet LP/F. These results show that there is an accommodation in urea kinetics during rapid catch-up weight gain, which becomes evident when the P:E ratio of the diet falls to 8.8%. It is proposed that, for a P:E ratio of 8.8%, protein is limiting for catch-up growth. When the intake has a P:E ratio of 8.8% the pattern of urea kinetics can be modified by the relative proportions of fat and carbohydrate in the diet. The measurement of urea kinetics provides a useful approach to the definition of the adequacy of the protein in the diet.
Field studies during the Tour de France indicated that cyclists consume 30% of daily energy intake as liquid carbohydrate (CHO)-enriched nutrition with the goal of maintaining energy and CHO balance. The aim of the present investigation was to study the effect of such dietary manipulation during 2 days of long-lasting exhausting cycling on food and fluid intake, energy balance, nitrogen balance, and nutrient oxidation.
Thirteen highly trained cyclists were divided into two subgroups receiving ad libitum either a primarily maltodextrin-based beverage (Mf) (20% w/v, 85% maltodextrin, 15% fructose) or a 50/50% composed fructosemaltodextrin (FM) beverage in addition to their normal diet. The study was performed during a 7-day stay in a respiration chamber (2 preparation days, 1 standardized resting day, 2 cycling days, 1.5 standardized recovery days), allowing for continuous gas analysis, weighed food and fluid intake procedure, and collection of excretes. The data of this study were compared with data from the same subjects receiving a normal CHO-rich diet (N) (60 En%) in a separate experiment.
The results showed that the cyclists receiving Mf were able to maintain EB during sustained exercise days in contrast to when receiving N and to subjects receiving FM. With Mf treatment CHO intake increased, up to 80 En% (17.5 ± 1.0 g · kg⁻¹ BW) and carbohydrate balance remained positive. The subjects receiving FM had the largest CHO oxidation, calculated from R. Protein oxidation significantly increased in N and FM as a result of exercise but not in Mf. The latter subjects were in slighly negative nitrogen balance at a protein intake level of 1.4 g · kg⁻¹ BW.
The results show that supplementation with maltodextrin beverages is an adequate measure to maintain EB and CHO balance and furthermore that increased CHO intake induces protein sparing. The protein requirement while being in energy and carbohydrate balance during days of sustained exhausting cycling was in the range of 1.5-1.8 g · kg⁻¹ BW.
The effects of regular submaximal exercise on dietary protein requirements, whole body protein turnover, and urinary 3-methylhistidine were determined in six young (26.8 +/- 1.2 yr) and six middle-aged (52.0 +/- 1.9 yr) endurance-trained men. They consumed 0.6, 0.9, or 1.2 g.kg-1.day-1 of high-quality protein over three separate 10-day periods, while maintaining training and constant body weight. Nitrogen measurements in diet, urine, and stool and estimated sweat and miscellaneous nitrogen losses showed that they were all in negative nitrogen balance at a protein intake of 0.6 g.kg-1.day-1. The estimated protein requirement was 0.94 +/- 0.05 g.kg-1.day-1 for the 12 men, with no effect of age. Whole body protein turnover, using [15N]glycine as a tracer, and 3-methylhistidine excretion were not different in the two groups, despite lower physical activity of the middle-aged men. Protein intake affected whole body protein flux and synthesis but not 3-methylhistidine excretion. These data show that habitual endurance exercise was associated with dietary protein needs greater than the current Recommended Dietary Allowance of 0.8 g.kg-1.day-1. However, whole body protein turnover and 3-methylhistidine excretion were not different from values reported for sedentary men.
Electron micrographs of negatively stained and metal-shadowed mitochondrial creatine kinase (Mi-CK) molecules purified as described by Schlegel et al. (Schlegel, J., Zurbriggen, B., Wegmann, E., Wyss, M., Eppenberger, H. M., and Wallimann, T. (1988) J. Biol Chem. 263, 16942-16953) revealed a homogeneous population (greater than or equal to 95%) of distinctly sized square-shaped, octameric particles with a side length of 10 nm that frequently exhibited a pronounced 4-fold axis of symmetry. The cube-like molecules consist of four dimers that are arranged around a stain-accumulating central cavity of 2.5-3 nm in diameter. This interpretation is supported by single particle averaging including correlation analysis by computer. Upon prolonged storage or high dilution, the cube-like octamers tended to dissociate into "banana-shaped" dimers. Sedimentation velocity and sedimentation equilibrium experiments yielded an s value of 12.8-13.5 S and an Mr of 328,000 +/- 25,000 for the octameric cubes. An s value of 5.0 S and a Mr of 83,000 +/- 8,000 was found under conditions which revealed banana-shaped dimers. These dimers proved to be very stable, as their dissociation into monomers of 45 kDa (s value = 2.0 S) required 6 M guanidine HCl. Thus, the oligomeric structures observed in the electron microscope are identified as Mi-CK dimers (banana-shaped structures) and cubical Mi-CK octamers assembled from four Mi-CK dimers. The octameric nature of native Mi-CK and the formation of Mi-CK dimers were confirmed by direct mass measurements of individual molecules by scanning transmission electron microscopy yielding a molecular mass of 340 +/- 55 kDa for the octamer and 89 +/- 27 kDa for the dimer. A structural model of Mi-CK octamers and the possible interaction with ATP/ADP-translocator molecules as well as with the outer mitochondrial membrane is proposed. The implications with respect to the physiological function of Mi-CK as an energy-channeling molecule at the producing side of the phosphoryl creatine shuttle are discussed.
L-Arginine-glycine amidinotransferase (transamidinase) is the first and rate-limiting step in creatine biosynthesis. Rats fed a creatine-supplemented diet or hypophysectomized rats have only 20% of the kidney transamidinase activity as intact rats fed a creatine-free diet. A cDNA clone corresponding to transamidinase was isolated by immunoscreening of a lambda gt11 expression library prepared from rat kidney mRNA. The transamidinase cDNA had an open reading frame containing the known sequence of the amino-terminal peptide of transamidinase. Based on the cDNA sequence, transamidinase is synthesized as a precursor with an amino-terminal extension of 50 amino acids, consistent with its mitochondrial localization. Comparison of the transamidinase sequence with the protein data base identified only a single, related protein. Remarkably, this protein, which has a 37% amino acid identity with transamidinase, is also an amidinotransferase, catalyzing streptomycin biosynthesis in Streptomyces griseus. Transamidinase cDNA was used to investigate the regulation of mRNA levels by creatine and growth hormone. Hypophysectomized rats were fed a creatine-free or a creatine-supplemented diet and maintained with and without injections of growth hormone. An excellent correlation was found between changes in transamidinase activity and mRNA levels in response to creatine and growth hormone. Thus, the regulation of transamidinase by creatine and growth hormone is at a pretranslational level. In addition, the two effectors do not act independently but interact at a pretranslational level to control transamidinase gene expression.
Nine male subjects performed two bouts of 30-s maximal isokinetic cycling before and after ingestion of 20 g creatine (Cr) monohydrate/day for 5 days. Cr ingestion produced a 23.1 +/- 4.7 mmol/kg dry matter increase in the muscle total creatine (TCr) concentration. Total work production during bouts 1 and 2 increased by approximately 4%, and the cumulative increases in both peak and total work production over the two exercise bouts were positively correlated with the increase in muscle TCr. Cumulative loss of ATP was 30.7 +/- 12.2% less after Cr ingestion, despite the increase in work production. Resting phosphocreatine (PCr) increased in type I and II fibers. Changes in PCr before exercise bouts 1 and 2 in type II fibers were positively correlated with changes in PCr degradation during exercise in this fiber type and changes in total work production. The results suggest that improvements in performance were mediated via improved ATP resynthesis as a consequence of increased PCr availability in type II fibers.
The effects of dietary supplementation with the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) were studied in two experiments. In study 1, subjects (n = 41) were randomized among three levels of HMB supplementation (0, 1.5 or 3.0 g HMB/day) and two protein levels (normal, 117 g/day, or high, 175 g/day) and weight lifted for 1.5 h 3 days/wk for 3 wk. In study 2, subjects (n = 28) were fed either 0 or 3.0 g HMB/day and weight lifted for 2-3 h 6 days/wk for 7 wk. In study 1, HMB significantly decreased the exercise-induced rise in muscle proteolysis as measured by urine 3-methylhistidine during the first 2 wk of exercise (linear decrease, P < 0.04). Plasma creatine phosphokinase was also decreased with HMB supplementation (week 3, linear decrease, P < 0.05). Weight lifted was increased by HMB supplementation when compared with the unsupplemented subjects during each week of the study (linear increase, P < 0.02). In study 2, fat-free mass was significantly increased in HMB-supplemented subjects compared with the unsupplemented group at 2 and 4-6 wk of the study (P < 0.05). In conclusion, supplementation with either 1.5 or 3 g HMB/day can partly prevent exercise-induced proteolysis and/or muscle damage and result in larger gains in muscle function associated with resistance training.
We determined the effect of the timing of glucose supplementation on fractional muscle protein synthetic rate (FSR), urinary urea excretion, and whole body and myofibrillar protein degradation after resistance exercise. Eight healthy men performed unilateral knee extensor exercise (8 sets/approximately 10 repetitions/approximately 85% of 1 single maximal repetition). They received a carbohydrate (CHO) supplement (1 g/kg) or placebo (Pl) immediately (t = 0 h) and 1 h (t = +1 h) postexercise. FSR was determined for exercised (Ex) and control (Con) limbs by incremental L-[1-13C]leucine enrichment into the vastus lateralis over approximately 10 h postexercise. Insulin was greater (P < 0.01) at 0.5, 0.75, 1.25, 1.5, 1.75, and 2 h, and glucose was greater (P < 0.05) at 0.5 and 0.75 h for CHO compared with Pl condition. FSR was 36.1% greater in the CHO/Ex leg than in the CHO/Con leg (P = not significant) and 6.3% greater in the Pl/Ex leg than in the Pl/Con leg (P = not significant). 3-Methylhistidine excretion was lower in the CHO (110.43 +/- 3.62 mumol/g creatinine) than P1 condition (120.14 +/- 5.82, P < 0.05) as was urinary urea nitrogen (8.60 +/- 0.66 vs. 12.28 +/- 1.84 g/g creatinine, P < 0.05). This suggests that CHO supplementation (1 g/kg) immediately and 1 h after resistance exercise can decrease myofibrillar protein breakdown and urinary urea excretion, resulting in a more positive body protein balance.
The effects of oral creatine supplementation on muscle phosphocreatine (PCr) concentration, muscle strength, and body composition were investigated in young female volunteers (n = 19) during 10 wk of resistance training (3 h/wk). Compared with placebo, 4 days of high-dose creatine intake (20 g/day) increased (P < 0.05) muscle PCr concentration by 6%. Thereafter, this increase was maintained during 10 wk of training associated with low-dose creatine intake (5 g/day). Compared with placebo, maximal strength of the muscle groups trained, maximal intermittent exercise capacity of the arm flexors, and fat-free mass were increased 20-25, 10-25, and 60% more (P < 0. 05), respectively, during creatine supplementation. Muscle PCr and strength, intermittent exercise capacity, and fat-free mass subsequently remained at a higher level in the creatine group than in the placebo group during 10 wk of detraining while low-dose creatine was continued. Finally, on cessation of creatine intake, muscle PCr in the creatine group returned to normal within 4 wk. It is concluded that long-term creatine supplementation enhances the progress of muscle strength during resistance training in sedentary females.
To determine the effects of 28 d of creatine supplementation during training on body composition, strength, sprint performance, and hematological profiles.
In a double-blind and randomized manner, 25 NCAA division IA football players were matched-paired and assigned to supplement their diet for 28 d during resistance/agility training (8 h x wk[-1]) with a Phosphagen HP (Experimental and Applied Sciences, Golden, CO) placebo (P) containing 99 g x d(-1) of glucose, 3 g x d(-1) of taurine, 1.1 g x d(-1) of disodium phosphate, and 1.2 g x d(-1) of potassium phosphate (P) or Phosphagen HP containing the P with 15.75 g x d(-1) of HPCE pure creatine monohydrate (HP). Before and after supplementation, fasting blood samples were obtained; total body weight, total body water, and body composition were determined; subjects performed a maximal repetition test on the isotonic bench press, squat, and power clean; and subjects performed a cycle ergometer sprint test (12 x 6-s sprints with 30-s rest recovery).
Hematological parameters remained within normal clinical limits for active individuals with no side effects reported. Total body weight significantly increased (P < 0.05) in the HP group (P 0.85 +/- 2.2; HP 2.42 +/- 1.4 kg) while no differences were observed in the percentage of total body water. DEXA scanned body mass (P 0.77 +/- 1.8; HP 2.22 +/- 1.5 kg) and fat/bone-free mass (P 1.33 +/- 1.1; HP 2.43 +/- 1.4 kg) were significantly increased in the HP group. Gains in bench press lifting volume (P -5 +/- 134; HP 225 +/- 246 kg), the sum of bench press, squat, and power clean lifting volume (P 1,105 +/- 429; HP 1,558 +/- 645 kg), and total work performed during the first five 6-s sprints was significantly greater in the HP group.
The addition of creatine to the glucose/taurine/electrolyte supplement promoted greater gains in fat/bone-free mass, isotonic lifting volume, and sprint performance during intense resistance/agility training.
We examined the effect of glycogen availability and branched-chain amino acid (BCAA) supplementation on branched-chain oxoacid dehydrogenase (BCOAD) activity during exercise. Six subjects cycled at approximately 75% of their maximal oxygen uptake to exhaustion on three occasions under different preexercise conditions: 1) low muscle glycogen (LOW), 2) low muscle glycogen plus BCAA supplementation (LOW+BCAA), and 3) high muscle glycogen (CON). The LOW trial was performed first, followed by the other two conditions in random order, and biopsies for all trials were obtained at rest, after 15 min of exercise (15 min), and at the point of exhaustion during the LOW trial (49 min). BCOAD activity was not different among the three conditions at rest; however, at 15 min BCOAD activity was higher (P < or = 0.05) for the LOW (31 +/- 5%) and LOW+BCAA (43 +/- 11%) conditions compared with CON (12 +/- 1%). BCOAD activity at 49 min was not different from respective values at 15 min for any condition. These data indicate that BCOAD is rapidly activated during submaximal exercise under conditions associated with low carbohydrate availability. However, there was no relationship between BCOAD activity and glycogen concentration or net glycogenolysis, which suggests that factors other than glycogen availability are important for BCOAD regulation during exercise in humans.
Creatine supplementation has been shown to augment muscle PCr content and increase the rate of ATP resynthesis. Thus, we hypothesized that creatine supplementation might enhance sprinting performance. Eighteen subjects completed both of two testing sessions (control and postsupplement) 1 week apart, wherein they sprinted three 60-m distance trials that were recorded with videotape. Following the control session, for 7 days, subjects in the treatment group ingested a creatine-glucose mixture, while the placebo group consumed a glucose powder, followed by the postsupplementation session. Velocities of the subjects through three testing zones within the 60-m sprint were calculated from the videotape. Resultant velocities were analyzed using a MANOVA with a2x2x3x3 (Group x Session x Trial x Zone) design. Results indicated that there were no statistically significant main or interaction effects on velocity between groups for session, trial, or zone. These data do not support the hypothesis that supplementary c...
Nutrient intake before, during, and after training will influence the adaptations that occur in response to the training stimulus. The influence of protein on training adaptations is receiving increasing attention from researchers. Methodological issues should be carefully considered when evaluating evidence of nutritional influence on training adaptations. Evidence suggests that adaptations to training are due to changes in the types and activities of various proteins in response to each exercise bout. Thus, study of the acute metabolic and molecular responses to exercise plus nutrition may provide valuable information about the expected influence on training adaptations. The type of protein, timing of protein ingestion relative to exercise, concurrent ingestion of other nutrients with protein, as well as the type of exercise training performed will impact the adaptations to training with the intake of protein. Protein is an important nutrient for muscle hypertrophy with training, but there is little support for the need for very high (e.g. >2.5–3.0 grams of protein per kilogram of body weight) intakes. Traditionally, endurance athletes have focused on carbohydrate intake, but recently protein has been touted to be critical during and after endurance exercise. There is evidence for and against the importance of protein for endurance exercise and more, well-controlled studies are required to delineate the importance of protein for endurance exercise adaptations. Whereas nutritional manipulations have customarily been focused on preventing protein degradation, muscle damage, and oxidative stress, recent evidence suggests that these processes may be critical for the optimal adaptive response to training.
The effects of supplementation of the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) were examined in a resistance training study. Thirty-nine men and 36 women between the ages of 20–40 y were randomized to either a placebo (P) supplemented or HMB supplemented (3.0 g HMB/d) group in two gender cohorts. All subjects trained three times per week for 4 wk. In the HMB group, plasma creatine phosphokinase levels tended to be suppressed compared to the placebo group following the 4 wk of resistance training (HMB:174.4 ± 26.8 to 173.5 ± 17.0 U/L; P:155.0 ± 20.8 to 195.2 ± 23.5 U/L). There were no significant differences in strength gains based on prior training status or gender with HMB supplementation. The HMB group had a greater increase in upper body strength than the placebo group (HMB:7.5 ± 0.6 kg; P:5.2 ± 0.6 kg; P = 0.008). The HMB groups increased fat-free weight by 1.4 ± 0.2 kg and decreased percent fat by 1.1% ± 0.2% while the placebo groups increased fat-free weight by 0.9 ± 0.2 kg and decreased percent fat by 0.5% ± 0.2% (fat-free weight P = 0.08, percent fat P = 0.08, HMB compared to placebo). In summary, this is the first short-term study to investigate the roles of gender and training status on the effects of HMB supplementation on strength and body composition. This study showed, regardless of gender or training status, HMB may increase upper body strength and minimize muscle damage when combined with an exercise program.
Plasma characteristics at high pressure YBa2Cu3O7−δ reactive magnetron sputtering were investigated with a probe technique and in situ film resistance measurements. The experimental features of probe measurements in oxygen plasma are discussed. Electron energy distribution is the sum of two Maxwell distributions with kTe ≈ 1.5 eV and kTe ≈ 0.3 eV. N2O addition to a gas mixture results in the generation of negative ions with a density virtually equal to the density of positive ions. The energies of ions, impinging the film surface under film biasing, are discussed in collisionless and drift approximations. Low energy ion bombardment of the film surface at temperatures ≈ 400 °C results in a reduction of film oxygen content. © 1997 American Institute of Physics.
The aim of this study was to examine the effects of short-term creatine monohydrate supplementation on multiple sprint running performance. Using a double-blind research design, 42 physically active men completed a series of 3 indoor multiple sprint running trials (15 3 30 m repeated at 35-second intervals). After the first 2 trials (familiarization and baseline), subjects were matched for fatigue score before being randomly assigned to 5 days of either creatine (4[middle dot]d-1 x 5 g creatine monohydrate 1 1g maltodextrin) or placebo (4[middle dot]d-1 x 6 g maltodextrin) supplementation. Sprint times were recorded via twin-beam photocells, and earlobe blood samples were drawn to evaluate posttest lactate concentrations. Relative to placebo, creatine supplementation resulted in a 0.7 kg increase in body mass (95% likely range: 0.02 to 1.3 kg) and a 0.4% reduction in body fat (95% likely range: 20.2 to 0.9%). There were no significant (p > 0.05) between-group differences in multiple sprint measures of fastest time, mean time, fatigue, or posttest blood lactate concentration. Despite widespread use as an ergogenic aid in sport, the results of this study suggest that creatine monohydrate supplementation conveys no benefit to multiple sprint running performance.
(C) 2006 National Strength and Conditioning Association
1. We investigated the effect of oral creatine supplementation during leg immobilization and rehabilitation on muscle volume and function, and on myogenic transcription factor expression in human subjects. 2. A double-blind trial was performed in young healthy volunteers (n = 22). A cast was used to immobilize the right leg for 2 weeks. Thereafter the subjects participated in a knee-extension rehabilitation programme (3 sessions week _1 , 10 weeks). Half of the subjects received creatine monohydrate (CR; from 20 g down to 5 g daily), whilst the others ingested placebo (P; maltodextrin). 3. Before and after immobilization, and after 3 and 10 weeks of rehabilitation training, the cross- sectional area (CSA) of the quadriceps muscle was assessed by NMR imaging. In addition, an isokinetic dynamometer was used to measure maximal knee-extension power (W max), and needle biopsy samples taken from the vastus lateralis muscle were examined to asses expression of the myogenic transcription factors MyoD, myogenin, Myf5, and MRF4, and muscle fibre diameters. 4. Immobilization decreased quadriceps muscle CSA (~10 %) and W max (~25 %) by the same magnitude in both groups. During rehabilitation, CSA and Wmax recovered at a faster rate in CR than in P (P < 0.05 for both parameters). Immobilization changed myogenic factor protein expression in neither P nor CR. However, after rehabilitation myogenin protein expression was increased in P but not in CR (P < 0.05), whilst MRF4 protein expression was increased in CR but not in P (P < 0.05). In addition, the change in MRF4 expression was correlated with the change in mean muscle fibre diameter (r = 0.73, P < 0.05). 5. It is concluded that oral creatine supplementation stimulates muscle hypertrophy during rehabilitative strength training. This effect may be mediated by a creatine-induced change in MRF4 and myogenin expression.
1. The present study was undertaken to test whether creatine given as a supplement to normal subjects was absorbed, and if continued resulted in an increase in the total creatine pool in muscle. An additional effect of exercise upon uptake into muscle was also investigated.
2. Low doses (1 g of creatine monohydrate or less in water) produced only a modest rise in the plasma creatine concentration, whereas 5 g resulted in a mean peak after 1 h of 795 (sd 104) μmol/l in three subjects weighing 76–87 kg. Repeated dosing with 5 g every 2 h sustained the plasma concentration at around 1000 μmol/l. A single 5 g dose corresponds to the creatine content of 1.1 kg of fresh, uncooked steak.
3. Supplementation with 5 g of creatine monohydrate, four or six times a day for 2 or more days resulted in a significant increase in the total creatine content of the quadriceps femoris muscle measured in 17 subjects. This was greatest in subjects with a low initial total creatine content and the effect was to raise the content in these subjects closer to the upper limit of the normal range. In some the increase was as much as 50%.
4. Uptake into muscle was greatest during the first 2 days of supplementation accounting for 32% of the dose administered in three subjects receiving 6 × 5 g of creatine monohydrate/day. In these subjects renal excretion was 40, 61 and 68% of the creatine dose over the first 3 days. Approximately 20% or more of the creatine taken up was measured as phosphocreatine. No changes were apparent in the muscle ATP content.
5. No side effects of creatine supplementation were noted.
6. One hour of hard exercise per day using one leg augmented the increase in the total creatine content of the exercised leg, but had no effect in the collateral. In these subjects the mean total creatine content increased from 118.1 (sd 3.0) mmol/kg dry muscle before supplementation to 148.5 (sd 5.2) in the control leg, and to 162.2 (sd 12.5) in the exercised leg. Supplementation and exercise resulted in a total creatine content in one subject of 182.8 mmol/kg dry muscle, of which 112.0 mmol/kg dry muscle was in the form of phosphocreatine.
Leucine kinetic and nitrogen balance (NBAL) methods were used to determine the dietary protein requirements of strength athletes (SA) compared with sedentary subjects (S). Individual subjects were randomly assigned to one of three protein intakes: low protein (LP) = 0.86 g protein.kg-1.day-1, moderate protein (MP) = 1.40 g protein.kg-1.day-1, or high protein (HP) = 2.40 g protein.kg-1.day-1 for 13 days for each dietary treatment. NBAL was measured and whole body protein synthesis (WBPS) and leucine oxidation were determined from L-[1-13C]leucine turnover. NBAL data were used to determine that the protein intake for zero NBAL for S was 0.69 g.kg-1.day-1 and for SA was 1.41 g.kg-1.day-1. A suggested recommended intake for S was 0.89 g.kg-1.day-1 and for SA was 1.76 g.kg-1.day-1. For SA, the LP diet did not provide adequate protein and resulted in an accommodated state (decreased WBPS vs. MP and HP), and the MP diet resulted in a state of adaptation [increase in WBPS (vs. LP) and no change in leucine oxidation (vs. LP)]. The HP diet did not result in increased WBPS compared with the MP diet, but leucine oxidation did increase significantly, indicating a nutrient overload. For S the LP diet provided adequate protein, and increasing protein intake did not increase WBPS. On the HP diet leucine oxidation increased for S. These results indicated that the MP and HP diets were nutrient overloads for S. There were no effects of varying protein intake on indexes of lean body mass (creatinine excretion, body density) for either group. In summary, protein requirements for athletes performing strength training are greater than for sedentary individuals and are above current Canadian and US recommended daily protein intake requirements for young healthy males.
The present study was conducted to investigate the metabolic regulation of the oxidation of branched-chain amino acids (BCAA) by exercise in human skeletal muscle. Five trained male volunteers were exercised on a cycle ergometer at 70% +/- 10% (mean +/- SD) of their maximal oxygen consumption (VO2max). Percutaneous quadriceps muscle biopsies were obtained under local anaesthesia at rest and after 30 and 120 min of exercise. In the muscle samples the active and total amount of the branched-chain 2-oxo acid dehydrogenase complex (BC-complex), the regulatory enzyme in the oxidative pathway of the BCAA, were measured. Glycogen content and activity of mitochondrial marker enzymes were also measured. Blood samples were obtained every 20 min for the measurement of metabolites. Heart rate and rated perceived exertion on the Borg scale were recorded every 10 min. At rest 4.0% +/- 2.5% of the BC complex was active, after 30 min of exercise 9.9% +/- 9.0% and after 120 min 17.5% +/- 8.5% (mean +/- SD). Exercise did not change the total activity. The largest activation was seen in two of the subjects who developed higher blood lactates early on during exercise and decreased their muscle glycogen more (indications of anaerobic metabolism). These data demonstrate that in trained individuals significant increases in the activity of the BC-complex occur only after prolonged intense exercise. In spite of the 4-fold activation, the data support the classical view that amino acids and protein do not contribute substantially as an energy source during exercise, since VO2 increased more than 20-fold.
On two separate occasions, five well-trained endurance runners (VO2max = 71 +/- 5 ml/kg/min; means +/- SD) consumed a meat-free diet for 6 days. For one trial the subjects consumed the recommended dietary allowance (RDA) of protein (REC-PRO = 0.86 +/- 0.23 g/kg body wt/day). Protein intake for the other trial was 1.7 times higher (HI-PRO = 1.49 +/- 0.29 g/kg body wt/day). Each subject followed his regular training program (12-16 km running/day), and on day 5 of each diet completed a treadmill run at a similar intensity and duration (75 min at 72% VO2max). Seventy-two hour urinary urea N loss (days 4, 5, and 6 of each diet) and day 5 exercise sweat urea N excretion were measured. Serum urea N and creatinine increased significantly during the treadmill run under both dietary conditions (P less than 0.05). No significances between diet differences were observed in sweat or urinary urea N excretion; however, excretion of both tended to be higher on the REC-PRO diet than on the HI-PRO diet. The differences in protein intake combined with the nitrogen excretion measures resulted in significant differences in estimated whole-body nitrogen retention between the two treatments. Nitrogen retention (means +/- SE) remained positive during the HI-PRO trial (2.41 +/- 1.99 g/day) but was significantly (P less than 0.005) reduced to -5.29 +/- 2.58 g/day during the REC-PRO trial. These results suggest that the current protein RDA may be inadequate for athletes engaging in chronic high-intensity endurance exercise. Future studies are needed to confirm this observation.
Strength performance depends not only on the quantity and quality of the involved muscles, but also upon the ability of the nervous system to appropriately activate the muscles. Strength training may cause adaptive changes within the nervous system that allow a trainee to more fully activate prime movers in specific movements and to better coordinate the activation of all relevant muscles, thereby effecting a greater net force in the intended direction of movement. The evidence indicating neural adaptation is reviewed. Electromyographic studies have provided the most direct evidence. They have shown that increases in peak force and rate of force development are associated with increased activation of prime mover muscles. Possible reflex adaptations related to high stretch loads in jumping and rapid reciprocal movements have also been revealed. Other studies, including those that demonstrate the "cross-training" effect and specificity of training, provide further evidence of neural adaptation. The possible mechanisms of neural adaptation are discussed in relation to motor unit recruitment and firing patterns. The relative roles of neural and muscular adaptation in short- and long-term strength training are evaluated.
Resistance training results in a wide spectrum of adaptations in various physiological systems. Increases in muscle size and strength, changes in body composition, neuroendocrine function and cardiovascular responses have been observed following resistance training. Additionally, resistance training may be an effective means by which the incidence of sports injuries can be reduced.
The physiological alterations induced by resistance training appear to be specific to the number of sets and repetitions and exercises performed. Thus, special attention is required when developing the exercise prescription for resistance training.
The present study examined the effects of training status (endurance exercise or body building) on nitrogen balance, body composition, and urea excretion during periods of habitual and altered protein intakes. Experiments were performed on six elite bodybuilders, six elite endurance athletes, and six sedentary controls during a 10-day period of normal protein intake followed by a 10-day period of altered protein intake. The nitrogen balance data revealed that bodybuilders required 1.12 times and endurance athletes required 1.67 times more daily protein than sedentary controls. Lean body mass (density) was maintained in bodybuilders consuming 1.05 g protein.kg-1.day-1. Endurance athletes excreted more total daily urea than either bodybuilders or controls. We conclude that bodybuilders during habitual training require a daily protein intake only slightly greater than that for sedentary individuals in the maintenance of lean body mass and that endurance athletes require daily protein intakes greater than either bodybuilders or sedentary individuals to meet the needs of protein catabolism during exercise.
Two studies were conducted to investigate the effects of mild exercise on nitrogen balance in men given diets supplying adequate or slightly limiting energy. In experiment A the diet supplied 91 mg N/kg body weight (0.57 g protein/kg, the FAO/WHO safe level of intake) as egg white; in experiment B the same source was used to provide the 1980 NRC-RDA for adult males, 128 mg N/kg body weight (0.8 g protein/kg). By adjusting energy intake and activity, periods of energy equilibrium and negative energy balance (-15%) were achieved at three levels of activity (X for exercise): no programmed work (0.85X), 1 hour of treadmill walking (1.0X) and 1 hour each of treadmill and cycle ergometry (1.15X). "True" nitrogen balance (TNbal) was more positive or less negative during periods of energy equilibrium as compared to those of energy deficit. This effect of energy balance on TNbal increased with physical activity. At the lower protein intake the mean difference in TNbal between the period of energy equilibrium and that of energy deficit at 1.0X was 0.19 g N/day (nonsignificant difference) and 0.54 g N/day at 1.15X. When protein intake was increased, the difference in TNbal between periods of equilibrium and deficit was significant at all levels of activity: 0.65 g N/day at 0.85X, 0.93 g N/day at 1.0X and 1.09 g N/day at 1.15X. Physical activity was anabolic when energy balance was maintained. In experiment A the addition of 1 hour of exercise (1.0X to 1.15X) spared 2.5 mg N/kg body weight; reducing activity by 1 hour (1.0X to 0.85X) cost 1.4 mg N/kg body weight. In experiment B, TNbal was more positive with increased activity (by 5.9 mg N/kg body weight) and more negative (by 11.5 mg N/kg body weight) when the men were sedentary. During periods of energy deficit, the anabolic effect of activity was also present, although less markedly. When activity increased from 1 to 2 hours in experiment A, TNbal improved by 2.1 mg N/kg body weight and in experiment B, by 3.5 mg N/kg body weight. Thus, circumstances of negative energy balance with adequate protein intake are better tolerated when the energy deficit is generated by physical activity than when it derives from reduced intake; the picture when protein intake is marginal requires further investigation.
Twelve patients who had undergone colon operations were randomized prospectively in the postoperative recovery room. Seven received a hypocaloric intravenous solution consisting of 3.5% amino acids plus 2.5% glucose and five received 3.5% amino acids plus 10% fat. Nitrogen balance data indicated that isocaloric amounts of glucose and fat seem equally effective when combined with amino acids. Although the albumin synthesis rates (measured by the 14C technique on the fourth postoperative day) were not significantly different between the two groups, when the results were included with pooled data from previous similar studies, there was a statistically significant difference which indicated a higher rate of albumin synthesis in patients who received the combination of amino acids and fat compared with those who received amino acids and glucose P < 0.05). In this clinical setting, fat may favor the uptake and synthesis of amino acids into visceral proteins, while glucose may have a more direct role in the synthesis of skeletal muscle protein.
Phosphocreatine (PCr) availability is likely to limit performance in brief, high-power exercise because the depletion of PCr results in an inability to maintain adenosine triphosphate (ATP) resynthesis at the rate required. It is now known that the daily ingestion of four 5-g doses of creatine for 5 days will significantly increase intramuscular creatine and PCr concentrations prior to exercise and will facilitate PCr resynthesis during recovery from exercise, particularly in those individuals with relatively low creatine concentrations prior to feeding. As a consequence of creatine ingestion, work output during repeated bouts of high-power exercise has been increased under a variety of experimental conditions. The reduced accumulation of ammonia and hypoxanthine in plasma and the attenuation of muscle ATP degradation after creatine feeding suggest that the ergogenic effect of creatine is achieved by better maintaining ATP turnover during contraction.
The rates of protein synthesis and degradation and of amino acid transport were determined in the leg muscle of untrained postabsorptive normal volunteers at rest and approximately 3 h after a resistance exercise routine. The methodology involved use of stable isotopic tracers of amino acids, arteriovenous catheterization of the femoral vessels, and biopsy of the vastus lateralis muscle. During postexercise recovery, the rate of intramuscular phenylalanine utilization for protein synthesis increased above the basal value by 108 +/- 18%, whereas the rate of release from proteolysis increased by 51 +/- 17%. Muscle protein balance improved (P < 0.05) after exercise but did not become positive (from -15 +/- 12 to -6 +/- 3 nmol phenylalanine.min-1.100 ml leg volume-1). After exercise, rates of inward transport of leucine, lysine, and alanine increased (P < 0.05) above the basal state from 132 +/- 16 to 208 +/- 29, from 122 +/- 8 to 260 +/- 8, and from 384 +/- 71 to 602 +/- 89 nmol.min-1.100 ml leg-1, respectively. Transport of phenylalanine did not change significantly. These results indicate that, during recovery after resistance exercise, muscle protein turnover is increased because of an acceleration of synthesis and degradation. A postexercise acceleration of amino acid transport may contribute to the relatively greater stimulation of protein synthesis.
The effect of dietary creatine (Cr) supplementation on performance during 3, 30 s bouts maximal isokinetic cycling and on plasma ammonia and blood lactate accumulation during exercise was investigated. Placebo (P) ingestion had no effect on peak power output (PPO), mean power output (MPO) and total work output during each bout of exercise. Cr ingestion (4 x 5 g.day-1 for 5 days) significantly increased PPO in exercise bout 1 (p < 0.05) and MPO and total work output in exercise bouts 1 (p < 0.05, p < 0.05, respectively) and 2 (p < 0.05, p < 0.05, respectively). Cr ingestion had no effect on any of the measures of performance during exercise bout 3. No difference was observed in peak plasma ammonia accumulation before (146 + 30 mumol.l-1) and after (122 +/- 17 mumol.l-1) P ingestion, however the corresponding concentration was lower following Cr ingestion (129 +/- 22 mumol.l-1) compared with before Cr ingestion (160 +/- 18 mumol.l-1, p < 0.05), despite subjects performing more work. No difference in peak blood lactate accumulation was observed before and after P or Cr ingestion. The results demonstrate that Cr ingestion can increase whole body exercise performance during the initial two, but not a third, successive bout of maximal exercise lasting 30 s. The lower accumulation of plasma ammonia under these conditions suggests this response is achieved by an effect on muscle ATP turnover.
A family of homologous, Na+/Cl- dependent plasma membrane transporters catalyze the uptake of a number of neurotransmitters and structurally related compounds into cells. Here, we report the cDNA cloning, sequencing and functional characterization of a non-mammalian member of this transporter family. A creatine transporter from the electric ray, Torpedo marmorata, displays 64% amino acid identity with its rabbit counterpart and has a similar substrate affinity and specificity. Sequence similarity generally is lowest in those regions where also the sequences of other members of the family, transporting different substrates, diverge. Only a few amino acids are better conserved between the two creatine transporters than with the other family members and are candidates for a role in conferring substrate specificity.
Biopsy samples were obtained from the vastus lateralis muscle of eight subjects after 0, 20, 60, and 120 s of recovery from intense electrically evoked isometric contraction. Later (10 days), the same procedures were performed using the other leg, but subjects ingested 20 g creatine (Cr)/day for the preceding 5 days. Muscle ATP, phosphocreatine (PCr), free Cr, and lactate concentrations were measured, and total Cr was calculated as the sum of PCr and free Cr concentrations. In five of the eight subjects, Cr ingestion substantially increased muscle total Cr concentration (mean 29 +/- 3 mmol/kg dry matter, 25 +/- 3%; range 19-35 mmol/kg dry matter, 15-32%) and PCr resynthesis during recovery (mean 19 +/- 4 mmol/kg dry matter, 35 +/- 6%; range 11-28 mmol/kg dry matter, 23-53%). In the remaining three subjects, Cr ingestion had little effect on muscle total Cr concentration, producing increases of 8-9 mmol/kg dry matter (5-7%), and did not increase PCr resynthesis. The data suggest that a dietary-induced increase in muscle total Cr concentration can increase PCr resynthesis during the 2nd min of recovery from intense contraction.
The current Canadian Recommended Nutrient Intake (RNI) for protein (0.86 g.kg-1.day-1) makes no allowance for an effect of habitual physical activity. In addition, Tarnopolsky et al. (J. Appl. Physiol. 68: 302-308, 1990) showed that males may catabolize more protein than females consequent to endurance exercise. We examined nitrogen (N) balance and leucine kinetics during submaximal endurance exercise to determine the adequacy of the current Canadian RNI for protein for male and female endurance athletes. Athletes were matched for equal training volume, competitive status, and conditioning and were fed diets isoenergetic with their habitual intake, containing protein at the Canadian RNI. Subjects were adapted to the diet for 10 days before completing a 3-day measurement of N balance. N balance showed that the RNI was inadequate for females (-15.9 +/- 6.0 mg.kg-1.day-1) and males (-26.3 +/- 11.0 mg.kg-1.day-1). Leucine kinetics during exercise were determined for each subject on day 3 of the N balance experiment by use of a primed continuous infusion of L-[1-13C]leucine and the reciprocal pool model. Exercise resulted in a significant (P < 0.01) increase in leucine oxidation for both groups. Males oxidized a greater amount of leucine during the infusion than females (P < 0.01). Leucine flux also increased significantly (P < 0.01) during exercise in both groups. We conclude that the current Canadian RNI for protein is inadequate for those who chronically engage in endurance exercise.(ABSTRACT TRUNCATED AT 250 WORDS)
1. The present experiment was undertaken to investigate the influence of oral creatine supplementation, shown previously to increase the total creatine content of human skeletal muscle (Harris RC, Soderlund K, Hultman E. Clin Sci 1992; 83: 367–74), on skeletal muscle isokinetic torque and the accumulation of plasma ammonia and blood lactate during five bouts of maximal exercise.
2. Twelve subjects undertook five bouts of 30 maximal voluntary isokinetic contractions, interspersed with 1 min recovery periods, before and after 5 days of placebo (4 × 6 g of glucose/day, n = 6) or creatine (4 × 5 g of creatine plus 1 g of glucose/day, n = 6) oral supplementation. Muscle torque production and plasma ammonia and blood lactate accumulation were measured during and after exercise on each treatment
3. No difference was seen when comparing muscle peak torque production during exercise before and after placebo ingestion. After creatine ingestion, muscle peak torque production was greater in all subjects during the final 10 contractions of exercise bout 1 (P <0.05), throughout the whole of exercise bouts 2 (P <0.01), 3 (P <0.05) and 4 (P = 0.057) and during contractions 11–20 of the final exercise bout (P <0.05), when compared with the corresponding measurements made before creatine ingestion. Plasma ammonia accumulation was lower during and after exercise after creatine ingestion. No differences were found when comparing blood lactate levels.
4. There is evidence to suggest that the decrease in the degree of muscle torque loss after dietary creatine supplementation may be a consequence of a creatine-induced acceleration of skeletal muscle phosphocreatine resynthesis. It is postulated that an increased availability of phosphocreatine would maintain better the required rate of ATP demand during contraction. This is supported by the observed lower accumulation of plasma ammonia during exercise after creatine ingestion.
This study examined the influence of oral creatine monohydrate supplementation on repeated 10 s cycle ergometer sprint performance. Seventeen recreationally active males (mean +/- SD age, body mass, height, and peak oxygen uptake = 20.5 +/- 1.2 yr, 72.1 +/- 10.3 kg, 176.8 +/- 6.6 cm and 3.87 +/- 0.91 l.min-1, respectively) participated in the 16 day experiment. All subjects initially completed a VO2peak test and were then administered glucose (4 x 10 g per day) in a single blind fashion for four days, after which they completed the first series of multiple sprints (7 x 10 s). Following the sprints, subjects were matched on sprint performance and divided into two groups (n = 8, placebo (Pl); and n = 9, creatine (Cr)). For the following four days, diets were supplemented with either Cr (4 x 70 mg.kg-1 body mass per day mixed with 5 g glucose) or glucose (4 x 10 g per day); supplementation during this phase was double-blind. Subjects then repeated the multiple sprint and VO2peak tests. Measures of peak power output (PPO), mean power output (MPO), end-power output (EPO), and percent power decline were recorded during the sprints. Each 10 s sprint was separated by 30 s of passive recovery except for sprints five and six which were separated by five minutes. Venous blood was sampled at rest, immediately after sprint five, before sprint six, and following sprint seven for the analysis of plasma lactate and blood pH. Expired air was sampled for five minutes following sprint seven for the calculation of post-exercise VO2. Analysis of variance revealed that four days of Cr supplementation did not influence multiple sprint performance, plasma lactate, blood pH and excess post-sprint oxygen consumption. Furthermore, VO2peak was unchanged following Cr supplementation. The data suggest that either the four day period of Cr supplementation failed to significantly raise resting muscle [Cr], or that multiple sprint performance was not enhanced by increases in resting muscle [Cr].
The effect of dietary creatine and supplementation on skeletal muscle creatine accumulation and subsequent degradation and on urinary creatinine excretion was investigated in 31 male subjects who ingested creatine in different quantities over varying time periods. Muscle total creatine concentration increased by approximately 20% after 6 days of creatine supplementation at a rate of 20 g/day. This elevated concentration was maintained when supplementation was continued at a rate of 2 g/day for a further 30 days. In the absence of 2 g/day supplementation, total creatine concentration gradually declined, such that 30 days after the cessation of supplementation the concentration was no different from the presupplementation value. During this period, urinary creatinine excretion was correspondingly increased. A similar, but more gradual, 20% increase in muscle total creatine concentration was observed over a period of 28 days when supplementation was undertaken at a rate of 3 g/day. In conclusion, a rapid way to "creatine load" human skeletal muscle is to ingest 20 g of creatine for 6 days. This elevated tissue concentration can then be maintained by ingestion of 2 g/day thereafter. The ingestion of 3 g creatine/day is in the long term likely to be as effective at raising tissue levels as this higher dose.
Creatine supplementation has been shown to augment muscle PCr content and increase the rate of ATP resynthesis. Thus, we hypothesized that creatine supplementation might enhance sprinting performance. Eighteen subjects completed both of two testing sessions (control and postsupplement) 1 week apart, wherein they sprinted three 60-m distance trials that were recorded with videotape. Following the control session, for 7 days, subjects in the treatment group ingested a creatine-glucose mixture, while the placebo group consumed a glucose powder, followed by the postsupplementation session. Velocities of the subjects through three testing zones within the 60-m sprint were calculated from the videotape. Resultant velocities were analyzed using a MANOVA with a 2 x 2 x 3 x 3 (Group x Session x Trial x Zone) design. Results indicated that there were no statistically significant main or interaction effects on velocity between groups for session, trial, or zone. These data do not support the hypothesis that supplementary creatine ingestion will enhance velocity during the early or latter segments of a 60-m sprint.
We examined the effect of glycogen availability and branched-chain amino acid (BCAA) supplementation on branched-chain oxoacid dehydrogenase (BCOAD) activity during exercise. Six subjects cycled at approximately 75% of their maximal oxygen uptake to exhaustion on three occasions under different preexercise conditions: 1) low muscle glycogen (LOW), 2) low muscle glycogen plus BCAA supplementation (LOW+BCAA), and 3) high muscle glycogen (CON). The LOW trial was performed first, followed by the other two conditions in random order, and biopsies for all trials were obtained at rest, after 15 min of exercise (15 min), and at the point of exhaustion during the LOW trial (49 min). BCOAD activity was not different among the three conditions at rest; however, at 15 min BCOAD activity was higher (P < or = 0.05) for the LOW (31 +/- 5%) and LOW+BCAA (43 +/- 11%) conditions compared with CON (12 +/- 1%). BCOAD activity at 49 min was not different from respective values at 15 min for any condition. These data indicate that BCOAD is rapidly activated during submaximal exercise under conditions associated with low carbohydrate availability. However, there was no relationship between BCOAD activity and glycogen concentration or net glycogenolysis, which suggests that factors other than glycogen availability are important for BCOAD regulation during exercise in humans.
Few studies examine ammonia and amino acid metabolism in response to endurance training. Trained humans generally experience less increase in plasma ammonia during either prolonged or intense exercise. This is probably a reflection of reduced ammonia production and release from the active muscle; it could be a reflection of decreased AMP deaminase activity, decreased glutamate dehydrogenase activity, and/or increased alanine and glutamine formation. Little is known regarding the associated enzyme systems in humans, but in experiments with animal models, aerobic training decreases AMP deaminase and increases the enzymes of amino acid transamination and oxidation.
Six normal untrained men were studied during the intravenous infusion of a balanced amino acid mixture (approximately 0.15 g.kg-1.h-1 for 3 h) at rest and after a leg resistance exercise routine to test the influence of exercise on the regulation of muscle protein kinetics by hyperaminoacidemia. Leg muscle protein kinetics and transport of selected amino acids (alanine, phenylalanine, leucine, and lysine) were isotopically determined using a model based on arteriovenous blood samples and muscle biopsy. The intravenous amino acid infusion resulted in comparable increases in arterial amino acid concentrations at rest and after exercise, whereas leg blood flow was 64 +/- 5% greater after exercise than at rest. During hyperaminoacidemia, the increases in amino acid transport above basal were 30-100% greater after exercise than at rest. Increases in muscle protein synthesis were also greater after exercise than at rest (291 +/- 42% vs. 141 +/- 45%). Muscle protein breakdown was not significantly affected by hyperminoacidemia either at rest or after exercise. We conclude that the stimulatory effect of exogenous amino acids on muscle protein synthesis is enhanced by prior exercise, perhaps in part because of enhanced blood flow. Our results imply that protein intake immediately after exercise may be more anabolic than when ingested at some later time.
Mixed muscle protein fractional synthesis rate (FSR) and fractional breakdown rate (FBR) were examined after an isolated bout of either concentric or eccentric resistance exercise. Subjects were eight untrained volunteers (4 males, 4 females). Mixed muscle protein FSR and FBR were determined using primed constant infusions of [2H5]phenylalanine and 15N-phenylalanine, respectively. Subjects were studied in the fasted state on four occasions: at rest and 3, 24, and 48 h after a resistance exercise bout. Exercise was eight sets of eight concentric or eccentric repetitions at 80% of each subject's concentric 1 repetition maximum. There was no significant difference between contraction types for either FSR, FBR, or net balance (FSR minus FBR). Exercise resulted in significant increases above rest in muscle FSR at all times: 3 h = 112%, 24 h = 65%, 48 h = 34% (P < 0.01). Muscle FBR was also increased by exercise at 3 h (31%; P < 0.05) and 24 h (18%; P < 0.05) postexercise but returned to resting levels by 48 h. Muscle net balance was significantly increased after exercise at all time points [(in %/h) rest = -0.0573 +/- 0.003 (SE), 3 h = -0.0298 +/- 0.003, 24 h = -0.0413 +/- 0.004, and 48 h = -0.0440 +/- 0.005], and was significantly different from zero at all time points (P < 0.05). There was also a significant correlation between FSR and FBR (r = 0.88, P < 0.001). We conclude that exercise resulted in an increase in muscle net protein balance that persisted for up to 48 h after the exercise bout and was unrelated to the type of muscle contraction performed.
In a double-blind and randomized manner, 18 male and female junior competitive swimmers supplemented their diets with 21 g.day-1 of creatine monohydrate (Cr) or a maltodextrin placebo (P) for 9 days during training. Prior to and following supplementation, subjects performed three 100-m freestyle sprint swims (long course) with 60 s rest/recovery between heats. In addition, subjects performed three 20-s arm ergometer maximal-effort sprint tests in the prone position with 60 s rest/recovery between sprint tests. Significant differences were observed among swim times, with Cr subjects swimming significantly faster than P subjects following supplementation in Heat 1 and significantly decreasing swim time in the second 100-m sprint. There was also some evidence that cumulative time to perform the three 100-m swims was decreased in the Cr group. Results indicate that 9 days of Cr supplementation during swim training may provide some ergogenic value to competitive junior swimmers during repetitive sprint performance.
Effects of a 10-week progressive strength training program composed of a mixture of exercises for increasing muscle mass, maximal peak force, and explosive strength (rapid force production) were examined in 8 young (YM) (29+/-5 yrs) and 10 old (OM) (61+/-4 yrs) men. Electromyographic activity, maximal bilateral isometric peak force, and maximal rate of force development (RFD) of the knee extensors, muscle cross-sectional area (CSA) of the quadriceps femoris (QF), muscle fiber proportion, and fiber areas of types I, IIa, IIb, and IIab of the vastus lateralis were evaluated. Maximal and explosive strength values remained unaltered in both groups during a 3-week control period with no training preceding the strength training. After the 10-week training period, maximal isometric peak force increased from 1311+/-123 N by 15.6% (p <.05) in YM and from 976+/-168 N by 16.5% (p <.01) in OM. The pretraining RFD values of 4049+/-791 N*s(-1) in YM and 2526+/-1197 N*s(-1) in OM remained unaltered. Both groups showed significant increases (p < .05) in the averaged maximum IEMGs of the vastus muscles. The CSA of the QF increased from 90.3+/-7.9 cm2 in YM by 12.2% (p <.05) and from 74.7+/-7.8 cm2 in OM by 8.5% (p <.001). No changes occurred in the muscle fiber distribution of type I during the training, whereas the proportion of subtype IIab increased from 2% to 6% (p < .05) in YM and that of type IIb decreased in both YM from 25% to 16% (p < .01) and in OM from 15% to 6% (p < .05). The mean fiber area of type I increased after the 10-week training in YM (p < .001) and OM (p < .05) as well as that of type IIa in both YM (p < .01) and OM (p < .01). The individual percentage values for type I fibers were inversely correlated with the individual changes recorded during the training in the muscle CSA of the QF (r=-.56, p < .05). The present results suggest that both neural adaptations and the capacity of the skeletal muscle to undergo training-induced hypertrophy even in older people explain the gains observed in maximal force in older men, while rapid force production capacity recorded during the isometric knee extension action remained unaltered during the present mixed strength training program.