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

Protein and Leucine Requirements for Maximal Muscular Development and Athletic Performance Are Achieved with Completely Plant-Based Diets Modeled to Meet Energy Needs in Adult Male Rugby Players

Rugby athletes consume large amounts of animal protein in accordance with conventional dietary guidance to increase muscle mass and strength. This misaligns with national dietary guidelines, which suggest limiting meat consumption for chronic disease prevention. The ability of completely plant-based diets to satisfy the nutritional needs of rugby players has not been explored. This study scaled nutrient data from a large population consuming completely plant-based diets with limited supplemental protein to meet the calorie requirements of adult male rugby athletes to assess whether protein and leucine recommendations for muscular development and athletic performance would be achieved. Calorie requirements were estimated from research that employed the doubly labeled water method, and dietary data from the Adventist Health Study-2 were scaled to this level. The modeled protein level was 1.68 g/kg/day, which meets recommendations for maximal gains in muscle mass, strength, and athletic performance. The modeled leucine level was 2.9 g/meal for four daily meals, which exceeds the threshold proposed to maximally stimulate muscle protein synthesis in young men. These results indicate that consuming large portions of completely plant-based meals can satisfy protein and leucine requirements for maximal muscular development and athletic performance in adult male rugby athletes while aligning with public health recommendations.

Protein Requirements for Maximal Muscle Mass and Athletic Performance Are Achieved with Completely Plant-Based Diets Scaled to Meet Energy Needs: A Modeling Study in Professional American Football Players

American football players consume large quantities of animal-sourced protein in adherence with traditional recommendations to maximize muscle development and athletic performance. This contrasts with dietary guidelines, which recommend reducing meat intake and increasing consumption of plant-based foods to promote health and reduce the risk of chronic disease. The capacity of completely plant-based diets to meet the nutritional needs of American football players has not been studied. This modeling study scaled dietary data from a large cohort following completely plant-based diets to meet the energy requirements of professional American football players to determine whether protein, leucine, and micronutrient needs for physical performance and health were met. The Cunningham equation was used to estimate calorie requirements. Nutrient intakes from the Adventist Health Study 2 were then scaled to this calorie level. Protein values ranged from 1.6-2.2 g/kg/day and leucine values ranged from 3.8-4.1 g/meal at each of four daily meals, therefore meeting and exceeding levels theorized to maximize muscle mass, muscle strength, and muscle protein synthesis, respectively. Plant-based diets scaled to meet the energy needs of professional American football players satisfied protein, leucine, and micronutrient requirements for muscle development and athletic performance. These findings suggest that completely plant-based diets could bridge the gap between dietary recommendations for chronic disease prevention and athletic performance in American football players.

Outcomes of the LEAP feasibility trial-A low-threshold, exercise programme with protein supplementation to target frailty and poor physical functioning in people experiencing homelessness and addiction issues

BACKGROUND

People experiencing homelessness are more likely to experience poor health with physical functioning deficits and frailty commonly reported. It is not well known how strategies to target physical functioning deficits and frailty work in practice in this group. The primary aim of this study was to explore the feasibility of an exercise intervention with protein supplementation to target physical functioning and frailty in people experiencing homelessness evaluated by recruitment and retention rates, adherence to the exercise sessions and protein supplement, adverse effects, programme feedback and characteristics of non-returners, sporadic and frequent attenders. The secondary aim was to evaluate changes in effectiveness outcomes of grip strength, muscle mass, lower extremity physical function, pain, frailty, and risk of malnutrition.

METHOD

This prospective single-arm study evaluated the feasibility of a 16-week rolling, low-threshold, 'drop-in' once weekly exercise programme with protein supplementation. The main recruitment site was a day-service centre for people who are homeless. Feasibility was assessed by the recruitment and retention rates, adherence to the exercise sessions and protein supplement as well as adverse effects, programme feedback and evaluation of characteristics of non-returners, sporadic (≤50% of available sessions) and frequent attenders (≥50% of available sessions). Effectiveness outcomes included pain (Visual Analogue Scale), physical functioning and performance (hand-grip dynamometry, limb circumference, the Short Physical Performance Battery), frailty (SHARE-FI and Clinical Frailty Scale) and nutritional status (Mini Nutritional Assessment).

RESULTS

Thirty-one participants were recruited mean (SD) age 45(16) years. There was a recruitment rate of a median (IQR) of 2(1-3) new participants per week. The retention rate was 45% (n = 14) to the main recruitment site. Adherence to the exercise sessions and nutritional intervention was 90% and 100% respectively. Three adverse events were recorded during 74 interventions over the 16-week programme. The acceptability of the programme was highlighted in participant feedback. Characteristics of frequent returners (≥50%) were older age, female, more stably housed and more stable in addiction. The programme did not induce any changes in effectiveness outcomes.

CONCLUSION

The feasibility of this programme was demonstrated. Overall, the programme was well received with higher retention rates in older participants, females, those more stably housed and those stable in addiction. A higher powered, more intense programme is needed to demonstrate programme effectiveness.

Acute Effects of Dairy or Soy Milk on Sex Hormones Following Resistance Exercise in Males: A Randomized, Crossover Pilot Trial

INTRODUCTION

Resistance exercise training (RET) can increase muscle mass and strength, and this adaptation is optimized when dietary protein is consumed to enhance muscle protein synthesis. Dairy milk has been endorsed for this purpose; however, allergy and lactose intolerance affect two-thirds of the global population making dairy milk unsuitable for many. Plant-based alternatives such as soy milk have gained popularity and exhibit comparable protein content. However, concerns regarding soy phytoestrogens potentially influencing circulating sex hormones and diminishing the anabolic response to RET have been raised. This study therefore aimed to assess the acute effects of dairy and soy milk consumption on circulating sex hormones (total, free testosterone, free testosterone percentage, total estrogen, progesterone, and sex hormone binding globulin) after RET.

MATERIALS AND METHODS

Six male participants were recruited for a double-blinded, randomized crossover study with either dairy or soy milk provided post RET. Venous samples were collected before and after milk consumption across seven timepoints (0-120 minutes) where circulating sex hormones were analyzed. Two-way ANOVA analyses were applied for repeated measures for each hormone. The area under the curve (AUC) was also calculated between dairy and soy milk. Significance was set at p<0.05.

RESULTS

No significant differences were observed in acute circulating serum for free (p=0.95), % free (p=0.56), and total testosterone (p=0.88), progesterone (p=0.67), or estrogen (p=0.21) between milk conditions. Likewise, no significant differences in AUC were observed between any hormones.

CONCLUSION

These findings suggest that consumption of dairy milk and soy milk have comparable acute effects on circulating sex hormones following RET. Further investigations with expanded sample sizes are needed to strengthen and broaden these initial findings.

Completely Plant-Based Diets That Meet Energy Requirements for Resistance Training Can Supply Enough Protein and Leucine to Maximize Hypertrophy and Strength in Male Bodybuilders: A Modeling Study

Despite increasing awareness of plant-based diets for health and athletic performance, athletes are cautioned that careful dietary monitoring is necessary. Whether commonly consumed plant-based diets are nutritionally adequate for maximal muscular hypertrophy remains unknown. This modeling study assessed the nutrient composition of completely plant-based diets scaled to the caloric demands of maximal muscle mass and strength development in adult male bodybuilders. To model calorie requirements, anthropometric data from bodybuilders were input into the Tinsley resting metabolic rate prediction equation, and an appropriate physical activity factor and calorie surplus were applied. Dietary data from a large cohort following completely plant-based diets were then scaled to meet these needs. Modeled intakes for nutrients of interest were calculated as 1.8 g/kg/day of protein and 2.75 g/meal of leucine, which surpass mean requirements for maximal increases in muscle mass and strength and muscle protein synthesis, respectively. Daily levels for all micronutrients, except vitamin D, also exceeded requirements. Saturated fat levels were aligned with dietary guidelines, although sodium levels exceeded recommended limits. Consumption of larger portions of commonplace plant-based diets, scaled to meet the energy demands of maximal accrual of muscle mass and strength, satisfied protein and leucine requirements without the need for additional planning.

Effect of breakfast protein intake on muscle mass and strength in adults: a scoping review

BACKGROUND

The distribution of protein intake throughout the day is frequently skewed, with breakfast having the lowest protein intake across all age groups. There is no review that addresses the association between breakfast protein intake and muscle mass and strength.

OBJECTIVE

This scoping review aims to summarize the literature on the relationship between protein intake during breakfast and muscle mass and strength in adults.

METHODS

This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. Two independent reviewers screened and appraised the articles identified from 3 electronic databases (Medline, Web of Science, and Scopus) that focused on protein intake per meal and its impact on muscle-related outcomes.

RESULTS

A total of 14 763 articles were retrieved from 3 databases, and after the screening process, 15 articles were included for analysis. Approximately 58.8% of findings from 11 studies examining the association between high protein intake during breakfast and muscle mass indicated an increase in muscle mass among participants. Half of 6 studies (50.0%) exploring the relationship between high protein intake at breakfast and muscle strength demonstrated an increase in muscle strength. Consuming high amounts of protein at breakfast or more protein in the morning than in the evening was associated with an increase in the skeletal muscle index and lean body mass.

CONCLUSION

Protein consumption at breakfast revealed potential benefits in increasing muscle mass across 5 studies involving an elderly population and 2 studies encompassing middle-aged women and young men in our review. However, the relationship between protein intake at breakfast and muscle strength remains unclear. Further high-quality randomized controlled trials are required to examine whether adults can preserve skeletal muscle health outcomes by consuming higher amounts of protein at breakfast.

Association of Elevated Serum Branched-chain Amino Acid Levels With Longitudinal Skeletal Muscle Loss

Context

Branched-chain amino acids (BCAA) are substrates for protein synthesis. Although their intake may contribute to an increase in skeletal muscle mass, elevated serum BCAA levels have been reported to be associated with insulin resistance, potentially resulting in decreased skeletal muscle mass.

Objective

This study aimed to explore the association between elevated serum BCAA levels and longitudinal skeletal muscle loss.

Design and Setting

A cohort analysis was conducted, in which serum amino acids were analyzed in healthy individuals who underwent a medical health checkup at Kameoka Municipal Hospital (HOZUGAWA study), Japan.

Patients

Seventy-one participants (37 men and 34 women) underwent follow-up checkups after the baseline visit. The follow-up duration was 1.2 ± .4 years.

Main Outcome Measures

The relationship between fasting baseline serum BCAA levels and lifestyle factors, body composition, blood test results, dietary history, and changes in skeletal muscle mass was evaluated.

Results

In both men and women, serum BCAA levels were positively correlated with body weight, body mass index, skeletal muscle mass index (SMI), and serum triglycerides but inversely correlated with serum high-density lipoprotein cholesterol. In men, fasting serum BCAA levels were inversely associated with the rate of change in SMI (adjusted β = -.529, P = .006), and elevated BCAA levels were independently associated with a longitudinal decrease in skeletal muscle mass (odds ratio: 1.740; 95% confidence interval: 1.023-2.960 per 50 nmol/mL serum BCAAs increase).

Conclusion

Increased circulating BCAAs could be an indicator of skeletal muscle loss in men.

Pre-heating stress associated with acute oral leucine supplementation effects in rat gastrocnemius muscle: Implications for protein synthesis signaling pathways

Skeletal muscle is a highly plastic tissue. The role of heat shock protein 72 (Hsp72) in heat stress-induced skeletal muscle hypertrophy has been well demonstrated; however, the precise mechanisms remain unclear. Essential amino acids, such as leucine, mainly mediate muscle protein synthesis. We investigated the effects of pre-heating and increased Hsp72 expression on the mechanistic target of rapamycin (mTOR) signaling and protein synthesis following leucine administration in rat gastrocnemius muscle. To ensure increased Hsp72 expression in both the red and white portions of the muscle, one leg of male Wistar rats (10-week-old, n = 23) was heat-stressed in 43 °C water for 30 min twice at a 48-h-interval (heat-stressed leg, HS leg). The contralateral leg served as a non-heated internal control (CT leg). After the recovery period (48 h), rats were divided into the pre-administration or oral leucine administration groups. We harvested the gastrocnemius muscle (red and white parts) prior to administration and 30 and 90 min after leucine treatment (n = 7-8 per group) and intramuscular signaling responses to leucine ingestion were determined using western blotting. Heat stress significantly upregulated the expression of Hsp72 and was not altered by leucine administration. Although the phosphorylation levels of mTOR/S6K1 and ERK were similar regardless of heating, 4E-BP1 was less phosphorylated in the HS legs than the CT legs after leucine administration in the red portion of the muscles (P < 0.05). Moreover, c-Myc expression differed significantly after leucine administration in both the red and white portions of the muscles. Our findings indicate that following oral leucine administration, pre-heating partially blunted the muscle protein synthesis signaling response in the rat gastrocnemius muscle.

Pre-sleep protein supplementation does not improve recovery from load carriage in British Army recruits (part 2)

British Army basic training (BT) is physically demanding with new recruits completing multiple bouts of physical activity each day with limited recovery. Load carriage is one of the most physically demanding BT activities and has been shown to induce acute exercise-induced muscle damage (EIMD) and impair muscle function. Protein supplementation can accelerate muscle recovery by attenuating EIMD and muscle function loss. This study investigated the impact of an additional daily bolus of protein prior to sleep throughout training on acute muscle recovery following a load carriage test in British Army recruits. Ninety nine men and 23 women (mean ± SD: age: 21.3 ± 3.5 yrs., height: 174.8 ± 8.4 cm, body mass 75.4 ± 12.2 kg) were randomized to dietary control (CON), carbohydrate placebo (PLA), moderate (20 g; MOD) or high (60 g; HIGH) protein supplementation. Muscle function (maximal jump height), perceived muscle soreness and urinary markers of muscle damage were assessed before (PRE), immediately post (POST), 24-h post (24 h-POST) and 40-h post (40 h-POST) a load carriage test. There was no impact of supplementation on muscle function at POST (p = 0.752) or 40 h-POST (p = 0.989) load carriage but jump height was greater in PLA compared to HIGH at 24 h-POST (p = 0.037). There was no impact of protein supplementation on muscle soreness POST (p = 0.605), 24 h-POST (p = 0.182) or 40 h-POST (p = 0.333). All groups had increased concentrations of urinary myoglobin and 3-methylhistidine, but there was no statistical difference between groups at any timepoint (p > 0.05). We conclude that pre-sleep protein supplementation does not accelerate acute muscle recovery following load carriage in British Army recruits during basic training. The data suggests that consuming additional energy in the form of CHO or protein was beneficial at attenuating EIMD, although it is acknowledged there were no statistical differences between groups. Although EIMD did occur as indicated by elevated urinary muscle damage markers, it is likely that the load carriage test was not arduous enough to reduce muscle function, limiting the impact of protein supplementation. Practically, protein supplementation above protein intakes of 1.2 g⸱kg-1⸱day-1 following load carriage over similar distances (4 km) and carrying similar loads (15-20 kg) does not appear to be warranted.

Japanese Clinical Practice Guidelines for Rehabilitation in Critically Ill Patients 2023 (J-ReCIP 2023)

Providing standardized, high-quality rehabilitation for critically ill patients is a crucial issue. In 2017, the Japanese Society of Intensive Care Medicine (JSICM) promulgated the "Evidence-Based Expert Consensus for Early Rehabilitation in the Intensive Care Unit" to advocate for the early initiation of rehabilitations in Japanese intensive care settings. Building upon this seminal work, JSICM has recently conducted a rigorous systematic review utilizing the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. This endeavor resulted in the formulation of Clinical Practice Guidelines (CPGs), designed to elucidate best practices in early ICU rehabilitation. The primary objective of this guideline is to augment clinical understanding and thereby facilitate evidence-based decision-making, ultimately contributing to the enhancement of patient outcomes in critical care settings. No previous CPGs in the world has focused specifically on rehabilitation of critically ill patients, using the GRADE approach. Multidisciplinary collaboration is extremely important in rehabilitation. Thus, the CPGs were developed by 73 members of a Guideline Development Group consisting of a working group, a systematic review group, and an academic guideline promotion group, with the Committee for the Clinical Practice Guidelines of Early Mobilization and Rehabilitation in Intensive Care of the JSICM at its core. Many members contributed to the development of the guideline, including physicians and healthcare professionals with multiple and diverse specialties, as well as a person who had been patients in ICU. Based on discussions among the group members, eight important clinical areas of focus for this CPG were identified. Fourteen important clinical questions (CQs) were then developed for each area. The public was invited to comment twice, and the answers to the CQs were presented in the form of 10 GRADE recommendations and commentary on the four background questions. In addition, information for each CQ has been created as a visual clinical flow to ensure that the positioning of each CQ can be easily understood. We hope that the CPGs will be a useful tool in the rehabilitation of critically ill patients for multiple professions.

Dietary Intake of Protein and Essential Amino Acids for Sustainable Muscle Development in Elite Male Athletes

Athletes need to develop a relatively high muscle mass and low body adipose tissue for the sake of better athletic performance. A full range of nine essential amino acids and eleven non-essential amino acids have to attend in appropriate amounts for protein biosynthesis. The aim of the observational comparative cross-sectional study was to assess the association between the diet quality profile and training-induced muscle mass estimated by bioelectrical impedance among elite male athletes. The research sample comprised 18.1 ± 3.1 year-old Lithuanian professional male athletes (n = 234). The study participants were enrolled to complete 24-h dietary recalls of three non-consecutive days. The body composition was assessed using the bioelectrical impedance analysis (BIA) method. The present study showed a significant insufficiency of the mean carbohydrate intake of 5.7 g/kg/day in a group of aerobic male athletes. The lower muscle mass of aerobic male athletes was related to the lower-carbohydrate diet (adjusted odd ratio (ORadj) 0.3; 95% confidence interval (CI): 0.1-0.7). The mean protein intake of 1.8 g/kg/day was optimal for anabolism in the samples of both anaerobic and aerobic male athletes. The protein intake in appropriate doses was potentially associated with an increase in muscle mass only in anaerobic male athletes (ORadj 2.2; 95% CI: 1.3-3.7). The positive relationship was revealed between the possible muscle mass gain and the increased intakes of amino acids such as isoleucine and histidine among anaerobic athletes (ORadj 2.9; 95% CI: 1.1-4.7 and ORadj 2.9; 95% CI: 1.0-4.3, respectively). An inverse feasible association was indicated between a higher intake of valine and lower muscle mass quantities among anaerobic male athletes (ORadj 0.1; 95% CI: 0.1-0.5). The recommendations for sports nutritionists should emphasize the necessity of advising professional athletes on dietary strategies on how to manipulate dietary amino acid composition with respect to achieving long-term body composition goals.

Combinatory Effects of Training and Nutritive Administration of Carbohydrates and Protein via Food on Strength in Postmenopausal Women, and Old Men and Women

The age-related loss of muscle mass promotes many impairments. Training and protein supplementation are suggested to prevent muscle wasting, but recommendations for all populations are not based on scientific evidence. This study combines protein/carbohydrate supplementation (PCS) and training for seniors and postmenopausal women. Project A: 51 postmenopausal women (PMW, 57.3 ± 3.0 years old) underwent health-oriented training (12 weeks, moderate-strength training + moderate-endurance training). The intervention group (IG) additionally received 110 g sour milk cheese (SMC) and toast. Project B: 25 women and 6 men (65.9 ± 4.9 years old) performed intense sling training (12 weeks). The IG additionally received 110 g SMC, toast, and buttermilk. Strength was tested before and after in both studies. Project A: there was significant increase in strength, no additional effect of PCS, and a reduction in body fat in the controls. Project B: there was significant increase in strength, significant additional effects of PCS for trunk strength, and a significant reduction in body weight. Combining training and PCS may counteract strength loss. Combined endurance/resistance training is recommended to PMW for whom the benefits of PCS are restricted. Aged subjects may benefit from PCS when training intensely, but these benefits may be strongly individual.

Mediterranean Diet and Sarcopenia Features in Apparently Healthy Adults over 65 Years: A Systematic Review

Low muscle mass combined with changes in physical function and muscle quality is defined as sarcopenia. In people > 60 years, sarcopenia reaches 10% and tends to increase with age. Individual nutrients, such as protein, may have a protective role against sarcopenia, but recent evidence suggests that protein alone has been ineffective in increasing muscle strength. Dietary patterns, instead, with a high "anti-inflammatory" potential, such as the Mediterranean dietary pattern, have been considered as an emerging dietary remedy against sarcopenia. The aim of this systematic review was to summarize the evidence of the role of Mediterranean diet in sarcopenia prevention and/or improvement, including recent data, in healthy elders. We searched published studies about sarcopenia and the Mediterranean diet until December 2022 in Pubmed, Cochrane, Scopus search engine and grey literature. In total, ten articles were identified as relevant: four cross-sectional studies and six prospective. No clinical trial was identified. Only three studies assessed sarcopenia presence and four measured muscle mass, which is an essential criterion in sarcopenia diagnosis. Mediterranean diet adherence had, in general, a positive role in muscle mass and muscle function, while the results were less clear with regard to muscle strength. Additionally, there was no evidence of a positive effect of the Mediterranean diet on sarcopenia. There is a need for conduction of clinical trials in order to reach cause-effects conclusions regarding the importance of the Mediterranean diet in sarcopenia prevention and management in Mediterranean and non-Mediterranean populations.

Effects of Whey Protein Supplement on 4-Week Resistance Exercise-Induced Improvements in Muscle Mass and Isokinetic Muscular Function under Dietary Control

(1) The purpose of this study was to investigate the effect of whey protein supplementation under dietary control on improvements in muscle mass and function following resistance exercise training. (2) Thirty-two men were randomly assigned to a whey protein supplementation group taking whey protein isolate (PSG, n = 17) and a placebo group (CON, n = 15). Participants were provided with three meals per day corresponding to the estimated individual daily energy intake. The supervised resistance exercise program was conducted 60 min per day, six days per week, for four weeks. (3) Post-intervention, there was a significant interaction between groups in terms of muscle mass increase (p = 0.033, η² = 0.14), with a greater increase in the PSG. There were also significant interactions between the groups and increases in peak torque of the dominant knee flexors (p = 0.048, η² = 0.12), dominant shoulder extensors, and non-dominant shoulder extensors (p = 0.028, η² = 0.15; p = 0.015, η² = 0.18), and the total work of the dominant knee and shoulder extensors (p = 0.012, η² = 0.19; p = 0.013, η² = 0.19), with greater increases in the PSG. (4) These results suggest that whey protein supplementation enhances resistance exercise-induced increase in muscle mass and overall muscular strength and endurance, independent of dietary influence.

Analysis and Screening of Commercialized Protein Supplements for Sports Practice

Recent years have seen a rise in the popularity of the consumption of sports-related supplements. However, the hypothesis is raised that it is necessary to analyze the quality aspects of these supplements in relation to the information provided on the label, to avoid associated risks and obtain the greatest possible benefit from their consumption. Therefore, the aim of this study has been to carry out an analysis or screening of the protein supplements that are currently marketed in Spain. We analyzed the labels of 52 protein sports supplements available both in physical stores and online. The analysis consisted of addressing three relevant aspects considering the labeling: (a) the legislative framework in which the supplements are marketed, (b) the quality of the protein, and (c) the presence of other ingredients according to the specifications of the label. In the legislative context, there do not seem to be any specific regulations to guarantee consumer protection, which can lead to unfair practices and misleading advertising. Most of the supplements analyzed to comply with the requirements of their current regulations. However, claims about their benefits that are not allowed under European legislation have been found in some of them. Regarding composition and according to label information, the supplements have been found to provide a sufficient dose of protein in terms of recommended protein intake per serving. Regarding the presence of other ingredients and according to the information on the label, most of them, except for egg supplements, contain other ingredients. Colostrum was also found in one of the supplements evaluated. The conclusions of the study reveal that, due to a lack of knowledge or misleading advertising practices, supplements are often not used properly. The information provided is essential for both professionals and consumers to avoid the risks associated with consumption, such as unintentional doping, interactions between ingredients that reduce the quality of the supplement, and consumption of supplements inappropriately, among others.

The Effects of Concurrent Training Combined with Low-Carbohydrate High-Fat Ketogenic Diet on Body Composition and Aerobic Performance: A Systematic Review and Meta-Analysis

(1) Background: Recently, studies have emerged to explore the effects of concurrent training (CT) with a low-carb, high-fat ketogenic diet (LCHF) on body composition and aerobic performance and observed its benefits. However, a large variance in the study design and observations is presented, which needs to be comprehensively assessed. We here thus completed a systematic review and meta-analysis to characterize the effects of the intervention combining CT and LCHF on body composition and aerobic capacity in people with training experience as compared to that combining CT and other dietary strategies. (2) Methods: A search strategy based on the PICOS principle was used to find literature in the databases of PubMed, Web of Science, EBSCO, Sport-discuss, and Medline. The quality and risk of bias in the studies were independently assessed by two researchers. (3) Result: Eight studies consisting of 170 participants were included in this work. The pooled results showed no significant effects of CT with LCHF on lean mass (SMD = -0.08, 95% CI -0.44 to 0.3, p = 0.69), body fat percentage (SMD = -0.29, 95% CI -0.66 to 0.08, p = 0.13), body mass (SMD = -0.21, 95% CI -0.53 to 0.11, p = 0.2), VO2max (SMD = -0.01, 95% CI -0.4 to 0.37, p = 0.95), and time (or distance) to complete the aerobic tests (SMD = -0.02, 95% CI -0.41 to 0.37, p = 0.1). Subgroup analyses also showed that the training background of participants (i.e., recreationally trained participants or professionally trained participants) and intervention duration (e.g., > or ≤six weeks) did not significantly affect the results. (4) Conclusions: This systematic review and meta-analysis provide evidence that compared to other dietary strategies, using LCHF with CT cannot induce greater benefits for lean mass, body fat percentage, body mass, VO2max, and aerobic performance in trained participants.

Functional Properties of Meat in Athletes' Performance and Recovery

Physical activity (PA) and sport play an essential role in promoting body development and maintaining optimal health status both in the short and long term. Despite the benefits, a long-lasting heavy training can promote several detrimental physiological changes, including transitory immune system malfunction, increased inflammation, and oxidative stress, which manifest as exercise-induced muscle damages (EIMDs). Meat and derived products represent a very good source of bioactive molecules such as proteins, lipids, amino acids, vitamins, and minerals. Bioactive molecules represent dietary compounds that can interact with one or more components of live tissue, resulting in a wide range of possible health consequences such as immune-modulating, antihypertensive, antimicrobial, and antioxidative activities. The health benefits of meat have been well established and have been extensively reviewed elsewhere, although a growing number of studies found a significant positive effect of meat molecules on exercise performance and recovery of muscle function. Based on the limited research, meat could be an effective post-exercise food that results in favorable muscle protein synthesis and metabolic performance.

Effects of 30 days of ketogenic diet on body composition, muscle strength, muscle area, metabolism, and performance in semi-professional soccer players

BACKGROUND

A ketogenic diet (KD) is a nutritional approach, usually adopted for weight loss, that restricts daily carbohydrates under 30 g/day. KD showed contradictory results on sport performance, whilst no data are available on team sports. We sought to investigate the influence of a KD on different parameters in semi-professional soccer players.

METHODS

Subjects were randomly assigned to a iso-protein (1.8 g/Kg body weight/day) ketogenic diet (KD) or western diet (WD) for 30 days. Body weight and body composition, resting energy expenditure (REE), respiratory exchange ratio (RER), cross sectional area (CSA) and isometric muscle strength of quadriceps, counter movement jump (CMJ) and yoyo intermittent recovery test time were measured.

RESULTS

There was a significantly higher decrease of body fat (p = 0.0359), visceral adipose tissue (VAT) (p = 0.0018), waist circumference (p = 0.0185) and extra-cellular water (p = 0.0060) in KD compared to WD group. Lean soft tissue, quadriceps muscle area, maximal strength and REE showed no changes in both groups. RER decreased significantly in KD (p = 0.0008). Yo-yo intermittent test improved significantly (p < 0.0001) in both groups without significant differences between groups. CMJ significantly improved (p = 0.0021) only in KD.

CONCLUSIONS

This is the first study investigating the effects of a KD on semi-professional soccer players. In our study KD athletes lost fat mass without any detrimental effects on strength, power and muscle mass. When the goal is a rapid weight reduction in such athletes, the use of a KD should be taken into account.

TRIAL REGISTRATION

registered retrospectively on Clinical Trial registration number NCT04078971 .

Distribution of dietary protein intake in daily meals influences skeletal muscle hypertrophy via the muscle clock

The meal distribution of proteins throughout the day is usually skewed. However, its physiological implications and the effects of better protein distribution on muscle volume are largely unknown. Here, using the two-meals-per-day feeding model, we find that protein intake at the early active phase promotes overloading-induced muscle hypertrophy, in a manner dependent on the local muscle clock. Mice fed branched-chain amino acid (BCAA)-supplemented diets at the early active phase demonstrate skeletal muscle hypertrophy. However, distribution-dependent effects are not observed in ClockΔ19 or muscle-specific Bmal1 knockout mice. Additionally, we examined the relationship between the distribution of proteins in meals and muscle functions, such as skeletal muscle index and grip strength in humans. Higher muscle functions were observed in subjects who ingested dietary proteins mainly at breakfast than at dinner. These data suggest that protein intake at breakfast may be better for the maintenance of skeletal muscle mass.

The effects of acute aerobic and resistance exercise on mTOR signaling and autophagy markers in untrained human skeletal muscle

PURPOSE

Aerobic (AE) and resistance (RE) exercise elicit unique adaptations in skeletal muscle. The purpose here was to compare the post-exercise response of mTOR signaling and select autophagy markers in skeletal muscle to acute AE and RE.

METHODS

In a randomized, cross-over design, six untrained men (27 ± 3 years) completed acute AE (40 min cycling, 70% HRmax) and RE (8 sets, 10 repetitions, 65% 1RM). Muscle biopsies were taken at baseline, and at 1 h and 4 h following each exercise. Western blot analyses were performed to examine total and phosphorylated protein levels. Upstream regulator analyses of skeletal muscle transcriptomics were performed to discern the predicted activation states of mTOR and FOXO3.

RESULTS

Compared to AE, acute RE resulted in greater phosphorylation (P < 0.05) of mTOR^Ser2448 at 4 h, S6K1^Thr389 at 1 h, and 4E- BP1^Thr37/46 during the post-exercise period. However, both AE and RE increased mTOR^Ser2448 and S6K1^Thr389 phosphorylation at 4 h (P < 0.05). Upstream regulator analyses revealed the activation state of mTOR was increased for both AE (z score, 2.617) and RE (z score, 2.789). No changes in LC3BI protein were observed following AE or RE (P > 0.05), however, LC3BII protein was decreased after both AE and RE at 1 h and 4 h (P < 0.05). p62 protein content was also decreased at 4 h following AE and RE (P < 0.05).

CONCLUSION

Both acute AE and RE stimulate mTOR signaling and similarly impact select markers of autophagy. These findings indicate the early adaptive response of untrained human skeletal muscle to divergent exercise modes is not likely mediated through large differences in mTOR signaling or autophagy.

Effects of the anti-oxidant PDTC in combination with a single bout of treadmill running on murine skeletal muscle

Objectives: Skeletal muscle adaptation to physical activity is dependent on various factors. Important signaling mediators are reactive oxygen species (ROS). However, recent research suggests that ROS have both beneficial and deleterious effects on exercise adaptation, dependent on training intensity and training status, so that the question of whether anti-oxidants should be taken in connection with exercise cannot easily be answered. Thus, it is important to gain more insight into the complex roles of ROS in regulating training adaptation.

Methods: The effects of ROS inhibition on skeletal muscle training adaptation were analyzed by applying the anti-oxidant PDTC, which is also an inhibitor of the ROS-activated transcription factor nuclear factor kappa B (NFκB), to juvenile mice in connection with a single bout of treadmill running.

Results: We found that PDTC inhibits exercise-mediated induction of specific stress- and inflammation-associated genes. Other genes, specifically those encoding metabolic and mitochondrial factors, were affected to a lesser extent and there appeared to be little effect on the microRNA (miR) profile.

Discussion: Our data suggest that anti-oxidants regulate distinct sets of adaptation-relevant genes, which might have important implications for the design of exercise-based preventive and therapeutic approaches.

Factors Associated With Skeletal Muscle Mass Increase by Rehabilitation in Older Adults With Vertebral Compression Fractures

Age-related sarcopenia and osteoporosis-related fractures are critical health issues. Therefore, this study aimed to assess skeletal muscle mass changes in older patients with vertebral compression fractures undergoing rehabilitation and to evaluate factors associated with muscle increases. This study included 179 patients aged ≥80 years in rehabilitation wards with vertebral compression fractures. Appendicular skeletal muscle index was significantly higher at discharge (5.22 ± 1.04 kg/m2, p < .001) than on admission (5.03 ± 1.00 kg/m2). Multiple logistic regression analysis showed that length of hospital stay was significantly associated with increased skeletal muscle index (odds ratios, 1.020; 95% confidence intervals [1.000, 1.032]), whereas age, sex, body mass index, functional independence measure, protein intake, and exercise therapy duration were not. Participants with vertebral compression fractures aged ≥80 years achieved significantly increased skeletal muscle mass in rehabilitation wards. In addition, length of hospital stay was the factor independently associated with increased skeletal muscle index.

Does Protein Supplementation Support Adaptations to Arduous Concurrent Exercise Training? A Systematic Review and Meta-Analysis with Military Based Applications

We evaluated the impact of protein supplementation on adaptations to arduous concurrent training in healthy adults with potential applications to individuals undergoing military training. Peer-reviewed papers published in English meeting the population, intervention, comparison and outcome criteria were included. Database searches were completed in PubMed, Web of science and SPORTDiscus. Study quality was evaluated using the COnsensus based standards for the selection of health status measurement instruments checklist. Of 11 studies included, nine focused on performance, six on body composition and four on muscle recovery. Cohen's d effect sizes showed that protein supplementation improved performance outcomes in response to concurrent training (ES = 0.89, 95% CI = 0.08-1.70). When analysed separately, improvements in muscle strength (SMD = +4.92 kg, 95% CI = -2.70-12.54 kg) were found, but not in aerobic endurance. Gains in fat-free mass (SMD = +0.75 kg, 95% CI = 0.44-1.06 kg) and reductions in fat-mass (SMD = -0.99, 95% CI = -1.43-0.23 kg) were greater with protein supplementation. Most studies did not report protein turnover, nitrogen balance and/or total daily protein intake. Therefore, further research is warranted. However, our findings infer that protein supplementation may support lean-mass accretion and strength gains during arduous concurrent training in physical active populations, including military recruits.

Protein Considerations for Athletes With a Spinal Cord Injury

Athlete participation in the Paralympic games is steadily increasing; prompting research focused on the unique needs of this population. While the Paralympic Games includes a diversity of athletes, athletes with a spinal cord injury (PARA-SCI) represent a subgroup that requires specialized recommendations. Nutritional guidelines designed to optimize performance, in the context of the neurological impairments, are required. This narrative review summarizes the current literature regarding the importance of dietary protein for optimal health and performance. Factors with the potential to affect protein needs in PARA-SCI including loss of active muscle mass, reduced energy expenditure, and secondary complications are examined in detail. Furthermore, we analyze protein intakes in PARA-SCI from the available research to provide context around current practices and trends. In conclusion, we make the case that protein recommendations for able-bodied athletes may not be directly transferable to PARA-SCI. Consequently, PARA-SCI need their own guidelines to maximize performance and ensure long-term health.

A Comprehensive Workflow for the Analysis of Bio-Macromolecular Supplements: Case Study of 20 Whey Protein Products

The presence of bio-macromolecules as major ingredients is a primary factor in marketing many biologically derived macromolecular supplements. Workflows for analyzing these supplements for quality assurance, adulteration, and other supply-chain difficulties must include a qualitative assessment of small-molecule and macromolecular components; however, no such integrated protocol has been reported for these bio-macromolecular supplements. Twenty whey protein supplements were analyzed using an integrated workflow to identify protein content, protein adulteration, inorganic elemental content, and macromolecular and small-molecule profiles. Orthogonal analytical methods were employed, including NMR profiling, LC-DAD-QToF analysis of small-molecule components, ICP-MS analysis of inorganic elements, determination of total protein content by a Bradford assay, SDS-PAGE protein profiling, and bottom-up shotgun proteomic analysis using LC-MS-MS. All 20 supplements showed a reduced protein content compared to the claimed content but no evidence of adulteration with protein from an unclaimed source. Many supplements included unlabeled small-molecule additives (but nontoxic) and significant deviations in metal content, highlighting the importance of both macromolecular and small-molecule analysis in the comprehensive profiling of macromolecular supplements. An orthogonal, integrated workflow allowed the detection of crucial product characteristics that would have remained unidentified using traditional workflows involving either analysis of small-molecule nutritional supplements or protein analysis.

High-intensity leg cycling alters the molecular response to resistance exercise in the arm muscles

This study examined acute molecular responses to concurrent exercise involving different muscles. Eight men participated in a randomized crossover-trial with two sessions, one where they performed interval cycling followed by upper body resistance exercise (ER-Arm), and one with upper body resistance exercise only (R-Arm). Biopsies were taken from the triceps prior to and immediately, 90- and 180-min following exercise. Immediately after resistance exercise, the elevation in S6K1 activity was smaller and the 4E-BP1:eIF4E interaction greater in ER-Arm, but this acute attenuation disappeared during recovery. The protein synthetic rate in triceps was greater following exercise than at rest, with no difference between trials. The level of PGC-1α1 mRNA increased to greater extent in ER-Arm than R-Arm after 90 min of recovery, as was PGC-1α4 mRNA after both 90 and 180 min. Levels of MuRF-1 mRNA was unchanged in R-Arm, but elevated during recovery in ER-Arm, whereas MAFbx mRNA levels increased slightly in both trials. RNA sequencing in a subgroup of subjects revealed 862 differently expressed genes with ER-Arm versus R-Arm during recovery. These findings suggest that leg cycling prior to arm resistance exercise causes systemic changes that potentiate induction of specific genes in the triceps, without compromising the anabolic response.

Significance of serum branched-chain amino acid to tyrosine ratio measurement in athletes with high skeletal muscle mass

BACKGROUND

Few nutritional markers reflect the hypermetabolic state of athletes with high levels of skeletal muscle. Although branched-chain amino acids (BCAA) play crucial roles in protein metabolism in skeletal muscle, the relationship between skeletal muscle mass and amino acid imbalances caused by the metabolism of BCAA and aromatic amino acids remains unclear. The aim of this study is to test the hypothesis that athletes with high levels of skeletal muscle mass have plasma amino acid imbalances, assessed by serum BCAA to tyrosine ratio (BTR) which can be measured conveniently.

METHODS

The study enrolled 111 young Japanese men: 70 wrestling athletes and 41 controls. None of them were under any medications, extreme dietary restrictions or intense exercise regimens. Each participant's body composition, serum concentrations of albumin and rapid turnover proteins including transthyretin and transferrin, BTR, and thyroid function were assessed.

RESULTS

Compared to the controls, the athletes had significantly higher skeletal muscle index (SMI) (p < 0.001), and lower serum albumin concentration (p < 0.001) and BTR (p < 0.001). Kruskal-Wallis tests showed that serum albumin concentration and BTR were significantly lower in the participants with higher SMI. Serum albumin concentration and BTR were inversely correlated with SMI by multiple regression analysis (logarithmic albumin, β = - 0.358, p < 0.001; BTR, β = - 0.299, p = 0.001). SMI was inversely and transthyretin was positively correlated with serum albumin (SMI, β = - 0.554, p < 0.001; transthyretin, β = 0.379, p < 0.001). Serum concentration of free 3,5,3'-triiodothyronine (FT₃) was inversely correlated with BTR, and, along with SMI and albumin, was independent predictor of BTR (SMI, β = - 0.321, p < 0.001; FT₃, β = - 0.253, p = 0.001; logarithmic albumin, β = 0.261, p = 0.003). However, FT₃ was not correlated with SMI or serum albumin. Serum concentrations of rapid turnover proteins were not correlated with BTR.

CONCLUSIONS

Increased skeletal muscle mass enhances the circulating amino acid imbalances, and is independently facilitated by thyroid hormones. Serum BTR may be a useful biomarker to assess the hypermetabolic state of wrestling athletes with high levels of skeletal muscle.

The Effects of Very Low Energy Diets and Low Energy Diets with Exercise Training on Skeletal Muscle Mass: A Narrative Review

In recent years, very-low-energy diets (VLEDs) have been recognised as a viable strategy for improving the extent of weight loss and cardio-metabolic outcomes in people who are either overweight or obese. However, concerns exist regarding the reductions in lean body mass (LBM) during VLEDs, particularly in vulnerable demographic groups, such as middle-aged and older adults already prone to developing sarcopenia. Sarcopenia is itself associated with multiple adverse outcomes, including frailty, cardio-metabolic deterioration and increased mortality. Therefore, a number of studies investigating strategies to ameliorate this detrimental effect of VLEDs have attempted to address this concern. This narrative review explores the potential benefits and limitations of exercise and/or protein supplementation for LBM retention during VLEDs based on the available evidence. Current studies suggest that both protein supplementation and exercise training may result in improved LBM retention (and skeletal muscle function) during VLEDs. However, uncertainty remains concerning the interactions between intervention types, based on discordant outcomes reported in the literature and the heterogeneity of exercise modalities in achieving this particular outcome.

Protein metabolism and related body function: mechanistic approaches and health consequences

The development and maintenance of body composition and functions require an adequate protein intake with a continuous supply of amino acids (AA) to tissues. Body pool and AA cellular concentrations are tightly controlled and maintained through AA supply (dietary intake, recycled from proteolysis and de novo synthesis), AA disposal (protein synthesis and other AA-derived molecules) and AA losses (deamination and oxidation). Different molecular regulatory pathways are involved in the control of AA sufficiency including the mechanistic target of rapamycin complex 1, the general control non-derepressible 2/activating transcription factor 4 system or the fibroblast growth factor 21. There is a tight control of protein intake, and human subjects and animals appear capable of detecting and adapting food and protein intake and metabolism in face of foods or diets with different protein contents. A severely protein deficient diet induces lean body mass losses and ingestion of sufficient dietary energy and protein is a prerequisite for body protein synthesis and maintenance of muscle, bone and other lean tissues and functions. Maintaining adequate protein intake with age may help preserve muscle mass and strength but there is an ongoing debate as to the optimal protein intake in older adults. The protein synthesis response to protein intake can also be enhanced by prior completion of resistance exercise but this effect could be somewhat reduced in older compared to young individuals and gain in muscle mass and function due to exercise require regular training over an extended period.

Long-term Effects of Calcium β-Hydroxy-β-Methylbutyrate and Vitamin D3 Supplementation on Muscular Function in Older Adults With and Without Resistance Training: A Randomized, Double-blind, Controlled Study

The primary aim of this study was to determine whether supplementation with calcium β-hydroxy-β-methylbutyrate (HMB) and vitamin D₃ (D) would enhance muscle function and strength in older adults. Older adults over 60 years of age with insufficient circulating 25-hydroxy-vitamin D (25OH-D) levels were enrolled in a double-blinded controlled 12-month study. Study participants were randomly assigned to treatments consisting of: (a) Control + no exercise, (b) HMB+D + no exercise, (c) Control + exercise, and (d) HMB+D + exercise. The study evaluated 117 participants via multiple measurements over the 12 months that included body composition, strength, functionality, and questionnaires. HMB+D had a significant benefit on lean body mass within the nonexercise group at 6 months (0.44 ± 0.27 kg, HMB+D vs −0.33 ± 0.28 kg, control, p < .05). In nonexercisers, improvement in knee extension peak torque (60°/s) was significantly greater in HMB+D-supplemented participants than in the nonsupplemented group (p = .04) at 3 months, 10.9 ± 5.7 Nm and −5.2 ± 5.9 Nm, respectively. A composite functional index, integrating changes in handgrip, Get Up, and Get Up and Go measurements, was developed. HMB+D + no exercise resulted in significant increases in the functional index compared with those observed in the control + no exercise group at 3 (p = .03), 6 (p = .04), and 12 months (p = .04). Supplementation with HMB+D did not further improve the functional index within the exercising group. This study demonstrated the potential of HMB and vitamin D₃ supplementation to enhance muscle strength and physical functionality in older adults, even in individuals not engaged in an exercise training program.

Rehabilitation Nutrition for Injury Recovery of Athletes: The Role of Macronutrient Intake

An adequate and balanced diet is of utmost importance in recovery and rehabilitation. "Rehabilitation nutrition" for injury recovery of athletes is similar to sports nutrition, except for the differences that concern the prevention of the risk or presence of sarcopenia, malnutrition, or dysphagia. Rehabilitation nutrition also aims, combined with training, to an adequate long-term nutritional status of the athlete and also in physical condition improvement, in terms of endurance and resistance. The aim of this paper is to define the proper nutrition for athletes in order to hasten their return to the sports after surgery or injury. Energy intake should be higher than the energy target in order to fight sarcopenia-that is 25-30 kcal/kg of body weight. Macro- and micro-nutrients play an important role in metabolism, energy production, hemoglobin synthesis, lean mass and bone mass maintenance, immunity, health, and protection against oxidative damage. Nutritional strategies, such as supplementation of suboptimal protein intake with leucine are feasible and effective in offsetting anabolic resistance. Thus, maintaining muscle mass, without gaining fat, becomes challenging for the injured athlete. A dietary strategy should be tailored to the athlete's needs, considering amounts, frequency, type and, most of all, protein quality. During rehabilitation, simultaneous carbohydrates and protein intake can inhibit muscle breakdown and muscle atrophy. The long-term intake of omega-3 fatty acids enhances anabolic sensitivity to amino acids; thus, it may be beneficial to the injured athlete. Adequate intakes of macronutrients can play a major role supporting athletes' anabolism.

Protein Supplementation in Sport: Source, Timing, and Intended Benefits

PURPOSE OF REVIEW

The purpose of this review is to provide background on the present literature regarding the utility and effectiveness of protein supplements, including protein source and nutrient timing.

RECENT FINDINGS

In the setting of adequate dietary protein consumption, research suggests some benefit particularly in sport or exercise activities. Protein supplements command a multi-billion-dollar market with prevalent use in sports. Many individuals, including athletes, do not consume optimal dietary protein on a daily basis. High-protein diets are remarkably safe in healthy subjects, especially in the short term. Some objective outcomes are physiologic and may not translate to clinically relevant outcomes. Athletes should, however, consider long-term implications when consuming high quantities of protein in dietary or supplement form.

Dose-response effects of dietary protein on muscle protein synthesis during recovery from endurance exercise in young men: a double-blind randomized trial

BACKGROUND

Protein ingestion increases skeletal muscle protein synthesis rates during recovery from endurance exercise.

OBJECTIVES

We aimed to determine the effect of graded doses of dietary protein co-ingested with carbohydrate on whole-body protein metabolism, and skeletal muscle myofibrillar (MyoPS) and mitochondrial (MitoPS) protein synthesis rates during recovery from endurance exercise.

METHODS

In a randomized, double-blind, parallel-group design, 48 healthy, young, endurance-trained men (mean ± SEM age: 27 ± 1 y) received a primed continuous infusion of l-[ring-2H5]-phenylalanine, l-[ring-3,5-2H2]-tyrosine, and l-[1-13C]-leucine and ingested 45 g carbohydrate with either 0 (0 g PRO), 15 (15 g PRO), 30 (30 g PRO), or 45 (45 g PRO) g intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled milk protein after endurance exercise. Blood and muscle biopsy samples were collected over 360 min of postexercise recovery to assess whole-body protein metabolism and both MyoPS and MitoPS rates.

RESULTS

Protein intake resulted in ∼70%-74% of the ingested protein-derived phenylalanine appearing in the circulation. Whole-body net protein balance increased dose-dependently after ingestion of 0, 15, 30, or 45 g protein (mean ± SEM: -0.31± 0.16, 5.08 ± 0.21, 10.04 ± 0.30, and 13.49 ± 0.55 μmol phenylalanine · kg-1 · h-1, respectively; P < 0.001). 30 g PRO stimulated a ∼46% increase in MyoPS rates (%/h) compared with 0 g PRO and was sufficient to maximize MyoPS rates after endurance exercise. MitoPS rates were not increased after protein ingestion; however, incorporation of dietary protein-derived l-[1-13C]-phenylalanine into de novo mitochondrial protein increased dose-dependently after ingestion of 15, 30, and 45 g protein at 360 min postexercise (0.018 ± 0.002, 0.034 ± 0.002, and 0.046 ± 0.003 mole percentage excess, respectively; P < 0.001).

CONCLUSIONS

Protein ingested after endurance exercise is efficiently digested and absorbed into the circulation. Whole-body net protein balance and dietary protein-derived amino acid incorporation into mitochondrial protein respond to increasing protein intake in a dose-dependent manner. Ingestion of 30 g protein is sufficient to maximize MyoPS rates during recovery from a single bout of endurance exercise.This trial was registered at trialregister.nl as NTR5111.

Novel Essential Amino Acid Supplements Following Resistance Exercise Induce Aminoacidemia and Enhance Anabolic Signaling Irrespective of Age: A Proof-of-Concept Trial

We investigated the effects of ingesting a leucine-enriched essential amino acid (EAA) gel alone or combined with resistance exercise (RE) versus RE alone (control) on plasma aminoacidemia and intramyocellular anabolic signaling in healthy younger (28 ± 4 years) and older (71 ± 3 years) adults. Blood samples were obtained throughout the three trials, while muscle biopsies were collected in the postabsorptive state and 2 h following RE, following the consumption of two 50 mL EAA gels (40% leucine, 15 g total EAA), and following RE with EAA (combination (COM)). Protein content and the phosphorylation status of key anabolic signaling proteins were determined via immunoblotting. Irrespective of age, during EAA and COM peak leucinemia (younger: 454 ± 32 µM and 537 ± 111 µM; older: 417 ± 99 µM and 553 ± 136 µM) occurred ~60–120 min post-ingestion (younger: 66 ± 6 min and 120 ± 60 min; older: 90 ± 13 min and 78 ± 12 min). In the pooled sample, the area under the curve for plasma leucine and the sum of branched-chain amino acids was significantly greater in EAA and COM compared with RE. For intramyocellular signaling, significant main effects were found for condition (mTOR (Ser2481), rpS6 (Ser235/236)) and age (S6K1 (Thr421/Ser424), 4E-BP1 (Thr37/46)) in age group analyses. The phosphorylation of rpS6 was of similar magnitude (~8-fold) in pooled and age group data 2 h following COM. Our findings suggest that a gel-based, leucine-enriched EAA supplement is associated with aminoacidemia and a muscle anabolic signaling response, thus representing an effective means of stimulating muscle protein anabolism in younger and older adults following EAA and COM.

Pre-sleep casein protein ingestion: new paradigm in post-exercise recovery nutrition

PURPOSE

Milk is a commonly ingested post-exercise recovery protein source. Casein protein, found in milk, is characterized by its slow digestion and absorption. Recently, several studies have been conducted with a focus on how pre-sleep casein protein intake could affect post-exercise recovery but our knowledge of the subject remains limited. This review aimed at presenting and discussing how pre-sleep casein protein ingestion affects post-exercise recovery and the details of its potential effector mechanisms.

METHODS

We systematically reviewed the topics of 1) casein nutritional characteristics, 2) pre-sleep casein protein effects on post-exercise recovery, and 3) potential effector mechanisms of pre-sleep casein protein on post-exercise recovery, based on the currently available published studies on pre-sleep casein protein ingestion.

RESULTS

Studies have shown that pre-sleep casein protein ingestion (timing: 30 minutes before sleep, amount of casein protein ingested: 40-48 g) could help post-exercise recovery and positively affect acute protein metabolism and exercise performance. In addition, studies have suggested that repeated pre-sleep casein protein ingestion for post-exercise recovery over a long period might also result in chronic effects that optimize intramuscular physiological adaptation (muscle strength and muscle hypertrophy). The potential mechanisms of pre-sleep casein protein ingestion that contribute to these effects include the following: 1) significantly increasing plasma amino acid availability during sleep, thereby increasing protein synthesis, inhibiting protein breakdown, and achieving a positive protein balance; and 2) weakening exercise-induced muscle damage or inflammatory responses, causing reduced muscle soreness. Future studies should focus on completely elucidating these potential mechanisms.

CONCLUSION

In conclusion, post-exercise ingestion of at least 40 g of casein protein, approximately 30 minutes before sleep and after a bout of resistance exercise in the evening, might be an effective nutritional intervention to facilitate muscle recovery.

No Significant Differences in Muscle Growth and Strength Development When Consuming Soy and Whey Protein Supplements Matched for Leucine Following a 12 Week Resistance Training Program in Men and Women: A Randomized Trial

There are conflicting reports regarding the efficacy of plant versus animal-derived protein to support muscle and strength development with resistance training. The purpose of this study was to determine whether soy and whey protein supplements matched for leucine would comparably support strength increases and muscle growth following 12 weeks of resistance training. Sixty-one untrained young men (n = 19) and women (n = 42) (18-35 year) enrolled in this study, and 48 completed the trial (17 men, 31 women). All participants engaged in supervised resistance training 3×/week and consumed 19 grams of whey protein isolate or 26 grams of soy protein isolate, both containing 2 g (grams) of leucine. Multi-level modeling indicated that total body mass (0.68 kg; 95% CI: 0.08, 1.29 kg; p < 0.001), lean body mass (1.54 kg; 95% CI: 0.94, 2.15 kg; p < 0.001), and peak torque of leg extensors (40.27 Nm; 95% CI: 28.98, 51.57 Nm, p < 0.001) and flexors (20.44 Nm; 95% CI: 12.10, 28.79 Nm; p < 0.001) increased in both groups. Vastus lateralis muscle thickness tended to increase, but this did not reach statistical significance (0.12 cm; 95% CI: -0.01, 0.26 cm; p = 0.08). No differences between groups were observed (p > 0.05). These data indicate that increases in lean mass and strength in untrained participants are comparable when strength training and supplementing with soy or whey matched for leucine.

Sarcopenia: A Contemporary Health Problem among Older Adult Populations

Sarcopenia, a geriatric disease characterized by a progressive loss of skeletal muscle mass and loss of muscle function, constitutes a rising, often undiagnosed health problem. Its prevalence in the elderly population is largely considered variable, as it ranges from 5% to 50% depending on gender, age, pathological conditions as well as diagnostic criteria. There is no one unified approach of treatment or assessment, which makes sarcopenia even harder to assess. There is a pressing need to provide better diagnosis, diagnostics, prevention, and individualized health care. Physical activity and nutrition are the main studied ways to prevent sarcopenia, and they also offer better outcomes. This review aims to report the prevalence of sarcopenia in older adults, its etiology, prevention, and treatment techniques.

Anti-Fatigue Effect of Prunus Mume Vinegar in High-Intensity Exercised Rats

Nowadays, new types of vinegar have been developed using various raw materials and biotechnological processes. The fruit of Prunus mume has been extensively distributed in East Asia and used as a folk medication for fatigue. In this study, the Prunus mume vinegar (PV) was produced by a two-step fermentation and was evaluated for its anti-fatigue activity by C2C12 myoblasts and high-intensity exercised rats. The administration of PV significantly improved running endurance and glycogen accumulation in the liver and muscle of PV supplemented rats compared to sedentary and exercised control groups. In addition, PV supplementation elicited lower fatigue-related serum biomarkers, for instance, ammonia, inorganic phosphate, and lactate. PV administered rats exhibited higher lactate dehydrogenase activity and glutathione peroxidase activity, and lower creatine kinase activity and malondialdehyde levels. Furthermore, phenolic compounds in PV were identified using HPLC analysis. The phenolic acids analyzed in PV were protocatechuic acid, syringic acid, chlorogenic acid, and its derivates. These results indicate that the administration of PV with antioxidative property contributes to the improvement of fatigue recovery in exhausted rats. The findings of this study suggest that the PV containing various bioactive constituents can be used as a functional material against fatigue caused by high-intensity exercise.

Nutrient-rich, high-quality, protein-containing dairy foods in combination with exercise in aging persons to mitigate sarcopenia

Sarcopenic declines in muscle mass and function contribute to the risk of falls, reduced mobility, and progression to frailty in older persons. Mitigation of sarcopenia can be achieved by consumption of higher quality protein in sufficient quantities, which current research suggests are greater than the recommended intakes of approximately 0.8 g/kg bodyweight/d. In addition, higher levels of physical activity and participation in exercise to support cardiovascular fitness and musculoskeletal function work additively with protein in attenuating sarcopenia. This narrative review provides evidence to support a recommendation for per-meal protein targets in older persons that are underpinned by knowledge of muscle protein turnover. Based on work examining acute dose-responses of muscle protein synthesis (MPS) to protein, a proposed per-meal target for protein intakes is set at approximately 0.4-0.6 g protein/kg bodyweight/meal for older persons. Habitual patterns of dietary protein intake tend to emphasize a skewed protein distribution, which would not maximize muscle anabolism. Observational studies show that more even patterns of protein intake are associated with increased muscle mass and improved muscle function. A food-based approach to achieving these protein targets would be advantageous, and the nutrient density of the protein-containing foods would be particularly important for older persons. Dairy foods provide high-quality protein and contain several nutrients of concern for older persons. This brief review provides an overview of the science underpinning why dairy foods should be a point of nutritional emphasis for older persons. Practical suggestions are provided for implementation of dairy foods into dietary patterns to meet the protein and other nutrient targets for older persons.

A word of caution against excessive protein intake

Dietary protein is crucial for human health because it provides essential amino acids for protein synthesis. In addition, dietary protein is more satiating than carbohydrate and fat. Accordingly, many people consider the protein content when purchasing food and beverages and report 'trying to eat more protein'. The global market for protein ingredients is projected to reach approximately US$90 billion by 2021, largely driven by the growing demand for protein-fortified food products. This Perspective serves as a caution against the trend of protein-enriched diets and provides an evidence-based counterpoint that underscores the potential adverse public health consequences of high protein intake.

Epigenetic Mechanisms of Maternal Dietary Protein and Amino Acids Affecting Growth and Development of Offspring

Nutrients can regulate metabolic activities of living organisms through epigenetic mechanisms, including DNA methylation, histone modification, and RNA regulation. Since the nutrients required for early embryos and postpartum lactation are derived in whole or in part from maternal and lactating nutrition, the maternal nutritional level affects the growth and development of fetus and creates a profound relationship between disease development and early environmental exposure in the offspring's later life. Protein is one of the most important biological macromolecules, involved in almost every process of life, such as information transmission, energy processing and material metabolism. Maternal protein intake levels may affect the integrity of the fetal genome and alter DNA methylation and gene expression. Most amino acids are supplied to the fetus from the maternal circulation through active transport of placenta. Some amino acids, such as methionine, as dietary methyl donor, play an important role in DNA methylation and body's one-carbon metabolism. The purpose of this review is to describe effects of maternal dietary protein and amino acid intake on fetal and neonatal growth and development through epigenetic mechanisms, with examples in humans and animals.

Effects of Leucine-Enriched Whey Protein Supplementation on Physical Function in Post-Hospitalized Older Adults Participating in 12-Weeks of Resistance Training Program: A Randomized Controlled Trial

Age-related strength and muscle mass loss is further increased after acute periods of inactivity. To avoid this, resistance training has been proposed as an effective countermeasure, but the additional effect of a protein supplement is not so clear. The aim of this study was to examine the effect of a whey protein supplement enriched with leucine after resistance training on muscle mass and strength gains in a post-hospitalized elderly population. A total of 28 participants were included and allocated to either protein supplementation or placebo supplementation following resistance training for 12 weeks (2 days/week). Physical function (lower and upper body strength, aerobic capacity and the Short Physical Performance Battery (SPPB) test), mini nutritional assessment (MNA) and body composition (Dual X-ray Absorptiometry) were assessed at baseline and after 12 weeks of resistance training. Both groups showed improvements in physical function after the intervention (p < 0.01), but there were no further effects for the protein group (p > 0.05). Muscle mass did not improve after resistance training in either group (p > 0.05). In conclusion, 12 weeks of resistance training are enough to improve physical function in a post-hospitalized elderly population with no further benefits for the protein-supplemented group.

Effectiveness of Whey Protein Hydrolysate and Milk-Based Formulated Drinks on Recovery of Strength and Power Following Acute Resistance Exercise

Intensive resistance exercise can result in exercise-induced-muscle-damage, which commonly leads to reductions in acute muscle function. Post-exercise ingestion of carbohydrate-protein mixtures intends to attenuate these effects. This study aimed to compare the effectiveness of whey protein hydrolysate and milk-based formulated drinks on recovery of muscle function following resistance exercise. Thirty resistance-trained males were randomly assigned to either whey hydrolysate and dextrose drink (WH), milk-based drink (MB) or flavored-dextrose (CHO), and performed baseline assessments of perceived-muscle-soreness, the countermovement jump, the seated-medicine-ball throw and isokinetic assessment of the knee extensors and flexors maximal strength. Subsequently, participants performed resistance exercise consisting of various multi-joint barbell exercises. Following resistance exercise participants then consumed either WH (533 Kcal, 32.6 g Protein, 98.3 g Carbohydrate, 1.1 g Fat), MB (532 Kcal, 32.8 g Protein, 98.4 g Carbohydrate, 0.6 g Fat) or CHO (531 Kcal, 0 g Protein, 132.7 g Carbohydrate, 0 g Fat). All assessments were repeated 24 and 48 h post-resistance exercise. Muscle soreness was markedly increased at 24 h and 48 h in all groups (p < 0.001). However, for dynamic power measures (countermovement jump, seated-medicine-ball throw), CHO experienced a decrease for the countermovement jump only at 48 h, whereas WH and MB experienced significant decreases across the countermovement jump and the seated-medicine-ball throw (p < 0.05). All groups experienced significant decreases in isokinetic-extension torque at both 24 h and 48 h; however, flexion torque was decreased for CHO only at these time points (p < 0.05). Consumption of WH or MB did not enhance recovery of dynamic power-producing ability or soreness compared to CHO. Based on within-group effects WH and MB ingestion had seemingly marginal to small positive effects on recovery of isokinetic strength, however, there were no between-group differences for these variables.

Ketogenic Diet and Skeletal Muscle Hypertrophy: A Frenemy Relationship?

Ketogenic diet (KD) is a nutritional regimen characterized by a high-fat and an adequate protein content and a very low carbohydrate level (less than 20 g per day or 5% of total daily energy intake). The insufficient level of carbohydrates forces the body to primarily use fat instead of sugar as a fuel source. Due to its characteristic, KD has often been used to treat metabolic disorders, obesity, cardiovascular disease, and type 2 diabetes. Skeletal muscle constitutes 40% of total body mass and is one of the major sites of glucose disposal. KD is a well-defined approach to induce weight loss, with its role in muscle adaptation and muscle hypertrophy less understood. Considering this lack of knowledge, the aim of this review was to examine the scientific evidence about the effects of KD on muscle hypertrophy. We first described the mechanisms of muscle hypertrophy per se, and secondly, we discussed the characteristics and the metabolic function of KD. Ultimately, we provided the potential mechanism that could explain the influence of KD on skeletal muscle hypertrophy.

No Difference between Spray Dried Milk and Native Whey Supplementation with Strength Training

Background

A rapid digestibility and high leucine content are considered important for maximal stimulation of muscle protein synthesis. Consequently, with these properties, native whey may hold greater anabolic potential than milk, when supplemented in combination with strength training. Our aim was to compare the effects of supplementation with milk or native whey, during a 12-wk strength training period, on gains in muscle mass and strength in young adults.

Methods

In this double-blinded, randomized, controlled study a total of 40 untrained young men and women received two daily servings of either milk or native whey containing 20 g of protein, during a 12-wk strength training intervention. Muscle strength, lean mass, thigh muscle cross-sectional area, m. vastus lateralis thickness and muscle fiber cross-sectional area were assessed before and after the training period. In addition, the acute phosphorylation of the anabolic kinases p70S6K, 4E-BP1 and eEF-2 in response to a standardized workout and supplementation was investigated before and after the 12-wk training period.

Results

Muscle mass and strength increased, by all measures applied (5%–16%, P < 0.001), with no differences between groups (P > 0.25). p70S6K phosphorylation increased (~1000%, P < 0.02) 2 h after exercise in the untrained and trained state, but no differences in anabolic signaling were observed between supplements (P > 0.40). No correlation between these acute measures and changes in muscle mass or strength were observed.

Conclusion

Supplementation with milk or native whey during a 12-wk strength training period did not differentially affect muscle mass and strength in young untrained individuals.

Differential Stimulation of Post-Exercise Myofibrillar Protein Synthesis in Humans Following Isonitrogenous, Isocaloric Pre-Exercise Feeding

The aim of this study was to test the effects of two disparate isonitrogenous, isocaloric pre-exercise feeds on deuterium-oxide (D2O) derived measures of myofibrillar protein synthesis (myoPS) in humans. Methods: In a double-blind parallel group design, 22 resistance-trained men aged 18 to 35 years ingested a meal (6 kcal·kg-1, 0.8 g·kg-1 carbohydrate, 0.2 g·kg-1 fat) with 0.33 g·kg-1 nonessential amino acids blend (NEAA) or whey protein (WHEY), prior to resistance exercise (70% 1RM back-squats, 10 reps per set to failure, 25% duty cycle). Biopsies of M. vastus lateralis were obtained pre-ingestion (PRE) and +3 h post-exercise (POST). The myofibrillar fractional synthetic rate (myoFSR) was calculated via deuterium labelling of myofibrillar-bound alanine, measured by gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Pyr-IRMS). Data are a mean percentage change (95% CI). Results: There was no discernable change in myoFSR following NEAA (10(-5, 25) %, p = 0.235), whereas an increase in myoFSR was observed after WHEY (28 (13, 43) %, p = 0.003). Conclusions: Measured by a D2O tracer technique, a disparate myoPS response was observed between NEAA and WHEY. Pre-exercise ingestion of whey protein increased post-exercise myoPS, whereas a NEAA blend did not, supporting the use of NEAA as a viable isonitrogenous negative control.