A brief review of critical processes in exercise-induced muscular hypertrophy

International society of sports nutrition position stand: nutrition and weight cut strategies for mixed martial arts and other combat sports

Following an extensive literature review, the International Society of Sports Nutrition (ISSN) has developed an official position on nutritional and weight cut strategies for combat sports. The type of combat sport, length of the fight camp, and time between weigh-in and competition are factors influencing nutritional and weight cut strategies. The following 16 points constitute the Position Statement of the Society; the Research Committee has approved them. 1. Combat sports have differing weight categories, official weigh-in times, and competition frequencies, influencing the nutritional and weight cut strategies for training and competition. 2. As the duration of a combat match increases, >4 min, contribution of the aerobic system can rise to >70%, yet anaerobic alactic pathways and anaerobic glycolytic pathways support high-output bursts. 3. During the off camp/general preparation phase, athletes should maintain a weight ranging 12% to 15% above the weight division requirement. 4. Supplements including creatine, beta-alanine, beta-hydroxy-beta-methylbutyrate, and caffeine have been shown to enhance performance and/or recovery during preparation phases, competition, and post-competition. 5. During fight camp, strategic decreases in calorie intake are necessary for an efficient longitudinal weight descent. Individual caloric needs can be determined using indirect calorimetry or validated equations such as Mifflin St. Jeor or Cunningham. 6. Protein should be prioritized during longitudinal weight descents to preserve lean body mass, and the timely delivery of carbohydrates supports training demands. Macronutrients should not drop below the following: carbohydrates 3.0-4.0 g/kg, protein 1.2-2.0 g/kg, and fat 0.5 to 1.0 g/kg/day. 7. Suitable losses in body mass range from 6.7% at 72 h, 5.7% at 48 h, and 4.4% at 24 h, prior to weigh-in. 8. Sodium restriction and water loading are effective for inducing polyuria and acute water loss. 9. During fight week, water-bound glycogen stores can be depleted through exercise and carbohydrate restriction, facilitating a 1% to 2% loss in body mass, with equivalent losses from a low-fiber intake of <10 g/day for 4 days. 10. During fight week, acute water loss strategies, including sauna, hot water immersion, and mummy wraps, can be used effectively with appropriate supervision (optimally ~2-4% of body mass within 24 h of weigh-in). 11. Post-weigh-in, rapid weight gain strategies are utilized to recover lost body fluid/mass before competition with the intent of gaining a competitive advantage. 12. Oral rehydration solutions (1 to 1.5 liters/h) combined with a sodium range of 50-90 mmol/dL should take precedence immediately post-weigh-in. 13. Fast-acting carbohydrates at a tolerable rate of ≤ 60 g/h should follow oral rehydration solutions. Post weigh-in intake of fiber should be limited to avoid gastrointestinal distress. 14. Post-weigh-in carbohydrate intake at 8-12 g/kg may be appropriate for combat athletes that undertook significant glycogen depletion strategies during fight week. About 4-7 g/kg may be suitable for modest carbohydrate restriction. 15. Post weigh-in, rehydration/refueling protocols should aim to regain ≥10% of body mass to mitigate declines in performance and the negative effects of rapid weight loss. 16. The long-term effects of frequent weight cuts on health and performance are unknown, necessitating further research.

Are plant-based and omnivorous diets the same for muscle hypertrophy? A narrative review of possible challenges of plant-based diets in resistance-trained athletes

This narrative review examines the potential challenges associated with plant-based diets in supporting muscle hypertrophy among resistance-trained athletes. Contrary to common assumptions, current evidence suggests that plant-based diets, when properly planned, can provide protein comparable to omnivorous diets. However, plant-based proteins are generally considered less anabolic due to lower digestibility, essential amino acid (EAA) content, and particularly lower leucine levels. The review discusses challenges and solutions for athletes aiming to maximize hypertrophy through plant-based diets, while highlighting the need for more robust research on advanced resistance-trained athletes.

Impact of Overnight Fasted State Versus Fed State on Adaptations to Resistance Training: A Randomized Clinical Trial

The aim was to verify the effects of 12 weeks of resistance training (RT) performed in the fasted state compared with the fed state on body composition and physical performance in young adults. Participants were randomly assigned into fasting RT group (Fast-RT, n = 15) and fed RT group (Fed-RT, n = 13). Both groups trained two weekly resistance exercise sessions after an overnight fast or between 1 and 2 hr after consumption of a carbohydrate-rich meal, associated with isocaloric nutritional guidance. Assessments of body composition (dual-energy X-ray absorption), quadriceps muscle thickness (ultrasonography), maximum dynamic strength (one repetition maximum test), and muscle power in bench press and knee-extension exercises were performed before and after 12 weeks of intervention. Both Fast-RT and Fed-RT groups showed increases (p time ≤ .01) in quadriceps muscle thickness (1.21 and 1.18 cm, respectively; p group = .371; p Group × Time = .871), maximum dynamic strength (bench press: 10.53 and 4.89 kg, respectively; p group = .251; p Group × Time = .268; knee extension: 28.53 and 29.31 kg, respectively; p group = .919; p Group × Time = .846), and muscle power (knee extension mean power 70% one repetition maximum: 59.28 and 46.21 W, respectively; p group = .833; p Group × Time = .616; knee extension maximal power 70% one repetition maximum: 100.65 and 54.76 W, respectively; p group = .812; p Group × Time = .409). Regardless of food consumption prior to the sessions (fasted state and fed state), RT performed twice weekly across 12 weeks was associated with improvements in muscle hypertrophy and neuromuscular performance in young adults.

Skeletal Muscle: A Critical Organ for Survival and Recovery in Critical Illness

The intensive care unit (ICU) environment is one of the most challenging for skeletal muscle health. Atrophy associated with clinical care is distinct from that seen with inactivity or immobilization in the absence of disease and is exacerbated by aging. The substantial muscle loss in the ICU is likely due to the presence of inflammation, elevated proteolysis, bedrest, and undernutrition. Skeletal muscle parameters at admission are predictive of mortality and other clinically important outcomes. Treatment goals to mitigate muscle loss are early mobilization and adequate nutrient supply, especially protein, using an individualized approach to support skeletal muscle maintenance and recovery.

Recycle, repair, recover: the role of autophagy in modulating skeletal muscle repair and post-exercise recovery

Skeletal muscle is a highly plastic tissue that can adapt relatively rapidly to a range of stimuli. In response to novel mechanical loading, e.g. unaccustomed resistance exercise, myofibers are disrupted and undergo a period of ultrastructural remodeling to regain full physiological function, normally within 7 days. The mechanisms that underpin this remodeling are believed to be a combination of cellular processes including ubiquitin-proteasome/calpain-mediated degradation, immune cell infiltration, and satellite cell proliferation/differentiation. A relatively understudied system that has the potential to be a significant contributing mechanism to repair and recovery is the autophagolysosomal system, an intracellular process that degrades damaged and redundant cellular components to provide constituent metabolites for the resynthesis of new organelles and cellular structures. This review summarizes our current understanding of the autophagolysosomal system in the context of skeletal muscle repair and recovery. In addition, we also provide hypothetical models of how this system may interact with other processes involved in skeletal muscle remodeling and provide avenues for future research to improve our understanding of autophagy in human skeletal muscle.

Myogenic differentiation markers in muscle tissue after aerobic training

Aerobic training induces a myriad of adaptations in muscle tissue, encompassing alterations in muscle fiber type composition, hypertrophy, and metabolic capacity. Understanding the potential role of myogenic differentiation markers (MDFs), such as Pax7, MyoD, Myogenin, and myosin heavy chain (MHC) isoforms, in mediating these adaptations is of paramount importance. The review delves into the intricate molecular mechanisms underlying the regulation of MDFs following aerobic training, elucidating the role of key signaling pathways including the MAPK/ERK, PI3K/Akt, and AMPK pathways, among others. These pathways play pivotal roles in orchestrating the expression and activity of MDFs, ultimately influencing muscle adaptation and regeneration. The comprehension of MDFs in the context of aerobic training is far-reaching, offering the potential for targeted interventions to optimize muscle adaptation and regeneration. This review identifies the need for further research to unveil the precise molecular mechanisms of the activation and interaction of myogenic differentiation markers with other signaling pathways, as well as to explore their potential as therapeutic targets for muscle-related conditions. This review article also provides a thorough analysis of MDFs in muscle tissue after aerobic training, highlighting their potential clinical implications and outlining future research directions in this area.

Photobiomodulation and aquatic training reduce TNF-α expression and enhance muscle fiber area in Wistar rats with compensatory hypertrophy

This study aims to assess the effects of aquatic training (AT) and its combination with photobiomodulation (PBM) on cytokine synthesis and plantar muscle morphology during compensatory hypertrophy (H) in Wistar rats. H was induced by bilateral ablation of synergistic muscles, and PBM using a laser (780 nm). AT involved 60 min sessions, 5 times/week, for 7 and 14 days. Muscle weight relative to body weight did not differ significantly between groups. TNF-α synthesis levels decreased in the H + AT + PBM group at 7 days compared to H Control. IL-6 and IL-1β levels showed no significant changes. Cross-sectional area (CSA) was higher in H + AT + PBM at 7 days and 14 days compared to H + AT and H Control. Fiber diameter increased in H + AT and H + AT + PBM compared to H at 14 days. AT with PBM decreased TNF-α expression, increased CSA and fiber diameter, whereas AT alone increased fiber diameter. In conclusion, the combination of photobiomodulation (PBM) therapy and aquatic training (AT) effectively reduced TNF-α levels while increasing muscle fiber diameter and cross-sectional area (CSA). Furthermore, AT alone demonstrated the capacity to maintain fiber diameter.

Dileucine ingestion, but not leucine, increases lower body strength and performance following resistance training: A double-blind, randomized, placebo-controlled trial

BACKGROUND

The essential amino acid leucine (LEU) plays a crucial role in promoting resistance-training adaptations. Dileucine (DILEU), a LEU-LEU dipeptide, increases MPS rates, however its impact on resistance training outcomes remains unexplored. This study assessed the effects of DILEU supplementation on resistance training adaptations.

METHODS

Using a randomized, double-blind, placebo-controlled approach, 34 resistance-trained males (age: 28.3 ± 5.9 years) consumed 2 grams of either DILEU monohydrate (RAMPS™, Ingenious Ingredients, L.P.), LEU, or placebo (PLA) while following a 4-day per week resistance training program for 10 weeks. Changes in body composition, 1-repetition maximum (1RM) and repetitions to failure (RTF) for leg press (LP) and bench press (BP), anaerobic capacity, countermovement jump (CMJ), and maximal voluntary contraction (MVC) were assessed after 0 and 10 weeks.

RESULTS

Significant main effects for time (p < 0.001) were realized for LP and BP 1RM and RTF. A significant group × time interaction was identified for changes in LP 1RM (p = 0.02) and LP RTF (p = 0.03). Greater increases in LP 1RM were observed in DILEU compared to PLA (p = 0.02; 95% CI: 5.8, 73.2 kg), and greater increases in LP RTF in DILEU compared to LEU (p = 0.04; 95% CI: 0.58, 20.3 reps). No significant differences were found in other measures.

CONCLUSIONS

DILEU supplementation at 2 grams daily enhanced lower body strength and muscular endurance in resistance-trained males more effectively than LEU or PLA. These findings suggest DILEU as a potentially effective supplement for improving adaptations to resistance training. NCT06121869 retrospectively registered.

Exploring the utility of ultrasound to assess disuse atrophy in different muscles of the lower leg

BACKGROUND

Skeletal muscle is a highly plastic tissue crucial for many functions associated with whole-body health across the life course. Magnetic resonance imaging (MRI) is the current gold standard for measuring skeletal muscle size. However, MRI is expensive, and access to facilities is often limited. B-mode ultrasonography (U/S) has been proposed as a potential alternative to MRI for the assessment of muscle size. However, to date, no work has explored the utility of U/S to assess disuse muscle atrophy (DMA) across muscles with different atrophy susceptibility profiles, an omission which may limit the clinical application of previous work.

METHODS

To address this significant knowledge gap, 10 young men (22 ±  years, 24.1 ± 2.3 kg/m2) underwent 15-day unilateral leg immobilization using a knee-brace and air boot. Cross-sectional area (CSA) and muscle thickness (MT) of the tibialis anterior (TA) and medial gastrocnemius (MG) were assessed via U/S before and after immobilization, with CSA and muscle volume assessed via MRI.

RESULTS

With both muscles combined, there were good correlations between each U/S and MRI measure, both before (e.g., CSAMRI vs. MTU/S and CSAU/S: r = 0.88 and 0.94, respectively, both P < 0.0001) and after (e.g., VOLMRI vs. MTU/S and CSAU/S: r = 0.90 and 0.96, respectively, both P < 0.0001) immobilization. The relationship between the methods was notably stronger for MG than TA at each time-point (e.g., CSAMRI vs. MTU/S: MG, r = 0.70, P = 0.0006; TA, r = 0.37, P = 0.10). There was no relationship between the degree of DMA determined by the two methods in either muscle (e.g., TA pre- vs. post-immobilization, VOLMRI: 136 ± 6 vs. 133 ± 5, P = 0.08; CSAU/S: 6.05 ± 0.3 vs. 5.92 ± 0.4, P = 0.70; relationship between methods: r = 0.12, P = 0.75).

CONCLUSIONS

Both MTU/S and CSAU/S provide comparable static measures of lower leg muscle size compared with MRI, albeit with weaker agreement in TA compared to MG. Although both MTU/S and CSAU/S can discern differences in DMA susceptibility between muscles, neither can reliably assess degree of DMA. Based on the growing recognition of heterogeneous atrophy profiles between muscles, and the topical importance of less commonly studied muscles (i.e., TA for falls prevention in older adults), future research should aim to optimize accessible methods to determine muscle losses across the body.

The biphasic activity of autophagy and heat shock protein response in peripheral blood mononuclear cells following acute resistance exercise in resistance-trained males

PURPOSE

Autophagy and heat shock protein (HSP) response are proteostatic systems involved in the acute and adaptive responses to exercise. These systems may upregulate sequentially following cellular stress including acute exercise, however, currently few data exist in humans. This study investigated the autophagic and HSP responses to acute intense lower body resistance exercise in peripheral blood mononuclear cells (PBMCs) with and without branched-chain amino acids (BCAA) supplementation.

METHODS

Twenty resistance-trained males (22.3 ± 1.5 yr; 175.4 ± .7 cm; 86.4 ± 15.6 kg) performed a bout of intense lower body resistance exercise and markers of autophagy and HSP70 were measured immediately post- (IPE) and 2, 4, 24, 48, and 72 h post-exercise. Prior to resistance exercise, 10 subjects were randomly assigned to BCAA supplementation of 0.22 g/kg/d for 5 days pre-exercise and up to 72 h following exercise while the other 10 subjects consumed a placebo (PLCB).

RESULTS

There were no difference in autophagy markers or HSP70 expression between BCAA and PLCB groups. LC3II protein expression was significantly lower 2 and 4 h post-exercise compared to pre-exercise. LC3II: I ratio was not different at any time point compared to pre-exercise. Protein expression of p62 was lower IPE, 2, and 4 h post-exercise and elevated 24 h post-exercise. HSP70 expression was elevated 48 and 72 h post-exercise.

CONCLUSIONS

Autophagy and HSP70 are upregulated in PBMCs following intense resistance exercise with autophagy increasing initially post-exercise and HSP response in the latter period. Moreover, BCAA supplementation did not affect this response.

Nutritional strategies for improving sarcopenia outcomes in older adults: A narrative review

Sarcopenia is characterized by a decline in muscle strength, generalized loss of skeletal muscle mass, and impaired physical performance, which are common outcomes used to screen, diagnose, and determine severity of sarcopenia in older adults. These outcomes are associated with poor quality of life, increased risk of falls, hospitalization, and mortality in this population. The development of sarcopenia is underpinned by aging, but other factors can lead to sarcopenia, such as chronic diseases, physical inactivity, inadequate dietary energy intake, and reduced protein intake (nutrition-related sarcopenia), leading to an imbalance between muscle protein synthesis and muscle protein breakdown. Protein digestion and absorption are also modified with age, as well as the reduced capacity of metabolizing protein, hindering older adults from achieving ideal protein consumption (i.e., 1-1.5 g/kg/day). Nutritional supplement strategies, like animal (i.e., whey protein) and plant-based protein, leucine, and creatine have been shown to play a significant role in improving outcomes related to sarcopenia. However, the impact of other supplements (e.g., branched-chain amino acids, isolated amino acids, and omega-3) on sarcopenia and related outcomes remain unclear. This narrative review will discuss the evidence of the impact of these nutritional strategies on sarcopenia outcomes in older adults.

Resistance Exercise and Skeletal Muscle-Related Outcomes in Patients with Cancer: A Systematic Review

BACKGROUND

Skeletal muscle loss is prevalent throughout the cancer continuum and correlated with morbidity and mortality. Resistance exercise has been trialed to mitigate skeletal muscle loss. This systematic review summarizes and qualitatively synthesizes the effects of resistance exercise on muscle-related outcomes in adult cancer populations, including skeletal muscle mass, performance and muscle-related biomarkers.

METHODS

The systematic review protocol was developed in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P). We searched electronic databases including AMED, CENTRAL, CINAHL, CIRRIE, EMBASE, MEDLINE, PEDro, REHABDATA, Scopus, and SPORTDiscus from inception to December 2021. We included randomized controlled trials that investigated the effects of resistance exercise on muscle-related outcomes in adult cancer populations. Interventions that involved any resistance exercise were included. Muscle-related outcomes were categorized as skeletal muscle mass (e.g., lean mass, appendicular muscle mass), muscle performance (e.g., muscle strength, physical function), and muscle-related biomarkers (e.g., muscle cells, metabolic/inflammatory markers). Risk of bias (RoB) was assessed using the Cochrane ROB tool.

RESULTS

A total of 102 studies from 101 randomized controlled trials were included. The majority of studies focused on breast cancer (46%) and those who completed treatment (43%). Resistance exercise interventions were largely 3-4 months long (48%), combined with aerobic exercise (56%), at a vigorous intensity (25%), and in-person/supervised settings (57%). Among the studies assessing muscle mass, performance, and biomarkers ( n = 42, 83, and 22, respectively), resistance exercise interventions improved upper/lower body or appendicular muscle mass (67%-100%), muscle strength (61%-68%), and physical function (74%-100%). Most biomarkers did not show significant changes (75%-100%) or showed inconsistent results.

CONCLUSIONS

Generally, resistance exercise had positive effects on skeletal muscle mass and performance with no negative effects compared to controls. Our findings demonstrated that resistance exercise may be an effective strategy to attenuate deterioration or exert improvements in muscle mass and performance outcomes.

Normative values for body composition in 22,191 healthy Norwegian adults 20-99 years: The HUNT4 study

BACKGROUND

Body mass, body mass index (BMI), and body composition components are essential for health and longevity. Considering the influence of demographic factors on body composition, there is a need for tailored reference values based on age-, sex-, and geography. We aimed to construct a comprehensive reference material on body composition in healthy Norwegian adults.

METHODS

In this cross-sectional study, we estimated age- and sex-specific reference values for body-, fat-, and muscle mass variables using multi-frequency bioelectrial impedance analysis (such as body fat percentage, skeletal muscle mass and visceral fat area) in 22,191 healthy adults aged 20-99 years participating in the Trøndelag Health Study 4 (HUNT4). We calculated the fat mass and skeletal muscle mass index as the total fat and muscle mass relative to height squared and used general linear models to explore the associations between physical activity (PA), BMI, and age.

RESULTS

With a BMI (kg/m2) of 25.4 (SD 5.1) and 26.0 (4.5) for women and men, respectively, the youngest age group (20-39 yrs) had a lower BMI compared to their counterparts aged 40-59 years (26.3 [4.5] and 27.5 [3.8]) and ≥ 60 years (25.7 [4.1] and 26.5 [3.4]), respectively. Those aged 20-39 years also had the lowest values for the different body fat variables measured. Fat mass index (kg/m2) was 8.41 (4.00) and 5.81 (3.29) for women and men aged 20-39 years, respectively, compared to 9.25 (3.21) and 6.86 (2.46) for those aged ≥60 years. The oldest age group had the lowest values for the various muscle mass variables; women and men aged 60+ years had a skeletal muscle mass index (kg/m2) of 8.91 (0.85) and 10.96 (1.00), respectively. Corresponding values for those aged 20-39 years were 9.33 (0.97) and 11.49 (1.15). For all age groups and both sexes, regular physical activity was associated with lower levels of fat mass, whereas the association between muscle mass and PAwas less conclusive. When using body fat percentage as an obesity measure, we observed a much higher obesity prevalence (41.2%) in the study population compared to BMI (17.3%).

CONCLUSIONS

Our study offers a comprehensive reference for body composition among healthy adults in Norway, aiding the identification of abnormal fat and muscle mass values across age groups. We also highlight that BMI often misclassifies individuals with adiposity levels in the overweight or obese category as lean. Therefore, incorporating body composition when defining obesity could enable early intervention to prevent cardiometabolic diseases.

Nuclear-localized androgen receptor content following resistance exercise training is associated with hypertrophy in males but not females

Androgen receptor (AR) content has been implicated in the differential response between high and low responders following resistance exercise training (RET). However, the influence of AR expression on acute skeletal muscle damage and whether it may influence the adaptive response to RET in females is poorly understood. Thus, the purpose of this exploratory examination was to 1) investigate changes in AR content during skeletal muscle repair and 2) characterize AR-mediated sex-based differences following RET. A skeletal muscle biopsy from the vastus lateralis was obtained from 26 healthy young men (n = 13) and women (n = 13) at baseline and following 300 eccentric kicks. Subsequently, participants performed 10 weeks of full-body RET and a final muscle biopsy was collected. In the untrained state, AR mRNA expression was associated with paired box protein-7 (PAX7) mRNA in males. For the first time in human skeletal muscle, we quantified AR content in the myofiber and localized to the nucleus where AR has been shown to trigger cellular outcomes related to growth. Upon eccentric damage, nuclear-associated AR (nAR) content increased (p < .05) in males and not females. Males with the greatest increase in cross-sectional area (CSA) post-RET had more (p < .05) nAR content than females with the greatest gain CSA. Collectively, skeletal muscle damage and RET increased AR protein, and both gene and hypertrophy measures revealed sex differences in relation to AR. These findings suggest that AR content but more importantly, nuclear localization, is a factor that differentiates RET-induced hypertrophy between males and females.

Investigating the Health Implications of Whey Protein Consumption: A Narrative Review of Risks, Adverse Effects, and Associated Health Issues

This narrative review critically examines the current research on the health implications of whey protein (WP) supplementation, with a focus on potential risks and adverse effects. WP, commonly consumed for muscle building and weight loss, has been associated with various health concerns. Our comprehensive analysis involved a thorough search of multiple databases, resulting in the inclusion of 21 preclinical and human studies that collectively offer a detailed overview of WP's health impacts. The review reveals significant findings, such as WP's potential link to liver and kidney damage, alterations in gut microbiota, increased acne incidence, impacts on bone mass, and emotional and behavioural changes. These findings underscore the complexity of WP's effects on human health, indicating both beneficial and detrimental outcomes in relation to different posologies in a variety of settings. Our study suggests caution for the protein intake in situations of hepatic and renal compromised functions, as well as in acne susceptibility, while possible beneficial effects can be achieved for the intestinal microbiota, humoral and behavioural level, and finally bone and muscle mass in elderly. We emphasizes the importance of balanced WP consumption and call for more in-depth research to understand its long-term health effects. Health professionals and individuals considering WP supplementation should be aware of these potential risks and approach its use with informed caution.

Dietary oleic acid intake increases the proportion of type 1 and 2X muscle fibers in mice

Skeletal muscle is one of the largest metabolic tissues in mammals and is composed of four different types of muscle fibers (types 1, 2A, 2X, and 2B); however, type 2B is absent in humans. Given that slow-twitch fibers are superior to fast-twitch fibers in terms of oxidative metabolism and are rich in mitochondria, shift of muscle fiber types in direction towards slower fiber types improves metabolic disorders and endurance capacity. We previously had reported that oleic acid supplementation increases type 1 fiber formation in C2C12 myotubes; however, its function still remains unclear. This study aimed to determine the effect of oleic acid on the muscle fiber types and endurance capacity. An in vivo mouse model was used, and mice were fed a 10% oleic acid diet for 4 weeks. Two different skeletal muscles, slow soleus muscle with the predominance of slow-twitch fibers and fast extensor digitorum longus (EDL) muscle with the predominance of fast-twitch fibers, were used. We found that dietary oleic acid intake improved running endurance and altered fiber type composition of muscles, the proportion of type 1 and 2X fibers increased in the soleus muscle and type 2X increased in the EDL muscle. The fiber type shift in the EDL muscle was accompanied by an increased muscle TAG content. In addition, blood triacylglycerol (TAG) and non-esterified fatty acid levels decreased during exercise. These changes suggested that lipid utilization as an energy substrate was enhanced by oleic acid. Increased proliferator-activated receptor γ coactivator-1β protein levels were observed in the EDL muscle, which potentially enhanced the fiber type transitions towards type 2X and muscle TAG content. In conclusion, dietary oleic acid intake improved running endurance with the changes of muscle fiber type shares in mice. This study elucidated a novel functionality of oleic acid in skeletal muscle fiber types. Further studies are required to elucidate the underlying mechanisms. Our findings have the potential to contribute to the field of health and sports science through nutritional approaches, such as the development of supplements aimed at improving muscle function.

Skeletal muscle mass in competitive physique-based athletes (bodybuilding, 212 bodybuilding, bikini, and physique divisions): A case series

OBJECTIVES

(1) To examine the muscle thickness of various muscle groups of the body to estimate the absolute and relative skeletal muscle mass (SM) in competitive physique-based athletes (Bodybuilding, 212 Bodybuilding, Bikini, and Physique divisions) and (2) to compare values across various divisions of competition and to resistance trained and non-resistance trained individuals.

METHODS

Eight competitive physique-based athletes (2 M and 6 F), two recreationally resistance trained (1 M and 1 F) and two non-resistance trained (1 M and 1 F) participants had muscle thickness measured by ultrasound at nine sites on the anterior and posterior aspects of the body. SM was estimated from an ultrasound-derived prediction equation and SM index was used to adjust for the influence of standing height (i.e., divided by height squared).

RESULTS

SM values ranged from 19.6 to 60.4 kg in the eight competitive physique-based athletes and 16.1 to 32.6 kg in the four recreationally resistance trained and non-resistance trained participants. SM index ranged from 7.2 to 17.9 kg/m2 in the eight competitive physique-based athletes and 5.8 to 9.3 kg/m2 in the four recreationally resistance trained and non-resistance trained participants.

CONCLUSION

Overall, varying magnitudes of SM and SM index were present across competitors and their respective divisions of bodybuilding. The Men's Open Bodybuilder in the present study had greater values of total SM and SM index compared to previously published values in the literature. Our data provides insight into the extent of SM present in this population and further extends the discussion regarding SM accumulation in humans.

Does the Paleo diet affect an athlete's health and sport performance?

The aim of the study was to assess the impact of an eight-week Paleo diet on the health status (body composition, haematology and biochemistry of blood and urine) and the level of physical capacity (aerobic and anaerobic) of professional handball players. Fifteen athletes were assigned to two groups: 9 in the experimental group (PD) and 6 in the control group (CD). Significant decreases in body mass (BM), body mass index (BMI), and fat mass (FM) as well as an increase in the fat-free mass (FFM) (%) in both groups were observed. There were no significant differences between groups in particular series during the experiment in all haematological and biochemical indicators of blood and urine. Only HDL-C was significantly higher in the last series in the PD compared to the CD (1.63 mmol/l vs. 1.23 mmol/l). In the Wingate test, there were only single intragroup changes, consisting of a significant decrease in the Wt, MAP and Pmean in the experimental group. There were no significant differences between the groups in individual series or intragroup differences during the experiment, determined by the VO2max, VEmax, VE ∙ VCO2 -1, RER, and the time of the test with a gradually increasing load on a treadmill, except for a significant decrease of maximum tidal volume (TVmax) in the PD. No adverse effect of the Paleo diet on the health status was found. The use of the Paleo diet slightly adversely affects anaerobic capacity and does not affect the level of aerobic capacity.

Physiology of sedentary behavior

Sedentary behaviors (SB) are characterized by low energy expenditure while in a sitting or reclining posture. Evidence relevant to understanding the physiology of SB can be derived from studies employing several experimental models: bed rest, immobilization, reduced step count, and reducing/interrupting prolonged SB. We examine the relevant physiological evidence relating to body weight and energy balance, intermediary metabolism, cardiovascular and respiratory systems, the musculoskeletal system, the central nervous system, and immunity and inflammatory responses. Excessive and prolonged SB can lead to insulin resistance, vascular dysfunction, shift in substrate use toward carbohydrate oxidation, shift in muscle fiber from oxidative to glycolytic type, reduced cardiorespiratory fitness, loss of muscle mass and strength and bone mass, and increased total body fat mass and visceral fat depot, blood lipid concentrations, and inflammation. Despite marked differences across individual studies, longer term interventions aimed at reducing/interrupting SB have resulted in small, albeit marginally clinically meaningful, benefits on body weight, waist circumference, percent body fat, fasting glucose, insulin, HbA1c and HDL concentrations, systolic blood pressure, and vascular function in adults and older adults. There is more limited evidence for other health-related outcomes and physiological systems and for children and adolescents. Future research should focus on the investigation of molecular and cellular mechanisms underpinning adaptations to increasing and reducing/interrupting SB and the necessary changes in SB and physical activity to impact physiological systems and overall health in diverse population groups.

Exploring the Potential of Olive Flounder Processing By-Products as a Source of Functional Ingredients for Muscle Enhancement

Olive flounder (OF) is a widely aqua-cultivated and recognized socioeconomic resource in Korea. However, more than 50% of by-products are generated when processing one OF, and there is no proper way to utilize them. With rising awareness and interest in eco-friendly bio-materialization recycling, this research investigates the potential of enzymatic hydrolysis of OF by-products (OFB) to produce functional ingredients. Various enzymatic hydrolysates of OFB (OFBEs) were generated using 11 commercial enzymes. Among them, Prozyme 2000P-assisted OFBE (OFBP) exhibited the highest protein content and yield, as well as low molecularization. The muscle regenerative potential of OFBEs was evaluated using C2C12 myoblasts, revealing that OFBP positively regulated myoblast differentiation. In an in vitro Dex-induced myotube atrophy model, OFBP protected against muscle atrophy and restored myotube differentiation and Dex-induced reactive oxygen species (ROS) production. Furthermore, zebrafish treated with OFBEs showed improved locomotor activity and body weight, with OFBP exhibiting outstanding restoration in the Dex-induced muscle atrophy zebrafish in vivo model. In conclusion, OFBEs, particularly OFBP, produce hydrolysates with enhanced physiological usability and muscle regenerative potential. Further research on its industrial application and mechanistic insights is needed to realize its potential as a high-quality protein food ingredient derived from OF processing by-products.

Thyroid Hormone Regulates the Lipid Content of Muscle Fibers, Thus Affecting Physical Exercise Performance

Skeletal muscle (SkM) lipid composition plays an essential role in physiological muscle maintenance and exercise performance. Thyroid hormones (THs) regulate muscle formation and fuel energy utilization by modulating carbohydrates and lipid and protein metabolism. The best-known effects of THs in SkM include the promotion of mitochondrial biogenesis, the fiber-type switch from oxidative to glycolytic fibers, and enhanced angiogenesis. To assess the role of THs on the lipidic composition of SkM fibers, we performed lipidomic analyses of SkM cells and tissues, glucose tolerance experiments, and exercise performance tests. Our data demonstrated that TH treatment induces remodeling of the lipid profile and changes the proportion of fatty acids in SkM. In brief, THs significantly reduced the ratio of stearic/oleic acid in the muscle similar to what is induced by physical activity. The increased proportion of unsaturated fatty acids was linked to an improvement in insulin sensitivity and endurance exercise. These findings point to THs as critical endocrine factors affecting exercise performance and indicate that homeostatic maintenance of TH signals, by improving cell permeability and receptor stability at the cell membrane, is crucial for muscle physiology.

Comparison of Traditional and Advanced Resistance Training Paradigms on Muscle Hypertrophy in Trained Individuals: A Systematic Review and Meta-Analysis

Trained individuals may require variations in training stimuli and advanced resistance training paradigms (ADV) to increase skeletal muscle hypertrophy. However, no meta-analysis has examined how ADV versus traditional (TRAD) approaches may differentially affect hypertrophic outcomes in trained populations. The aim of this review was to determine whether the skeletal muscle hypertrophy responses induced by TRAD differed from ADV in resistance-trained individuals. Furthermore, we sought to examine potential effects of dietary factors, participants' training status, and training loads. We searched for peer-reviewed, randomized controlled trials (published in English) conducted in healthy resistance-trained adults performing a period of TRAD and ADV with pre-to-post measurement(s) of muscle hypertrophy in PubMed, Web of Science, SPORTDiscus, and MEDLINE databases up to October 2022. A formal meta-analysis was conducted in Revman5, and risk of bias was assessed by ROB2. Ten studies met the inclusion criteria. Results indicated no difference between ADV and TRAD for muscle thickness (SMD = 0.05, 95% CI: -0.20 0.29, p = 0.70), lean mass (SMD = -0.01, 95% CI: -0.26 0.23, p = 0.92), muscle cross-sectional area (SMD = -0.07, 95% CI: -0.36 0.22, p = 0.64), or all measurements analyzed together (SMD = -0.00, 95% CI: -0.15 0.14, p = 0.95). No heterogeneity or inconsistencies were observed; however, unclear risk of bias was present in most of the studies. Short-term ADV does not induce superior skeletal muscle hypertrophy responses when compared with TRAD in trained individuals. This review was not previously registered.

The molecular athlete: exercise physiology from mechanisms to medals

Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle function and exercise capacity encompass a broad spectrum, from inactive individuals with low levels of endurance and strength to elite athletes who produce prodigious performances underpinned by pleiotropic training-induced muscular adaptations. Our current understanding of the signal integration, interpretation, and output coordination of the cellular and molecular mechanisms that govern muscle plasticity across this continuum is incomplete. As such, training methods and their application to elite athletes largely rely on a "trial-and-error" approach, with the experience and practices of successful coaches and athletes often providing the bases for "post hoc" scientific enquiry and research. This review provides a synopsis of the morphological and functional changes along with the molecular mechanisms underlying exercise adaptation to endurance- and resistance-based training. These traits are placed in the context of innate genetic and interindividual differences in exercise capacity and performance, with special consideration given to aging athletes. Collectively, we provide a comprehensive overview of skeletal muscle plasticity in response to different modes of exercise and how such adaptations translate from "molecules to medals."

Molecular predictors of resistance training outcomes in young untrained female adults

We sought to determine if the myofibrillar protein synthetic (MyoPS) response to a naïve resistance exercise (RE) bout, or chronic changes in satellite cell number and muscle ribosome content, were associated with hypertrophic outcomes in females or differed in those who classified as higher (HR) or lower (LR) responders to resistance training (RT). Thirty-four untrained college-aged females (23.4 ± 3.4 kg/m2) completed a 10-wk RT protocol (twice weekly). Body composition and leg imaging assessments, a right leg vastus lateralis biopsy, and strength testing occurred before and following the intervention. A composite score, which included changes in whole body lean/soft tissue mass (LSTM), vastus lateralis (VL) muscle cross-sectional area (mCSA), midthigh mCSA, and deadlift strength, was used to delineate upper and lower HR (n = 8) and LR (n = 8) quartiles. In all participants, training significantly (P < 0.05) increased LSTM, VL mCSA, midthigh mCSA, deadlift strength, mean muscle fiber cross-sectional area, satellite cell abundance, and myonuclear number. Increases in LSTM (P < 0.001), VL mCSA (P < 0.001), midthigh mCSA (P < 0.001), and deadlift strength (P = 0.001) were greater in HR vs. LR. The first-bout 24-hour MyoPS response was similar between HR and LR (P = 0.367). While no significant responder × time interaction existed for muscle total RNA concentrations (i.e., ribosome content) (P = 0.888), satellite cell abundance increased in HR (P = 0.026) but not LR (P = 0.628). Pretraining LSTM (P = 0.010), VL mCSA (P = 0.028), and midthigh mCSA (P < 0.001) were also greater in HR vs. LR. Female participants with an enhanced satellite cell response to RT, and more muscle mass before RT, exhibited favorable resistance training adaptations.NEW & NOTEWORTHY This study continues to delineate muscle biology differences between lower and higher responders to resistance training and is unique in that a female population was interrogated. As has been reported in prior studies, increases in satellite cell numbers are related to positive responses to resistance training. Satellite cell responsivity, rather than changes in muscle ribosome content per milligrams of tissue, may be a more important factor in delineating resistance-training responses in women.

Pathophysiological Aspects of Muscle Atrophy and Osteopenia Induced by Chronic Constriction Injury (CCI) of the Sciatic Nerve in Rats

Skeletal muscle atrophy is a condition characterized by a loss of muscle mass and muscle strength caused by an imbalance between protein synthesis and protein degradation. Muscle atrophy is often associated with a loss of bone mass manifesting as osteoporosis. The aim of this study was to evaluate if chronic constriction injury (CCI) of the sciatic nerve in rats can be a valid model to study muscle atrophy and consequent osteoporosis. Body weight and body composition were assessed weekly. Magnetic resonance imaging (MRI) was performed on day zero before ligation and day 28 before sacrifice. Catabolic markers were assessed via Western blot and Quantitative Real-time PCR. After the sacrifice, a morphological analysis of the gastrocnemius muscle and Micro-Computed Tomography (Micro-CT) on the tibia bone were performed. Rats that underwent CCI had a lower body weight increase on day 28 compared to the naive group of rats (p < 0.001). Increases in lean body mass and fat mass were also significantly lower in the CCI group (p < 0.001). The weight of skeletal muscles was found to be significantly lower in the ipsilateral hindlimb compared to that of contralateral muscles; furthermore, the cross-sectional area of muscle fibers decreased significantly in the ipsilateral gastrocnemius. The CCI of the sciatic nerve induced a statistically significant increase in autophagic and UPS (Ubiquitin Proteasome System) markers and a statistically significant increase in Pax-7 (Paired Box-7) expression. Micro-CT showed a statistically significant decrease in the bone parameters of the ipsilateral tibial bone. Chronic nerve constriction appeared to be a valid model for inducing the condition of muscle atrophy, also causing changes in bone microstructure and leading to osteoporosis. Therefore, sciatic nerve constriction could be a valid approach to study muscle-bone crosstalk and to identify new strategies to prevent osteosarcopenia.

Nutritional Strategies in the Rehabilitation of Musculoskeletal Injuries in Athletes: A Systematic Integrative Review

It is estimated that three to five million sports injuries occur worldwide each year. The highest incidence is reported during competition periods with mainly affectation of the musculoskeletal tissue. For appropriate nutritional management and correct use of nutritional supplements, it is important to individualize based on clinical effects and know the adaptive response during the rehabilitation phase after a sports injury in athletes. Therefore, the aim of this PRISMA in Exercise, Rehabilitation, Sport Medicine and Sports Science PERSiST-based systematic integrative review was to perform an update on nutritional strategies during the rehabilitation phase of musculoskeletal injuries in elite athletes. After searching the following databases: PubMed/Medline, Scopus, PEDro, and Google Scholar, a total of 18 studies met the inclusion criteria (Price Index: 66.6%). The risk of bias assessment for randomized controlled trials was performed using the RoB 2.0 tool while review articles were evaluated using the AMSTAR 2.0 items. Based on the main findings of the selected studies, nutritional strategies that benefit the rehabilitation process in injured athletes include balanced energy intake, and a high-protein and carbohydrate-rich diet. Supportive supervision should be provided to avoid low energy availability. The potential of supplementation with collagen, creatine monohydrate, omega-3 (fish oils), and vitamin D requires further research although the effects are quite promising. It is worth noting the lack of clinical research in injured athletes and the higher number of reviews in the last 10 years. After analyzing the current quantitative and non-quantitative evidence, we encourage researchers to conduct further clinical research studies evaluating doses of the discussed nutrients during the rehabilitation process to confirm findings, but also follow international guidelines at the time to review scientific literature.

Dietary intakes and daily distribution patterns of macronutrients in youth soccer players

Introduction

There has been an abundance of dietary analysis research conducted on adult male soccer players, while studies on youth players are lacking. Furthermore, the daily distribution of energy and macronutrient intake throughout the day has been reported to influence training adaptations, but this is often not considered in the literature. This study aims to quantify daily energy and macronutrient intake and assess their distribution over 5 days, and compare daily energy intakes and predicted daily energy expenditure in under-16 male soccer players.

Methods

The sample included 25 soccer participants aged 14.8-15.7 years. Five-day self-reported food diaries were used to record the food/drink consumption. Intake was analyzed for total daily energy, macronutrient intakes, and distribution among meals (breakfast, lunch, dinner, and snacks). Daily energy expenditure was predicted by resting energy expenditure and physical activity levels developed for youth sports participants.

Results

The mean total energy intake was 1,928 ± 388 kcal∙day^-1, whereas the estimated daily energy expenditure was 3,568 kcal∙day^-1. Relative daily protein intakes were lower at breakfast, morning snack, afternoon snack, and night snack compared to lunch and dinner.

Discussion

Youth soccer players do not appear to meet energy requirements and daily CHO guidelines. Fluctuations in protein intake throughout the day were noted and may influence training adaptations (i.e., muscle protein synthesis and recovery).

Changes in vastus lateralis fibre cross-sectional area, pennation angle and fascicle length do not predict changes in muscle cross-sectional area

NEW FINDINGS

What is the central question of this study? Do changes in myofibre cross-sectional area, pennation angle and fascicle length predict vastus lateralis whole-muscle cross-sectional area changes following resistance training? What is the main finding and its importance? Changes in vastus lateralis mean myofibre cross-sectional area, fascicle length and pennation angle following a period of resistance training did not collectively predict changes in whole-muscle cross-sectional area. Despite the limited sample size in this study, these data reiterate that it remains difficult to generalize the morphological adaptations that predominantly drive tissue-level vastus lateralis muscle hypertrophy.

ABSTRACT

Myofibre hypertrophy during resistance training (RT) poorly associates with tissue-level surrogates of hypertrophy. However, it is underappreciated that, in pennate muscle, changes in myofibre cross-sectional area (fCSA), fascicle length (Lf ) and pennation angle (PA) likely coordinate changes in whole-muscle cross-sectional area (mCSA). Therefore, we determined if changes in fCSA, PA and Lf predicted vastus lateralis (VL) mCSA changes following RT. Thirteen untrained college-aged males (23 ± 4 years old, 25.4 ± 5.2 kg/m2 ) completed 7 weeks of full-body RT (twice weekly). Right leg VL ultrasound images and biopsies were obtained prior to (PRE) and 72 h following (POST) the last training bout. Regression was used to assess if training-induced changes in mean fCSA, PA and Lf predicted VL mCSA changes. Correlations were also performed between PRE-to-POST changes in obtained variables. Mean fCSA (+18%), PA (+8%) and mCSA (+22%) increased following RT (P < 0.05), but not Lf (0.1%, P = 0.772). Changes in fCSA, Lf and PA did not collectively predict changes in mCSA (R2 = 0.282, adjusted R2 = 0.013, F3,8  = 1.050, P = 0.422). Moderate negative correlations existed for percentage changes in PA and Lf (r = -0.548, P = 0.052) and changes in fCSA and Lf (r = -0.649, P = 0.022), and all other associations were weak (|r| < 0.500). Although increases in mean fCSA, PA and VL mCSA were observed, inter-individual responses for each variable and limitations for each technique make it difficult to generalize the morphological adaptations that predominantly drive tissue-level VL muscle hypertrophy. However, the small subject pool is a significant limitation, and more research in this area is needed.

Use It or Lose It? A Meta-Analysis on the Effects of Resistance Training Cessation (Detraining) on Muscle Size in Older Adults

This review aimed to explore the effect of resistance training cessation (detraining) on muscle size in older adults. Five databases were searched to find eligible studies. Their methodological quality was assessed using the PEDro checklist. The data were pooled in a random-effects meta-analysis. Six studies, with eight groups, were included in the review. Resistance training interventions lasted from 9 to 24 weeks. The detraining duration was from 12 to 52 weeks. Studies were classified as being of fair or good methodological quality. Compared to the baseline data, muscle size significantly increased following the resistance training intervention (Cohen's d: 0.99; 95% confidence interval: 0.63, 1.36). Compared to the post-resistance training data, there was a significant decrease in muscle size following training cessation (Cohen's d: -0.83; 95% confidence interval: -1.30, -0.36). In subgroup analyses, there was no significant decrease in muscle size following 12-24 weeks of training cessation (Cohen's d: -0.60; 95% confidence interval: -1.21, 0.01). There was a significant decrease in muscle size following 31-52 weeks of training cessation (Cohen's d: -1.11; 95% confidence interval: -1.75, -0.47). In summary, resistance training increases muscle size in older adults. In contrast, training cessation is associated with a decrease in muscle size. However, the loss of muscle size might be related to detraining duration, with greater muscle loss occurring during longer duration detraining periods. Future studies are required to establish the time course of muscle size changes during detraining in older adults.

The non-modifiable factors age, gender, and genetics influence resistance exercise

Muscle mass and force are key for movement, life quality, and health. It is well established that resistance exercise is a potent anabolic stimulus increasing muscle mass and force. The response of a physiological system to resistance exercise is composed of non-modifiable (i.e., age, gender, genetics) and modifiable factors (i.e., exercise, nutrition, training status, etc.). Both factors are integrated by systemic responses (i.e., molecular signaling, genetic responses, protein metabolism, etc.), consequently resulting in functional and physiological adaptations. Herein, we discuss the influence of non-modifiable factors on resistance exercise: age, gender, and genetics. A solid understanding of the role of non-modifiable factors might help to adjust training regimes towards optimal muscle mass maintenance and health.

The Role of Diets and Dietitians for Para-Athletes: A Pilot Study Based on Interviews

Efforts to provide nutrition support to para-athletes have not been established to date, and are far behind those established for athletes without disabilities. In the present study, we attempted to clarify the actual situation regarding dietary challenges of para-athletes. The aim of this study was to obtain clues to effective intervention methods that encourage the practice of sports nutrition. Six active elite para-athletes (30–70 years, four males) and a female physical therapist without physical disability participated in semi-structured interviews. All para-athletes had lower-limb disabilities and participated in the international wheelchair sports competitions (tennis, softball, and table tennis, with 2–26 years of player history). The interview items were on the ideal diet for improving competitive performance, evaluation of their typical diets, and the role of the dietitian as support. Responses obtained from participants were analyzed using quantitative content analysis by language analysis software. There are differences in the ideal diet based on the characteristics of the sport, but most participants believed that a nutritionally well-balanced diet with abundant vegetables was ideal for improving competitive performance. Para-athletes who use a wheelchair daily pay attention to their total calorie intake, because gaining weight is a critical issue for operating their wheelchairs and transferring themselves to and from their wheelchairs. Despite their world-class competition levels, none of them received routine dietary advice from dietitians. Some para-athletes did not even feel the need to engage with dietitians. Even for these para-athletes at a high level of competition, the “ideal diet” they considered was not always the optimal diet for improving their competitive performance. In addition, there are various barriers to practicing their optimal diet due to disability characteristics. Dietitians need to understand these barriers, their concerns and conflicts, and how to help them plan the optimal diet to improve their performance and maintain overall health.

The health effects of soy: A reference guide for health professionals

Soy is a hotly debated and widely discussed topic in the field of nutrition. However, health practitioners may be ill-equipped to counsel clients and patients about the use of soyfoods because of the enormous, and often contradictory, amount of research that has been published over the past 30 years. As interest in plant-based diets increases, there will be increased pressure for practitioners to gain a working knowledge of this area. The purpose of this review is to provide concise literature summaries (400-500 words) along with a short perspective on the current state of knowledge of a wide range of topics related to soy, from the cholesterol-lowering effects of soy protein to the impact of isoflavones on breast cancer risk. In addition to the literature summaries, general background information on soyfoods, soy protein, and isoflavones is provided. This analysis can serve as a tool for health professionals to be used when discussing soyfoods with their clients and patients.

Targeting skeletal muscle mitochondrial health in obesity

Metabolic demands of skeletal muscle are substantial and are characterized normally as highly flexible and with a large dynamic range. Skeletal muscle composition (e.g., fiber type and mitochondrial content) and metabolism (e.g., capacity to switch between fatty acid and glucose substrates) are altered in obesity, with some changes proceeding and some following the development of the disease. Nonetheless, there are marked interindividual differences in skeletal muscle composition and metabolism in obesity, some of which have been associated with obesity risk and weight loss capacity. In this review, we discuss related molecular mechanisms and how current and novel treatment strategies may enhance weight loss capacity, particularly in diet-resistant obesity.

Effects of Protein Supplementation Associated with Resistance Training on Body Composition and Muscle Strength in Older Adults: A Systematic Review of Systematic Reviews with Meta-analyses

BACKGROUND

There are some controversial findings regarding the benefits of combining protein supplementation with resistance training in order to optimize adaptations to training in older adults.

OBJECTIVE

The aim of this review was to summarize the evidence from meta-analyses assessing the effects of protein supplementation combined with resistance training on body composition and muscle strength in the older population.

METHODS

We included systematic reviews with meta-analyses of randomized clinical trials that examined the effects of protein and/or amino acid supplementation associated with resistance training compared with resistance training alone on lean body mass, muscle mass, and muscle strength in older people. The search was performed using the MEDLINE (PubMed), Embase, Cochrane Database of Systematic Reviews, Google Scholar, and OpenGrey databases. Methodological quality was assessed using the Assessing the Methodological Quality of Systematic Reviews 2 checklist, and the quality of evidence was determined using the Grading of Recommendations Assessment, Development and Evaluation system. The pooled effect estimates were computed from the standardized mean difference and the 95% confidence interval achieved by each meta-analysis, using random effects models.

RESULTS

Five reviews were included, all of moderate methodological quality. In the analyses, protein supplementation combined with resistance training was associated with greater increases in lean body mass and muscle mass when compared with resistance training alone. However, no differences were observed between the interventions on muscle strength increases. The quality of evidence ranged from moderate to very low.

CONCLUSION

Protein supplementation associated with resistance training induces greater increases in lean body mass compared with resistance training alone. In addition, it is suggested that the use of protein supplementation enhances gains in muscle mass but does not promote greater increases in muscle strength.

Weight Gain Recommendations for Athletes and Military Personnel: a Critical Review of the Evidence

PURPOSE OF REVIEW

Sports nutrition guidelines typically state that athletes desiring weight gain follow a regimen that includes increasing energy intake by ~ 300-500 kcal/day with an emphasis on adequate protein and carbohydrate and judicious inclusion of energy-dense foods, in combination with rigorous resistance training. This regimen is thought to promote weekly gains of ~ 0.45 kg (1 lb), mostly as lean body mass (LBM). This review summarizes the evidence supporting these intentional weight gain regimens in athletes.

RECENT FINDINGS

Although some research has been conducted in the past 5 years, research on intentional weight gain is lacking. Currently, available data suggests that weekly weight gain of 0.45 kg (1 lb), primarily as LBM, may be difficult for some athletes to achieve. Available evidence, however, suggests that commonly recommended strategies to promote calorie surplus, including consuming larger portions, incorporating energy-dense foods, and prioritizing liquid over solid foods, may prove helpful.

Plant-based food patterns to stimulate muscle protein synthesis and support muscle mass in humans: a narrative review

The interest in a diet with a higher proportion of plant-based foods to animal-based foods is a global food pattern trend. However, there are concerns regarding adopting plants as the main dietary protein source to support muscle protein synthesis and muscle mass. These concerns are centred on three issues: lower protein bioavailability due to antinutritional compounds in plants, lower per-serve scores of protein at similar energy intake, and amino acid scores of plants being lower than optimal. We aimed here to synthesize and discuss evidence around plant protein in human nutrition focusing on the capacity of these proteins to stimulate muscle protein synthesis as a key part of gaining or maintaining muscle mass. In this review, we address the issues of plant protein quality and provide evidence for how plant proteins can be made more effective to stimulate muscle protein synthesis and support muscle mass in partial or total replacement of consumption of products of animal origin. Novelty: ● Plant proteins are known, in general, to have lower protein quality scores than animal proteins, and this may have important implications, especially for those aiming to increase their skeletal muscle mass through exercise. ● A plant-based diet has been postulated to have lower protein quality limiting MPS responses and potentially compromising exercise-induced gains in muscle mass. ● Current evidence shows that plant proteins can stimulate MPS, as can whole foods, especially when combining food groups, increasing portion sizes, and optimizing amino acid bioavailability through processing or common preparation methods.

Ribosome accumulation during early phase resistance training in humans

Aim

To describe ribosome biogenesis during resistance training, its relation to training volume and muscle growth.

Methods

A training group (n = 11) performed 12 sessions (3‐4 sessions per week) of unilateral knee extension with constant and variable volume (6 and 3‐9 sets per session respectively) allocated to either leg. Ribosome abundance and biogenesis markers were assessed from vastus lateralis biopsies obtained at baseline, 48 hours after sessions 1, 4, 5, 8, 9 and 12, and after eight days of de‐training, and from a control group (n = 8). Muscle thickness was measured before and after the intervention.

Results

Training led to muscle growth (3.9% over baseline values, 95% CrI: [0.2, 7.5] vs. control) with concomitant increases in total RNA, ribosomal RNA, upstream binding factor (UBF) and ribosomal protein S6 with no differences between volume conditions. Total RNA increased rapidly in response to the first four sessions (8.6% [5.6, 11.7] per session), followed by a plateau and peak values after session 8 (49.5% [34.5, 66.5] above baseline). Total RNA abundance was associated with UBF protein levels (5.0% [0.2, 10.2] per unit UBF), and the rate of increase in total RNA levels predicted hypertrophy (0.3 mm [0.1, 0.4] per %‐point increase in total RNA per session). After de‐training, total RNA decreased (−19.3% [−29.0, −8.1]) without muscle mass changes indicating halted biosynthesis of ribosomes.

Conclusion

Ribosomes accumulate in the initial phase of resistance training with abundances sensitive to training cessation and associated with UBF protein levels. The average accumulation rate predicts muscle training‐induced hypertrophy.

Energy Requirements and Nutritional Strategies for Male Soccer Players: A Review and Suggestions for Practice

Soccer is a high intensity intermittent sport, featuring critical events completed at high/maximal intensity which is superimposed onto an aerobic base of lower intensity activities and rest. Due to these varying energic demands and the duration of competition the need for optimal nutritional strategies to offset and delay fatigue are paramount. Over the last 50 years, several investigations have been reported on aspects of soccer be they nutrition-focused or those concerning the demands of the sport. Emanating from these scientific papers, observations have been made on the likely factors which result in the fatigue during match-play. Factors such as muscle glycogen depletion and hypoglycaemia are discussed. Studies on the energy demands of soccer have employed a variety of methodologies which are briefly reviewed and vary between the use of heart rate telemetry to the use of global positioning systems (GPS). Moving on from observations of the energy demands of the sport leads to the major focus of this review which highlights key nutritional strategies to support the preparation and recovery of male soccer players to enhance performance, or at least to enable players to perform adequately. This review examines relevant methodologies in assessing training and competitive energy costs as well as the concomitant energy intakes demanded for successful performance outcomes. In order to bring an applied aspect to the overall findings from areas discussed, some practical ideas of feeding strategies are presented.

The Effects of Dietary Protein Supplementation on Acute Changes in Muscle Protein Synthesis and Longer-Term Changes in Muscle Mass, Strength, and Aerobic Capacity in Response to Concurrent Resistance and Endurance Exercise in Healthy Adults: A Systematic Review

BACKGROUND

Engaging in both resistance and endurance exercise within the same training program, termed 'concurrent exercise training,' is common practice in many athletic disciplines that require a combination of strength and endurance and is recommended by a number of organizations to improve muscular and cardiovascular health and reduce the risk of chronic metabolic disease. Dietary protein ingestion supports skeletal muscle remodeling after exercise by stimulating the synthesis of muscle proteins and can optimize resistance exercise-training mediated increases in skeletal muscle size and strength; however, the effects of protein supplementation on acute and longer-term adaptive responses to concurrent resistance and endurance exercise are unclear.

OBJECTIVES

The purpose of this systematic review is to evaluate the effects of dietary protein supplementation on acute changes in muscle protein synthesis and longer-term changes in muscle mass, strength, and aerobic capacity in responses to concurrent resistance and endurance exercise in healthy adults.

METHODS

A systematic search was conducted in five databases: Scopus, Embase, Medline, PubMed, and Web of Science. Acute and longer-term controlled trials involving concurrent exercise and protein supplementation in healthy adults (ages 18-65 years) were included in this systematic review. Main outcomes of interest were changes in skeletal muscle protein synthesis rates, muscle mass, muscle strength, and whole-body aerobic capacity (i.e., maximal/peak aerobic capacity [VO_2max/peak]). The quality of studies was assessed using the National Institute of Health Quality Assessment for Controlled Intervention Studies.

RESULTS

Four acute studies including 84 trained young males and ten longer-term studies including 167 trained and 391 untrained participants fulfilled the eligibility criteria. All included acute studies demonstrated that protein ingestion enhanced myofibrillar protein synthesis rates, but not mitochondrial protein synthesis rates during post-exercise recovery after an acute bout of concurrent exercise. Of the included longer-term training studies, five out of nine reported that protein supplementation enhanced concurrent training-mediated increases in muscle mass, while five out of nine studies reported that protein supplementation enhanced concurrent training-mediated increases in muscle strength and/or power. In terms of aerobic adaptations, all six included studies reported no effect of protein supplementation on concurrent training-mediated increases in VO_2max/peak.

CONCLUSION

Protein ingestion after an acute bout of concurrent exercise further increases myofibrillar, but not mitochondrial, protein synthesis rates during post-exercise recovery. There is some evidence that protein supplementation during longer-term training further enhances concurrent training-mediated increases in skeletal muscle mass and strength/power, but not whole-body aerobic capacity (i.e., VO_2max/peak).

The exercise-induced long noncoding RNA CYTOR promotes fast-twitch myogenesis in aging

[Figure: see text].

A randomized clinical trial on the effects of exercise on muscle remodelling following bariatric surgery

BACKGROUND

Muscle atrophy and strength loss are common adverse outcomes following bariatric surgery. This randomized, controlled trial investigated the effects of exercise training on bariatric surgery-induced loss of muscle mass and function. Additionally, we investigated the effects of the intervention on molecular and histological mediators of muscle remodelling.

METHODS

Eighty women with obesity were randomly assigned to a Roux-en-Y gastric bypass (RYGB: n = 40, age = 42 ± 8 years) or RYGB plus exercise training group (RYGB + ET: n = 40, age = 38 ± 7 years). Clinical and laboratory parameters were assessed at baseline, and 3 (POST3) and 9 months (POST9) after surgery. The 6 month, three-times-a-week, exercise intervention (resistance plus aerobic exercise) was initiated 3 months post-surgery (for RYGB + ET). A healthy, lean, age-matched control group was recruited to provide reference values for selected variables.

RESULTS

Surgery resulted in a similar (P = 0.66) reduction in lower-limb muscle strength in RYGB and RYGB+ET (-26% vs. -31%), which was rescued to baseline values in RYGB + ET (P = 0.21 vs. baseline) but not in RYGB (P < 0.01 vs. baseline). Patients in RYGB+ET had greater absolute (214 vs. 120 kg, P < 0.01) and relative (2.4 vs. 1.4 kg/body mass, P < 0.01) muscle strength compared with RYGB alone at POST9. Exercise resulted in better performance in timed-up-and-go (6.3 vs. 7.1 s, P = 0.05) and timed-stand-test (18 vs. 14 repetitions, P < 0.01) compared with RYGB. Fat-free mass was lower (POST9-PRE) after RYBG than RYGB + ET (total: -7.9 vs. -4.9 kg, P < 0.01; lower-limb: -3.8 vs. -2.7 kg, P = 0.02). Surgery reduced Types I (~ - 21%; P = 0.99 between-group comparison) and II fibre cross-sectional areas (~ - 27%; P = 0.88 between-group comparison), which were rescued to baseline values in RYGB+ET (P > 0.05 vs. baseline) but not RYGB (P > 0.01 vs. baseline). RYGB + ET showed greater Type I (5187 vs. 3898 μm² , P < 0.01) and Type II (5165 vs. 3565 μm² , P < 0.01) fCSA than RYGB at POST9. RYGB + ET also resulted in increased capillarization (P < 0.01) and satellite cell content (P < 0.01) than RYGB at POST9. Gene-set normalized enrichment scores for the muscle transcriptome revealed that the ubiquitin-mediated proteolysis pathway was suppressed in RYGB + ET at POST9 vs. PRE (NES: -1.7; P < 0.01), but not in RYGB. Atrogin-1 gene expression was lower in RYGB + ET vs. RYGB at POST9 (0.18 vs. 0.71-fold change, P < 0.01). From both genotypic and phenotypic perspectives, the muscle of exercised patients resembled that of healthy lean individuals.

CONCLUSIONS

This study provides compelling evidence-from gene to function-that strongly supports the incorporation of exercise into the recovery algorithm for bariatric patients so as to counteract the post-surgical loss of muscle mass and function.

Aerobic exercise and resistance exercise alleviate skeletal muscle atrophy through IGF-1/IGF-1R-PI3K/Akt pathway in mice with myocardial infarction

OBJECTIVES

Myocardial infarction (MI)-induced heart failure (HF) is commonly accompanied with profound effects on skeletal muscle. With the process of MI-induced HF, perturbations in skeletal muscle contribute to muscle atrophy. Exercise is viewed as a feasible strategy to prevent muscle atrophy. The aims of this study were to investigate whether exercise could alleviate MI-induced skeletal muscle atrophy via insulin-like growth factor 1 (IGF-1) pathway in mice.

MATERIALS AND METHODS

Male C57/BL6 mice were used to establish the MI model and divided into three groups: sedentary MI group, MI with aerobic exercise group and MI with resistance exercise group, sham-operated group was used as control. Exercise-trained animals were subjected to four-weeks of aerobic exercise (AE) or resistance exercise (RE). Cardiac function, muscle weight, myofiber size, levels of IGF-1 signaling and proteins related to myogenesis, protein synthesis and degradation and cell apoptosis in gastrocnemius muscle were detected. And H₂O₂-treated C2C12 cells were intervened with recombinant human IGF-1, IGF-1R inhibitor NVP-AEW541 and PI3K inhibitor LY294002 to explore the mechanism. Results：Exercises up-regulated the IGF-1/IGF-1R-phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling, increased the expressions of Pax7, myogenic regulatory factors (MRFs) and protein synthesis, reduced protein degradation and cell apoptosis in MI-mice. In vitro, IGF-1 up-regulated the levels of Pax7 and MRFs, mTOR and P70S6K, reduced MuRF1, MAFbx and inhibited cell apoptosis via IGF-1R-PI3K/Akt pathway.

CONCLUSION

AE and RE, safely and effectively, alleviate skeletal muscle atrophy by regulating the levels of myogenesis, protein degradation and cells apoptosis in mice with MI via activating IGF-1/IGF-1R-PI3K/Akt pathway.

Socioeconomic position and body composition in childhood in high- and middle-income countries: a systematic review and narrative synthesis

BACKGROUND

The relation between socioeconomic position (SEP) and obesity measured by body mass index (BMI), a measure of weight for height, has been extensively reviewed in children, showing consistent associations between disadvantaged SEP and higher BMI in high-income countries (HICs) and lower BMI in middle-income countries (MICs). Fat mass (FM), a more accurate measure of adiposity, and fat-free mass (FFM) are not captured by BMI, but have been shown to track from childhood to adulthood, and be important for cardiovascular health and functional outcomes in later life. It is not clear whether body composition is associated with SEP. We systematically reviewed the association between SEP and body composition in childhood.

METHODS

A systematic review was carried out following PRISMA guidelines. The protocol was pre-registered with PROSPERO (CRD42019119937). Original studies in the English language, which examined the association between SEP and body composition in childhood, were included. An electronic search of three databases was conducted. Two independent reviewers carried out screening, data extraction and quality assessment. Due to heterogeneity in results, a narrative synthesis was conducted. Heterogeneity in findings according to SEP, sex, body composition measure and country income level was investigated.

RESULTS

50 papers were included, the majority from HICs. No papers were from low-income countries. Disadvantage in childhood was associated with greater FM and lower FFM in HICs, but with lower FM and lower FFM in MICs. When measures of FFM indexed to height were used there was no evidence of associations with SEP. In HICs, more studies reported associations between disadvantaged SEP and higher FM among girls comparative to boys.

CONCLUSIONS

Inequalities in FM are evident in HICs and, in the opposite direction, in MICs and follow similar trends to inequalities for BMI. Inequalities in height are likely important in understanding inequalities in FFM.

How to Increase Muscle Mass in Critically Ill Patients: Lessons Learned from Athletes and Bodybuilders

PURPOSE OF REVIEW

Decades of research on nutrition and exercise on athletes and bodybuilders has yielded various strategies to promote anabolism and improve muscle health and growth. We reviewed these interventions in the context of muscle loss in critically ill patients.

RECENT FINDINGS

For critically ill patients, ensuring optimum protein intake is important, potentially using a whey-containing source and supplemented with vitamin D and leucine. Agents like hydroxyl β-methylbutyrate and creatine can be used to promote muscle synthesis. Polyunsaturated fatty acids stimulate muscle production as well as have anti-inflammatory properties that may be useful in critical illness. Adjuncts like oxandralone promote anabolism. Resistance training has shown mixed results in the ICU setting but needs to be explored further with specific outcomes. Critically ill patients suffer from severe proteolysis during hospitalization as well as persistent inflammation, immunosuppression, and catabolism syndrome after discharge. High protein supplementation, ergogenic aids, anti-inflammatories, and anabolic adjuncts have shown potential in alleviating muscle loss and should be used in intensive care units to optimize patient recovery.

Elderly Patients after Stroke Increase Skeletal Muscle Mass by Exercise Therapy in Rehabilitation Wards

BACKGROUND

Loss of skeletal muscle is a critical health issue that frequently occurs due to aging and various pathologies. No studies have reported increases in appendicular skeletal muscle mass among elderly patients after stroke. Our hypothesis was that even older individuals after stroke could increase skeletal muscle mass by rehabilitation.

OBJECTIVES

This study aimed to evaluate changes to skeletal muscle mass in elderly patients after stroke rehabilitation and to assess factors associated with skeletal muscle mass increases.

MATERIALS AND METHODS

Participants in this case-control study were 159 patients ≥ 80 years old in rehabilitation wards after stroke. Body mass index (BMI), appendicular skeletal muscle index (SMI), Functional Independence Measure (FIM), interval from onset to transfer, presence of hemiplegia, National Institutes of Health Stroke Scale (NIHSS), length of hospital stay for rehabilitation, period of exercise therapy per day, and protein intake were examined. Multivariate logistic regression analysis was performed to identify association between these values and SMI increases.

RESULTS

SMI at discharge was significantly increased (5.30 kg/m²) compared to baseline (5.20kg/m²; p = 0.002). Multiple logistic regression analysis showed that length of hospital stay and protein intake were significantly associated with SMI increases, with odds ratios of 1.013 (95% confidence interval, 1.005-1.022) and 3.746 (95% confidence interval, 1.077-13.028), respectively.

CONCLUSIONS

The SMI of patients ≥ 80 years old increased significantly with rehabilitation after stroke. In addition, length of hospital stay and protein intake were independently associated with increases in SMI.

Wheel running improves fasting-induced AMPK signaling in skeletal muscle from tumor-bearing mice

Disruptions to muscle protein turnover and metabolic regulation contribute to muscle wasting during the progression of cancer cachexia. The initiation of cachexia is also associated with decreased physical activity. While chronic muscle AMPK activation occurs during cachexia progression in ApcMin/+ (MIN) mice, a preclinical cachexia model, the understanding of muscle AMPK's role during cachexia initiation is incomplete. Therefore, we examined if voluntary wheel exercise could improve skeletal muscle AMPK signaling in pre-cachectic MIN mice. Next, we examined muscle AMPK's role in aberrant catabolic signaling in response to a 12-h fast in mice initiating cachexia. Male C57BL/6 (B6: N = 26) and MIN (N = 29) mice were subjected to ad libitum feeding, 12-h fast, or 4 wks. of wheel access and then a 12-h fast during the initiation of cachexia. Male tamoxifen-inducible skeletal muscle AMPKα1 α2 (KO) knockout mice crossed with ApcMin/+ and floxed controls were examined (WT: N = 8, KO: N = 8, MIN: N = 10, MIN KO: N = 6). Male mice underwent a 12-h fast and the gastrocnemius muscle was analyzed. MIN gastrocnemius mass was reduced compared to B6 mice. A 12-h fast induced MIN muscle AMPKT172 , FOXOS413 , and ULK-1S555 phosphorylation compared to B6. Wheel running attenuated these inductions. A 12-h fast induced MIN muscle MuRF-1 protein expression compared to B6 and was suppressed by wheel running. Additionally, fasting induced muscle autophagy signaling and disrupted mitochondrial quality protein expression in the MIN, which was prevented in the MIN KO. We provide evidence that increased skeletal muscle AMPK sensitivity to a 12-h fast is an adverse event in pre-cachectic MIN mice, and exercise can improve this regulation.

Resistance Exercise, Aging, Disuse, and Muscle Protein Metabolism

Skeletal muscle is the organ of locomotion, its optimal function is critical for athletic performance, and is also important for health due to its contribution to resting metabolic rate and as a site for glucose uptake and storage. Numerous endogenous and exogenous factors influence muscle mass. Much of what is currently known regarding muscle protein turnover is owed to the development and use of stable isotope tracers. Skeletal muscle mass is determined by the meal- and contraction-induced alterations of muscle protein synthesis and muscle protein breakdown. Increased loading as resistance training is the most potent nonpharmacological strategy by which skeletal muscle mass can be increased. Conversely, aging (sarcopenia) and muscle disuse lead to the development of anabolic resistance and contribute to the loss of skeletal muscle mass. Nascent omics-based technologies have significantly improved our understanding surrounding the regulation of skeletal muscle mass at the gene, transcript, and protein levels. Despite significant advances surrounding the mechanistic intricacies that underpin changes in skeletal muscle mass, these processes are complex, and more work is certainly needed. In this article, we provide an overview of the importance of skeletal muscle, describe the influence that resistance training, aging, and disuse exert on muscle protein turnover and the molecular regulatory processes that contribute to changes in muscle protein abundance. © 2021 American Physiological Society. Compr Physiol 11:2249-2278, 2021.

Effects of intermittent fasting combined with resistance training on body composition: a systematic review and meta-analysis

This systematic review and meta-analysis evaluated the influence of intermittent fasting (IF) in combination with resistance training (RT) on body composition outcomes. Studies examining IF vs. non-IF diets in individuals performing RT, published up to February 2021, were identified through PubMed, the Cochrane Library, Web of Science, Embase, and SCOPUS databases. Eight studies, including 221 participants were analyzed using a random-effects model to calculate weighted mean differences (WMDs) with 95% confidence intervals (CIs). Results indicated that IF had a significant effect on body mass (WMD = -2.08 kg; 95% CI: -3.04, -1.13), fat mass (WMD = -1.36 kg; 95% CI: -1.94, -0.78), body mass index (WMD = -0.52 kg/m²; 95% CI: -0.85, -0.19), and body fat percentage (WMD = -1.49%; 95% CI: -2.24, -0.74) relative to non-IF diets, without a significant effect for fat-free mass (WMD = -0.27 kg; 95% CI: -0.82, 0.28). The present systematic review and meta-analysis demonstrates potentially beneficial effects of IF in combination with RT for reducing body mass and body fat relative to non-IF control diets, with similar preservation of fat-free mass.

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.