Free amino acid pool and muscle protein balance after resistance exercise

Enzymatically modified isoquercitrin in soy protein temporarily enhanced the plasma amino-acid concentrations, antioxidant index, and plasma hormone levels: a randomized, double-blind cross-over trial

This study investigated the effects of a dietary protein supplement containing enzymatically modified isoquercitrin (EMIQ) on plasma amino-acid levels in healthy people. A randomized double-blind cross-over trial (UMIN000044791) was conducted with a sample of nine healthy individuals. These participants ingested soy protein with or without 42 mg EMIQ for 7 days after performing mild exercise. Plasma amino-acid levels were measured before ingestion and at 15, 30, 45, 60, 90, 120, 180, and 240 min after ingestion on the last day. The concentrations of total amino acids at 0 and 120 min and easily oxidized amino acids at 120 min were significantly higher in the plasma of individuals who consumed 42 mg EMIQ. Oxidative stress levels were lower and plasma testosterone levels were higher in participants who ingested soy protein with 42 mg EMIQ than in those who did not. These results suggest that daily ingestion of soy protein with 42 mg EMIQ can be useful for effective protein absorption.

Effect of Sucrose on Amino Acid Absorption of Whey: A Randomized Crossover Trial

Protein intake has been reported to secrete insulin and lower glucose levels, but the effect of carbohydrate and protein co-ingestion on amino acid absorption has not been well documented. A randomized, placebo-controlled, single-blinded, crossover trial was conducted to evaluate the effect of sucrose on blood amino acid levels. Eleven volunteers (both sexes aged 20–60 years with body mass index 21.4 ± 2.4 kg/m2) randomly received one of four test solutions: water (P-group), 10 g sucrose (S-group), 10 g whey protein (W-group), or 10 g whey protein + 10 g sucrose (W-S-group), and blood amino acid concentration, glucose levels, and insulin levels were monitored over 180 min. Following the wash-out period, randomized treatment and blood parameter monitoring were repeated. Consequently, amino acid concentration was significantly lower in the S-group than in the P-group, showing that single ingestion of sucrose decreased blood amino acid levels in a fasted state. However, there was no significant difference between blood amino acid levels of the W- and W-S-groups, suggesting that co-ingestion of sucrose does not affect blood amino acid concentration. Insulin levels were significantly higher in the W-S than in the S-group, and glucose levels were significantly lower in the W-S- than in the S-group, suggesting positive impact on glycotoxicity by reducing blood glucose levels. Therefore, whey protein co-ingestion with sucrose suppresses glucose levels and increases insulin levels as opposed to the sucrose ingestion, but does not affect amino acid absorption of whey protein, indicating that this co-ingestion may not be a problem for protein supplementation.

Should nutritional therapy be modified to account for mitochondrial dysfunction in critical illness?

Metabolic dysfunction, and its associated muscle atrophy, remains the most common complication of critical care. At the centre of this is mitochondrial dysfunction, secondary to hypoxia and systemic inflammation. This leads to a bioenergetic crisis, with decreased intramuscular adenosine tri-phosphate content and a reduction in the highly energy dependent process of protein synthesis. Numerous methods have been studied to try and reduce these effects, with only limited success. Trials investigating the use of increased calorie and protein administration have instead found a decrease in relative lean body mass, and a potential increase in morbidity and mortality. Ketone bodies have been proposed as alternative substrates for metabolism in critical illness, with promising results seen in animal models. They are currently being investigated in critical care patients in the Alternative Substrates in the Critically Ill Subjects trial. The evidence to date suggests that individualised feeding regimens may be key in the nutritional approach to critical illness. Consideration of individual patient factors will need to be combined with personalised protein content, total energy load received, and the timings of such feeds. This review covers mitochondrial dysfunction in critical illness, and how it contributes to muscle wasting and the resultant morbidity and mortality and the scientific basis of why current nutritional approaches to date have not been successful in negating this effect. These two factors underpin the need for consideration of alternative nutritional strategies in the critically ill patient. This article is protected by copyright. All rights reserved.

Prognostic value of leucine/phenylalanine ratio as an amino acid profile of heart failure

Heart failure (HF) causes a hypercatabolic state that enhances the catabolic activity of branched-chain amino acids (BCAA; leucine, isoleucine, and valine) in the heart and skeletal muscles and reduces protein synthesis in the liver. Consequently, free plasma aromatic amino acids (AAA, tyrosine and phenylalanine) are increased. To date, we have reported the prognostic value of the BCAA/AAA ratio (Fischer's ratio) in patients with HF. However, the leucine/phenylalanine ratio, which is a simpler index than the Fischer's ratio, has not been examined. Therefore, the prognostic value of the leucine/phenylalanine ratio in patients with HF was investigated. Overall 157 consecutive patients hospitalized for worsening HF (81 men, median age 78 years) were enrolled in the study. Plasma amino acid levels were measured when the patients were stabilized at discharge. Cardiac events were defined as a composite of cardiac death and hospitalization for worsening HF. A total of 46 cardiac events occurred during the median follow-up period of 238 (interquartile range 93-365) days. The median leucine/phenylalanine ratio was significantly lower in patients with cardiac events than in those without cardiac events (1.4 vs. 1.8, P < 0.001). The best cutoff value of the leucine/phenylalanine ratio was determined as 1.7 in the receiver operating characteristic (ROC) curve for cardiac events. Following a Kaplan-Meier survival analysis, the low group (leucine/phenylalanine ratio < 1.7, n = 72) had more cardiac events than the high group (leucine/phenylalanine ratio ≥ 1.7, n = 85) (log-rank, P < 0.001). Multivariate Cox proportional hazards regression analysis showed that the leucine/phenylalanine ratio was an independent predictor of cardiac events. Furthermore, on comparing the prognostic values for cardiac events based on ROC curves of leucine levels, BCAA levels, Fischer's ratio, and leucine/phenylalanine ratio, the leucine/phenylalanine ratio was the most accurate in predicting future cardiac events (area under the curve 0.763,; sensitivity 0.783,; specificity 0.676,; P < 0.001). The leucine/phenylalanine ratio could be a useful predictor of future cardiac events in patients with HF, reflecting an imbalance in amino acid metabolism.

Whey protein supplementation and its potentially adverse effects on health: a systematic review

Whey protein comprises soluble whey proteins and its benefits are well described in the literature. However, there are not many studies investigating the potential adverse effect of a diet with indiscriminate use of this supplement. The aim of this study was to perform a systematic review of papers that addressed this theme. A search was conducted in Medline, LILACS, TOXNET, Web of science, and Scopus electronic databases. In the end, 11 documents comprised this review. The majority of the papers associated the damaging effect with the chronic and abusive use of whey protein, with the kidneys and liver being the main organs affected. The other studies related whey protein to aggravation of aggression, presence of acne, and modification of the microbiota. Therefore, excessive consumption over a long period of protein supplementation may have some adverse effects on the body, which is aggravated when associated with sedentary lifestyle. PROSPERO registration no.: CRD42020140466. Novelty: A systematic review of experimental and randomized studies about the use of whey proteins supplements and its impact on physical health. Analysis revealed that chronic and without professional guidance use of whey protein supplementation may cause some adverse effects specially on kidney and liver function. Presented data support a need for future studies co-relating the use of different types of whey protein with and without exercise to better see the impact on human physical health.

[Ornitine-dependent mechanisms of muscle fatigue correction and recovery from physical activity]

The article analyzes the literature data characterizing modern concepts of the mechanisms of muscle fatigue and metabolic features of recovery processes after exhausting loads. The significance of transient hyperammonium in the formation of the developed complex of fatigue manifestations in the central and peripheral links of motor units, its pathogenetic links with oxygen debt, lactacidosis, violation of ATP resynthesis, deficiency of energy-supplying substrates in working skeletal muscles, damage to muscle fibre structures, and dysfunction of various parts of the CNS is shown. The necessity of correction of hyperammoniemia associated with physical activity has been confirmed to reduce the speed of formation and expression of fatigue feeling, to reduce the risks of development of fatigue and overtraining states in sportsmen and to ensure effective course of recovery processes after exhausting physical activity. It was revealed that ornithine-containing preparations can be used for correction of post-load hyperammonium and acceleration of recovery processes. The data characterizing the high efficiency of L-ornitine-L-aspartate in sports medicine practice are presented.

Effects of whey protein supplementation prior to, and following, resistance exercise on body composition and training responses: A randomized double-blind placebo-controlled study

PURPOSE

The composition of protein supplements, the consumption timing immedi¬ately before and after resistance exercise training (RET), and the quantity of protein supplementation may be important factors for the im-provement of muscle mass and function. Although these factors should be considered comprehensively for effective improvement of muscular function in protein supplementation, relatively few studies have focused on this area. Therefore, this study was designed to investigate whether a protein blend supplement before and after resistance exercise for 12 weeks would be effective in increasing muscular function.

METHODS

In total, 18 participants were randomly assigned to a placebo (PLA) or protein blend supplement (PRO) group. All subjects followed the same training routine 3 times per week for 12 weeks, taking placebo or protein supplements immediately before and after each exercise session. The protein supplement consisted of 40 g of blend protein, including hydrolyzed whey protein. The RET consisted of lower body (barbell squat, dead lift, seated leg extension, and lying leg curl) and upper body (bench press, barbell rowing, preacher bench biceps curl, and dumbbell shoulder press) exercises. A repetition was defined as three sets of 10-12 times with 80% of one repetition maximum (1RM).

RESULTS

Although the PRO group had a lower protein intake in terms of total food intake than the PLA group, the mean changes in muscle circumference, strength, and exercise volume increased, especially at week 12, compared to the PLA group.

CONCLUSION

These results suggest that the composition and timing of protein intake are more important than the total amount.

Impact of cow's milk intake on exercise performance and recovery of muscle function: a systematic review

Dairy products are thought to improve recovery after both resistance and endurance exercises due to their nutritional proprieties. We systematically reviewed the effects of dairy product intake on exercise performance and recovery of muscle function in humans. A literature search was conducted in the MEDLINE (via PubMed) and Web of Science databases from their inception to 15th April 2018. The initial search retrieved 7708 articles, and a total of 11 studies were finally included after applying inclusion and exclusion criteria. All the selected studies were conducted with cow's milk. Whereas some studies found significant positive effect of cow's milk on exercise performance and recovery of muscle function, others did not find any effect. These controversies could be due to the heterogeneity of cow's milk ingestion (e.g., amount of cow's milk, timing of consuming the cow's milk), to the type of intervention, and to the large heterogeneity of outcomes measured. Limited studies exist examining the effects of cow's milk consumption and its influence on exercise performance and recovery of muscle function, therefore further studies are needed to draw more definitive conclusions.

Whey protein hydrolysate supplementation accelerates recovery from exercise-induced muscle damage in females

A number of different forms of protein and their analogues have been investigated for their efficacy in ameliorating exercise-induced muscle damage (EIMD) and recovery. Preliminary data regarding whey protein hydrolysate (WPH) supplementation are promising. However, its efficacy beyond acute eccentric/resistance exercise bouts or longer term training programmes are limited and all investigations have been conducted in male or mixed-sex groups. This study sought to elucidate whether the benefits of WPH previously reported can be demonstrated in females following repeated-sprint exercise. Twenty physically active females were assigned to consume 2 doses of 70 mL WPH or isoenergetic carbohydrate (CHO) for 4 days post-EIMD. Measures of muscle soreness, limb girth, flexibility, muscle function, and creatine kinase were collected before, immediately after, and 24, 48, and 72 h postexercise. Time effects were observed for all variables (p < 0.05) except limb girth, which is indicative of EIMD. Flexibility improved beyond baseline measures following WPH by 72 h, but had failed to recover in the CHO group (p = 0.011). Reactive strength index was higher throughout recovery in the WPH group compared with CHO (p = 0.016). Reductions in creatine kinase were greater following WPH compared with CHO at 48 h post-EIMD (p = 0.031). The findings suggest that 4-day supplementation of WPH is beneficial for reducing symptoms of EIMD and improving recovery of muscle function in physically active females.

Role of Ingested Amino Acids and Protein in the Promotion of Resistance Exercise-Induced Muscle Protein Anabolism

The goal of this critical review is to comprehensively assess the evidence for the molecular, physiologic, and phenotypic skeletal muscle responses to resistance exercise (RE) combined with the nutritional intervention of protein and/or amino acid (AA) ingestion in young adults. We gathered the literature regarding the translational response in human skeletal muscle to acute exposure to RE and protein/AA supplements and the literature describing the phenotypic skeletal muscle adaptation to RE and nutritional interventions. Supplementation of protein/AAs with RE exhibited clear protein dose-dependent effects on translational regulation (protein synthesis) through mammalian target of rapamycin complex 1 (mTORC1) signaling, which was most apparent through increases in p70 ribosomal protein S6 kinase 1 (S6K1) phosphorylation, compared with postexercise recovery in the fasted or carbohydrate-fed state. These acute findings were critically tested via long-term exposure to RE training (RET) and protein/AA supplementation, and it was determined that a diminishing protein/AA supplement effect occurs over a prolonged exposure stimulus after exercise training. Furthermore, we found that protein/AA supplements, combined with RET, produced a positive, albeit minor, effect on the promotion of lean mass growth (when assessed in >20 participants/treatment); a negligible effect on muscle mass; and a negligible to no additional effect on strength. A potential concern we discovered was that the majority of the exercise training studies were underpowered in their ability to discern effects of protein/AA supplementation. Regardless, even when using optimal methodology and large sample sizes, it is clear that the effect size for protein/AA supplementation is low and likely limited to a subset of individuals because the individual variability is high. With regard to nutritional intakes, total protein intake per day, rather than protein timing or quality, appears to be more of a factor on this effect during long-term exercise interventions. There were no differences in strength or mass/muscle mass on RET outcomes between protein types when a leucine threshold (>2 g/dose) was reached. Future research with larger sample sizes and more homogeneity in design is necessary to understand the underlying adaptations and to better evaluate the individual variability in the muscle-adaptive response to protein/AA supplementation during RET.

Plasma amino acid profiling identifies specific amino acid associations with cardiovascular function in patients with systolic heart failure

BACKGROUND

The heart has close interactions with other organs' functions and concomitant systemic factors such as oxidative stress, nitric oxide (NO), inflammation, and nutrition in systolic heart failure (HF). Recently, plasma amino acid (AA) profiling as a systemic metabolic indicator has attracted considerable attention in predicting the future risk of human cardiometabolic diseases, but it has been scarcely studied in HF.

METHODS

Thirty-eight stable but greater than New York Heart Association class II symptomatic patients with left ventricular (LV) ejection fraction <45% and 33 asymptomatic individuals with normal B-type natriuretic peptide (BNP) value were registered as the HF and control groups, respectively. We analyzed fasting plasma concentrations of 41 AAs using high-performance liquid chromatography, serum NO metabolite concentration, hydroperoxide and high-sensitivity C-reactive protein measurements, echocardiography, and flow-mediated dilatation.

RESULTS

We found that 17 AAs and two ratios significantly changed in the HF group compared with those in the control group (p < 0.05). In the HF group, subsequent univariate and stepwise multivariate analyses with clinical variables revealed that Fischer ratio and five specific AAs, ie, monoethanolamine, methionine, tyrosine, 1-methylhistidine, and histidine have significant correlation with BNP, LV ejection fraction, LV end-diastolic volume index, inferior vena cava diameter, the ratio of early diastolic velocity of the mitral inflow to mitral annulus, and BNP, respectively (p < 0.05). Interestingly, further exploratory factor analysis categorized these AAs into hepatic-related (monoethanolamine, tyrosine, and Fischer ratio) and skeletal muscle-related (histidine, methionine, and 1-methylhistidine) components. Some categorized AAs showed unique correlations with concomitant factors: monoethanolamine, tyrosine, and Fischer ratio with serum NO concentration; histidine with serum albumin; and 1-methylhistidine with flow-mediated dilatation (p < 0.05).

CONCLUSIONS

Plasma AA profiling identified correlations of specific AAs with cardiac function and concomitant factors, highlighting the cardio-hepatic-skeletal muscle axis in patients with systolic HF.

Effects of protein supplements on muscle damage, soreness and recovery of muscle function and physical performance: a systematic review

BACKGROUND

Protein supplements are frequently consumed by athletes and recreationally-active individuals, although the decision to purchase and consume protein supplements is often based on marketing claims rather than evidence-based research.

OBJECTIVE

To provide a systematic and comprehensive analysis of literature examining the hypothesis that protein supplements enhance recovery of muscle function and physical performance by attenuating muscle damage and soreness following a previous bout of exercise.

DATA SOURCES

English language articles were searched with PubMed and Google Scholar using protein and supplements together with performance, exercise, competition and muscle, alone or in combination as keywords.

STUDY SELECTION

Inclusion criteria required studies to recruit healthy adults less than 50 years of age and to evaluate the effects of protein supplements alone or in combination with carbohydrate on performance metrics including time-to-exhaustion, time-trial or isometric or isokinetic muscle strength and markers of muscle damage and soreness. Twenty-seven articles were identified of which 18 dealt exclusively with ingestion of protein supplements to reduce muscle damage and soreness and improve recovery of muscle function following exercise, whereas the remaining 9 articles assessed muscle damage as well as performance metrics during single or repeat bouts of exercise.

STUDY APPRAISAL AND SYNTHESIS METHODS

Papers were evaluated based on experimental design and examined for confounders that explain discrepancies between studies such as dietary control, training state of participants, sample size, direct or surrogate measures of muscle damage, and sensitivity of the performance metric.

RESULTS

High quality and consistent data demonstrated there is no apparent relationship between recovery of muscle function and ratings of muscle soreness and surrogate markers of muscle damage when protein supplements are consumed prior to, during or after a bout of endurance or resistance exercise. There also appears to be insufficient experimental data demonstrating ingestion of a protein supplement following a bout of exercise attenuates muscle soreness and/or lowers markers of muscle damage. However, beneficial effects such as reduced muscle soreness and markers of muscle damage become more evident when supplemental protein is consumed after daily training sessions. Furthermore, the data suggest potential ergogenic effects associated with protein supplementation are greatest if participants are in negative nitrogen and/or energy balance.

LIMITATIONS

Small sample numbers and lack of dietary control limited the effectiveness of several investigations. In addition, studies did not measure the effects of protein supplementation on direct indices of muscle damage such as myofibrillar disruption and various measures of protein signaling indicative of a change in rates of protein synthesis and degradation. As a result, the interpretation of the data was often limited.

CONCLUSIONS

Overwhelmingly, studies have consistently demonstrated the acute benefits of protein supplementation on post-exercise muscle anabolism, which, in theory, may facilitate the recovery of muscle function and performance. However, to date, when protein supplements are provided, acute changes in post-exercise protein synthesis and anabolic intracellular signaling have not resulted in measureable reductions in muscle damage and enhanced recovery of muscle function. Limitations in study designs together with the large variability in surrogate markers of muscle damage reduced the strength of the evidence-base.

Nutrient timing revisited: is there a post-exercise anabolic window?

Nutrient timing is a popular nutritional strategy that involves the consumption of combinations of nutrients--primarily protein and carbohydrate--in and around an exercise session. Some have claimed that this approach can produce dramatic improvements in body composition. It has even been postulated that the timing of nutritional consumption may be more important than the absolute daily intake of nutrients. The post-exercise period is widely considered the most critical part of nutrient timing. Theoretically, consuming the proper ratio of nutrients during this time not only initiates the rebuilding of damaged muscle tissue and restoration of energy reserves, but it does so in a supercompensated fashion that enhances both body composition and exercise performance. Several researchers have made reference to an anabolic “window of opportunity” whereby a limited time exists after training to optimize training-related muscular adaptations. However, the importance - and even the existence - of a post-exercise ‘window’ can vary according to a number of factors. Not only is nutrient timing research open to question in terms of applicability, but recent evidence has directly challenged the classical view of the relevance of post-exercise nutritional intake with respect to anabolism. Therefore, the purpose of this paper will be twofold: 1) to review the existing literature on the effects of nutrient timing with respect to post-exercise muscular adaptations, and; 2) to draw relevant conclusions that allow practical, evidence-based nutritional recommendations to be made for maximizing the anabolic response to exercise.

Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein

Regardless of age or gender, resistance training or provision of adequate amounts of dietary protein (PRO) or essential amino acids (EAA) can increase muscle protein synthesis (MPS) in healthy adults. Combined PRO or EAA ingestion proximal to resistance training, however, can augment the post-exercise MPS response and has been shown to elicit a greater anabolic effect than exercise plus carbohydrate. Unfortunately, chronic/adaptive response data comparing the effects of different protein sources is limited. A growing body of evidence does, however, suggest that dairy PRO, and whey in particular may: 1) stimulate the greatest rise in MPS, 2) result in greater muscle cross-sectional area when combined with chronic resistance training, and 3) at least in younger individuals, enhance exercise recovery. Therefore, this review will focus on whey protein supplementation and its effects on skeletal muscle mass when combined with heavy resistance training.

Additive effect of diets and training on total insulin-like growth factor-1 (IGF-1) in rats

OBJECTIVES

Although it is known that circulating levels of insulin-like growth factor-1 (IGF-1) are influenced by both physical exercise and dietary intake separately, there is little information regarding the additive effect of diets and training on IGF-1 regulation. To test this, we examined the combined effect of 30 days of two different diets (high-protein and high-carbohydrate) and exercise training on total IGF-1.

MATERIALS AND METHODS

The study was carried out with four groups of rats; the sedentary group with standard diet (SS) (control group), standard diet with exercise (SE), high-protein diet with exercise (PE) and high-carbohydrate diet with exercise (CE). Serum IGF-1, insulin, corticosterone were analyzed.

RESULTS

IGF-1 concentrations were decreased by exercise training (p<0.001) and only with protein diet (p<0.05). Physical training, with and without diet, decreased body weight and food intake (p<0.01) and increased corticosterone levels (p<0.05). Carbohydrate diet did not cause major hormonal and metabolic alterations.

CONCLUSION

The main result of this study was the decreased levels of IGF-1 in spite of high-protein diet, which is known to enhance IGF-1 secretion, and the little changes with carbohydrate diet. This may be related to the negative energy balance as a result of the catabolic state induced by exercise training and decreased calorie intake in protein diet. Thus, it can be concluded that the caloric restriction, regardless of dietary composition, decreased IGF-1 secretion.

Effect of strength training session on plasma amino acid concentration following oral ingestion of leucine, BCAAs or glutamine in men

We examined the acute effects of a 1-h strength training session (STS) on plasma amino acid concentration following orally ingestion of leucine, branched-chain amino acids (BCAAs) or glutamine in nine physically active men who participated in double-blinded and randomised experiments. The subjects took placebo, leucine, BCAAs, or glutamine capsules (50 mg/kg) in either rest (REST) or STS condition. Blood samples were taken before and at 30, 60, 90, and 120 min after the beginning of the treatment and they were assayed for plasma amino acids with HPLC. Following both leucine and BCAA ingestion the peak concentration of leucine was similar at rest (524 +/- 46 and 530 +/- 29 nmol/ml, respectively) and similar after STS (398 +/- 43 and 387 +/- 46 nmol/ml, respectively) but the rest and STS concentrations differed from each other (P < 0.01-0.001). The modelled polynomial data for the leucine treatment showed that the peak concentration of leucine occurred at 67 min at rest and at 90 min in STS (difference between REST and STS: P = 0.012). For the BCAA treatment the polynomial data showed that the peak concentration of leucine occurred at 72 min at rest and at 78 min in STS (P = 0.067). The peak concentration of glutamine was similar in both rest and STS condition and occurred at 60 min at rest and at 57 min in STS. In conclusion, 1-h of STS slows the increase in the peak concentration of plasma leucine similarly after oral ingestion of leucine or BCAAs but after oral ingestion of glutamine it has no slowing effect on glutamine concentration.

International Society of Sports Nutrition position stand: nutrient timing

Position Statement: The position of the Society regarding nutrient timing and the intake of carbohydrates, proteins, and fats in reference to healthy, exercising individuals is summarized by the following eight points: 1.) Maximal endogenous glycogen stores are best promoted by following a high-glycemic, high-carbohydrate (CHO) diet (600 – 1000 grams CHO or ~8 – 10 g CHO/kg/d), and ingestion of free amino acids and protein (PRO) alone or in combination with CHO before resistance exercise can maximally stimulate protein synthesis. 2.) During exercise, CHO should be consumed at a rate of 30 – 60 grams of CHO/hour in a 6 – 8% CHO solution (8 – 16 fluid ounces) every 10 – 15 minutes. Adding PRO to create a CHO:PRO ratio of 3 – 4:1 may increase endurance performance and maximally promotes glycogen re-synthesis during acute and subsequent bouts of endurance exercise. 3.) Ingesting CHO alone or in combination with PRO during resistance exercise increases muscle glycogen, offsets muscle damage, and facilitates greater training adaptations after either acute or prolonged periods of supplementation with resistance training. 4.) Post-exercise (within 30 minutes) consumption of CHO at high dosages (8 – 10 g CHO/kg/day) have been shown to stimulate muscle glycogen re-synthesis, while adding PRO (0.2 g – 0.5 g PRO/kg/day) to CHO at a ratio of 3 – 4:1 (CHO: PRO) may further enhance glycogen re-synthesis. 5.) Post-exercise ingestion (immediately to 3 h post) of amino acids, primarily essential amino acids, has been shown to stimulate robust increases in muscle protein synthesis, while the addition of CHO may stimulate even greater levels of protein synthesis. Additionally, pre-exercise consumption of a CHO + PRO supplement may result in peak levels of protein synthesis. 6.) During consistent, prolonged resistance training, post-exercise consumption of varying doses of CHO + PRO supplements in varying dosages have been shown to stimulate improvements in strength and body composition when compared to control or placebo conditions. 7.) The addition of creatine (Cr) (0.1 g Cr/kg/day) to a CHO + PRO supplement may facilitate even greater adaptations to resistance training. 8.) Nutrient timing incorporates the use of methodical planning and eating of whole foods, nutrients extracted from food, and other sources. The timing of the energy intake and the ratio of certain ingested macronutrients are likely the attributes which allow for enhanced recovery and tissue repair following high-volume exercise, augmented muscle protein synthesis, and improved mood states when compared with unplanned or traditional strategies of nutrient intake.

Efeito da oferta dietética de proteína sobre o ganho muscular, balanço nitrogenado e cinética da 15N-glicina de atletas em treinamento de musculação

O efeito da oferta crescente de proteína sobre o ganho muscular, balanço nitrogenado e cinética da 15N-glicina de atletas de musculação foi estudado em seis jovens saudáveis, praticantes de treinamento com pesos (> 2 anos), sem uso de anabolizantes e concordes com os princípios éticos da pesquisa. Todos receberam adequações dietéticas (0,88g de proteína/kg/dia) pré-experimento de 2 semanas (D1) após o que se ofereceu, por idêntico período, dieta contendo 1,5g de proteína/kg de peso corporal/dia com 30kcal/g de proteína (dieta D2). A seguir receberam, nas próximas 2 semanas, a dieta D3, contendo 2,5g de proteína/kg de peso corporal/dia e 30 kcal/g proteína. As avaliações antropométricas, alimentares, biquímicas, balanço nitrogenado (BN) e cinética com 15N-glicina foram realizadas no início do estudo, pós D1 (M0) e no último dia das dietas D2 (M1) e D3 (M2). Ao final do estudo (4 semanas) houve aumento significativo na massa muscular (1,63±0,9kg), sem diferença entre D2 e D3. O BN acompanhou o consumo protéico/energético (M0 = -7,8g/dia; M1 = 5,6g/dia e M2 = 16,6g/dia) e a síntese protéica acompanhou o BN, com significância estatística (p<0,05) em relação ao basal (M0) mas semelhante entre D2 e D3 (M1 = 49,8±12,2g N/dia e M2 = 52,5±14,0g N/dia) e sem alteração significativa do catabolismo. Assim, os dados de BN e cinética da 15N-glicina indicam que a ingestão protéica recomendável para esses atletas é superior ao preconizado para sedentários (0,88g/kg) e inferior a 2,5g/kg de peso, sendo no caso, 1,5g de proteína/kg de peso/dia com ajuste do consumo energético para 30 kcal/g de proteína.

Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis

The present study was designed to assess the impact of coingestion of various amounts of carbohydrate combined with an ample amount of protein intake on postexercise muscle protein synthesis rates. Ten healthy, fit men (20 +/- 0.3 yr) were randomly assigned to three crossover experiments. After 60 min of resistance exercise, subjects consumed 0.3 g x kg(-1) x h(-1) protein hydrolysate with 0, 0.15, or 0.6 g x kg(-1) x h(-1) carbohydrate during a 6-h recovery period (PRO, PRO + LCHO, and PRO + HCHO, respectively). Primed, continuous infusions with L-[ring-(13)C(6)]phenylalanine, L-[ring-(2)H(2)]tyrosine, and [6,6-(2)H(2)]glucose were applied, and blood and muscle samples were collected to assess whole body protein turnover and glucose kinetics as well as protein fractional synthesis rate (FSR) in the vastus lateralis muscle over 6 h of postexercise recovery. Plasma insulin responses were significantly greater in PRO + HCHO compared with PRO + LCHO and PRO (18.4 +/- 2.9 vs. 3.7 +/- 0.5 and 1.5 +/- 0.2 U.6 h(-1) x l(-1), respectively, P < 0.001). Plasma glucose rate of appearance (R(a)) and disappearance (R(d)) increased over time in PRO + HCHO and PRO + LCHO, but not in PRO. Plasma glucose R(a) and R(d) were substantially greater in PRO + HCHO vs. both PRO and PRO + LCHO (P < 0.01). Whole body protein breakdown, synthesis, and oxidation rates, as well as whole body protein balance, did not differ between experiments. Mixed muscle protein FSR did not differ between treatments and averaged 0.10 +/- 0.01, 0.10 +/- 0.01, and 0.11 +/- 0.01%/h in the PRO, PRO + LCHO, and PRO + HCHO experiments, respectively. In conclusion, coingestion of carbohydrate during recovery does not further stimulate postexercise muscle protein synthesis when ample protein is ingested.

Nutrient administration and resistance training

Skeletal muscle tissue is tightly regulated throughout our bodies by balancing its synthesis and breakdown. Many factors are known to exist that cause profound changes on the overall status of skeletal muscle, some of which include exercise, nutrition, hormonal influences and disease. Muscle hypertrophy results when protein synthesis is greater than protein breakdown. Resistance training is a popular form of exercise that has been shown to increase muscular strength and muscular hypertrophy. In general, resistance training causes a stimulation of protein synthesis as well as an increase in protein breakdown, resulting in a negative balance of protein. Providing nutrients, specifically amino acids, helps to stimulate protein synthesis and improve the overall net balance of protein. Strategies to increase the concentration and availability of amino acids after resistance exercise are of great interest and have been shown to effectively increase overall protein synthesis. 123 After exercise, providing carbohydrate has been shown to mildly stimulate protein synthesis while addition of free amino acids prior to and after exercise, specifically essential amino acids, causes a rapid pronounced increase in protein synthesis as well as protein balance.13 Evidence exists for a dose-response relationship of infused amino acids while no specific regimen exists for optimal dosing upon ingestion. Ingestion of whole or intact protein sources (e.g., protein powders, meal-replacements) has been shown to cause similar improvements in protein balance after resistance exercise when compared to free amino acid supplements. Future research should seek to determine optimal dosing of ingested intact amino acids in addition to identifying the cellular mechanistic machinery (e.g. transcriptional and translational mechanisms) for causing the increase in protein synthesis.

Mixed muscle and hepatic derived plasma protein metabolism is differentially regulated in older and younger men following resistance exercise

We sought to determine whether exercise-induced muscle protein turnover alters the subsequent production of hepatically derived acute-phase plasma proteins, and whether age affects how these proteins are regulated. We measured arteriovenous (a-v) balance and the synthesis of mixed muscle protein, albumin (A) and fibrinogen (F) before exercise (REST) and from the beginning of exercise to 10, 60, and 180 min following a single bout of moderate-intensity leg extension exercise (POST-EX) in postabsorptive untrained older (n = 6) and younger (n = 6) men using L-[ring-2H5]phenylalanine (Phe). Subjects performed 6 sets of 8 repetitions of leg extension at 80% of their 1-RM (one-repetition maximum). All data are presented as the difference from REST (Delta from REST at 10, 60, and 180 min POST-EX). Mixed muscle fractional synthesis rate (FSR-M) increased significantly from the beginning of exercise until 10 min POST-EX in the older men (DeltaFSR-M: 0.044%/h), whereas FSR-M in the younger men was not elevated until 180 min POST-EX (DeltaFSR-M: 0.030%/h). FSR-A and FSR-F increased at all POST-EX periods in the older men (DeltaFSR-A = 10 min: 1.90%/day; 60 min: 2.72%/day; 180 min: 2.78%/day; DeltaFSR-F = 10 min: 1.00%/day; 60 min: 3.01%/day; 180 min: 3.73%/day). No change occurred in FSR-A in the younger men, but FSR-F was elevated from the beginning of exercise until 10 and 180 min POST-EX (10 min: 3.07%/day and 180 min: 3.96%/day). Net balance of Phe was positive in the older men in the immediate POST-EX period. Our data indicate that mixed muscle and hepatic derived protein synthesis is differentially regulated in younger and older men in response to a single bout of moderate-intensity leg extension exercise. Moreover, our data suggest that with age may come a greater need to salvage or make available amino acids from exercise-induced muscle protein breakdown to mount an acute-phase response.

Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects

The present study was designed to determine postexercise muscle protein synthesis and whole body protein balance following the combined ingestion of carbohydrate with or without protein and/or free leucine. Eight male subjects were randomly assigned to three trials in which they consumed drinks containing either carbohydrate (CHO), carbohydrate and protein (CHO+PRO), or carbohydrate, protein, and free leucine (CHO+PRO+Leu) following 45 min of resistance exercise. A primed, continuous infusion of L-[ring-13C6]phenylalanine was applied, with blood samples and muscle biopsies collected to assess fractional synthetic rate (FSR) in the vastus lateralis muscle as well as whole body protein turnover during 6 h of postexercise recovery. Plasma insulin response was higher in the CHO+PRO+Leu compared with the CHO and CHO+PRO trials (+240 +/- 19% and +77 +/- 11%, respectively, P < 0.05). Whole body protein breakdown rates were lower, and whole body protein synthesis rates were higher, in the CHO+PRO and CHO+PRO+Leu trials compared with the CHO trial (P < 0.05). Addition of leucine in the CHO+PRO+Leu trial resulted in a lower protein oxidation rate compared with the CHO+PRO trial. Protein balance was negative during recovery in the CHO trial but positive in the CHO+PRO and CHO+PRO+Leu trials. In the CHO+PRO+Leu trial, whole body net protein balance was significantly greater compared with values observed in the CHO+PRO and CHO trials (P < 0.05). Mixed muscle FSR, measured over a 6-h period of postexercise recovery, was significantly greater in the CHO+PRO+Leu trial compared with the CHO trial (0.095 +/- 0.006 vs. 0.061 +/- 0.008%/h, respectively, P < 0.05), with intermediate values observed in the CHO+PRO trial (0.0820 +/- 0.0104%/h). We conclude that coingestion of protein and leucine stimulates muscle protein synthesis and optimizes whole body protein balance compared with the intake of carbohydrate only.

The effect of resistance training combined with timed ingestion of protein on muscle fiber size and muscle strength

Acute muscle protein metabolism is modulated not only by resistance exercise but also by amino acids. However, less is known about the long-term hypertrophic effect of protein supplementation in combination with resistance training. The present study was designed to compare the effect of 14 weeks of resistance training combined with timed ingestion of isoenergetic protein vs carbohydrate supplementation on muscle fiber hypertrophy and mechanical muscle performance. Supplementation was administered before and immediately after each training bout and, in addition, in the morning on nontraining days. Muscle biopsy specimens were obtained from the vastus lateralis muscle and analyzed for muscle fiber cross-sectional area. Squat jump and countermovement jump were performed on a force platform to determine vertical jump height. Peak torque during slow (30 degrees s-1) and fast (240 degrees s-1) concentric and eccentric contractions of the knee extensor muscle was measured in an isokinetic dynamometer. After 14 weeks of resistance training, the protein group showed hypertrophy of type I (18% +/- 5%; P < .01) and type II (26% +/- 5%; P < .01) muscle fibers, whereas no change above baseline occurred in the carbohydrate group. Squat jump height increased only in the protein group, whereas countermovement jump height and peak torque during slow isokinetic muscle contraction increased similarly in both groups. In conclusion, a minor advantage of protein supplementation over carbohydrate supplementation during resistance training on mechanical muscle function was found. However, the present results may have relevance for individuals who are particularly interested in gaining muscle size.

Effect of carbohydrate intake on net muscle protein synthesis during recovery from resistance exercise

The purpose of this study was to determine the effect of ingestion of 100 g of carbohydrates on net muscle protein balance (protein synthesis minus protein breakdown) after resistance exercise. Two groups of eight subjects performed a resistance exercise bout (10 sets of 8 repetitions of leg presses at 80% of 1-repetition maximum) before they rested in bed for 4 h. One group (CHO) received a drink consisting of 100 g of carbohydrates 1 h postexercise. The other group (Pla) received a noncaloric placebo drink. Leg amino acid metabolism was determined by infusion of2H5- or13C6-labeled phenylalanine, sampling from femoral artery and vein, and muscle biopsies from vastus lateralis. Drink intake did not affect arterial insulin concentration in Pla, whereas insulin increased several times after the drink in CHO ( P < 0.05 vs. Pla). Arterial phenylalanine concentration fell slightly after the drink in CHO. Net muscle protein balance between synthesis and breakdown did not change in Pla, whereas it improved in CHO from -17 ± 3 nmol·ml-1·100 ml leg-1before drink to an average of -4 ± 4 and 0 ± 3 nmol·ml-1·100 ml leg-1during the second and third hour after the drink, respectively ( P < 0.05 vs. Pla during last hour). The improved net balance in CHO was due primarily to a progressive decrease in muscle protein breakdown. We conclude that ingestion of carbohydrates improved net leg protein balance after resistance exercise. However, the effect was minor and delayed compared with the previously reported effect of ingestion of amino acids.