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Protein requirements and supplementation in strength sports
Abstract
Daily requirements for protein are set by the amount of amino acids that is irreversibly lost in a given day. Different agencies have set requirement levels for daily protein intakes for the general population; however, the question of whether strength-trained athletes require more protein than the general population is one that is difficult to answer. At a cellular level, an increased requirement for protein in strength-trained athletes might arise due to the extra protein required to support muscle protein accretion through elevated protein synthesis. Alternatively, an increased requirement for protein may come about in this group of athletes due to increased catabolic loss of amino acids associated with strength-training activities. A review of studies that have examined the protein requirements of strength-trained athletes, using nitrogen balance methodology, has shown a modest increase in requirements in this group. At the same time, several studies have shown that strength training, consistent with the anabolic stimulus for protein synthesis it provides, actually increases the efficiency of use of protein, which reduces dietary protein requirements. Various studies have shown that strength-trained athletes habitually consume protein intakes higher than required. A positive energy balance is required for anabolism, so a requirement for "extra" protein over and above normal values also appears not to be a critical issue for competitive athletes because most would have to be in positive energy balance to compete effectively. At present there is no evidence to suggest that supplements are required for optimal muscle growth or strength gain. Strength-trained athletes should consume protein consistent with general population guidelines, or 12% to 15% of energy from protein.
... Muscle mass accrual following resistance training results from the synergistic action of resistance exercise and amino acid/protein consumption on stimulating muscle protein synthesis (MPS;Phillips 2004;Rennie et al. 2004;Rennie and Tipton 2000). Various studies have shown that resistance exercise per se is stimulatory for MPS (Biolo et al. 1995b;Chesley et al. 1992;Hasten et al. 2000;Phillips et al. 1997;Phillips et al. 1999;Yarasheski et al. 1993); however, net protein balance (the algebraic difference between MPS and muscle protein breakdown -MPB) remains negative in the absence of amino acid/protein consumption (Biolo et al. 1995b;Phillips et al. 1997;Phillips et al. 1999). ...
... We report here that ingestion of only a small dose of whey protein (10g total protein, 4.2g of essential amino acids) with 21g of carbohydrate (as fructose) can stimulate muscle MPS in resistance trained individuals following exercise. Following high-force resistance exercise, hyperaminoacidemia resulting from amino acid infusion (Biolo et al. 1997) or consumption (Borsheim et al. 2002;Rasmussen et al. 2000;Tipton et al. 1999;Tipton et al. 2001) stimulates MPS such that net balance becomes more positive (Phillips 2004;Rennie et al. 2004;Rennie and Tipton 2000). Our data are consistent with previous studies in which consumption of intact proteins have been shown to stimulate a net uptake of amino acids by leg muscle and an even greater uptake when combined with exercise (Elliot et al. 2006;Tipton et al. 2004;Tipton et al. 2006). ...
... We acknowledge that by not measuring MPB we may have underestimated the impact of the supplements consumed after exercise. However, the magnitude of the change in MPS is consistently shown to be 4-5 fold greater than that of MPB; hence, it is MPS that is the regulated and, ultimately, determinant variable in substantively affecting muscle protein balance in healthy individuals (Phillips 2004;Phillips et al. 2005;Rennie and Tipton 2000). Moreover, it has been shown that when amino acids are provided post-exercise that the exercise-induced rise in proteolysis (Phillips et al. 1997;Phillips et al. 1999), that the rise in protein breakdown does not occur (Biolo et al. 1997;Biolo et al. 1999;Phillips et al. 2002). ...
... O exercício resistido é capaz de estimular aumento na síntese e degradação de proteínas musculares, além de amplificar a resposta das proteínas no turnover proteico (PHILLIPS, 2004;. A síntese de todos os tipos de proteína, incluindo o processo de hipertrofia das fibras musculares, ocorrerá caso a taxa de síntese exceda a degradação proteica MORTON;MCGLORY, PHILLIPS, 2015). ...
... Após a sessão de exercício resistido, com o término da contração muscular, há um aumento da via de sinalização do complexo 1 do alvo da rapamicina em mamíferos (mTORC1), bem como da síntese de proteínas musculares, principalmente devido à fosforilação da proteína ribossômica S6 quinase (P70S6K) (DRUMMOND et al., 2009;DREYER et al., 2006). A hiperaminoacidemia associada à hiperinsulinemia, induzidas pelo consumo de proteínas no período pós treino, são capazes de elevar a taxa de síntese proteica muscular e, ao mesmo tempo, suprimir a quebra de proteínas musculares, contribuindo para promover de forma imediata no reparo de danos celulares e no posterior remodelamento adaptativo das fibras musculares (PHILLIPS, 2004;. ...
... A elevação na taxa da síntese de proteínas pode durar de 24 a 72 horas em indivíduos treinados, dependendo da intensidade do exercício (BURD et al., 2011;MILLER et al., 2005). Para induzir um balanço nitrogenado positivo em praticantes de treinamento resistido intenso, é necessária uma ingestão de proteínas de no mínimo 49% acima do recomendado pela Dietary Reference Intake (DRI's) (PHILLIPS, 2004;JAGER et al., 2017). A ingestão de proteínas também auxilia na manutenção dos estoques de creatina fosfato. ...
O objetivo do estudo foi analisar o efeito de dietas hiperproteicas nas adaptações musculares em indivíduos praticantes de treinamento resistido, assim como relatar possíveis alterações em dosagens bioquímicas de hormônios anabólicos. Foi realizada uma revisão da literatura nas bases de dados online PubMed, Scopus e Web of Science. Os estudos encontrados analisaram o efeito da ingestão de proteínas em quantidades a partir de 0,8 g/kg/dia até 4,4 g/kg/dia em períodos de duas a dezesseis semanas. Corroborando com a International Society of Sports Nutrition, Academy of Nutrition and Dietetics, Dietitians of Canada, American College of Sports Medicine e Nutrition guidelines for strentgh sports: Sprinting, weightlifting, throwing events, and bodybuilding, a presente revisão aponta que a ingestão de proteínas visando a hipertrofia muscular em praticantes de treinamento resistido, deve ser de aproximadamente 2 g/kg/dia. Quantidades acima deste valor não resultam em maior aumento de massa muscular em praticantes de treinamento resistido.
... The regulation of skeletal muscle is a complex process that hinges on the dynamic balance between muscle protein synthesis (MPS) and muscle protein breakdown (1)(2)(3)(4). Although promoting skeletal muscle anabolism is important for general health and performance, maintaining skeletal muscle across the life span is particularly important given its multifaceted role in maintaining whole-body metabolic homeostasis and locomotory capabilities. ...
... EAA, essential amino acid; MPS, muscle protein synthesis; Myo, myofibrillar; NR, not reported; NSD, no significant difference; RM, repetition maximum. 2 Where EAA and/or leucine content was not provided, total content is provided as estimates based on information provided within each study, where possible. 3 BMI reported in the absence of body mass. 4 Estimates based on range of doses provided relative to body mass. ...
... Where EAA content was not provided, total content is provided as estimates based on information provided within each study, where possible. 3 Age ranges provided in the absence of means ± SDs. 4 The 27-g protein supplement was provided in addition to high dairy/soy protein diet, respectively. ...
Background:
There is much debate regarding the source/quality of dietary proteins in supporting indices of skeletal muscle anabolism.
Objective:
We performed a systematic review and meta-analysis to determine the effect of protein source/quality on acute muscle protein synthesis (MPS) and changes in lean body mass (LBM) and strength, when combined with resistance exercise (RE).
Methods:
A systematic search of the literature was conducted to identify studies that compared the effects of ≥2 dose-matched, predominantly isolated protein sources of varying "quality." Three separate models were employed as follows: 1) protein feeding alone on MPS, 2) protein feeding combined with a bout of RE on MPS, and 3) protein feeding combined with longer-term resistance exercise training (RET) on LBM and strength. Further subgroup analyses were performed to compare the effects of protein source/quality between young and older adults. A total of 27 studies in young (18-35 y) and older (≥60 y) adults were included.
Results:
Analysis revealed an effect favoring higher-quality protein for postprandial MPS at rest [mean difference (MD): 0.014%/h; 95% CI: 0.006, 0.021; P < 0.001] and following RE (MD: 0.022%/h; 95% CI: 0.014, 0.030; P < 0.00001) in young (model 1: 0.016%/h; 95% CI: -0.004, 0.036; P = 0.12; model 2: 0.030%/h; 95% CI: 0.015, 0.045; P < 0.0001) and older (model 1: 0.012%/h; 95% CI: 0.006, 0.018; P < 0.001; model 2: 0.014%/h; 95% CI: 0.007, 0.021; P < 0.001) adults. However, although higher protein quality was associated with superior strength gains with RET [standardized mean difference (SMD): 0.24 kg; 95% CI: 0.02, 0.45; P = 0.03)], no effect was observed on changes to LBM (SMD: 0.05 kg; 95% CI: -0.16, 0.25; P = 0.65).
Conclusions:
The current review suggests that protein quality may provide a small but significant impact on indices of muscle protein anabolism in young and older adults. However, further research is warranted to elucidate the importance of protein source/quality on musculoskeletal aging, particularly in situations of low protein intake.
... Рекомендуемое количество белка для поддержания положительного азотистого баланса и удовлетворения метаболических потребностей указывают в пределах 1,2-2,1 г/кг/сут [5][6][7]. Белок при физических нагрузках выступает в роли триггера и субстрата для синтеза со кратительных мышечных волокон и метаболических белков, а также способствует структурным изменени ям в связочном аппарате и костной ткани спортсменов [8,9]. Исследования показывают, что стимуляция син теза мышечных белков в ответ на даже однократную спортивную нагрузку происходит как минимум в тече ние 24 часов, при этом повышается чувствительности к включению белка, поступающего в организм из пище вых продуктов, в мышечные ткани [10]. ...
... Однако для спортсменов с более высокими потребностями в энергии может потребоваться относительно непро должительное потребление белка до 2,5 г/кг/сут. В от чете Phillips [7] были обобщены результаты, касающи еся потребности в белке у спортсменов силовых видов спорта. Используя регрессионный подход, он пришел к выводу, что следует рекомендовать потребление бел ка в количестве 1,2 г/кг массы тела в день, а при вклю чении верхнего предела 95 % доверительного интервала приближенное количество составляет 1,33 г/кгМТ/сут. ...
... Для здоро вья или физической активности человека употребление рациона, содержащего жира менее 15 % от калорийности рациона, малоэффективно. Потребление жиров в диа пазоне от 1,0 до 1,5 г/кг МТ/сут является достаточным, хотя при определенных условиях спортсменам может потребоваться потребление жиров, близкое к 2,0 г/кг МТ/сут [1,7]. Один из подходов к потреблению макро нутриентов для изменения метаболических процессов в пользу окисления жиров -это использование кето генных диет. ...
A balanced diet and intake of Specialized foodstuffs products play a key role in expanding the adaptive potential of athletes and affect the effectiveness of the training process. The review examines the current scientific evidence regarding the nutritional and energy needs of athletes to increase endurance. Comparative characteristics of various sources of protein, carbohydrates are given, the value of fats in sports practice, as well as the effectiveness of the use of combinations of various macronutrients during intense physical exertion are characterized.
... Skeletal muscles play an important role not only in improving the performance of athletes but also in maintaining health in the general population [1][2][3][4][5]. Skeletal muscle protein synthesis (MPS) is essential for the growth and homeostasis of skeletal muscle [6]. In recent years, agerelated muscle atrophy, known as sarcopenia, has become a major issue in our aging society. ...
... kg/m 2 were recruited by a public clinical research volunteer recruitment system administered by QST from June 28, 2019 to November 29, 2019. Volunteers who met the following criteria were excluded: (1) receiving medication on the test day, (2) severe or progressive diseases such as malignancies, (3) obvious abnormalities on physical or laboratory examinations, (4) milk allergy or lactose intolerance, (5) smokers, (6) engaging in habitual moderate to high intensity exercise, (7) claustrophobia, (8) participation in other clinical trials within the previous month, and (9) prior examination involving radiation exposure for medical treatment purposes within the past 12 months or for research purposes within the past 6 months. ...
Although the standard method to evaluate skeletal muscle protein synthesis (MPS) is muscle biopsy, the method is invasive and problematic for multisite use. We conducted a small pilot study in volunteers to investigate changes in MPS according to skeletal muscle site using a noninvasive method in which 6 healthy young men were given yogurt (containing 20 g milk protein) or water, and 1 h later, l-[¹¹C]methionine ([¹¹C]Met) was administered intravenously. Dynamic PET/CT imaging of their thighs was performed for 60 min. The influx constant Ki of [¹¹C]Met in skeletal muscle protein was calculated as an index of MPS using a Patlak plot, and found to be 0.6%–28% higher after ingesting yogurt than after water in 5 of the 6 volunteer participants, but it was 34% lower in the remaining participant. Overall, this indicated no significant increase in Ki after ingesting milk protein. However, when the quadriceps and hamstring muscles were analyzed separately, we found a significant difference in Ki. This demonstrates the potential of visualizing MPS by calculating the Ki for each voxel and reconstructing it as an image, which presents unique advantages of [¹¹C]Met PET/CT for evaluating MPS, such as site-specificity and visualization.
... Improving skeletal muscle health increases physical function [12], insulin sensitivity [13], and lowers the risks of cardiovascular disease and hypertension [11,14], increases the chances of osteoporosis and mortality [15]. Resistance exercise increases the demand for protein to sustain increased protein synthesis for hypertrophy and to compensate for muscle protein breakdown caused by exercise [16]. While the RDA of 0.8g protein/kg body weight/day fulfills most people's nitrogen balance demands [16] while1.4-2.0g/kg ...
... Resistance exercise increases the demand for protein to sustain increased protein synthesis for hypertrophy and to compensate for muscle protein breakdown caused by exercise [16]. While the RDA of 0.8g protein/kg body weight/day fulfills most people's nitrogen balance demands [16] while1.4-2.0g/kg body weight/day is recommended by experts for those persons who perform extensive exercise [17]. ...
Once the consumer acknowledges that foods containing dietary cholesterol are not a risk factor for
cardiovascular disease. The eggs contain dietary cholesterol and must be valued for their other nutritional
components. Egg protein is one of the components in eggs that demands special attention. Egg protein has
a high biological value and provides essential amino acids. Egg protein has been shown to be beneficial to
musculoskeletal health. Egg protein may also suppress appetite, resulting in a reduction in calorie intake
which leads to weight loss.
... Early literature maintained that athletes were recommended to consume protein at levels consistent with those of the general population, which equates to roughly 12-15% of energy from protein [30]; however, more recent research suggests that athletes' protein intake requirements exceed the general population's [11]. Recent indicator amino acid oxidation studies by Bandegan et al. demonstrate athletes' protein requirements are around 1.9 g/kg of bodyweight [31,32]; thus, plant-based diets risk falling short of optimal levels Content courtesy of Springer Nature, terms of use apply. ...
... Plant-based diets are on average less proteinaceous than non-plant-based diets, however, both diet styles can attain appropriate daily protein intake levels [28,30], suggesting that adequate protein ingestion is not necessarily dependent solely on its source. Micronutrient intake, however, is dependent on source, as some micronutrients are derived strictly from animal-based products, which places plantbased dieters at higher risk of micronutrient deficiency if unaware [12,19,36,37]. ...
Purpose
Plant-based diets have become increasingly popular in Western culture. Although studies have examined physiologic health improvements of plant-based diets, there is little data on plant-based diets as it relates to sports performance.
Methods
Clinical review of systematic reviews, randomized trials, prospective and retrospective cohort studies available in English on PubMed and Google Scholar databases utilizing combinations of the search terms “athlete, sport, nutrition, diet, vegan, vegetarian, strength, endurance, health, performance, and exercise.”
Results
There are no significant differences in athletic performance in participants maintaining plant-based diets compared to those consuming omnivorous diets specifically related to strength, power, and endurance. Plant-based diets are at higher risk of predisposing individuals to certain micronutrient deficiencies, reduced protein intake, and lower serum creatine and sex testosterone levels, though supplementation may effectively replace the lacking components. Non-plant-based diets are associated with a higher risk of obesity, type II diabetes mellitus, certain malignancies, and cardiovascular disease, though several studies demonstrate that a particular meat- and fish-filled diet may reduce body weight, blood pressure, fat composition, and all-cause mortality.
Conclusion
Though plant-based and mixed omnivorous eaters may vary in their macronutrient and micronutrient intake, disease propensities, and oxygen consumption during exertion, a plant-based diet does not translate into a significantly different physical performance compared to a non-plant-based diet across measures of strength, power, and aerobic/anaerobic performance. For athletes, trainers, nutritionists and dieticians, and physicians, the most important recommendation is to maintain a nutritionally sufficient diet that provides the appropriate levels of vital nutrients and vitamins.
... the overall risk of all-cause mortality [34]. Resistance exercise training, also important for skeletal muscle health, increases the need for protein to support elevated protein synthesis for hypertrophy and to counteract muscle protein breakdown resulting from training [35]. While the RDA of 0.8 g protein/kg body weight/day meets the needs for nitrogen balance for the majority of people, nitrogen balance is not an indicator of optimal muscle health and does not take the increased needs associated with exercise training into consideration [35]. ...
... Resistance exercise training, also important for skeletal muscle health, increases the need for protein to support elevated protein synthesis for hypertrophy and to counteract muscle protein breakdown resulting from training [35]. While the RDA of 0.8 g protein/kg body weight/day meets the needs for nitrogen balance for the majority of people, nitrogen balance is not an indicator of optimal muscle health and does not take the increased needs associated with exercise training into consideration [35]. Experts recommend a range of 1.4-2.0 ...
Once the general public accepts that dietary cholesterol is not a concern for cardiovascular disease risk, foods that have been labeled as high-cholesterol sources, including eggs, may be appreciated for their various other dietary components. One of the nutrients in eggs that deserves further discussion is egg protein. Egg protein has been recognized to be highly digestible and an excellent source of essential amino acids, with the highest attainable protein digestibility-corrected amino acid score. Egg protein has been shown to decrease malnutrition in underdeveloped countries, possibly increase height in children, and protect against kwashiorkor. Egg protein has been demonstrated to be important to skeletal muscle health and protective against sarcopenia. Egg protein also can decrease appetite, resulting in a reduction in the caloric intake from the next meal and weight reduction. Other protective effects of egg protein addressed in this review include protection against infection as well as hypotensive and anti-cancer effects.
... A single bout of resistance exercise increased basal muscle protein synthesis for at least 48 h [39]. However, this single resistance exercise bout concomitantly increased muscle protein breakdown, such that muscle protein balance was negative in the fasted state [40]. Substrates (i.e., amino acids, the building blocks of protein) are necessary to build body protein. ...
... Substrates (i.e., amino acids, the building blocks of protein) are necessary to build body protein. Not only is dietary protein anabolic, albeit transiently [41], the combination of protein with exercise enhances the protein synthetic response in skeletal tissue to produce an acutely positive, net anabolic effect [40,42,43]. A meta-analysis of 49 RCTs identified that in healthy adults engaged in at least 6 weeks of resistance training, The coenzyme nicotinamide adenine dinucleotide is involved in processes that generate adenosine triphosphate from protein; nicotinamide adenine dinucleotide phosphate is involved in anabolic processes Poultry, fish, meat, whole grains, fortified breakfast cereals, nuts and seeds protein supplementation produced significant gains in fat-free mass and strength compared to a control [44••]. ...
Purpose of Review
Prehabilitation prepares patients to withstand the rigors of surgery; however, there is little consensus on nutritional prehabilitative support for surgical patients. In this narrative review, we offer our perspectives on the role of protein in surgical prehabilitation.
Recent Findings
While the exact dietary protein requirements of pre-surgical patients are unknown, protein is an important piece of any nutritional care plan. Body protein, in particular skeletal muscle, is catabolized to support surgery-related systemic responses such as inflammation and wound healing. Older adults and patients with cancer, who may be sarcopenic, undernourished, or cachectic, often experience perturbations in protein metabolism that deplete skeletal muscle tissue prior to surgery. Reduced body protein combined with surgery-induced stress can result in a concomitant loss of physiologic function.
Summary
Multi-modal prehabilitation that includes nutrition and exercise can augment patients’ body protein reserve before surgery and mitigate losses post-surgery to improve functional outcomes.
... Moreover, in both an immobilization period (atrophy) and a late reloading period (hypertrophy), the rates of protein synthesis of animals fed an HICAcontaining diet were maintained or were increased relative to the rats fed Leu-fortified or control diets [16]. In principle, the skeletal muscle mass reflects a net balance of skeletal muscle protein synthesis (MPS) and breakdown (MPB) [17], and thus, there is not a contradiction in this relationship between muscle mass and protein synthesis in atrophied and hypertrophied periods. However, the rate of protein synthesis in the non-immobilized gastrocnemius muscle was decreased by the inclusion of HICA in the diet, although those in the heart and liver were not affected [16]. ...
... These results suggest that HICA pretreatment might inhibit cytokine-induced acute increases of iNOS expression and IL-6 production via the suppression of basal protein synthesis. Generally, skeletal muscle hypertrophy and atrophy are prescribed by a net balance of MPS and MPB [17]. Therefore, we investigated the secretion of 3-MeHis, which reflects MPB, and we examined the expression of atrogin-1 and MURF-1, which are two of the major muscle-specific F-box-type E3 ubiquitin ligases that accelerate MPB via the ubiquitinproteasome system [38,39]. ...
There is ongoing debate as to whether or not α-hydroxyisocaproic acid (HICA) positively regulates skeletal muscle protein synthesis resulting in the gain or maintenance of skeletal muscle. We investigated the effects of HICA on mouse C2C12 myotubes under normal conditions and during cachexia induced by co-exposure to TNFα and IFNγ. The phosphorylation of AMPK or ERK1/2 was significantly altered 30 min after HICA treatment under normal conditions. The basal protein synthesis rates measured by a deuterium-labeling method were significantly lowered by the HICA treatment under normal and cachexic conditions. Conversely, myotube atrophy induced by TNFα/IFNγ co-exposure was significantly improved by the HICA pretreatment, and this improvement was accompanied by the inhibition of iNOS expression and IL-6 production. Moreover, HICA also suppressed the TNFα/IFNγ co-exposure-induced secretion of 3-methylhistidine. These results demonstrated that HICA decreases basal protein synthesis under normal or cachexic conditions; however, HICA might attenuate skeletal muscle atrophy via maintaining a low level of protein degradation under cachexic conditions.
... Besoin et référence nutritionnelle pour les protéines proposés par l'AFSSA (2007) selon les RN : Référence Nutritionnelle ; ND : Non déterminé * La RN est de 10 g/j pour les enfants de 0 à 2 ans et de 12 g/j pour les enfants de 3 ans ** Valeurs basées sur les travaux de Tarnopolsky (2004) etPhillips (2004) [107,108] ...
... Besoin et référence nutritionnelle pour les protéines proposés par l'AFSSA (2007) selon les RN : Référence Nutritionnelle ; ND : Non déterminé * La RN est de 10 g/j pour les enfants de 0 à 2 ans et de 12 g/j pour les enfants de 3 ans ** Valeurs basées sur les travaux de Tarnopolsky (2004) etPhillips (2004) [107,108] ...
Pour une alimentation plus durable, il est nécessaire d’identifier des alternatives végétales aux protéines animales. Le pois présente de nombreux avantages, mais sa digestibilité doit être évaluée.Or, l’évaluation de la digestibilité iléale des acides aminés (AA) est sujette à des difficultés méthodologiques. Chez le rat, il n’existe pas de méthode validée. Chez l’Homme, la méthode directe standard est très invasive car elle nécessite de collecter les pertes digestives par intubation. Une nouvelle méthode plasmatique minimalement invasive, dite « double traceur », a été proposée. Elle repose sur l’ingestion simultanée d’une protéine test marquée au 2H et d’une protéine de référence de digestibilité connue, marquée au 13C. Les objectifs de nos travaux étaient : 1) évaluer la qualité nutritionnelle de la protéine de pois jaune en comparaison à la caséine et au gluten par l’étude de la digestibilité et d’autres critères de qualité, chez le rat et chez l’Homme ; 2) développer les méthodes de mesure de la digestibilité iléale des AA dans ces deux modèles. Chez l’Homme, il s’agissait de comparer la méthode double traceur à la méthode directe par l’étude d’isolats protéiques marqués au 15N et au 2H.La digestibilité élevée obtenue pour les AA de la protéine de pois, chez le rat (95%) et chez l’Homme (94%), révèle sa haute qualité nutritionnelle. Sa comparaison à la caséine et au gluten la positionne favorablement parmi l’offre de protéines disponibles. La composition en AA équilibrée de la protéine de pois couplée à sa haute digestibilité a abouti à des scores de qualité DIAAS satisfaisants (1,00 chez l’Homme, 0,88 chez le rat). Chez le rat, nous avons montré que la digestibilité cæcale vraie pourrait approximer la digestibilité iléale vraie. Chez l’Homme, la méthode double traceur a fourni des valeurs de digestibilité variables, qui étaient physiologiques pour certains AA et incohérentes pour d’autres. Cette méthode nécessite davantage de mises au point mais reste prometteuse.
... Skeletal muscle proteins are in a constant state of dynamic turnover affecting cellular proteostasis. Muscle protein is simultaneously being synthesized, broken down, and the resultant amino acids are either reused (approximately 85-90%) or converted to other metabolic products (211). The constant renewal and removal of bodily proteins, cell-types, and organelles are critical to maintain a fully functional proteome that supports the maintenance of cellular function. ...
... In young, growing children MPS must exceed MPB and muscle mass increases, a process that predominates in the first two decades of our lives. However, in healthy adults (who are not regularly engaging in structured exercise training) consuming adequate dietary protein, the balance between MPS and MPB is at equilibrium and skeletal muscle mass remains relatively constant (211). We propose that this is the net state of muscle for most of the third and fourth decades of life before age-related processes begin to tip NBAL to favor MPB, and age-related sarcopenia begins. ...
Skeletal muscle is the organ of locomotion, its optimal function is critical for athletic performance, and is also important for health due to its contribution to resting metabolic rate and as a site for glucose uptake and storage. Numerous endogenous and exogenous factors influence muscle mass. Much of what is currently known regarding muscle protein turnover is owed to the development and use of stable isotope tracers. Skeletal muscle mass is determined by the meal- and contraction-induced alterations of muscle protein synthesis and muscle protein breakdown. Increased loading as resistance training is the most potent nonpharmacological strategy by which skeletal muscle mass can be increased. Conversely, aging (sarcopenia) and muscle disuse lead to the development of anabolic resistance and contribute to the loss of skeletal muscle mass. Nascent omics-based technologies have significantly improved our understanding surrounding the regulation of skeletal muscle mass at the gene, transcript, and protein levels. Despite significant advances surrounding the mechanistic intricacies that underpin changes in skeletal muscle mass, these processes are complex, and more work is certainly needed. In this article, we provide an overview of the importance of skeletal muscle, describe the influence that resistance training, aging, and disuse exert on muscle protein turnover and the molecular regulatory processes that contribute to changes in muscle protein abundance. © 2021 American Physiological Society. Compr Physiol 11:2249-2278, 2021.
... hypertrophy; lean body mass; protein accretion; weightlifting MUSCLE PROTEIN SYNTHESIS (MPS) is synergistically increased by resistance exercise (3,12,17,18,48,61) and feeding (4,25,51,57). Although there are resistance exercise-induced changes in muscle protein breakdown (3,48,49), they are small by comparison to changes in MPS, which varies 3-to 4-fold between the fed and postabsorptive states and also with performance of resistive exercise (47,52,53). These observations point to the regulation of MPS as the primary locus of control in determining resistance exercise-induced changes in muscle protein mass. ...
... Several studies have demonstrated that the resistance exercise-induced increase in MPS persists for several hours (e.g., 8 -48 h) (33,43,46,48,55). As feeding synergistically interacts with resistance exercise to further increase MPS (4,46,51,57), it is likely that feeding at any time after acute resistance exercise would increase MPS to a greater degree than feeding alone (47). For this reason, a biopsy sampling time point of 6 h following resistance exercise was selected to examine how muscle contractile activity (or skeletal muscle loading) affects the anabolic response to feeding late into recovery. ...
... For strength athletes, a carbohydrate intake of 6-10 g/kg/d is recommended in order to maintain blood glucose levels during exercise and replace muscle glycogen following exercise (40,43,50). In addition, team and strength athletes should obtain 1.2 to 1.7 g/kg/d of protein to maintain muscle mass (20, 38,50). ...
... The inflammatory state associated with PC renders several amino-acids conditionally essential [59,60], and places a high demand on aromatic and sulphur-amino acids [61]. Supplemental dietary protein consumption and resistance exercise training are known to exert independent, as well as synergistic anabolic effects [62]. Despite this information, 25% of studies included the review did not incorporate a nutritional intervention in their PH protocols. ...
... Skeletal muscle 'senses' a complex interplay of mechanical (i.e., via loading/unloading or aerobic exercise) and molecular (i.e., substrate availability as amino acids, glucose or lipids) perturbations and integrates a series of protein signalling events to modify the rates of muscle protein synthesis (MPS) and muscle protein breakdown (MPB) (McKendry et al., 2021). The algebraic difference between MPS and MPB determines the net protein balance within muscle (Phillips, 2004) and, thus, whether muscle proteins are accrued or degraded. ...
The gradual deterioration of physiological systems with ageing makes it difficult to maintain skeletal muscle mass (sarcopenia), at least partly due to the presence of ‘anabolic resistance’, resulting in muscle loss. Sarcopenia can be transiently but markedly accelerated through periods of muscle disuse‐induced (i.e., unloading) atrophy due to reduced physical activity, sickness, immobilisation or hospitalisation. Periods of disuse are detrimental to older adults' overall quality of life and substantially increase their risk of falls, physical and social dependence, and early mortality. Disuse events induce skeletal muscle atrophy through various mechanisms, including anabolic resistance, inflammation, disturbed proteostasis and mitochondrial dysfunction, all of which tip the scales in favour of a negative net protein balance and subsequent muscle loss. Concerningly, recovery from disuse atrophy is more difficult for older adults than their younger counterparts. Resistance training (RT) is a potent anabolic stimulus that can robustly stimulate muscle protein synthesis and mitigate muscle losses in older adults when implemented before, during and following unloading. RT may take the form of traditional weightlifting‐focused RT, bodyweight training and lower‐ and higher‐load RT. When combined with sufficient dietary protein, RT can accelerate older adults' recovery from a disuse event, mitigate frailty and improve mobility; however, few older adults regularly participate in RT. A feasible and practical approach to improving the accessibility and acceptability of RT is through the use of resistance bands. Moving forward, RT must be prescribed to older adults to mitigate the negative consequences of disuse atrophy.
... In the context of a multimodal prehabilitation program, supplementing patients with whey protein might potentiate the anabolic effect resistance exercise and increase preoperative muscle mass [62]. Although this type of supplementation has not yet been studied in CD patients, oral supplementation with 20 g of whey protein has been shown to be clinically effective in improve preoperative functional walking capacity in patients with colorectal cancer [63]. ...
Approximately 15–50% of patients with Crohn’s disease (CD) will require surgery within ten years following the diagnosis. The management of modifiable risk factors before surgery is essential to reduce postoperative complications and to promote a better postoperative recovery. Preoperative malnutrition reduced functional capacity, sarcopenia, immunosuppressive medications, anemia, and psychological distress are frequently present in CD patients. Multimodal prehabilitation consists of nutritional, functional, medical, and psychological interventions implemented before surgery, aiming at optimizing preoperative status and improve postoperative recovery. Currently, studies evaluating the effect of multimodal prehabilitation on postoperative outcomes specifically in CD are lacking. Some studies have investigated the effect of a single prehabilitation intervention, of which nutritional optimization is the most investigated. The aim of this narrative review is to present the physiologic rationale supporting multimodal surgical prehabilitation in CD patients waiting for surgery, and to describe its main components to facilitate their adoption in the preoperative standard of care.
... 24 Moreover, transport of amino acids into muscle fibres is also essential for the synthesis of mitochondrial proteins required for aerobic metabolism and thus aerobic fitness. [24][25][26] Hence, as previously pointed out by Gillis et al, interventions to improve physical fitness should be designed to draw on this synergetic effect between physical exercise training and nutrition. 24 Taken together, in the current study, frail patients with ESLD awaiting OLT will be invited to partake in a semisupervised home-based bimodal prehabilitation programme, comprising a physical exercise programme and nutritional intervention. ...
Introduction
Patients with end-stage liver disease awaiting orthotopic liver transplantation (OLT) are generally classified as frail due to disease-related malnutrition and a progressive decline in musculoskeletal and aerobic fitness, which is associated with poor pre-OLT, peri-OLT and post-OLT outcomes. However, frailty in these patients may be reversable with adequate exercise and nutritional interventions.
Methods and analysis
Non-randomised clinical trial evaluating the effect of a home-based bimodal lifestyle programme in unfit patients with a preoperative oxygen uptake (VO 2 ) at the ventilatory anaerobic threshold ≤13 mL/kg/min and/or VO 2 at peak exercise ≤18 mL/kg/min listed for OLT at the University Medical Center Groningen (UMCG). The programme is patient tailored and comprises high-intensity interval and endurance training, and functional exercises three times per week, combined with nutritional support. Patients will go through two training periods, each lasting 6 weeks.
The primary outcome of this study is the impact of the programme on patients’ aerobic fitness after the first study period. Secondary outcomes include aerobic capacity after the second study period, changes in sarcopenia, anthropometry, functional mobility, perceived quality of life and fatigue, incidence of hepatic encephalopathy and microbiome composition. Moreover, number and reasons of intercurrent hospitalisations during the study and postoperative outcomes up to 12 months post OLT will be recorded. Finally, feasibility of the programme will be assessed by monitoring the participation rate and reasons for non-participation, number and severity of adverse events, and dropout rate and reasons for dropout.
Ethics and dissemination
This study was approved by the Medical Research Ethics Committee of the UMCG (registration number NL83612.042.23, August 2023) and is registered in the Clinicaltrials.gov register ( NCT05853484 ). Good Clinical Practice guidelines and the principles of the Declaration of Helsinki will be applied. Results of this study will be submitted for presentation at (inter)national congresses and publication in peer-reviewed journals.
Trial registration number
NCT05853484 .
... Skeletal muscle quantity and quality are important for healthy living in all people, as skeletal muscle is associated with not only improved performance in athletes [25,26] but also reduced risk of various diseases [27], maintenance of locomotor function in the elderly [28] and prolonged life span [29]. Skeletal muscle mass is specified by the net balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB) [30]. In other words, if the total MPS exceeds the total MPB within a time period, skeletal muscle mass will increase, although MPS and MPB are constantly fluctuating. ...
Yogurt is a traditional fermented food that is accepted worldwide for its high palatability and various health values. The milk protein contained in yogurt exhibits different physical and biological properties from those of non-fermented milk protein due to the fermentation and manufacturing processes. These differences are suggested to affect the time it takes to digest and absorb milk protein, which in turn will influence the blood levels of amino acids and/or hormones, such as insulin, and thereby, the rate of skeletal muscle protein synthesis via the activation of intracellular signaling, such as the mTORC1 pathway. In addition, based on the relationship between gut microbiota and skeletal muscle conditions, yogurt, including lactic acid bacteria and its metabolites, has been evaluated for its role as a protein source. However, the substantial value of yogurt as a protein source and the additional health benefits on skeletal muscle are not fully understood. The purpose of this review is to summarize the research to date on the digestion and absorption characteristics of yogurt protein, its effect on skeletal muscle, and the contribution of lactic acid bacterial fermentation to these effects.
... For athletes among young adults [18,[28][29][30][31][32][33] as well as general young adults, the value of protein requirement was high value within or higher the current recommendations for athletes (1.2 to 2.0 g/kg body weight/d) [44]. Additionally, the value of protein requirement by the IAAO method was higher than that of protein requirement by the nitrogen balance method for both resistance training and endurance athletes in the previous studies [45][46][47]. This finding is the result of the unique feature of the IAAO method for identifying protein requirements that maximize systemic protein synthesis [48]. ...
Background:
The indicator amino acid oxidation (IAAO) method has been accepted as an approach to evaluate habitual protein requirements under free-living conditions.
Objective:
This scoping review reports on literature that evaluated protein requirements in humans using the IAAO methods.
Methods:
Three databases (PubMed/Medline, Web of Science, and ProQuest) were systematically searched to identify studies that evaluated protein requirements using the IAAO method published in English until June 5, 2023. We evaluated the study quality using previously developed criteria. We extracted the characteristics of the study design and the results of protein requirements. Two reviewers conducted both reviews and quality assessments independently; any differences among them were resolved by consensus or agreement of all team members.
Results:
We extracted 16 articles targeting children, young adults (including pregnant women, resistance training athletes, endurance training athletes, and team sports), and older adults. For quality assessment, 14 studies were evaluated "strong", but the remaining two were "moderate". These studies were conducted in only three countries and not for all sexes or life stages. The range of the estimated average protein requirements of each life stage were 1.3 g/kg body weight/day for children, 0.87 to 2.1 (0.87 - 0.93 for general young adults, 1.22 - 1.52 for pregnant women, 1.49 - 2.0 for resistance-trained athletes, 1.65 - 2.1 for endurance athletes and 1.2 - 1.41 for team sports athletes) g/kg body weight/day for young adults, and 0.85 to 0.96 g/kg body weight/day for older adults.
Conclusions:
Protein requirements in 14 studies were higher than the current reference for each sex, life stage and physical activity that are related to protein requirement. In the future, protein requirements of various population including sex, life stage could be assessed using the IAAO methods worldwide.
... It brings a new, highly interactive and expressive interactive experience [1][2][3][4]. The sport of tai chi is a representative sport in Chinese traditional sports and occupies a very important position in Chinese traditional sports [5][6][7][8]. The Taiji culture in Chinese martial arts is a culture of body bonding, a culture of health, and a culture that differs from Western fitness culture [9][10][11][12]. ...
As a pearl in the treasury of Chinese traditional culture, taijiquan is the crystallization of the wisdom of the entire Chinese nation and contains a rich cultural connotation. Its role and influence in the field of cross-cultural studies is increasing as China’s comprehensive power grows. This paper aims to promote Chinese civilization and the essence of Taiji culture to the world. Through the artificial intelligence algorithm calculations, the path of international promotion of taijiquan is inferred. By using the implementation of taijiquan teaching programs in groups as a medium to promote the culture of taijiquan from groups to the world in all aspects, thus promoting cultural exchanges around the world and thus promoting the deeper development of Chinese martial arts culture. The results of the experiment showed that students, for example, were very curious about using VR technology to learn taijiquan at 27%. Most of the students were looking forward to learning taijiquan using VR technology, indicating that VR technology in the context of artificial intelligence is important for the public to understand taijiquan and to promote taijiquan internationally.
... Гипертрофия мышечных волокон также нуждается в положительном азотистом балансе -синтез мышечного белка обязательно должен превышать его распад. Различные исследования демонстрируют, что силовые тренировки стимулируют синтез мышечного белка, как у тренированных, так и нетренированных людей [3]. ...
... Strength-trained athletes have advocated high protein diets for many years. While debate continues on the need for additional protein among resistancetrained individuals, general guidelines now recommend athletes undertaking strength training ingest approximately twice current recommendations for protein of their sedentary counterparts or as much as 1.6-1.7 g protein Á kg 71 Á day 71 (Phillips, 2004). Given the relatively wide distribution of protein in the meal plan and increased energy intake of athletes, it should not be surprising to learn that the majority of strength-trained athletes easily achieve these increased protein needs (Tables I and II). ...
... There is an ongoing debate as to what amounts of protein strength athletes should consume, but general guidelines now recommend that athletes engaging in strength training consume about 1.6-1.7 g of protein / kg bw / day [9], although even 3.3 g of protein / kg bw / day, no negative effects on the body of a healthy athlete were observed [10]. ...
Introduction: For strength training to be effective, proper nutrition is necessary, based on providing the right amount of energy, as well as optimally balanced macronutrients. Nutrition among bodybuilders, weightlifters and powerlifters differs because the training aims, training methodology and competition itself are different.
Objective: Strength sports athletes differ from each other in body structure, training methodology and form of competition. The aim of the study was to try to answer the question whether their diets affect somatic variables and leg power.
Materials and Methods: 60 people remained, which were divided into 4 groups, including 15 weightlifting competitors, 15 powerlifters, 15 bodybuilders and 15 men not training competitive sport
Results: The quality of the diet used had an impact on the body composition in the control group. In the group of powerlifters, there was a significantly positive correlation between the daily intake of carbohydrates and the percentage of body fat (p
... Comumente o uso de proteínas, hipercalóricos e carboidratos que está associado ao aumento de massa muscular. Quando estimuladas com exercícios, as proteínas são constantemente e simultaneamente sintetizadas e degradadas com objetivo de reparar ou remodelar estruturas [34]. O principal pressuposto para a grande utilização de suplementos nutricionais com alta quantida-de de proteína está relacionado com a ressíntese proteica e o balanço nitrogenado positivo [35,36]. ...
A prática de atividade física auxiliada por uma alimentação equilibrada trazem resultados satisfatórios, mas fatores como a falta de informação, orientação ou recurso financeiro, somados ao anseio de atingir os resultados rapidamente, fazem com que os indivíduos busquem os recursos ergogênicos. O presente estudo teve como objetivo realizar uma revisão de literatura a respeito do consumo de suplementos alimentares e esteroides (recursos ergogênicos) em academias do Brasil. Foram utilizadas as bases de dados eletrônicas Scielo, Revista Brasileira de Fisiologia do Exercício (RBFE) e Revista Brasileira de Nutrição Esportiva (RBNE), e as seguintes palavras-chave: anabolizantes, esteroides anabólicos androgênicos, suplementos alimentares, recursos ergogênicos, consumo, praticantes de musculação. Foram selecionados 29 artigos. Verificou-se que de 4.877 pessoas praticantes de academia, 40,8% consomem recursos ergogênicos com finalidade estética. Na maioria dos estudos, a indicação para o consumo dos recursos ergogênicos foi de profissionais não habilitados. Apesar das leis de restrição para o comércio dos recursos ergogênicos, visando í proteção dos consumidores, percebe-se que os usuários conseguem ter acesso aos recursos sem a devida orientação profissional, colocando-os em risco. Necessita-se de novas medidas para que haja maior controle sobre a comercialização dos recursos ergogênicos.Palavras-chave: esteroides anabólicos androgênicos, suplementos nutricionais, recursos ergogênicos, praticantes de musculação.
... Interestingly, nutritional optimization alone is not as effective as the multimodal approach that also incorporates physical conditioning [43]. Indeed, exercise stimulates both breakdown and buildup of muscle, and the combination of protein intake and lean muscle regeneration is what ultimately favors the anabolic process [56][57][58]. In addition to synthesis of skeletal muscle proteins, mitochondrial proteins are also produced, which contributes to increased aerobic and functional capacity [39••, 59]. ...
Purpose of Review
Poor nutritional status is common among inpatients, and particularly so among surgical patients. The problem is even more pronounced among elderly surgical patients, with age itself being an independent risk factor for malnutrition. With older adults representing a large proportion of patients undergoing emergency operations, and with malnutrition contributing to worse surgical outcomes, peri-operative nutritional optimization has garnered significant interest in the surgical literature. We sought to review the literature, specifically over the last five years, regarding the approach to nutritional evaluation and optimization in the pre- and post-operative settings in the elderly surgical patient.
Recent Findings
Recent research has focused on the pathophysiologic mechanisms that drive cachexia, including inflammatory and endocrine pathways and their interplay in patients subjected to the stress of surgery, as well as on the important differences between cachexia and sarcopenia. Emphasis has been placed on approaching nutritional status in a systematic fashion and on using context-specific validated screening tools in addition to biochemical and anthropometric parameters. In the elective setting, Enhanced Recovery After Surgery (ERAS) pathways have become the norm. With this, the concept of multimodal prehabilitation has been extensively studied and societal recommendations have been made.
Summary
Elderly surgical patients constitute a particularly vulnerable population who is at risk of poor post-operative outcomes by virtue of both advanced age and poor nutritional status. Serum albumin, BMI, and history of recent involuntary weight loss or poor intake should be supplemented with screening tools such as the Nutritional Risk Screening (NRS-2002) to evaluate each patient’s nutritional risk. Nutritional and physical activity interventions lead to better outcomes, and should be implemented well before surgery and continued in the post-operative setting. It will be interesting and useful in the future to evaluate how these strategies translate to patients undergoing emergency surgery and who therefore do not usually have the benefit of pre-operative optimization.
... Shrinking the structure by extracting constituents, or swelling the structure by supplying solvents, will generally result in weakening effects such as collapse or fracture [1,2]. In comparison, with the continuous supplement of water and amino acids, natural biological tissues like skeletal muscles become stronger after repeated growth cycles, during which new components are formed within the original tissue [3,4] (Fig. 1). This self-growing and self-strengthening phenomenon has inspired researchers to develop intelligent materials that exhibit dynamic and programmable properties. ...
Natural tissues possess the self-strengthening ability through biological growth, during which additional building blocks are transported into the tissues and attached to the pre-existing microstructures. In contrast, synthetic materials are typically static, meaning neither their dimensions nor their mechanical properties are able to be altered after the materials are manufactured into specific structures. Recently the concept of bio-inspired synthetic material arises, aiming at developing materials with dynamically programmable performances. Based on the idea of multinetwork (MN) elastomer, we propose a solvent-free elastomer composite system that can be strengthened through tunable self-growth cycles. Resembling biological tissues, chemical structures of the composite remain constant after self-growing, while its dimension, modulus, strength and swelling ability can be programmed on demand. The elastomer composite is naturally compatible with Digital Light Processing (DLP) 3D printing, which directly enables the fast manufacturing of high-precision structures. Applications of the self-growing composites in metamaterials with tunable mechanical performance and waterproof structures are exhibited at the same time.
... Protein requirements during resistance training have been suggested to be highest at training onset (13,14), with evidence suggesting moderate daily intakes (∼1.2-1.4 g/kg -1 /d -1 ) can support chronic adaptations (15)(16)(17), although recent suggestions are that slightly higher intakes (∼1.6 g/kg -1 /d -1 ) may optimize lean mass growth (18). Resistance training is associated with a reduction in whole-body protein turnover but an increased net protein balance, suggesting greater efficiency of whole-body amino acid utilization with training in males (16,17), although whether this also extends to females is unknown. ...
Background
Acute exercise increases the incorporation of dietary amino acids into de novo myofibrillar proteins after a single meal in controlled laboratory studies in males. It is unclear whether this extends to free-living settings or is influenced by training or sex.
Objectives
We determined the effects of exercise, training status, and sex on 24-hour free-living dietary phenylalanine incorporation into skeletal muscle proteins.
Methods
In a parallel group design, recreationally active males (mean ± SD age, 23 ± 3 years; BMI. 23.4 ± 2.9 kg/m2; n = 10) and females (age 24 ± 5 years; BMI, 23.1 ± 3.9 kg/m2; n = 9) underwent 8 weeks of whole-body resistance exercise 3 times a week. Controlled diets containing 1.6 g/kg–1/d–1 (amino acids modelled after egg), enriched to 10% with [13C6] or [2H5]phenylalanine, were consumed before and after an acute bout of resistance exercise. Fasted muscle biopsies were obtained before [untrained, pre-exercise condition (REST ] and 24 hours after an acute bout of resistance exercise in untrained (UT) and trained (T) states to determine dietary phenylalanine incorporation into myofibrillar (ΔMyo) and sarcoplasmic (ΔSarc) proteins, intracellular mechanistic target of rapamycin (mTOR) colocalization with ulex europaeus agglutinin–1 (UEA-1; capillary marker; immunofluorescence), and amino acid transporter expression (Western blotting).
Results
The ΔMyo values were ∼62% greater (P < 0.01) in females than males at REST. The ΔMyo values increased above REST by ∼51% during UT and ∼30% in T (both P < 0.01) in males, remained unchanged in females during UT, and were ∼33% lower at T when compared to UT (P = 0.013). Irrespective of sex, ΔMyo and ΔSarc were decreased at T compared to UT (P ≤ 0.026). Resistance training increased mTOR colocalization with UEA-1 (P = 0.004), while L amino acid transporter 1, which was greater in males (P < 0.01), and sodium-coupled neutral amino acid transporter 2 protein expression were not affected by acute exercise (P ≥ 0.33) or training (P ≥ 0.45).
Conclusions
The exercise-induced incorporation of dietary phenylalanine into myofibrillar and sarcoplasmic proteins is attenuated after training regardless of sex, suggesting a reduced reliance on dietary amino acids for postexercise skeletal muscle remodeling in the T state.
... When hyperaminoacidemia occurs in the post-RT period, then MPS is stimulated to an even greater degree and for a longer duration (48), and net protein balance becomes even more positive (49). The persistent and greater stimulation of MPS over MPB with regular RT results in small but significant increases in muscle protein net balance (50), which then eventually results in muscle hypertrophy (51). ...
Hypertrophy can be operationally defined as an increase in the axial cross-sectional area of a muscle fiber or whole muscle, and is due to increases in the size of pre-existing muscle fibers. Hypertrophy is a desired outcome in many sports. For some athletes, muscular bulk and, conceivably, the accompanying increase in strength/power, are desirable attributes for optimal performance. Moreover, bodybuilders and other physique athletes are judged in part on their muscular size, with placings predicated on the overall magnitude of lean mass. In some cases, even relatively small improvements in hypertrophy might be the difference between winning and losing in competition for these athletes. This position stand of leading experts in the field synthesizes the current body of research to provide guidelines for maximizing skeletal muscle hypertrophy in an athletic population. The recommendations represent a consensus of a consortium of experts in the field, based on the best available current evidence. Specific sections of the paper are devoted to elucidating the constructs of hypertrophy, reconciliation of acute vs long-term evidence, and the relationship between strength and hypertrophy to provide context to our recommendations.
... Bu nedenle, protein için şu anda önerilen diyet önerileri bazı vejetaryen popülasyonlar için yeterli olmayabilir (Phillips, 2004 ...
... In addition to preventing malnutrition and correcting nutrition-identified problems, the nutrition component of a multimodal prehabilitation program should work in synergy with the exercise intervention to support optimal gains in mass, strength, physical fitness, and recovery (10,40,82). While resistance exercise is regarded as the main anabolic stimulus, nutrition, including adequate dietary protein, provides the necessary substrate to achieve anabolic gains (83). For a review of nutrition within surgery, we refer the reader to Gillis and Carli (84), for nutrition prehabilitation see Gillis and Wischmeyer (40), and for treating low muscle mass see Prado et al. (85). ...
The nutrition care process is a standardized and systematic method used by nutrition professionals to assess, diagnose, treat, and monitor patients. Using the nutrition care process model, we demonstrate how nutrition prehabilitation can be applied to the pre-surgical oncology patient.
... Muscle protein synthesis (MPS) 6 is intimately sensitive to changes in amino acid availability (1)(2)(3). Provision of amino acids, either i.v. or orally, stimulates a marked rise in MPS (4,5). These changes in MPS respond in a curvilinear manner that tracks closely with increasing extracellular amino acid concentrations (6). ...
... At the end of our study, mice in. the Con+T, HPHF, and HPHF+T groups had approximately the same grip power, which was higher than that in the LPHF+T group. Many studies have shown that extra protein is required to support muscle protein accretion and compensate catabolic loss of amino acids during strength training [41]. Protein deficiency in LPHF may be the reason why training failed to enhance grip power in the LPHF groups [42]. ...
Obesity has become a worldwide health problem over the past three decades. During obesity, metabolic dysfunction of white adipose tissue (WAT) is a key factor increasing the risk of type 2 diabetes. A variety of diet approaches have been proposed for the prevention and treatment of obesity. The low-protein high-fat diet (LPHF) is a special kind of high-fat diet, characterized by the intake of a low amount of protein, while compared to typical high-fat diet, may induce weight loss and browning of WAT. Physical activity is another effective intervention to treat obesity by reducing WAT mass, inducing browning of WAT. In order to determine whether an LPHF, along with exercise enhanced body weight loss and body fat loss as well as the synergistic effect of an LPHF and exercise on energy expenditure in a mice model, we combined a 10-week LPHF with an 8-week forced treadmill training. Meanwhile, a traditional high-fat diet (HPHF) containing the same fat and relatively more protein was introduced as a comparison. In the current study, we further analyzed energy metabolism-related gene expression, plasma biomarkers, and related physiological changes. When comparing to HPHF, which induced a dramatic increase in body weight and WAT weight, the LPHF led to considerable loss of body weight and WAT, without muscle mass and strength decline, while it exhibited a risk of liver and pancreas damage. The mechanism underlying the LPHF-induced loss of body weight and WAT may be attributed to the synergistically upregulated expression of Ucp1 in WAT and Fgf21 in the liver, which may enhance energy expenditure. The 8-week training did not further enhance weight loss and increased plasma biomarkers of muscle damage when combined with LPHF. Furthermore, LPHF reduced the expression of fatty acid oxidation-related genes in adipose tissues, muscle tissues, and liver. Our results indicated that an LPHF has potential for obesity treatment, while the physiological condition should be monitored during application.
... Muscle mass is regulated via the balance between rates of muscle protein synthesis (MPS) and breakdown (MPB) [1]. It has been well established that both resistance exercise and protein ingestion can independently [2][3][4][5] or synergistically [6,7] stimulate MPS, over time yielding muscle hypertrophy [8]. ...
Background
Acute protein turnover studies suggest lower anabolic response after ingestion of plant vs. animal proteins. However, the effects of an exclusively plant-based protein diet on resistance training-induced adaptations are under investigation.
Objective
To investigate the effects of dietary protein source [exclusively plant-based vs. mixed diet] on changes in muscle mass and strength in healthy young men undertaking resistance training.
Methods
Nineteen young men who were habitual vegans (VEG 26 ± 5 years; 72.7 ± 7.1 kg, 22.9 ± 2.3 kg/m²) and nineteen young men who were omnivores (OMN 26 ± 4 years; 73.3 ± 7.8 kg, 23.6 ± 2.3 kg/m²) undertook a 12-week, twice weekly, supervised resistance training program. Habitual protein intake was assessed at baseline and adjusted to 1.6 g kg⁻¹ day⁻¹ via supplemental protein (soy for VEG or whey for OMN). Dietary intake was monitored every four weeks during the intervention. Leg lean mass, whole muscle, and muscle fiber cross-sectional area (CSA), as well as leg-press 1RM were assessed before (PRE) and after the intervention (POST).
Results
Both groups showed significant (all p < 0.05) PRE-to-POST increases in leg lean mass (VEG: 1.2 ± 1.0 kg; OMN: 1.2 ± 0.8 kg), rectus femoris CSA (VEG: 1.0 ± 0.6 cm²; OMN: 0.9 ± 0.5 cm²), vastus lateralis CSA (VEG: 2.2 ± 1.1 cm²; OMN: 2.8 ± 1.0 cm²), vastus lateralis muscle fiber type I (VEG: 741 ± 323 µm²; OMN: 677 ± 617 µm²) and type II CSA (VEG: 921 ± 458 µm²; OMN: 844 ± 638 µm²), and leg-press 1RM (VEG: 97 ± 38 kg; OMN: 117 ± 35 kg), with no between-group differences for any of the variables (all p > 0.05).
Conclusion
A high-protein (~ 1.6 g kg⁻¹ day⁻¹), exclusively plant-based diet (plant-based whole foods + soy protein isolate supplementation) is not different than a protein-matched mixed diet (mixed whole foods + whey protein supplementation) in supporting muscle strength and mass accrual, suggesting that protein source does not affect resistance training-induced adaptations in untrained young men consuming adequate amounts of protein.
Clinical Trial Registration
NCT03907059. April 8, 2019. Retrospectively registered.
Hypohydration can impair aerobic performance and deteriorate cognitive function during exercise. To minimize hypohydration, athletes are recommended to commence exercise at least euhydrated, ingest fluids containing sodium during long-duration and/or high-intensity exercise to prevent body mass loss over 2% and maintain elevated plasma osmolality, and rapidly restore and retain fluid and electrolyte homeostasis before a second exercise session. To achieve these goals, the compositions of the fluids consumed are key; however, it remains unclear what can be considered an optimal formulation for a hydration beverage in different settings. While carbohydrate–electrolyte solutions such as sports drinks have been extensively explored as a source of carbohydrates to meet fuel demands during intense and long-duration exercise, these formulas might not be ideal in situations where fluid and electrolyte balance is impaired, such as practicing exercise in the heat. Alternately, hypotonic compositions consisting of moderate to high levels of electrolytes (i.e., ≥45 mmol/L), mainly sodium, combined with low amounts of carbohydrates (i.e., <6%) might be useful to accelerate intestinal water absorption, maintain plasma volume and osmolality during exercise, and improve fluid retention during recovery. Future studies should compare hypotonic formulas and sports drinks in different exercise settings, evaluating different levels of sodium and/or other electrolytes, blends of carbohydrates, and novel ingredients for addressing hydration and rehydration before, during, and after exercise.
While “rehabilitation” as a medical term is well known and well defined in medicine, the term “prehabilitation” is now being rediscovered in surgery and oncology. It is currently defined either as “the process of expanding patient’s functional and psychological capacity to reduce potential deleterious effects of a significant stressor, which is the surgical procedure itself” or as “a process on the cancer continuum of care that occurs between the time of cancer diagnosis and the beginning of acute treatment and includes physical and psychological assessments that establish a baseline functional level, identify impairments, and provide interventions that promote physical and psychological health to reduce the incidence and/or severity of future impairments.” Basically, all definitions of “prehabilitation” are currently, one way or the other predominantly linked to surgery.
The aim of this chapter is to emphasize the synergies between prehabilitation and predictive, preventive, and personalized medicine (PPPM or 3 PM) in practical implementation of both, thus unlocking great potential for future health-oriented healthcare. According to our perception of the complexity of healthcare, as we envisage it in the future, the prehabilitation, may (and must) play an important role in the preparation of the patient not only for surgical procedures, and/or cancer treatment procedures such as chemotherapy, radiotherapy and hormonal treatment which are all known to have a negative impact on functional capacity in an unprepared patient but prehabilitation, as an attitude, should be gradually used in much wider spectrum of medical and therapeutic procedures thus complementing and implementing the attitude of PPPM/3 PM.
Prehabilitation can use all the tools and knowledge accumulated and published so far in PPPM, including the research outcomes and tools in suboptimal health state which were proved to be very valuable for prediction, prevention, and personalized attitude. The health status, together with mitochondrial health of the patient should be assessed with the help of available medical technologies in order to predict potential problems and avoiding them through using adequate preventive actions taken in particular person. In practical prehabilitation, a personalized nutritional support based on the particular analysis of the patient’s blood, particular physical exercises to assess and consequently increase fitness, the psychological support, disease/procedure-related education of the patient, as well as using health-supporting environmental factors should become a routine in the future PPPM/3 PM healthcare, starting primarily with surgery, organ transplantation, oncology, obstetrics, dentistry, neurodegenerative diseases, genetically determined diseases, pandemic management, and continuing then with other fields of medical care in which prehabilitation may prove to be important and enriching for effective patient care and better outcomes.
Polyaniline (PANi) hydrogels that combine advantages of hydrogels and conductive PANi have recently emerged in areas of wearable devices and personal healthcare. Nevertheless, their mechanical performance often gradually degrades after being used for a period, caused by destruction of the inner structures when external forces are applied. Inspired by biological structures with persistent durability, we develop here a phytic acid-assisted PANi/poly(vinyl alcohol) (PVA) hydrogel that shows self-reinforcing features. As a natural product holding plenty of phosphate groups, phytic acid (PA) plays two crucial roles when preparing this hydrogel: (1) aniline is salinized by PA in aqueous solution to promote in situ polymerization, making the resulting PANi conductive; (2) PA/PANi particles form hydrogen bonds with PVA, acting as stress concentration points to induce structure orientation. The optimal PVA/PA/PANi hydrogel displays dark green color with a uniform distribution of PA/PANi particles. After experiencing repetitive 4 × 100 stretching at a strain of 10%, the hydrogel exhibits an enhanced fracture strength (20.35 MPa), Young's modulus (22.66 MPa), and toughness (36.24 MJ·m-3) compared with the original hydrogel. This self-reinforcing feature is mainly attributed to the formation of anisotropic structures fixed by hydrogen bonds between PA/PANi particles and PVA chains upon repetitive external forces. Moreover, anisotropic structures can be disassembled by swelling the post-stretched hydrogel in water, and the swollen hydrogel shows similar self-reinforcing behaviors. The good mechanical durability and reusable characteristics make the PVA/PA/PANi hydrogel a reliable strain sensor. This work provides a structural growing-reviving approach for conductive hydrogels with persistent durability.
El objetivo consistió en determinar el grado de incidencia que tiene el consumo de huevo en la masa muscular en la población masculina del gimnasio en Lima Metropolitana. La metodología fue cuantitativa y el desarrollo fue comparando a través de muestras aleatorias usando variables tipo: edad, índice de masa corporal, tiempo de entrenamiento, cantidad de huevos de consumo al día, forma de consumo, medida de masa muscular, presión arterial, grado de diabetes. La base de datos registró una población masculina de 13,909 clientes y 504 entrenadores. Se calculó el tamaño de la muestra a través del método de poblaciones finitas, llegando a ser entrevistados 30 para clientes y 29 instructores. Entre los resultados, que la población de entrenadores aumenta 23% la masa muscular por el consumo de huevo, sin embargo, no se descarta que estos consuman productos que le ayuden a sintetizar con mayor velocidad las proteínas, como son los anabólicos.
Resumo Introdução: A dieta vegetariana, alimentação baseada em plantas, se mostra eficiente no ganho de massa muscular, uma vez que contém alimentos de boa qualidade, resultando em benefícios para os praticantes de exercício físico de força. Objetivo: Realizar revisão integrativa de literatura sobre a influência da dieta vegetariana aplicada a praticantes de atividade física com o intuito de aumento de massa muscular. Metodologia: Para a análise do estudo, foram realizadas coletas de artigos referentes à aplicação de dietas vegetarianas em praticantes de atividade física intensa e/ou de força com o intuito de ganho de massa muscular, para que se tenha grande aporte de informações sobre o tema tratado. Resultados: A alimentação vegetariana pode contribuir para hipertrofia muscular e ganho de massa magra tanto ou mais que a dieta onívora desde que seja bem planejada e balanceada. O teor de massa magra e a força podem ser superiores no grupo de onívoros quando comparados aos indivíduos vegetarianos. Conclusão: A dieta vegetariana demonstra-se positiva para o ganho de massa muscular através de exercícios de força, desde que haja uma adequação de proteínas e aminoácidos na dieta. Palavras-Chave: HIPERTROFIA; DIETA VEGETARIANA; EXERCÍCIO. Abstract Introduction: The vegetarian diet, a plant-based diet, is efficient in gaining muscle mass, as it contains good quality foods, resulting in benefits for strength training practitioners. Objective: Carry out an integrative literature review on the influence of the vegetarian diet applied to physical activity practitioners in order to increase muscle mass gain. Methodology: For the study analysis, articles referring to the application of vegetarian diets in practitioners of intense physical activity and/or strength training in order to gain muscle mass were collected, so that there is a large amount of information on the subject treated. Results: Vegetarian food can contribute to muscle hypertrophy and lean mass gain as much or more than the omnivorous diet, provided it is well-planned and balanced. Lean mass content and strength may be higher in the omnivore group when compared to vegetarian individuals. Conclusion: The vegetarian diet is positive for muscle mass gain through strength training exercises, as long as there is an adequacy of proteins and amino acids in the diet.
Rationale:
Heavy water can be used as a tracer for the evaluation of protein turnover. By adding heavy water (D2 O) to the precursor pool, non-essential amino acids, including alanine, can be isotopically labeled in vivo. Protein turnover can then be quantified by measuring the hydrogen isotope ratio of protein-bound alanine.
Methods:
In this study, we constructed a novel method to apply deuterium labeling of alanine to the evaluation of protein turnover using elemental analysis coupled to isotope ratio mass spectrometry (EA-IRMS). We established a preparative HPLC method to isolate alanine from protein hydrolysates. EA-IRMS was then used to determine the hydrogen isotope ratio of alanine isolated from hydrolysates of protein from mouse myoblast C2C12 cells that had been treated with D2 O over the course of 72 hours.
Results:
In cells treated with 4% D2 O, the deuterium enrichment of alanine increased to approximately 0.9% over time, while that of cells treated with 0.017% D2 O increased to approximately 0.006%. The rate of protein synthesis calculated by fitting the increase of deuterium excess to rise-to-plateau kinetics was similar regardless of the concentration of D2 O. When C2C12 cells treated with insulin and rapamycin were analyzed 24 hours after the addition of 0.017% D2 O, protein turnover was found to be accelerated by insulin, but this effect was offset by co-treatment with rapamycin.
Conclusion:
The derivative-free measurement of the hydrogen isotope ratio of protein-bound alanine using EA-IRMS can be applied to the evaluation of protein turnover. The proposed method is a accessible option for many laboratories to perform highly sensitive IRMS-based evaluations of protein metabolic turnover.
Relato de Experiência: o projeto de intervenção foi realizado em 3 momentos. O primeiro momento foi feito a coleta de amostras microbiológicas da mão dominante do aluno e eventualmente incubadas em placas de petri. No segundo momento foi demonstrado as placas de petri identificadas de cada aluno como forma de visualização da contaminação das mãos e no mesmo dia foi ministrado uma palestra explicando a importância da higienização das mãos. No 3 momento e último foi aplicado um questionário como forma de avaliação do projeto realizado. Considerações Finais: Por meio do projeto foi possível perceber que o mesmo teve um resultado positivo em relação a conscientização dos alunos sobre a importância de práticas higiênicas nas mãos.
Many living tissues, such as muscle, become mechanically stronger with growth. Yet, synthetic hydrogels usually exhibit an opposite size‐mechanical property relation, that is, swelling‐weakening behavior. Herein, a series of swollen yet strengthened polyampholyte (PA) hydrogels are developed via a simple metal‐ion solution soaking strategy. In this strategy, a dynamic PA hydrogel (with ionic bonds) is dialyzed in ZrOCl2 solutions (Step‐I) and deionized water (Step‐II) successively to obtain equilibrated hydrogels. Due to the specific Zr⁴⁺ ions and PA network structure, Step‐I takes several months with sample size and mechanical performance increasing continuously, while Step‐II only needs several days. Through this strategy, the resultant hydrogel networks are reorganized and eventually constructed by ionic and metalligand bonds, enabling the swelling yet strengthening behavior. A systematic study confirms that dialysis time in Step‐I and corresponding ZrOCl2 concentration can significantly affect the multiphase microstructures of the hydrogels, resulting in different mechanical enhancements. The optimized hydrogel possesses 39.2 MPa of Young's modulus and 3.7 MPa of tensile strength, which are 302 and 5.5 times these of the original PA gel, respectively. Despite distinct swelling, these hydrogels still mechanically surpass many existing high‐performance hydrogels. This study opens a novel pathway for fabricating swollen yet strengthened hydrogels.
Protein is a critical part of the diet in individuals with inherited metabolic diseases (IMDs).Current Dietary Reference Intakes may underestimate protein needs for individuals with IMD.Distributing protein intake throughout the day facilitates anabolism.Additional protein and energy is required for catch-up growth in patients with growth failure.Proper use of protein substitutes (medical foods) is essential in assuring adequate balance of serum amino acids and promoting growth and development. Protein is a critical part of the diet in individuals with inherited metabolic diseases (IMDs). Current Dietary Reference Intakes may underestimate protein needs for individuals with IMD. Distributing protein intake throughout the day facilitates anabolism. Additional protein and energy is required for catch-up growth in patients with growth failure. Proper use of protein substitutes (medical foods) is essential in assuring adequate balance of serum amino acids and promoting growth and development.
Bodybuilding involves an intricate combination of training and dieting focused around periodic mesocycles to tailor time towards preparation and competition. In contrast to other muscle sports (such as weightlifting and powerlifting), bodybuilding competitors are judged on appearance (muscle size, definition and posing) as opposed to physical performance. Professional competitors achieve this by altering training variables (such as intensity and volume) as well as dietary and supplementation strategies throughout the 'season'. These mesocycles follow protocols based on a scientific literature, with the intention to achieve better results and preserve the health of each competitor. In order to achieve the long term improvements to health and skill-related components of fitness, a programme and strategy must be implemented that incorporates components of both dietary restriction as well as systematic variations to training and exercise selection. Because of the nature of body aesthetics and muscularity in bodybuilding, off-season training follows hypertrophic goals to increase muscular size. Increased caloric intake as well as increased training volume and intensity are the most common adaptations to a hypertrophic mesocycle. A positive energetic caloric balance (~10-20%) and high protein consumption provide necessary nutrients for muscle protein synthesis and energy storage and usage. During any cycle, weight gain and loss should not surpass 5% bodyweight per week to reduce the health concerns associated with rapid weight fluctuations. Current literature suggests that macronutrient intakes of protein 1.6-2.2 g•kg-1 •d-1 (25-30% TDC), carbohydrates 5-6 g•kg-1 •d-1 (50-60% TDC) and fat 1-1.5 g•kg-1 •d-1 (20-25% TDC) are suggested as optimal for professional bodybuilders to meet the physiological needs of an off-season mesocycle focusing on lean muscle gain. Bodybuilding • Nutrition • Hypertrophy • Performance • Physique
Sports medicine has had considerable success in different domains, including injury prevention, disease treatment, and patient recovery. By integrating genetic and phenotype data, this research is primarily utilized to promote the development of sports medicine. Recently, studies have begun to focus on the genetic basis of sports phenotypes, and they have discovered genetic variation underlying these traits. The relationships between genetic variation and phenotype changes in sports medicine, as well as genetic models and databases connected to sports medicine, are examined in detail in this chapter. Furthermore, in the future, exercise prescriptions could be based on this comprehensive analysis and contribute to the creation of personalized healthcare, based on individual differences in genotypes and phenotypes of different populations.
Sarcopenia is a progressive and generalized skeletal muscle disorder associated with accelerated loss of muscle mass and function, leading to falls, functional decline, frailty, and mortality. Sarcopenia is a progressive aging-related syndrome that can be accelerated by other concomitant metabolic disease states, including diabetes and obesity. It is widely believed that low-grade chronic inflammation associated with aging, known as inflammaging, contributes to the sarcopenia process. Inflammaging can be a result of excessive stimulation of proinflammatory responses, but an ineffective anti-inflammatory reaction is also an important factor affecting aging-related diseases. In addition, advanced age is associated with a redistribution of fat depots, causing muscle inflammation and dysfunction, as well as releasing proinflammatory cytokines and adipokines.
Inflammatory mediators, including proinflammatory cytokines, anti-inflammatory cytokines and adipokines, play significant roles in the regulation of muscle mass and function as well as metabolic homeostasis. Myokines secreted by muscle manage to maintain physiological homeostasis. However, abnormal myokine signaling might trigger and aggravate the pathogenesis underlying age-related metabolic diseases and sarcopenia. We believe these molecules can be the correlation between inflammaging and sarcopenia and the possible underlying mechanisms. Here, we will mainly focus on the effects of these molecules on regulating muscle and metabolic homeostasis. Furthermore, the potential roles of these factors as biomarkers or therapeutic targets for sarcopenia or sarcopenia obesity will also be evaluated.
Due to the utilization of milk proteins such as whey protein (WP) and casein as sports nutrition ergogenic aids, the present study investigated the effects of the association of WP and casein in a ratio of 80:20, a similar ratio of human breast milk, on blood branched-chain amino acid (BCAA) profiles, markers of protein metabolism and delayed onset muscle soreness (DOMS), after a single bout of resistance exercise. A double-blind, crossover and acute study was carried out with ten men (age 29 ± 8 years; BMI: 25.4 ± 2.9 kg/m2; 77 ± 12 kg; 1.74 ± 0.09 m); each one consumed the following supplements randomly, one per session: WP, CAS (casein), WP/CAS (80% WP/20% CAS), CAS/WP (80% CAS/20% WP) and PLA (placebo). They were also subjected to the following evaluations: the one repetition maximum (1RM) test; resistance training session; blood extraction during each session to determine the BCAA profile; two food records; 3-day evaluation of DOMS (24 h, 48 h and 72 h) and nitrogen balance in each treatment. The intervention resulted in similar nitrogen urinary, creatinine and urea plasma levels and showed a positive nitrogen balance in all the trials. Regarding the BCAAs, the peak occurred at 60 min post-ingestion and remained higher until 120 min for WP, WP/CAS and CAS/WP. The DOMS was significantly lower for WP, WP/CAS and CAS/WP compared to the CAS and PLA treatments. There were no advantages in the association of WP and CAS in the BCAAs profile when compared to WP itself, but it induced a lower DOMS compared to CAS and PLA (Clinical Trial registration number: clinicaltrials.gov, NCT04648384).
Extensive studies of lactic acid bacteria (LAB), have been undertaken since Metchnikoff's hypothesis was proposed in the 1990s. LAB are found in decomposing plants and milk products, producing lactic acid as the major metabolic end product of carbohydrate fermentation. Fermented products containing LAB are considered to have a variety of health benefits for humans. In the present section, the health benefits of LAB are briefly reviewed focusing on the nutritional aspects of LAB fermented milk, and the impact on intestinal microflora, and host functions.
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.
The effects of resistance exercise upon leucine oxidation and whole body protein synthesis were studied using stable isotope methodology. L-[1-13C]leucine was used as a tracer to calculate leucine oxidation and whole body protein synthesis in six healthy, fed, male athletes in response to a 1 h bout of circuit-set resistance exercise. The measurements were performed prior to, during, and for 2 h after exercise, and corrections were made for background 13CO2/12CO2 breath enrichment and bicarbonate retention factor changes. Results demonstrated significant (P less than 0.01) increases in the background 13CO2/12CO2 breath enrichment at 1 and 2h after exercise and in the bicarbonate retention factor (P less than 0.01) during exercise. At 15 min after exercise, the bicarbonate retention factor was significantly (P less than 0.05) lower than at rest. There were no significant effects of exercise on leucine oxidation or flux, whole body protein synthesis, or the rate of appearance of endogenous leucine. We concluded that circuit-set resistance exercise did not affect the measured variables of leucine metabolism. In addition, large errors in calculating leucine oxidation and whole body protein synthesis during resistance exercise can occur if background 13CO2/12CO2 breath enrichment and bicarbonate retention factor changes are not accounted for.
Nitrogen (N) balance, fed-state leucine kinetics, and urinary 3-methylhistidine (3-MeH) excretion were examined in 12 men and women, aged 56-80 yr, before and during 12 wk of resistance training (RT). Subjects were randomized to groups that consumed diets providing either 0.80 +/- 0.02 g protein.kg-1.day-1 (lower protein, LP) or 1.62 +/- 0.02 g protein.kg-1.day-1 (higher protein, HP). At baseline, mean N balance was negative for LP (-4.6 +/- 3.4 mg N.kg-1.day-1) and positive for HP (13.6 +/- 1.0 mg N.kg-1.day-1). N retention increased similarly in LP and HP at the 11th wk of RT by 12.8 and 12.7 mg N.kg-1.day-1, respectively. Thus LP had an increased efficiency of N retention. LP had decreased leucine flux (P < 0.001), oxidation (P < 0.001), and uptake for protein synthesis (P < 0.02), relative to HP, both at baseline and after RT. Leucine flux increased with RT in both diet groups (P < 0.05) and was associated mainly with an increase in protein synthesis in LP (91% of change in flux) and an increase in oxidation in HP (72% of change in flux; RT-diet interaction, P < 0.05). RT increased actomyosin protein breakdown (increased 3-MeH-to-creatinine ratio, P < 0.01). Diet-related differences in protein metabolism did not influence body composition changes with RT. These data show that the efficiency of N retention and protein utilization during RT is higher in older subjects who consume 0.8 vs. 1.6 g protein.kg-1.day-1 dietary protein.
Muscle ultrastructure and contractile properties were examined before and after a single bout of resistance exercise (8 sets of 8 repetitions at 80% of 1 repetition maximum). Eight untrained males performed the concentric (Con) phase of arm-curl exercise with one arm and the eccentric (Ecc) phase with the other arm. Needle biopsies were obtained from biceps brachii before exercise (Base), immediately postexercise from each arm (post-Con and post-Ecc), and 48 h postexercise from each arm (48 h-Con and 48 h-Ecc). Electron microscopy was used to quantify the presence of disrupted fibers in each sample. Analysis of variance revealed a greater (P < or = 0.05) proportion of disrupted fibers in post-Con, post-Ecc, 48 h-Con, and 48 h-Ecc samples compared with Base. Significantly more fibers were disrupted in post-Ecc (82%) and 48 h-Ecc (80%) samples compared with post-Con (33%) and 48 h-Con (37%), respectively. Voluntary and evoked strength measurements recovered to Base values within 24 h in the Con arm but remained depressed (P < or = 0.05) for 72-96 h in the Ecc arm. These data indicate that both the raising and lowering phases of weightlifting produced myofibrillar disruption, with the greatest disruption occurring during the lowering phase.
An 8-wk progressive resistance training program for the lower extremity was performed twice a week to investigate the time course for skeletal muscle adaptations in men and women. Maximal dynamic strength was tested biweekly. Muscle biopsies were extracted at the beginning and every 2 wk of the study from resistance-trained and from nontrained (control) subjects. The muscle samples were analyzed for fiber type composition, cross-sectional area, and myosin heavy chain content. In addition, fasting blood samples were measured for resting serum levels of testosterone, cortisol, and growth hormone. With the exception of the leg press for women (after 2 wk of training) and leg extension for men (after 6 wk of training), absolute and relative maximal dynamic strength was significantly increased after 4 wk of training for all three exercises (squat, leg press, and leg extension) in both sexes. Resistance training also caused a significant decrease in the percentage of type IIb fibers after 2 wk in women and 4 wk in men, an increase in the resting levels of serum testosterone after 4 wk in men, and a decrease in cortisol after 6 wk in men. No significant changes occurred over time for any of the other measured parameters for either sex. These data suggest that skeletal muscle adaptations that may contribute to strength gains of the lower extremity are similar for men and women during the early phase of resistance training and, with the exception of changes in the fast fiber type composition, that they occur gradually.
a3 Nutritional Research Unit, London School of Hygiene and Tropical Medicine, St Pancras Hospital, 4 St Pancras Way, London NW1 2PE
Muscle mass and function are improved in the elderly during resistance exercise training. These improvements must result from alterations in the rates of muscle protein synthesis and breakdown. We determined the rate of quadriceps muscle protein synthesis using the in vivo rate of incorporation of intravenously infused [13C]leucine into mixed-muscle protein in both young (24 yr) and elderly (63-66 yr) men and women before and at the end of 2 wk of resistance exercise training. Before training, the fractional rate of muscle protein synthesis was lower in the elderly than in the young (0.030 +/- 0.003 vs. 0.049 +/- 0.004%/h; P = 0.004) but increased (P < 0.03) to a comparable rate of muscle protein synthesis in both young (0.075 +/- 0.009%/h) and elderly subjects (0.076 +/- 0.011%/h) after 2 wk of exercise. In the elderly, muscle mass, 24-h urinary 3-methylhistidine and creatinine excretion, and whole body protein breakdown rate determined during the [13C]leucine infusion were not changed after 2 wk of exercise. These findings demonstrate that, during the initial phase of a resistance exercise training program, a marked increase in quadriceps muscle protein synthesis rate occurs in elderly and young adults without an increase in the rate of whole body protein breakdown. In the elderly, this was not accompanied by an increase in urinary 3-methylhistidine excretion, an index of myofibrillar protein breakdown.
The purpose of this study was to compare the ability of various body-composition assessment techniques to detect changes in soft tissue in older, weight-stable women (50-70 y of age) completing a 1-y randomized, controlled trial of progressive resistance training. The intervention group (n = 20) performed high-intensity strength-training 2 d/wk with five different exercises; the control group (n = 19) was untreated. Hydrostatic weighing, 24-h urinary creatinine, computed tomography of thigh sections, total body potassium, and tritium dilution techniques were used to measure increases in total fat-free mass (FFM) and the muscle and water components of FFM. A decrease in fat mass (by hydrostatic weighing) was seen in the strength-trained women compared with the control subjects (P - 0.01-0.0001). Anthropometry, bioelectric impedance, dual-energy X-ray absorptiometry, and total body nitrogen and carbon did not measure any significant change in soft tissue. The choice of a body-composition technique is important when designing a study expected to affect soft tissue, because not all techniques available are precise enough to detect small changes.
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.
McCall, G. E., W. C. Byrnes, A. Dickinson, P. M. Pattany, and S. J. Fleck. Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training. J. Appl. Physiol. 81(5): 2004–2012, 1996.—Twelve male subjects with recreational resistance training backgrounds completed 12 wk of intensified resistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groups were trained, with four exercises emphasizing the forearm flexors. After training, strength (1-repetition maximum preacher curl) increased by 25% ( P < 0.05). Magnetic resonance imaging scans revealed an increase in the biceps brachii muscle cross-sectional area (CSA) (from 11.8 ± 2.7 to 13.3 ± 2.6 cm ² ; n = 8; P < 0.05). Muscle biopsies of the biceps brachii revealed increases ( P < 0.05) in fiber areas for type I (from 4,196 ± 859 to 4,617 ± 1,116 μm ² ; n = 11) and II fibers (from 6,378 ± 1,552 to 7,474 ± 2,017 μm ² ; n = 11). Fiber number estimated from the above measurements did not change after training (293.2 ± 61.5 × 10 ³ pretraining; 297.5 ± 69.5 × 10 ³ posttraining; n = 8). However, the magnitude of muscle fiber hypertrophy may influence this response because those subjects with less relative muscle fiber hypertrophy, but similar increases in muscle CSA, showed evidence of an increase in fiber number. Capillaries per fiber increased significantly ( P < 0.05) for both type I (from 4.9 ± 0.6 to 5.5 ± 0.7; n = 10) and II fibers (from 5.1 ± 0.8 to 6.2 ± 0.7; n = 10). No changes occurred in capillaries per fiber area or muscle area. In conclusion, resistance training resulted in hypertrophy of the total muscle CSA and fiber areas with no change in estimated fiber number, whereas capillary changes were proportional to muscle fiber growth.
Reliable standards relating to physiological requirements are needed in order to estimate nutritional needs of populations. Probably the most important standards in terms of national and international planning are those for energy and protein, because the need for these nutrients determines to a major extent the amount, composition and cost of food supplies. These standards, reflecting physiological requirements, are properly used to set nutritional targets and to assess intakes of populations. Comparison of an array of intake and requirements values, for households in communities or for groups of individuals of a given age sex category, can indicate nutritional risk: that is, the probability of deficiency in the populations examined, even though deficient individuals or households cannot be identified from this information alone. Requirements figures are often used to estimate the food energy and protein needs of communities and nations. This is commonly done to compare availability of food supplies with population needs in deriving food balance sheets. All that these balances can show is whether or not a nation has enough food potentially to meet its needs, not who or how many may be malnourished, as this depends upon how equitably the foods are distributed. (Journal received 31 Jan. 1977)
Muscle mass declines with aging. Amino acids alone stimulate muscle protein synthesis in the elderly. However, mixed nutritional supplementation failed to improve muscle mass. We hypothesized that the failure of nutritional supplements is due to altered responsiveness of muscle protein anabolism to increased amino acid availability associated with endogenous hyperinsulinemia. We measured muscle protein synthesis and breakdown, and amino acid transport in healthy young (30 +/- 3 yr) and elderly (72 +/- 1 yr) volunteers in the basal postabsorptive state and during the administration of an amino acid-glucose mixture, using L-[ring-(2)H(5)]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Basal muscle amino acid turnover was similar in young and elderly subjects. The mixture increased phenylalanine leg delivery and transport into the muscle in both groups. Phenylalanine net balance increased in both groups (young, -27 +/- 8 to 64 +/- 17; elderly, -16 +/- 4 to 29 +/- 7 nmol/(min.100 mL); P: < 0.0001, basal vs. mixture), but the increase was significantly blunted in the elderly (P: = 0.030 vs. young). Muscle protein synthesis increased in the young, but remained unchanged in the elderly [young, 61 +/- 17 to 133 +/- 30 (P: = 0. 005); elderly, 62 +/- 9 to 70 +/- 14 nmol/(min.100 mL) (P: = NS)]. In both groups, protein breakdown decreased (P: = 0.012) and leg glucose uptake increased (P: = 0.0258) with the mixture. We conclude that the response of muscle protein anabolism to hyperaminoacidemia with endogenous hyperinsulinemia is impaired in healthy elderly due to the unresponsiveness of protein synthesis.
J Physiol 2001 August 15: 535(1): 301–11(1) Age-associated loss of skeletal muscle mass and strength can partly be counteracted by resistance training, causing a net synthesis of muscular proteins. Protein synthesis is influenced synergistically by post-exercise amino acid supplementation, but the importance of the timing of protein intake remains unresolved. (2) The study investigated the importance of immediate (P0) or delayed (P2) intake of an oral protein supplement upon muscle hypertrophy and strength over a period of resistance training in elderly males. (3) Thirteen men (age 74 ± 1 years; body mass index (BMI), 25 ± 1 kg m- 2 (means ± SEM)) completed a 12-week resistance training program (three times per week) receiving oral protein in liquid form (10 g protein, 7 g carbohydrate, 3 g fat) immediately after (P0) or 2 h after (P2) each training session. Muscle hypertrophy was evaluated by magnetic resonance imaging (MRI) and from muscle biopsies and muscle strength was determined using dynamic and isokinetic strength measurements. Body composition was determined from dual-energy X-ray absorptiometry (DEXA) and food records were obtained over 4 days. The plasma insulin response to protein supplementation was also determined. (4) In response to training, the cross-sectional area of m. quadriceps femoris (54.6 ± 0.5–58.3 ± 0.5 cm2) and mean fiber area (4047 ± 320–5019 ± 615 μ m2) increased in the P0 group, whereas no significant increase was observed in P2. For P0 both dynamic and isokinetic strength increased, by 46 and 15%, respectively (P P
Thesis (M.S.)--Boston University, 1995. Includes bibliographical references.
A diet supplying 0.5 or 1 g egg and milk protein/kg per day and adequate energy for maintenance of body weight was given to seven healthy men aged 18 to 21. After 2 weeks for adaptation to the diet they participated in 75 min of daily isometric exercises for 4 to 6 weeks. Two men on each protein intake continued to exercise for 4 to 5 additional weeks after undergoing changes in their daily protein intake from 0.5 to 1 g/kg or vice versa. A progressive decrease in total body potassium became significant by the fourth week of exercises in all men who began on the 0.5 g protein diet. Two men on that diet who remained as nonexercising controls lost no body K. These findings indicated that 0.5 g of egg and milk protein/kg per day was insufficient for men performing isometric exercises without prior training, whereas 1 g/kg per day appeared to be adequate. Two other nonexercising men on the 0.5 g diet who lost weight showed a marked negative nitrogen balance and loss of total body potassium which improved after their dietary energy intake increased. The changes in nitrogen balance and body weight observed in this investigation support the concept that protein requirements vary with energy intakes. Conversely, they suggest that energy requirements are influenced by the level of protein intake.
The quantitative effect on protein utilization of an isoenergetic exchange of dietary fat for carbohydrate was studied in 10 healthy young men. Milk protein (0.57 g/kg body weight per day, a safe level of protein intake as recommended by FAO/WHO) was given for two 21-day experimental periods with two ratios of carbohydrate to fat calories: diet A, a ratio supplying an equal proportion of energy from carbohydrate and from fat, generally representative of the usual Western diet, and diet B, a ratio supplying twice as much energy from carbohydrate as from fat, chosen in view of recommendations to reduce the amount of fat in the diet. Total calorie intake for each subject was constant over the two experimental periods. During each period, five subjects showed a consistent gain and five a loss of body weight. Urinary creatinine excretion was essentially unchanged. Nitrogen (N) balance and dietary protein utilization were significantly (P < 0.05) improved on diet B. The protein-sparing effect was greatest in those subjects who were on marginal energy and protein intakes and who were losing weight. The additional carbohydrate in diet B resulted in significant reductions in fasting serum urea N (P < 0.001), total urinary N (P < 0.01), and urinary urea N (P < 0.001); fasting plasma insulin values were unchanged. Whether or not the longer-term effects of the change in dietary carbohydrate:fat ratio on N metabolism are mediated solely by the action of insulin remains to be determined. Am. J. Clin. Nutr. 32: 22 17-2226, 1979.
Nine healthy subjects were studied under control conditions and following 5 mo of heavy resistance training and 5 wk of immobilization in elbow casts. Needle biopsies were taken from triceps brachii and analyzed for adenosine triphosphate (ATP), adenosine diphosphate (ADP), creatine (C), creatine phosphate (CP, and glycogen concentrations. Training resulted in an 11% increase in arm circumference and a 28% increase in maximal elbow extension strength. Immobilization resulted in decreases in arm circumference and elbow extension strength of 5% and 35%, respectively. Training also resulted in significant increases in resting concentrations of muscle creatine (by 39%), CP (by 22%), ATP (by 18%), and glycogen (by 66%). Conversely, immobilization significantly reduced CP concentration by 25% and glycogen concentration by 40%. It was concluded that heavy-resistance training results in increases in muscle energy reserves which may be reversed by a period of immobilization-induced disuse.
Protein requirement studies in man generally avoid deficient dietary energy intakes because they decrease the efficiency of nitrogen utilization, but the opposite effect of excess dietary energy is usually overlooked. Four young men were fed the 1973 FAO/WHO safe level of egg protein (0.57 g/kg) at several levels of dietary energy. The data indicate that a significant proportion of the population may require excess energy intakes to maintain nitrogen balance at this level of dietary protein. Variations in dietary energy ranging from submaintenance to 15 to 20% above estimated maintenance needs altered net egg protein utilization in three subjects by 2 to 4.5 units/kcal per kg body wt.
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.
This investigation examines the effect of progressive resistance weight training exercise on urinary 3-methylhistidine (3-MH) excretions in untrained subjects. For 19 consecutive days, 11 males were fed a weight maintenance, lactovegetarian diet which contained the Recommended Dietary Allowance (0.8g.kg-1.d-1) for protein. No exercise was performed for the first 7 d of the study. Subjects were strength tested on day 8 and performed upper and lower body weight training exercises from days 9-19. Complete, 24-h urine collections were obtained from each subject on a daily basis. Samples were assayed for creatinine and 3-MH. Stable baseline 3-MH values were present during the pre-exercise control period. Significant increases in 3-MH occurred by study day 11, which was the third day of weight training exercise. This was true regardless of whether the data were expressed by daily excretions (microM.d-1; P less than 0.01), per unit of body weight (microM.kg-1.d-1; P less than 0.005), or per unit of creatinine excretion (microM.g Creat-1.d-1; P less than 0.001). Since urinary 3-MH is an index of actin and myosin catabolism, these data support the hypothesis that the rate of skeletal muscle degradation is increased during strength building exercises.
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.
The micronutrient intake of a group of 76 body-builders was studied. Sixty-three per cent of the subjects supplemented their diets with vitamin and mineral pills. The highest pill consumption was 87 pills per day. Fifty-nine per cent of the subjects used high-protein powders. The benefits of these powders is open to question, since the diet already supplied a high 2.2 g protein per kilogram of body weight. Thirty-nine per cent of the subjects used vitamin/mineral pills as well as protein powders. Because of the use of dietary supplements, the food in the diet supplied only a small fraction of the total intake of most of the micronutrients. The food supplied adequate amounts of nutrients according to the US Recommended Dietary Allowances, and the use of dietary supplements can therefore not be justified.
Previous results of short-term diet studies of leucine kinetics have suggested that the currently accepted requirement value for the amino acid in adults is too low. In the present study the effects of a more prolonged diet period at low leucine intakes on leucine kinetics and nitrogen balance (NB) were explored in healthy young men. They (4 or 5 subjects per group) received an adequate leucine intake (80 mg/kg/d) for 1 or 2 weeks (Period 1) followed by either 7, 14 or 30 mg/kg/d for 3 weeks (Period 2) with a return to 80 mg/kg/d for 1 week (Period 3). Estimates of leucine fluxes (LF), oxidation (LO) and balance (LB) were based on a constant intravenous infusion of L-[1-13C]leucine, at end of Period 1, at 1 and 3 weeks of Period 2 and on days 1 and 3 of Period 3. At all three intakes LF and LO, during the fed state, fell between 1 and 3 weeks of Period 2. LB was negative at 1 week of Period 2 for all groups but had approached equilibrium by 3 weeks. N balance at 3 weeks was similar for all groups but during Period 3 was significantly higher (P less than 0.05) and markedly positive (+18 mgN/kg/d) for the 7 and 14 mg groups, compared with the 30 mg group (+4 mgN/kg/d), indicating that 'depletion' had occurred at the lower leucine intakes during Period 2. Our interpretation is that LB was approached by an adaptation in the 30 mg group whereas it was achieved in the 7 and 14 mg groups by an accommodation, associated with a reduced and low rate of leucine uptake into protein (LF minus LO). Thus, the leucine requirement was judged to be greater than 14 mg/kg/d, a level currently accepted as the upper range of the requirement for healthy adults. The significance of these findings for assessment of nutrient requirements is discussed, with emphasis on the limitation of NB measurements for evaluation of human amino acid requirements.
It is commonly believed by some athletes that strength building exercise "tears down" skeletal muscle tissue, thereby enhancing the dietary need for protein, but this has not been demonstrated. Ten college-age males served as subjects in a 15-d, controlled feeding study. The men were 23.1 +/- 2.2 yr old (mean +/- SD), 177 +/- 5 cm in height, and 71.7 +/- 9.1 kg in body weight (study days = 1 to 15). The lacto-ovo-vegetarian diet provided 0.9 g/kg protein and 15.1 +/- 0.4 MJ (3,604 +/- 104 kcal) . d-1 energy (study days = 6 to 15). On days 8 and 12, subjects participated in a standardized strength building, weight training exercise regimen. Post-exercise days 9 to 11 and 13 to 15 were designated for recovery. Daily (24-h) urine collections were analyzed for ammonia, creatinine, 3-methylhistidine, total nitrogen, and urea. There was no acute (24-h) effect of weight training exercise on any excretion levels. In particular, urinary 3-methylhistidine excretion data indicate that skeletal muscle protein catabolism was not changed by isolated bouts of weight training exercise.
We previously reported that 3-methylhistidine excretion was increased in human subjects after a strenuous bout of exercise. Because other investigators have not corroborated this finding, we undertook the present study to investigate the conditions that result in decreased and increased 3-methylhistidine excretion in human subjects after exercise. Four experiments were performed: a cross-sectional study comparing 3-methylhistidine excretion in endurance-trained subjects with untrained controls, a longitudinal study of 3-methylhistidine excretion by female basketball players before the start of the season and again during the competitive season, an experiment to determine changes in 3-methylhistidine excretion as a result of 2 h of exercise each day for 7 consecutive days, and a study to determine changes in 3-methylhistidine excretion during 4-h intervals after a strenuous exercise bout. The 3-methylhistidine-to-creatinine ratio was approximately 20% higher for trained than nontrained subjects. In three separate experiments a biphasic change of 3-methylhistidine excretion was observed in response to exercise with an immediate decrease in the 3-methylhistidine-to-creatinine ratio during exercise followed by a prolonged increase. The magnitudes of the negative and positive responses determine whether one observes an increase, no change, or a decrease in the total daily excretion of 3-methylhistidine.
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.
Protein utilization in young men under circumstances of one or two periods of work and both adequate and surfeit energy intake was determined by nitrogen balance; protein intake was constant at the FAO/WHO (1973) safe level (0.57 g/kg body-weight). Physical activity affected protein utilization negatively by increasing sweat and faecal N losses, and positively by supporting increased energy intake. Efficiency with which surfeit energy improved N utilization (mg N retained/added kJ) was greater under circumstances of increased activity. Changes in body composition as determined by total body potassium and hydrostatic weighing supported the N retention values.
The athletes in this study were eager for nutritional knowledge and advice and were motivated to change their eating habits because they believed that such a change would be to their advantage in competition.
“There is no area of nutrition where faddism, misconceptions and ignorance are more obvious than in athletics” (1). Often coaches, trainers, and even team physicians dispense misleading nutrition information. Professional
Studies of leg exchange and urine output of 3-methylhistidine provide the most unequivocal demonstrations to date of the discrepancy between urinary excretion and skeletal muscle protein degradation. We believe that such demonstrations, taken with the evidence previously presented above, leave little room for doubt that the use of 3-methylhistidine production in urine or of the urinary 3-methylhistidine/creatinine ratio as indices of skeletal muscle protein breakdown should be discontinuid. However, we believe that the measurement of arteriovenous differences of 3-methylhistidine across skeletal muscle can be used to provide useful information about the regulation of myofibrillar protein breakdown, and this method deserves wider use.
This study was undertaken to investigate whether an exercise bout increases muscle protein degradation and amino acid catabolism. The excretion of urea and N tau -methylhistidine before and after an exercise bout was determined for both rats and human subjects. The rats ran on a treadmill until they could no longer run. Two groups of human subjects completed strenuous exercise bouts: one group (runners) ran 10-12 miles while the other group (weight lifters) performed a standard power lift routine that lasted approximately 1 h. In rats, urea excretion was elevated for the first 12 h after the exercise bout whereas N tau -methylhistidine excretion was elevated for 48 h following exercise. The increased N tau -methylhistidine excretion after exercise supports previous reports of increased protein degradation in the perfused hindquarter and increased levels of essential amino acids in muscle, liver, and plasma of exercised rats. In human subjects, both running and weight lifting resulted in increased excretion of urea and N tau -methylhistidine. The results of the present study support the hypothesis that muscle protein breakdown and amino acid catabolism are increased by exercise.
Athletes have a keen interest in informed nutrition counsel. They recognize that food intakes are important determinants of energy availability and body fitness. For many sports, participation will prompt a general upgrading of dietary practices and nutrition-related well-being. Specific nutrition guidance can prevent abuses and can enhance the performance of the athlete and the team in many sports.
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.