An Evidence-Based Narrative Review of Mechanisms of Resistance Exercise-Induced Human Skeletal Muscle Hypertrophy

Biomarkers of aging: from molecules and surrogates to physiology and function

Many countries face an unprecedented challenge in aging demographics. This has led to an exponential growth in research on aging, which, coupled to a massive financial influx of funding in the private and public sectors, has resulted in seminal insights into the underpinnings of this biological process. However, critical validation in humans has been hampered by the limited translatability of results obtained in model organisms, additionally confined by the need for extremely time-consuming clinical studies in the ostensible absence of robust biomarkers that would allow monitoring in shorter time frames. In the future, molecular parameters might hold great promise in this regard. In contrast, biomarkers centered on function, resilience, and frailty are available at the present time, with proven predictive value for morbidity and mortality. In this review, the current knowledge of molecular and physiological aspects of human aging, potential antiaging strategies, and the basis, evidence, and potential application of physiological biomarkers in human aging are discussed.

Reproducibility and quality of hypertrophy-related training plans generated by GPT-4 and Google Gemini as evaluated by coaching experts

Large Language Models (LLMs) are increasingly utilized in various domains, including the generation of training plans. However, the reproducibility and quality of training plans produced by different LLMs have not been studied extensively. This study aims to: i) investigate and compare the quality of muscle hypertrophy-related resistance training (RT) plans generated by Google Gemini (GG) and GPT-4, and ii) the reproducibility of the RT plans when the same prompts are provided multiple times concomitantly. Two distinct prompts were used, one providing little information about the training plan requirements and the other providing detailed information. These prompts were input into GG and GPT-4 by two different individuals, resulting in the generation of eight RT plans. These plans were evaluated by 12 coaching experts using a 5-point Likert scale, based on quality criteria derived from the literature. The results indicated a high degree of reproducibility, as indicated by coaching expert evaluation, when the same distinct prompts were provided multiple times to the LLMs of interest, with 27 out of 28 items showing no differences (p > 0.05). Overall, GPT-4 was rated higher on several aspects of RT quality criteria (p = 0.000-0.043). Additionally, compared to little information, higher information density within the prompts resulted in higher rated RT quality (p = 0.000-0.037). Our findings show that RT plans can be generated reproducibly with the same quality when using the same prompts. Furthermore, quality improves with more detailed input, and GPT-4 outperformed GG in generating higherquality plans. These results suggest that detailed information input is crucial for LLM performance.

Effect of Oral Contraceptive Use on Muscle Hypertrophy Following Strength Training

Oral contraceptives (OC) are widely used by women, while their interactions with strength training are yet to be resolved. This study investigated the effects of OC use on muscle hypertrophy and strength adaptation to heavy strength training in young adult women. Fifteen habitual OC users and 17 non-OC users (NOC) with regular menstrual cycles completed ~12 weeks of strength training, which spanned three menstrual cycles for the NOC group. All participants were young, healthy, and strength-untrained. Isometric knee-extensor strength, muscle cross-sectional area of the vastus lateralis (ultrasound imaging), and body composition (DXA) were used to evaluate training adaptations. Blood samples for estradiol and progesterone analyses, dietary registrations, and questionnaires assessing appetite, vitality, motivation, recovery status, and sleep duration were collected during the intervention period. Both groups experienced gains in lean mass and muscle strength. However, the OC group demonstrated a significantly larger increase in arm lean mass (5.5% ± 3.9% [mean ± standard deviation] vs. 2.9% ± 2.8%, p < 0.05) and vastus lateralis cross-sectional area (10.0% ± 4.1% vs. 5.3% ± 4.4%, p < 0.05) compared to the NOC group. Despite these differences, there was no significant group difference in lower body strength gains. Both groups reported similar levels of appetite, dietary intake, vitality, motivation to exercise, and perceived recovery throughout the study, although the OC group slept an average of 42 min longer per day. Our findings suggest that OC use potentiates muscle growth during strength training, although further research is needed to elucidate the underlying mechanisms and long-term effects.

Acute effects of a single bout structured resistance and combined exercise on blood glucose profile during exercise in patients with type 2 diabetes and healthy adults: A randomized crossover study

AIMS

The effects of postprandial resistance and combined exercise on blood glucose profiles, particularly in patients with type 2 diabetes, remain unclear. Comprehending these responses may aid in diabetes management.

METHODS

Three trials were conducted: trial A examined aerobic, resistance, and combined exercise; trials B and C focused on three intensities of resistance and combined exercise. Participants including patients with type 2 diabetes and healthy adults completed a randomized crossover experiment with two arrangements of three interventions and continuous glucose monitoring. Blood glucose iAUC and slope were analyzed via repeated measures two-way ANOVA.

RESULTS

A total of 21 patients with type 2 diabetes (47.81±11.88 years) and 26 healthy adults (31.77±6.66 years) were assigned. In trials A-C, the main effect of subject group on iAUC/min was significant (p＜0.001, p = 0.003, and p＜0.001). The exercise in trial A (p = 0.006) and subject group in trial C (p = 0.005) significantly impacted the blood glucose slope.

CONCLUSIONS

Resistance and combined exercise reduce postprandial hyperglycemia in type 2 diabetes patients. Monitoring glucose before exercise may help prevent extreme events.

Comparison of the Effectiveness of Protein Supplementation Combined with Resistance Training on Body Composition and Physical Function in Healthy Elderly Adults

BACKGROUND

The global population of individuals over 65 y is expected to reach 426 million by 2050. Aging is associated with a progressive loss of muscle mass, strength, and function, leading to sarcopenia and adverse outcomes such as physical disability and increased mortality. Interventions such as resistance training and protein supplementation have shown promise in mitigating these effects.

OBJECTIVES

To determine the comparative effectiveness of protein supplementation, resistance training, and their combination on body composition and physical function in healthy older adults through a network meta-analysis.

METHODS

We conducted a systematic review and network meta-analysis following PRISMA guidelines and registered it in PROSPERO (CRD42021226561). We included randomized controlled trials comparing protein supplementation, resistance training, and their combination in participants aged ≥50 y. Data were extracted from PubMed, Web of Science, Embase, and Cochrane Library. The risk of bias was assessed using the Cochrane Collaboration Risk of Bias Tool.

RESULTS

A total of 38 randomized controlled trials involving 2610 participants were included. The combined intervention of protein supplementation and resistance training significantly improved lean body mass (standardized mean difference [SMD]: 0.44; 95% confidence interval [CI]: 0.05, 0.95) compared with protein supplementation alone. The combined intervention also showed significant improvements in muscle mass (SMD: 1.49; 95% CI: 0.11, 2.67). The combined intervention (SMD: 2.74; 95% CI: 0.76, 4.74) and resistance training alone (SMD: 2.53, 95% CI: 0.29, 4.84) significantly improved muscle strength compared with controls. The combined intervention (SMD: 4.98; 95% CI: 2.72, 7.17) and resistance training alone (SMD: 4.52; 95% CI: 2.30, 6.64) significantly improved physical function compared with protein supplementation alone.

CONCLUSIONS

Combining exercise and protein supplementation is the most effective method for improving muscle mass, strength, and physical function in older adults. This approach should be considered to enhance physical health in this population. Future large-scale trials are necessary to confirm these findings.

Nutritional Interventions to Attenuate Quadriceps Muscle Deficits following Anterior Cruciate Ligament Injury and Reconstruction

Following anterior cruciate ligament (ACL) injury, quadriceps muscle atrophy persists despite rehabilitation, leading to loss of lower limb strength, osteoarthritis, poor knee joint health and reduced quality of life. However, the molecular mechanisms responsible for these deficits in hypertrophic adaptations within the quadriceps muscle following ACL injury and reconstruction are poorly understood. While resistance exercise training stimulates skeletal muscle hypertrophy, attenuation of these hypertrophic pathways can hinder rehabilitation following ACL injury and reconstruction, and ultimately lead to skeletal muscle atrophy that persists beyond ACL reconstruction, similar to disuse atrophy. Numerous studies have documented beneficial roles of nutritional support, including nutritional supplementation, in maintaining and/or increasing muscle mass. There are three main mechanisms by which nutritional supplementation may attenuate muscle atrophy and promote hypertrophy: (1) by directly affecting muscle protein synthetic machinery; (2) indirectly increasing an individual's ability to work harder; and/or (3) directly affecting satellite cell proliferation and differentiation. We propose that nutritional support may enhance rehabilitative responses to exercise training and positively impact molecular machinery underlying muscle hypertrophy. As one of the fastest growing knee injuries worldwide, a better understanding of the potential mechanisms involved in quadriceps muscle deficits following ACL injury and reconstruction, and potential benefits of nutritional support, are required to help restore quadriceps muscle mass and/or strength. This review discusses our current understanding of the molecular mechanisms involved in muscle hypertrophy and disuse atrophy, and how nutritional supplements may leverage these pathways to maximise recovery from ACL injury and reconstruction.

The correlation between serum alkaline phosphatase and grip strength in middle-aged and elderly people: NHANES 2011-2014

BACKGROUND

Serum alkaline phosphatase (ALP) plays a crucial role in bone and muscle health. Previous studies have demonstrated that serum alkaline phosphatase (ALP) is closely associated with muscle mass. Nevertheless, the association between serum alkaline phosphatase (ALP) and grip strength remains unclear. Therefore, the present study focused on exploring the association of serum ALP with grip strength in middle-aged and elderly people.

METHODS

We conducted a cross-sectional study using data from the National Health and Nutrition Examination Survey conducted from 2011 to 2014. A total of 3514 participants (1891 males and 1623 females) aged 40-80 years were included in this study. Serum ALP and pelvic grip strength were analyzed as independent and dependent variables, additional variables were the possible impact modifiers. weighted generalized linear models and stratified analysis by gender, age group, and race were applied to assess the relationship between serum ALP and grip strength. Smooth curve fitting and threshold effect analysis/saturation effect analysis were used to analyze the nonlinear relationship between the 2 variables.

RESULTS

In the gender-stratified subgroup analysis, we observed an inverse association between serum ALP and grip strength in both male and female. When stratified by age group, the association remained significant among participants 40-59 years of age, but not among those ≥ 60 years old. When stratified by race, the association remained significant among Non-Hispanic White and Non-Hispanic Black. It is noteworthy that serum ALP and grip strength showed a significant negative correlation among female aged 40-59 years, but not among female aged ≥ 60 years. Additionally, Smooth curve fitting showed that serum ALP had a nonlinear relationship with grip strength in male aged 40-59 years and male aged over 60 years, the inflection points are 54 IU and 97 IU respectively.

CONCLUSION

Our study revealed an inverse relationship between serum ALP and grip strength, this finding offers new insights and avenues for understanding how serum alkaline phosphatase affects skeletal muscle health.

Turning over new ideas in human skeletal muscle proteostasis: What do we know and where to from here?

Understanding the turnover of proteins in tissues gives information as to how external stimuli result in phenotypic change. Nowhere is such phenotypic change more conspicuous than skeletal muscle, which can be effectively remodelled by increased loading, ageing and unloading (disuse), all of which are subject to modification by nutrition and other environmental stimuli. The understanding of muscle proteome remodelling has undergone a renaissance recently with the reintroduction of deuterated water (D2O) and its ingestion to label amino acids and measure their incorporation into proteins. However, there is confusion around the use of the deuterated water methodology and the interpretation of the data it provides. Here, we provide a short review of some of the more salient features of the method and clarify some of the confusion around the method of deuterated water methods and its use in humans and how the interpretation of the data is in contrast to that of rodents.

Physical activity, cathepsin B, and cognitive health

Regular physical activity (PA) is beneficial for cognitive health, and cathepsin B (CTSB) - a protease released by skeletal muscle during PA - acts as a potential molecular mediator of this association. PA-induced metabolic and mechanical stress appears to increase plasma/serum CTSB levels. CTSB facilitates neurogenesis and synaptic plasticity in brain regions (e.g., hippocampus and prefrontal cortex) that support performance in specific cognitive domains including memory, learning, and executive function. However, the evidence regarding the role of PA-induced changes in CTSB as a mediator of PA-induced cognitive health in humans is mixed. To guide future research, this article identifies key factors that may explain the observed heterogeneity in the findings from human studies and proposes a PA-CTSB-cognition model.

Exerkines and Sarcopenia: Unveiling the Mechanism Behind Exercise-Induced Mitochondrial Homeostasis

Background/Objectives: Sarcopenia, characterized by the progressive loss of muscle mass and strength, is linked to physical disability, metabolic dysfunction, and an increased risk of mortality. Exercise therapy is currently acknowledged as a viable approach for addressing sarcopenia. Nevertheless, the molecular mechanisms behind exercise training or physical activity remain poorly understood. The disruption of mitochondrial homeostasis is implicated in the pathogenesis of sarcopenia. Exercise training effectively delays the onset of sarcopenia by significantly maintaining mitochondrial homeostasis, including promoting mitophagy, improving mitochondrial biogenesis, balancing mitochondrial dynamics, and maintaining mitochondrial redox. Exerkines (e.g., adipokines, myokines, hepatokines, and osteokines), signaling molecules released in response to exercise training, may potentially contribute to skeletal muscle metabolism through ameliorating mitochondrial homeostasis, reducing inflammation, and regulating protein synthesis as a defense against sarcopenia. Methods: In this review, we provide a detailed summary of exercise-induced exerkines and confer their benefit, with particular focus on their impact on mitochondrial homeostasis in the context of sarcopenia. Results: Exercise induces substantial adaptations in skeletal muscle, including increased muscle mass, improved muscle regeneration and hypertrophy, elevated hormone release, and enhanced mitochondrial function. An expanding body of research highlights that exerkines have the potential to regulate processes such as mitophagy, mitochondrial biogenesis, dynamics, autophagy, and redox balance. These mechanisms contribute to the maintenance of mitochondrial homeostasis, thereby supporting skeletal muscle metabolism and mitochondrial health. Conclusions: Through a comprehensive investigation of the molecular mechanisms within mitochondria, the context reveals new insights into the potential of exerkines as key exercise-protective sensors for combating sarcopenia.

The impact of different exercise modalities on chronic kidney disease: an umbrella review of meta-analyses

Introduction

Exercise is widely recognized for its benefits to chronic kidney disease (CKD) patients. However, the specific impact of different exercise modalities on CKD-related outcomes remains unclear. This study sought to summarize the effects of different exercise modalities on the main outcomes impacted by CKD.

Methods

We searched for systematic review with meta-analysis in PubMed, Embase, Web of Science, Scopus, and Cochrane databases. We evaluated the methodological quality of included studies by AMSTAR2 tool and by individually evaluating the heterogeneity, sample power, and statistical significances from meta-analyses.

Results

We included 44 meta-analyses, encompassing 35,432 CKD patients in pre-dialysis and dialysis stages (peritoneal and hemodialysis). Data from meta-analyses with highly suggestive or strong evidence grading suggests that aerobic and combined training were most effective in improving cardiorespiratory fitness (main effect: 2.1, 95% CI: 0.8-3.4, and main effect: 3.4; 95% CI: 2.4-4.6, respectively). Combined training showed a consistent benefit in psychosocial domains (main effect: -7.3; 95% CI: -9.31 to -53). All exercise modalities significantly improve functional performance, except isometric training, which impacted just fistula maturation (main effect: 0.84; 95% CI: 0.5-1.2).

Conclusion

Exercise emerges as a potential non-pharmacological therapy for CKD patients. Tailoring exercise to specific outcomes appears to be crucial, as different exercise modalities exhibit varying effectiveness.

Luteolin alleviates muscle atrophy, mitochondrial dysfunction and abnormal FNDC5 expression in high fat diet-induced obese rats and palmitic acid-treated C2C12 myotubes

Obesity is associated with a series of skeletal muscle impairments and dysfunctions, which are characterized by metabolic disturbances and muscle atrophy. Luteolin is a phenolic phytochemical with broad pharmacological activities. The present study aimed to evaluate the protective effects of Luteolin on muscle function and explore the potential mechanisms in high-fat diet (HFD)-induced obese rats and palmitic acid (PA)-treated C2C12 myotubes. Male Sprague-Dawley (SD) rats were fed with a control diet or HFD and orally administrated 0.5% sodium carboxymethyl cellulose (vehicle) or Luteolin (25, 50, and 100 mg/kg, respectively) for 12 weeks. The results showed that Luteolin ameliorated HFD-induced body weight gain, glucose intolerance and hyperlipidemia. Luteolin also alleviated muscle atrophy, decreased ectopic lipid deposition and prompted muscle-fiber-type conversion in the skeletal muscle. Meanwhile, we observed an evident improvement in mitochondrial quality control and respiratory capacity, accompanied by reduced oxidative stress. Mechanistic studies indicated that AMPK/SIRT1/PGC-1α signaling pathway plays a key role in the protective effects of Luteolin on skeletal muscle in the obese states, which was further verified by using specific inhibitors of AMPK and SIRT1. Moreover, the mRNA expression levels of markers in brown adipocyte formation were significantly up-regulated post Luteolin supplementation in different adipose depots. Taken together, these results revealed that Luteolin supplementation might be a promising strategy to prevent obesity-induced loss of mass and biological dysfunctions of skeletal muscle.

Appendicular Skeletal Muscle Index Is Positively Related to Mediterranean Diet Adherence in University Students

Skeletal muscle is associated with cardiometabolic health. The appendicular skeletal muscle index (aSMI) represents the skeletal muscle mass "corrected" for height and constitutes a clinically applicable feature of sarcopenia. The relation of the aSMI with dietary habits is not clear, especially in young adults. The present pilot study aimed to investigate the relationship between the aSMI and Mediterranean diet adherence in young adults. A cross-sectional study of 151 university students was conducted. Anthropometry and bioimpedance analysis (TANITA-MC780) were performed. The aSMI was calculated as the sum of the upper and lower extremity muscle masses divided by height squared. The HPAQ questionnaire was used for physical activity evaluation. A validated food frequency questionnaire was used for dietary assessment, and the Mediterranean Diet Score (MedDietScore) was calculated. Multivariate linear regression models with log-aSMI as a dependent variable were applied. The MedDietScore was positively related to log-aSMI in the total sample (B = 0.009, SE = 0.004, p = 0.05, R2 for total model = 71%) irrespective of gender, age, ΒΜΙ, smoking, physical activity, and academic year and in males (B = 0.027, SE = 0.011, p = 0.023 R2 for total model = 37%) irrespective οf age and ΒΜΙ. The positive association of the MedDietScore with aSMI supports the importance of the adoption of a Mediterranean dietary pattern-rich in plant proteins and antioxidant/anti-inflammatory compounds-in maintaining/attaining muscle mass in young subjects.

A single, maximal dose of celecoxib, ibuprofen, or flurbiprofen does not reduce the muscle signalling response to plyometric exercise in young healthy adults

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) possess analgesic and anti-inflammatory properties by inhibiting cyclooxygenase (COX) enzymes. Conflicting evidence exists on whether NSAIDs influence signaling related to muscle adaptations and exercise with some research finding a reduction in muscle protein synthesis signaling via the AKT-mTOR pathway, changes in satellite cell signaling, reductions in muscle protein degradation, and reductions in cell proliferation. In this study, we determined if a single maximal dose of flurbiprofen (FLU), celecoxib (CEL), ibuprofen (IBU), or a placebo (PLA) affects the short-term muscle signaling responses to plyometric exercise.

METHODS

This was a block randomized, double-masked, crossover design, where 12 participants performed four plyometric exercise bouts consisting of 10 sets of 10 plyometric jumps at 40% 1RM. Two hours before exercise, participants consumed a single dose of celecoxib (CEL 200 mg), IBU (800 mg), FLU (100 mg) or PLA with food. Muscle biopsy samples were collected before and 3-h after exercise from the vastus lateralis. Data were analyzed using a repeated measures (RM) ANOVA, ANOVA, or a Friedman test. Significance was considered at p < 0.05.

RESULTS

We found no treatment effects on the mRNA expression of PTSG1, PTSG2, MYC, TBP, RPLOP, MYOD1, Pax7, MYOG, Atrogin-1, or MURF1 (all, p > 0.05). We also found no treatment effects on AKT-mTOR signaling or MAPK signaling measured through the phosphorylation status of mTORS2441, mTORS2448, RPS6 235/236, RPS 240/244, 4EBP1, ERK1/2, p38 T180/182 normalized to their respective total abundance (all, p > 0.05). However, we did find a significant difference between MNK1 T197/202 in PLA compared to FLU (p < .05).

CONCLUSION

A single, maximal dose of IBU, CEL, or FLU taken prior to exercise did not affect the signaling of muscle protein synthesis, protein degradation, or ribosome biogenesis three hours after a plyometric training bout.

Resistance training, skeletal muscle hypertrophy, and glucose homeostasis: how related are they? A Systematic review and Meta-analysis

Resistance training (RT) promotes skeletal muscle (Skm) hypertrophy, increases muscular strength, and improves metabolic health. Whether changes in fat-free mass (FFM; a surrogate marker of muscle hypertrophy) moderate RT-induced improvements in glucose homeostasis has not been determined, despite extensive research on the benefits of RT for health and performance. The aim of this meta-analysis is to examine whether RT-induced Skm hypertrophy drives improvements in glucose metabolism and to explore confounders, such as biological sex and training parameters. Random-effects meta-analyses were performed using variance random effects. Meta-regressions were performed for confounding factors depending on the heterogeneity (I2). Analyses from 33 intervention studies revealed significant within-study increases in FFM with a moderate effect size (within-studies: (effect size; ES = 0.24 [0.10; 0.39]; p = 0.002; I2 = 56%) and a tendency for significance when compared with control groups (ES = 0.42 [-0.04-0.88]; p = 0.07). Within-study significant increases in glucose tolerance (2 h glucose: ES = -0.3 [-0.50; -0.11]; p < 0.01; I2 = 43%; glucose area under the curve (AUC): -0.40 [-0.66; -0.13] I2 = 76.1%; p < 0.01) and insulin sensitivity (ES = 0.38 [0.13; 0.62]; I2 = 53.0%; p < 0.01) were also apparent with RT. When compared to control groups, there was no significant difference in 2 h glucose, nor in glucose AUC from baseline in RT intervention groups. Meta-regression analyses failed to consistently reveal increases in FFM as a moderator of glucose homeostasis. Other mixed-effect models were also unsuccessful to unveil biological sex or training parameters as moderators of FFM increases and glucose homeostasis changes. Although Skm hypertrophy and improvements in glycemic control occur concurrently during RT, changes in these variables were not always related. Well-controlled trials including detailed description of training parameters are needed to inform RT guidelines for improving metabolic health. Registration and protocol number (Prospero): CRD42023397362.

Androgen receptor regulates the differentiation of myoblasts under cyclic mechanical stretch and its upstream and downstream signals

Our previous studies have demonstrated the important roles of androgen receptor (AR) in myoblast proliferation regulated by 15 % (mimic appropriate exercise) and 20 % (mimic excessive exercise) mechanical stretches. Except for myoblast proliferation, differentiation is also an important factor affecting muscle mass and strength. But the role of AR in stretch-regulated myoblast differentiation and AR's upstream and downstream signals remain unknown. In the present study, firstly the differences of myogenic differentiation between C2C12 (with AR expression) and L6 (without AR expression) myoblasts induced by 15 % and 20 % mechanical stretches were compared; secondly, AR antagonist flutamide and AR agonist GTx-007 were used in 15 % and 20 % stretched myoblasts respectively to confirm AR's roles in stretch-regulated myoblast differentiation; thirdly, RNA-seq, molecular dynamic simulation (MD) and co-immunoprecipitation were performed to screen the downstream and upstream molecules of AR during stretches. We found that (1) 15 % stretch increased while 20 % stretch decreased myotube number in differentiating C2C12 and L6 myoblasts, with more significant changes in C2C12 cells than L6 cells; (2) in stretched C2C12 myoblasts, AR antagonist flutamide inhibited 15 % stretch-promoted differentiation while AR agonist GTx-007 reversed 20 % stretch-inhibited differentiation (reflected by changes in myotube number, MHC contents of fast-twitch and slow-twitch fiber, and the levels of myogenic regulatory factors (MRFs) such as MyoD and myogenin); (3) KEGG analysis of RNA-seq showed that the differently expressed genes (DEGs) in C2C12 cells induced by 15 % stretch were enriched in FoxO and JAK-STAT signaling pathways, while DEGs by 20 % stretch were enriched in FoxO and MAPK signaling pathways; (4) MD and co-immunoprecipitation showed that β1 integrin could interact with AR and influence AR's activity in C2C12 cells. In conclusion, AR plays important roles in myoblast differentiation promoted by 15 % stretch while inhibited by 20 % stretch, which was fulfilled through FoxO-MRFs. In addition, α7β1 integrin may be a bridge linking mechanical stretch and AR. This study is beneficial to deeply understand the roles and mechanisms of AR in stretch-regulated muscle mass and strength; and reports firstly that myoblasts sense mechanical stimulus and transmit into intracellular AR via α7β1 integrin.

Interleukin 15: A new intermediary in the effects of exercise and training on skeletal muscle and bone function

Interleukin-15 (IL-15), a pro-inflammatory cytokine, is produced mainly by skeletal muscle cells, macrophages and epithelial cells. Recent research has demonstrated that IL-15 is closely related to the functions of bone and skeletal muscle in the locomotor system. There is growing evidence that exercise, an important means to regulate the immune and locomotor systems, influences IL-15 content in various tissues, thereby indirectly affecting the function of bones and muscles. Furthermore, the form, intensity, and duration of exercise determine the degree of change in IL-15 and downstream effects. This paper reviews the structure, synthesis and secretion of IL-15, the role of IL-15 in regulating the metabolism of bone tissue cells and myofibers through binding to the IL-15 receptor-α (IL-15Rα), and the response of IL-15 to different types of exercise. This review provides a reference for further analyses of the role and mechanism of action of IL-15 in the regulation of metabolism during exercise.

Exercise-induced interactions between skeletal muscle and bone via myokines and osteokine in mice: Role of FNDC5/irisin, IGF-1, and osteocalcin

Skeletal muscle and bone interact to maintain their structure and function. Physical exercise is the most effective and easily applicable strategy to maintain their functions; however, exercise-induced interactions by soluble factors remained elusive. Our study aimed to identify exercise-induced interactions between muscle and bone by examining (1) the effects of myokine on bone and (2) the effects of osteocalcin (OCN) on skeletal muscle. To understand the effects of exercise-induced myokines on bone, we examined the effects of FNDC5 for aerobic exercise and IGF-1 for resistance exercise using a muscle-specific myokine overexpression model. To examine OCN effects on muscle, mice were intraperitoneally administered OCN-neutralizing antibody during long-term exercise. Our result showed that aerobic exercise tended to increase serum HA-tag protein attached to FNDC5 in muscle-specific overexpression groups. In addition, osteoblastic activation was increased only after aerobic exercise with HA/FNDC5 overexpression. Resistance exercise did not alter circulating HA-tag (muscle-derived IGF-1) and bone metabolism after IGF-1/HA overexpression. In the OCN study, aerobic exercise enhanced endurance capacity by restoring muscle glycogen content; however, OCN neutralization returned these to baseline. After resistance exercise, OCN suppression inhibited muscle hypertrophy and strength gains by preventing protein synthesis. Our results suggest that aerobic exercise following FNDC5 muscle overexpression promotes osteoblast activity, which may be partially caused by muscle-derived FNDC5 secretion. In addition, OCN was necessary for muscle adaptation in both aerobic and resistance exercises.

Mitigating disuse-induced skeletal muscle atrophy in ageing: Resistance exercise as a critical countermeasure

The gradual deterioration of physiological systems with ageing makes it difficult to maintain skeletal muscle mass (sarcopenia), at least partly due to the presence of 'anabolic resistance', resulting in muscle loss. Sarcopenia can be transiently but markedly accelerated through periods of muscle disuse-induced (i.e., unloading) atrophy due to reduced physical activity, sickness, immobilisation or hospitalisation. Periods of disuse are detrimental to older adults' overall quality of life and substantially increase their risk of falls, physical and social dependence, and early mortality. Disuse events induce skeletal muscle atrophy through various mechanisms, including anabolic resistance, inflammation, disturbed proteostasis and mitochondrial dysfunction, all of which tip the scales in favour of a negative net protein balance and subsequent muscle loss. Concerningly, recovery from disuse atrophy is more difficult for older adults than their younger counterparts. Resistance training (RT) is a potent anabolic stimulus that can robustly stimulate muscle protein synthesis and mitigate muscle losses in older adults when implemented before, during and following unloading. RT may take the form of traditional weightlifting-focused RT, bodyweight training and lower- and higher-load RT. When combined with sufficient dietary protein, RT can accelerate older adults' recovery from a disuse event, mitigate frailty and improve mobility; however, few older adults regularly participate in RT. A feasible and practical approach to improving the accessibility and acceptability of RT is through the use of resistance bands. Moving forward, RT must be prescribed to older adults to mitigate the negative consequences of disuse atrophy.

Hormones, Hypertrophy, and Hype: An Evidence-Guided Primer on Endogenous Endocrine Influences on Exercise-Induced Muscle Hypertrophy

We review the evidence indicating that endogenous changes in these hormones, including testosterone, growth hormone, insulin growth factor-1, and estrogen, and their proposed anabolic effects contribute to and augment resistance exercise training (RET)-induced hypertrophy. Additionally, we provide recommendations for gold-standard methodological rigor to establish best practices for verifying menstrual phases as part of their research, ultimately enhancing our understanding of the impact of ovarian hormones on RET-induced adaptations.

Exercise-specific adaptations in human skeletal muscle: Molecular mechanisms of making muscles fit and mighty

The mechanisms leading to a predominantly hypertrophied phenotype versus a predominantly oxidative phenotype, the hallmarks of resistance training (RT) or aerobic training (AT), respectively, are being unraveled. In humans, exposure of naïve persons to either AT or RT results in their skeletal muscle exhibiting generic 'exercise stress-related' signaling, transcription, and translation responses. However, with increasing engagement in AT or RT, the responses become refined, and the phenotype typically associated with each form of exercise emerges. Here, we review some of the mechanisms underpinning the adaptations of how muscles become, through AT, 'fit' and RT, 'mighty.' Much of our understanding of molecular exercise physiology has arisen from targeted analysis of post-translational modifications and measures of protein synthesis. Phosphorylation of specific residue sites has been a dominant focus, with canonical signaling pathways (AMPK and mTOR) studied extensively in the context of AT and RT, respectively. These alone, along with protein synthesis, have only begun to elucidate key differences in AT and RT signaling. Still, key yet uncharacterized differences exist in signaling and regulation of protein synthesis that drive unique adaptation to AT and RT. Omic studies are required to better understand the divergent relationship between exercise and phenotypic outcomes of training.

Fundamental Body Composition Principles Provide Context for Fat-Free and Skeletal Muscle Loss With GLP-1 RA Treatments

During weight loss, reductions in body mass are commonly described using molecular body components (eg, fat mass and fat-free mass [FFM]) or tissues and organs (eg, adipose tissue and skeletal muscle). While often conflated, distinctions between body components established by different levels of the 5-level model of body composition-which partitions body mass according to the atomic, molecular, cellular, tissue/organ, or whole-body level-are essential to recall when interpreting the composition of weight loss. A contemporary area of clinical and research interest that demonstrates the importance of these concepts is the discussion surrounding body composition changes with glucagon-like peptide-1 receptor agonists (GLP-1RA), particularly in regard to changes in FFM and skeletal muscle mass. The present article emphasizes the importance of fundamental principles when interpreting body composition changes experienced during weight loss, with a particular focus on GLP-1RA drug trials. The potential for obligatory loss of FFM due to reductions in adipose tissue mass and distribution of FFM loss from distinct body tissues are also discussed. Finally, selected countermeasures to combat loss of FFM and skeletal muscle, namely resistance exercise training and increased protein intake, are presented. Collectively, these considerations may allow for enhanced clarity when conceptualizing, discussing, and seeking to influence body composition changes experienced during weight loss.

Pulsed Electromagnetic Field (PEMF) stimulation as an adjunct to exercise: a brief review

Pulsed Electromagnetic Field (PEMF) therapy is a non-invasive treatment that utilizes electromagnetic fields to stimulate and promote natural healing processes within the body. PEMF therapy works by emitting low-frequency electromagnetic pulses, which penetrate deep into tissues and cells, enhancing cellular function and health. PEMF applications are vast, ranging from enhancing recovery in athletes to supporting overall well-being in everyday individuals. PEMF therapy is increasingly recognized in the realm of sports and physical activity for its profound benefits in enhancing performance, accelerating recovery, and preventing injuries. By improving circulation, enhancing tissue oxygenation, and promoting the body's natural healing processes, PEMF therapy has become an invaluable tool in sports medicine, contributing to optimized physical health and prolonged athletic careers. In this review, we explore the effects of PEMF on exercise and the underlying physiological mechanisms.

Progression of total training volume in resistance training studies and its application to skeletal muscle growth

Progressive overload describes the gradual increase of stress placed on the body during exercise training, and is often quantified (i.e. in resistance training studies) through increases in total training volume (i.e. sets × repetitions × load) from the first to final week of the exercise training intervention. Within the literature, it has become increasingly common for authors to discuss skeletal muscle growth adaptations in the context of increases in total training volume (i.e. the magnitude progression in total training volume). The present manuscript discusses a physiological rationale for progressive overload and then explains why, in our opinion, quantifying the progression of total training volume within research investigations tells very little about muscle growth adaptations to resistance training. Our opinion is based on the following research findings: (1) a noncausal connection between increases in total training volume (i.e. progressively overloading the resistance exercise stimulus) and increases in skeletal muscle size; (2) similar changes in total training volume may not always produce similar increases in muscle size; and (3) the ability to exercise more and consequently amass larger increases in total training volume may not inherently produce more skeletal muscle growth. The methodology of quantifying changes in total training volume may therefore provide a means through which researchers can mathematically determine the total amount of external 'work' performed within a resistance training study. It may not, however, always explain muscle growth adaptations.

Association between changes in lean mass, muscle strength, endurance, and power following resistance or concurrent training with differing high protein diets in resistance-trained young males

Background

We assessed the relationship of changes in upper and lower body lean mass with muscle strength, endurance and power responses following two high protein diets (1.6 or 3.2 g.kg-1.d-1) during 16 weeks of either concurrent training (CT) or resistance training (RT) in resistance-trained young males.

Methods

Forty-eight resistance-trained young males (age: 26 ± 6 yr., body mass index: 25.6 ± 2.9 kg.m-2) performed 16 weeks (four sessions·wk.-1) of CT or RT with either 1.6 g.kg-1.d-1 protein (CT + 1.6; n = 12; RT + 1.6; n = 12) or 3.2 g.kg-1.d-1 protein (CT + 3.2; n = 12; RT + 3.2; n = 12). Relationships between upper (left arm + right arm + trunk lean mass) and lower body (left leg + right leg lean mass) lean mass changes with changes in muscle performance were assessed using Pearson's correlation coefficients.

Results

For upper body, non-significant weak positive relationships were observed between change in upper body lean mass and change in pull-up (r = 0.183, p = 0.234), absolute chest press strength (r = 0.159, p = 0.302), chest press endurance (r = 0.041, p = 0.792), and relative chest press strength (r = 0.097, p = 0.529) while non-significant weak negative relationships were observed for changes in absolute upper body power (r = -0.236, p = 0.123) and relative upper body power (r = -0.203, p = 0.185). For lower body, non-significant weak positive relationships were observed between the change in lower body lean mass with change in vertical jump (r = 0.145, p = 0.346), absolute lower body power (r = 0.109, p = 0.480), absolute leg press strength (r = 0.073, p = 0.638), leg press endurance (r < 0.001, p = 0.998), relative leg press strength (r = 0.089, p = 0.564), and relative lower body power (r = 0.150, p = 0.332).

Conclusion

Changes in muscle strength, endurance and power adaptation responses following 16 weeks of either CT or RT with different high protein intakes were not associated with changes in lean mass in resistance-trained young males. These findings indicate that muscle hypertrophy has a small, or negligible, contributory role in promoting functional adaptations with RT or CT, at least over a 16-week period.

Acute Resistance Exercise Modifies Extracellular Vesicle miRNAs Targeting Anabolic Gene Pathways: A Prospective Cohort Study

BACKGROUND

Resistance training confers numerous health benefits that are mediated in part by circulating factors. Toward an enhanced molecular understanding, there is growing interest in a class of signaling biomarkers called extracellular vesicles (EV). EVs support physiological adaptations to exercise by transporting their cargo (e.g., microRNA (miRNA)) to target cells. Previous studies of changes in EV cargo have focused on aerobic exercise, with limited data examining the effects of resistance exercise. We examined the effect of acute resistance exercise on circulating EV miRNAs and their predicted target pathways.

METHODS

Ten participants (5 men; age, 26.9 ± 5.5 yr; height, 173.4 ± 10.5 cm; body mass, 74.0 ± 11.1 kg; body fat, 25.7% ± 11.6%) completed an acute heavy resistance exercise test (AHRET) consisting of six sets of 10 repetitions of back squats using 75% one-repetition maximum. Pre-/post-AHRET, EVs were isolated from plasma using size exclusion chromatography, and RNA sequencing was performed. Differentially expressed miRNAs between pre- and post-AHRET EVs were analyzed using Ingenuity Pathway Analysis to predict target messenger RNAs and their target biological pathways.

RESULTS

Overall, 34 miRNAs were altered by AHRET ( P < 0.05), targeting 4895 mRNAs, with enrichment of 175 canonical pathways ( P < 0.01), including 12 related to growth/metabolism (p53, IGF-I, STAT3, PPAR, JAK/STAT, growth hormone, WNT/β-catenin, ERK/MAPK, AMPK, mTOR, and PI3K/AKT) and 8 to inflammation signaling (TGF-β, IL-8, IL-7, IL-3, IL-6, IL-2, IL-17, IL-10).

CONCLUSIONS

Acute resistance exercise alters EV miRNAs targeting pathways involved in growth, metabolism, and immune function. Circulating EVs may serve as significant adaptive signaling molecules influenced by exercise training.

Association between remote resistance exercises programs delivered by a smartphone application and skeletal muscle mass among elderly patients with type 2 diabetes- a retrospective real-world study

Objective

We aimed to explore the relationship between remote resistance exercise programs delivered via a smartphone application and skeletal muscle mass among elderly patients with type 2 diabetes, utilizing real-world data.

Methods

The resistance exercises were provided through Joymotion®, a web-based telerehabilitation smartphone application (Shanghai Medmotion Medical Management Co., Ltd). The primary outcome was the changes in skeletal muscle index (SMI) before and after the remote resistance exercises programs. The secondary outcomes were changes in skeletal muscle cross-sectional area (SMA), skeletal muscle radiodensity (SMD) and intermuscular adipose tissue (IMAT).

Results

A total of 101 elderly patients with type 2 diabetes were analyzed. The participants had an average age of 72.9 ± 6.11 years for males and 74.4 ± 4.39 years for females. The pre- and post-intervention SMI mean (± SE) was 31.64 ± 4.14 vs. 33.25 ± 4.22 cm2/m2 in male, and 22.72 ± 3.24 vs. 24.28 ± 3.60 cm2/m2 in female respectively (all P < 0.001). Similarly, a statistically significant improvement in SMA, IMAT, and SMD for both male and female groups were also observed respectively (P < 0.001). Multiple linear regression models showed potential confounding factors of baseline hemoglobin A1c and duration of diabetes with changes in SMI in male, while hemoglobin A1c and high density lipoprotein cholesterol with changes in SMI in female.

Conclusion

Remote resistance exercises programs delivered by a smartphone application were feasible and effective in helping elderly patients with type 2 diabetes to improve their skeletal muscle mass.

Post-natal muscle growth and protein turnover: a narrative review of current understanding

A model explaining the dietary-protein-driven post-natal skeletal muscle growth and protein turnover in the rat is updated, and the mechanisms involved are described, in this narrative review. Dietary protein controls both bone length and muscle growth, which are interrelated through mechanotransduction mechanisms with muscle growth induced both from stretching subsequent to bone length growth and from internal work against gravity. This induces satellite cell activation, myogenesis and remodelling of the extracellular matrix, establishing a growth capacity for myofibre length and cross-sectional area. Protein deposition within this capacity is enabled by adequate dietary protein and other key nutrients. After briefly reviewing the experimental animal origins of the growth model, key concepts and processes important for growth are reviewed. These include the growth in number and size of the myonuclear domain, satellite cell activity during post-natal development and the autocrine/paracrine action of IGF-1. Regulatory and signalling pathways reviewed include developmental mechanotransduction, signalling through the insulin/IGF-1-PI3K-Akt and the Ras-MAPK pathways in the myofibre and during mechanotransduction of satellite cells. Likely pathways activated by maximal-intensity muscle contractions are highlighted and the regulation of the capacity for protein synthesis in terms of ribosome assembly and the translational regulation of 5-TOPmRNA classes by mTORC1 and LARP1 are discussed. Evidence for and potential mechanisms by which volume limitation of muscle growth can occur which would limit protein deposition within the myofibre are reviewed. An understanding of how muscle growth is achieved allows better nutritional management of its growth in health and disease.

Effects of effortful swallowing against kinesiology taping resistance on the swallowing function in patients with poststroke dysphagia: A randomized controlled trial

BACKGROUND

A dysphagia rehabilitation method using kinesiology taping (KT) was recently introduced, and its potential for clinical efficacy was demonstrated by evaluating muscle activity and thickness. However, its effect on the swallowing function in patients with dysphagia remains unclear. This study aimed to investigate the effects of effortful swallowing against KT resistance on the swallowing function in patients with post stroke dysphagia.

METHODS

Thirty patients with poststroke dysphagia were recruited and randomly assigned to the experimental and placebo groups. In the experimental group, the KT was attached to the front of the neck (the hyoid bone between the sternum) with a tension of approximately 70% to 80%, and effortful swallowing was performed against the KT tension. In contrast, the placebo group performed effortful swallowing with KT applied at the same location without tension. The intervention was performed 30 times/day, 5 days/week for 6 weeks. The videofluoroscopic dysphagia scale (VDS) and penetration-aspiration scale (PAS) based on a videofluoroscopic swallowing study were used to analyze oropharyngeal swallowing function.

RESULTS

The experimental group showed statistically significant improvements in the oral and pharyngeal phases of the VDS (P = .029 and .007, respectively) and PAS (P = .034) compared with the placebo group. Effect sizes were observed for the oral (0.3) and pharyngeal phases (0.5) of the VDS and PAS (1.1).

CONCLUSION

This study demonstrated that effortful swallowing against resistance to KT is an effective therapeutic exercise for improving the swallowing function in patients with poststroke dysphagia.

Radiopharmaceuticals for Skeletal Muscle PET Imaging

The skeletal muscles account for approximately 40% of the body weight and are crucial in movement, nutrient absorption, and energy metabolism. Muscle loss and decline in function cause a decrease in the quality of life of patients and the elderly, leading to complications that require early diagnosis. Positron emission tomography/computed tomography (PET/CT) offers non-invasive, high-resolution visualization of tissues. It has emerged as a promising alternative to invasive diagnostic methods and is attracting attention as a tool for assessing muscle function and imaging muscle diseases. Effective imaging of muscle function and pathology relies on appropriate radiopharmaceuticals that target key aspects of muscle metabolism, such as glucose uptake, adenosine triphosphate (ATP) production, and the oxidation of fat and carbohydrates. In this review, we describe how [18F]fluoro-2-deoxy-D-glucose ([18F]FDG), [18F]fluorocholine ([18F]FCH), [11C]acetate, and [15O]water ([15O]H2O) are suitable radiopharmaceuticals for diagnostic imaging of skeletal muscles.

Not Only Protein: Dietary Supplements to Optimize the Skeletal Muscle Growth Response to Resistance Training: The Current State of Knowledge

Regarding skeletal muscle hypertrophy, resistance training and nutrition, the most often discussed and proposed supplements include proteins. Although, the correct amount, quality, and daily distribution of proteins is of paramount importance for skeletal muscle hypertrophy, there are many other nutritional supplements that can help and support the physiological response of skeletal muscle to resistance training in terms of muscle hypertrophy. A healthy muscle environment and a correct whole muscle metabolism response to the stress of training is a prerequisite for the increase in muscle protein synthesis and, therefore, muscle hypertrophy. In this review, we discuss the role of different nutritional supplements such as carbohydrates, vitamins, minerals, creatine, omega-3, polyphenols, and probiotics as a support and complementary factors to the main supplement i.e., protein. The different mechanisms are discussed in the light of recent evidence.

Paraspinal muscles in individuals undergoing surgery for lumbar spine pathology lack a myogenic response to an acute bout of resistance exercise

Background

Lumbar spine pathology (LSP) is a common source of low back or leg pain, and paraspinal muscle in these patients demonstrates fatty and fibrotic infiltration, and cellular degeneration that do not reverse with exercise-based rehabilitation. However, it is unclear of this lack of response is due to insufficient exercise stimulus, or an inability to mount a growth response. The purpose of this study was to compare paraspinal muscle gene expression between individuals with LSP who do and do not undergo an acute bout of resistance exercise.

Methods

Paraspinal muscle biopsies were obtained from 64 individuals with LSP undergoing spinal surgery. Eight participants performed an acute bout of machine-based lumbar extension resistance exercise preoperatively. Gene expression for 42 genes associated with adipogenic/metabolic, atrophic, fibrogenic, inflammatory, and myogenic pathways was measured, and differential expression between exercised and non-exercised groups was evaluated for (a) the full cohort, and (b) an age, gender, acuity, and etiology matched sub-cohort. Principal components analyses were used to identify gene expression clustering across clinical phenotypes.

Results

The exercised cohort demonstrated upregulation of inflammatory gene IL1B, inhibition of extracellular matrix components (increased MMP3&9, decreased TIMP1&3, COL1A1) and metabolic/adipogenic genes (FABP4, PPARD, WNT10B), and downregulation of myogenic (MYOD, ANKRD2B) and atrophic (FOXO3) genes compared to the non-exercised cohort, with similar patterns in the matched sub-analysis. There were no clinical phenotypes significantly associated with gene expression profiles.

Conclusion

An acute bout of moderate-high intensity resistance exercise did not result in upregulation of myogenic genes in individuals with LSP. The response was characterized by mixed metabolic and fibrotic gene expression, upregulation of inflammation, and downregulation of myogenesis.

The effect of periodic resistance training on obese patients with type 2 diabetic nephropathy

Resistance training is an exercise against resistance designed to train the endurance and strength of muscle. To observe the effect of intervention of periodic resistance training on obese patients with type 2 diabetic nephropathy. A total of 60 obese patients with type 2 diabetic nephropathy were randomized into resistance training group and aerobic exercise group (30 patients each group) for observing the changes of blood glucose, body weight, blood lipid, insulin resistance, serum creatinine (Scr), urinary microalbumin, urinary albumin excretion rate (UAER) calculated by urinary creatinine, and glomerular filtration rate (GFR) after 12 weeks of intervention, and relevant significance as well. The number of patients with hypoglycemia during the intervention was also recorded. After 12 weeks of intervention, the weight, Body mass index (BMI), Waist, Triglyceride (TG), Cholesterol (TC), Low-density lipoprotein cholesterol (LDL), Fasting glucose (FBG), Fasting insulin (FINS), Glycosylated hemoglobin (HbA1c) and urine Albumin-Creatinine Ratio (uACR) were decreased and GFR was increased in both groups (P < 0.05), but the effect was more significant in the resistance training group. GFR was increased from 92.21 ± 10.67 mL/(min·1.73 m2) to 100.13 ± 12.99 mL/(min·1.73 m2) in resistance training group (P < 0.05). In the aerobic exercise group, GFR was increased from 89.98 ± 9.48 mL/(min·1.73 m2) to 92.51 ± 11.35 mL/(min·1.73 m2) (P > 0.05). Periodic resistance training can not only control the weight, blood sugar and blood lipid of obese patients with type 2 diabetic nephropathy, but also improve the urinary albumin excretion rate and glomerular filtration rate of early obese patients with type 2 diabetic nephropathy, and delay the progression of diabetic nephropathy. It is an effective non-drug intervention.

The Plateau in Muscle Growth with Resistance Training: An Exploration of Possible Mechanisms

It is hypothesized that there is likely a finite ability for muscular adaptation. While it is difficult to distinguish between a true plateau following a long-term training period and short-term stalling in muscle growth, a plateau in muscle growth has been attributed to reaching a genetic potential, with limited discussion on what might physiologically contribute to this muscle growth plateau. The present paper explores potential physiological factors that may drive the decline in muscle growth after prolonged resistance training. Overall, with chronic training, the anabolic signaling pathways may become more refractory to loading. While measures of anabolic markers may have some predictive capabilities regarding muscle growth adaptation, they do not always demonstrate a clear connection. Catabolic processes may also constrain the ability to achieve further muscle growth, which is influenced by energy balance. Although speculative, muscle cells may also possess cell scaling mechanisms that sense and regulate their own size, along with molecular brakes that hinder growth rate over time. When considering muscle growth over the lifespan, there comes a point when the anabolic response is attenuated by aging, regardless of whether or not individuals approach their muscle growth potential. Our goal is that the current review opens avenues for future experimental studies to further elucidate potential mechanisms to explain why muscle growth may plateau.

Effect of Ginseng Intake on Muscle Damage Induced by Exercise in Healthy Adults

One of the most popular herbal supplements in the world is ginseng. Several studies have evaluated the capacity of ginseng as a protective element in the physiological response to exercise. The result produced by the exercise causes an increase in cellular biomarkers of damage in the skeletal muscle, mainly in the pro-inflammatory types. The different types of ginseng are composed of ginsenosides, which are active ingredients that act on the central nervous system and have antioxidant and anti-inflammatory properties, as well as effects on cortisol modulation. The use of ginseng as a nutritional supplement can help muscle regeneration and renewal. The objective of this review is to enrich the knowledge regarding the consumption of ginseng for a specific situation, such as exercise, which would cause an improvement in the tolerance to chronic load stimuli in sport, thus helping the subjects to recover between training sessions. Due to these benefits, it could also be an ideal food supplement for regenerative processes in muscle injuries in which inflammatory markers increase significantly. This review aims to summarise that biological factors can be attenuated after exercise due to the consumption of ginseng in healthy subjects, accelerating and improving muscle regeneration and, therefore, improving the ability to adapt to the stimuli generated by said exercise.

Menstrual cycle hormones and oral contraceptives: a multimethod systems physiology-based review of their impact on key aspects of female physiology

Hormonal changes around ovulation divide the menstrual cycle (MC) into the follicular and luteal phases. In addition, oral contraceptives (OCs) have active (higher hormone) and placebo phases. Although there are some MC-based effects on various physiological outcomes, we found these differences relatively subtle and difficult to attribute to specific hormones, as estrogen and progesterone fluctuate rather than operating in a complete on/off pattern as observed in cellular or preclinical models often used to substantiate human data. A broad review reveals that the differences between the follicular and luteal phases and between OC active and placebo phases are not associated with marked differences in exercise performance and appear unlikely to influence muscular hypertrophy in response to resistance exercise training. A systematic review and meta-analysis of substrate oxidation between MC phases revealed no difference between phases in the relative carbohydrate and fat oxidation at rest and during acute aerobic exercise. Vascular differences between MC phases are also relatively small or nonexistent. Although OCs can vary in composition and androgenicity, we acknowledge that much more work remains to be done in this area; however, based on what little evidence is currently available, we do not find compelling support for the notion that OC use significantly influences exercise performance, substrate oxidation, or hypertrophy. It is important to note that the study of females requires better methodological control in many areas. Previous studies lacking such rigor have contributed to premature or incorrect conclusions regarding the effects of the MC and systemic hormones on outcomes. While we acknowledge that the evidence in certain research areas is limited, the consensus view is that the impact of the MC and OC use on various aspects of physiology is small or nonexistent.

Exploring the acute muscle fatigue response in resistance trained individuals during eccentric quasi-isometric elbow flexions-a cross-sectional comparison of repetition and sex

Eccentric quasi-isometrics (EQIs) are a novel, low-velocity resistance exercise technique that incorporates a holding isometric contraction to positional fatigue, followed by voluntary resistance of the resulting eccentric muscle action. As females are typically more fatigue resistant than males during isometric and low-velocity dynamic muscle actions, this study explored sex-differences in the muscle fatigue response to an EQI protocol. Twenty-five (n = 12 female) participants completed 4 unilateral EQI elbow flexions. Absolute and relative surface electromyography (sEMG) amplitude (iEMG, LE peak), mean power frequency (MPF), angular impulse (aIMP), and elbow angle were compared across repetitions and between sexes using discrete values and statistical parametric/non-parametric mapping. There were significant and substantial sex and repetition differences in absolute iEMG, MPF, and aIMP, however, males and females had statistically similar absolute aIMP by repetition 4. When expressed relatively, there were no significant sex-differences. Additionally, there were significant between repetition changes in sEMG amplitude and elbow angle with an increasing number of repetitions, largely in the first-two thirds of repetition time. The current study suggests that there are absolute, but not relative sex-differences in EQI induced muscle fatigue, and the effects across repetitions occur predominately in the first two-thirds of repetition time.

The impact and utility of very low-calorie diets: the role of exercise and protein in preserving skeletal muscle mass

PURPOSE OF REVIEW

Very low-calorie diets (VLCD) are used as a weight loss intervention, but concerns have been raised about their potential negative impact on lean mass. Here, we review the available evidence regarding the effects of VLCD on lean mass and explore their utility and strategies to mitigate reductions in skeletal muscle.

RECENT FINDINGS

We observed that VLCD, despite their effects on lean mass, may be suitable in certain populations but have a risk in reducing lean mass. The extent of the reduction in lean mass may depend on various factors, such as the duration and degree of energy deficit of the diet, as well as the individual's starting weight and overall health.

SUMMARY

VLCD may be a viable option in certain populations; however, priority needs to be given to resistance exercise training, and secondarily to adequate protein intake should be part of this dietary regime to mitigate losing muscle mass.

Resistance training alters body composition in middle-aged women depending on menopause - A 20-week control trial

BACKGROUND

Resistance training (RT) is effective in counteracting the age- and menopause-related loss of muscle mass (MM) and strength in middle-aged women (40-60 years). Research on RT with free weights is limited in pre- and post-menopausal women. Based on this, a 20-week training intervention was conducted with this population to investigate the effects of systematic RT with free weights on strength capacity and body composition.

METHOD

Forty-one healthy women (52.0 ± 3.6 years) participated in this study. After 10-week control phase (no RT, T0-T1) followed by a 10-week intervention phase (T1-T2) with RT twice a week and 6-8 sets of each muscle per week. Subjects were randomly assigned to a low-intensity (50% 1-RM) or moderate-intensity (75% 1-RM) RT group and divided into pre-menopausal and post-menopausal according to their hormone profile. Fat-free mass (FFM), MM, fat mass (FM), muscle thickness (Vastus lateralis (VL), Rectus femoris (RF), Triceps brachii (TB)), grip strength, 1-RM squat and bench press were assessed before and after each phase. Statistical analysis was performed using a linear mixed model to account for fixed (time and group) and random (individual) effects.

RESULTS

A total of 31 women successfully completed the study. No injuries occurred during the intervention. Significant increases in 1-RM squat and bench press were observed in all groups. No interaction effect was observed for the strength parameters. In pre-menopausal women, FFM, MM and RF muscle thickness increased significantly, while VL showed a trend. These effects were not present in post-menopausal women regardless of RT intensity.

CONCLUSION

RT with free weight is safe and effective for middle-aged women to increase 1-RM. Hypertrophy effects were found exclusively in pre-menopausal women. To achieve hypertrophy and/or body composition changes in post-menopausal women, larger training volumes (> 6-8 sets/muscle per week) are likely required.

Resistance training prescription for muscle strength and hypertrophy in healthy adults: a systematic review and Bayesian network meta-analysis

OBJECTIVE

To determine how distinct combinations of resistance training prescription (RTx) variables (load, sets and frequency) affect muscle strength and hypertrophy.

DATA SOURCES

MEDLINE, Embase, Emcare, SPORTDiscus, CINAHL, and Web of Science were searched until February 2022.

ELIGIBILITY CRITERIA

Randomised trials that included healthy adults, compared at least 2 predefined conditions (non-exercise control (CTRL) and 12 RTx, differentiated by load, sets and/or weekly frequency), and reported muscle strength and/or hypertrophy were included.

ANALYSES

Systematic review and Bayesian network meta-analysis methodology was used to compare RTxs and CTRL. Surface under the cumulative ranking curve values were used to rank conditions. Confidence was assessed with threshold analysis.

RESULTS

The strength network included 178 studies (n=5097; women=45%). The hypertrophy network included 119 studies (n=3364; women=47%). All RTxs were superior to CTRL for muscle strength and hypertrophy. Higher-load (>80% of single repetition maximum) prescriptions maximised strength gains, and all prescriptions comparably promoted muscle hypertrophy. While the calculated effects of many prescriptions were similar, higher-load, multiset, thrice-weekly training (standardised mean difference (95% credible interval); 1.60 (1.38 to 1.82) vs CTRL) was the highest-ranked RTx for strength, and higher-load, multiset, twice-weekly training (0.66 (0.47 to 0.85) vs CTRL) was the highest-ranked RTx for hypertrophy. Threshold analysis demonstrated these results were extremely robust.

CONCLUSION

All RTx promoted strength and hypertrophy compared with no exercise. The highest-ranked prescriptions for strength involved higher loads, whereas the highest-ranked prescriptions for hypertrophy included multiple sets.

PROSPERO REGISTRATION NUMBER

CRD42021259663 and CRD42021258902.

The isolated effects of local cold application on proteolytic and myogenic signaling

Post-exercise cooling studies reveal inhibitory effects on markers of skeletal muscle growth. However, the isolated effect of local cold application has not been adequately addressed. It is unclear if the local cold or the combination of local cold and exercise is driving negatively altered skeletal muscle gene expression. The purpose was to determine the effects of a 4 h local cold application to the vastus lateralis on the myogenic and proteolytic response. Participants (n = 12, 27 ± 6 years, 179 ± 9 cm, 82.8 ± 13.0 kg, 18.4 ± 7.1 %BF) rested with a thermal wrap placed on each leg with either circulating cold fluid (10 °C, COLD) or no fluid circulation (room temperature, RT). Muscle samples were collected to quantify mRNA (RT-qPCR) and proteins (Western Blot) associated with myogenesis and proteolysis. Temperatures in COLD were lower than RT at the skin (13.2 ± 1.0 °C vs. 34.8 ± 0.9 °C; p < 0.001) and intramuscularly (20.5 ± 1.3 °C vs. 35.6 ± 0.8 °C, p < 0.001). Myogenic-related mRNA, MYO-G and MYO-D1, were lower in COLD (p = 0.001, p < 0.001, respectively) whereas myogenic-mRNA, MYF6, was greater in COLD (p = 0.002). No other myogenic associated genes were different between COLD and RT (MSTN, p = 0.643; MEF2a, p = 0.424; MYF5, p = 0.523; RPS3, p = 0.589; RPL3-L, p = 0.688). Proteolytic-related mRNA was higher in COLD (FOXO3a, p < 0.001; Atrogin-1, p = 0.049; MURF-1, p < 0.001). The phosphorylation:total protein ratio for the translational repressor of muscle mass, 4E-BP1Thr37/46, was lower in COLD (p = 0.043), with no differences in mTORser2448 (p = 0.509) or p70S6K1Thr389 (p = 0.579). Isolated local cooling over 4 h exhibits inhibited myogenic and higher proteolytic skeletal muscle molecular response.

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."

T-score discordance between hip and lumbar spine: risk factors and clinical implications

Background

T-score discordance is common in osteoporosis diagnosis and leads to problems for clinicians formulating treatment plans.

Objectives

This study investigated the potential predictors of T-score discordance and compared fracture risk among individuals with varying T-score discordance status.

Design

This was a single-center cross-sectional study conducted at Wan Fang Hospital, Taipei City, between 1 February 2020 and 31 January 2022.

Methods

The present study enrolled patients aged ⩾50 years who received advanced bone health examination. Participants with a history of fracture surgery or underlying musculoskeletal diseases were excluded. Bioelectrical impedance analysis and dual-energy X-ray absorptiometry were used to determine the body composition and T-score, respectively. Discordance was defined as different T-score categories between the lumbar spine and hip. The impact of discordance on an individual's fracture risk was assessed using the Fracture Risk Assessment Tool (FRAX).

Results

This study enrolled 1402 participants (181 men and 1221 women). Of the 912 participants diagnosed with osteoporosis, 47 (5%) and 364 (40%) were categorized as having major and minor discordance, respectively. Multinomial logistic regression revealed that decreased walking speed was significantly correlated with major discordance but not osteoporosis in both the hip and lumbar spine (odds ratio of 0.25, p = 0.04). The adjusted FRAX scores for the major osteoporotic fracture risks of the major and minor discordance groups were approximately 14%, which was significantly lower than that of people having osteoporosis in both the hip and lumbar spine.

Conclusions

Walking speed exhibited the most significant correlation with major discordance in patients with osteoporosis. Although adjusted major fracture risks were similar between the major and minor discordance groups, further longitudinal studies are warranted to confirm this finding.

Registrations

This study was approved by the Ethics Committee of Taipei Medical University on 01/04/2022 (TMU-JIRB N202203088).

Fortetropin supplementation prevents the rise in circulating myostatin but not disuse-induced muscle atrophy in young men with limb immobilization: A randomized controlled trial

Supplementation with Fortetropin® (FOR), a naturally occurring component from fertilized egg yolks, reduces circulating myostatin concentration. We hypothesized that FOR would mitigate muscle atrophy during immobilization. We examined the effect of FOR supplementation on muscle size and strength during 2-wk of single-leg immobilization and recovery. Twenty-four healthy young men (22 ± 2 yrs; BMI = 24.3 ± 2.9 kg/m2) were randomly allocated to either a Fortetropin® supplement (FOR-SUPP, n = 12) group consuming 19.8 g/d of FOR or placebo (PLA-SUPP, n = 12) group consuming energy- and macronutrient-matched cheese powder for 6-wk. The 6-wk period consisted of 2-wk run-in, 2-wk single-leg immobilization, and 2-wk recovery phase returning to habitual physical activities. Ultrasonography, dual-energy X-ray absorptiometry, muscle biopsies and isometric peak torque assessments were performed prior to and following each phase (days 1, 14, 28, and 42) to measure vastus lateralis and muscle fiber cross-section area (CSA), leg lean mass (LM), and muscular strength. Blood samples were taken on days 1 and 42 for measurement of plasma myostatin concentration, which increased in PLA-SUPP (4221 ± 541 pg/mL to 6721 ± 864 pg/mL, P = 0.013) but not in FOR-SUPP (5487 ± 489 pg/mL to 5383 ± 781 pg/mL, P = 0.900). After the immobilization phase, vastus lateralis CSA, LM, and isometric peak torque were decreased by 7.9 ± 1.7% (P < 0.001), -1.6 ± 0.6% (P = 0.037), and -18.7 ± 2.7% (P < 0.001) respectively, with no difference between groups. The decreased peak torque was recovered after 2-wk of normal activity (vs. day 1, P = 0.129); however, CSA and LM were not recovered (vs. day 1, P < 0.001 and P = 0.003, respectively), with no differences between groups. Supplementation with FOR prevented the rise in circulating myostatin but not disuse-induced muscle atrophy in young men after 2-wk of single-leg immobilization.

Muscle Thickness, Echo-Intensity, Peak Force, Time Under Tension, Total Load Lifted, and Perception of Effort Comparisons Between Two Abdominal Crunch Resistance Training Protocols in Recreationally-Trained Participants

The primary purpose of this study was to evaluate acute dose response of different intensities with total volume equalized during the abdominal crunch exercise on muscle thickness, echo-intensity, peak force, time under tension, total load lifted, and perception of effort in recreationally-trained participants. Fifteen resistance-trained participants (23 ± 3 years) performed the abdominal crunch exercise in one of two different resistance training (RT) protocols in a randomized order: RT4×10RM (4 sets of 10RM / 1-min rest) or RT1×40RM (1 set of 40RM). Muscle thickness (MT), echo-intensity (EI), peak force (PF), time under tension (TUT), total load lifted (TLL), and session rating of perceived exertion (sRPE) were measured pre-test and post-test (0-min and 15-min). Two-way repeated-measures ANOVAs (2 × 3) were used to test differences between RT protocols (RT4×10RM and RT1×40RM) and time (pre-test, post-0, and post-15) for MT, EI, and PF. Paired t-test was used to compare RT protocols for sRPE, TLL, and TUT. For MT, there were significant differences for RT4×10RM between pre-x post-0 (p = 0.011), pre-x post-15 (p < 0.001), and post-0 × post-15 (p = 0.02); and for RT1×40RM between pre-x post-0 (p < 0.001) and pre-x post-15 (p = 0.003). For EI, there was a significant difference for RT4×10RM between pre-x post-0 (p = 0.002). For sRPE, there was no significant difference between RT protocols. For TLL and TUT, there were significant differences between RT protocols (p < 0.05). In conclusion, both RT protocols (RT4×10RM and RT1×40RM) induced similar increases in MT but not for EI. TLL and TUT were higher for RT4×10RM. PF and sRPE were similar between RT protocols.

Gluteal Muscle Forces during Hip-Focused Injury Prevention and Rehabilitation Exercises

PURPOSE

This study aimed to compare and rank gluteal muscle forces in eight hip-focused exercises performed with and without external resistance and describe the underlying fiber lengths, velocities, and muscle activations.

METHODS

Motion capture, ground reaction forces, and electromyography (EMG) were used as input to an EMG-informed neuromusculoskeletal model to estimate gluteus maximus, medius, and minimus muscle forces. Participants were 14 female footballers (18-32 yr old) with at least 3 months of lower limb strength training experience. Each participant performed eight hip-focused exercises (single-leg squat, split squat, single-leg Romanian deadlift [RDL], single-leg hip thrust, banded side step, hip hike, side plank, and side-lying leg raise) with and without 12 repetition maximum (RM) resistance. For each muscle, exercises were ranked by peak muscle force, and k-means clustering separated exercises into four tiers.

RESULTS

The tier 1 exercises for gluteus maximus were loaded split squat (95% confidence interval [CI] = 495-688 N), loaded single-leg RDL (95% CI = 500-655 N), and loaded single-leg hip thrust (95% CI = 505-640 N). The tier 1 exercises for gluteus medius were body weight side plank (95% CI = 338-483 N), loaded single-leg squat (95% CI = 278-422 N), and loaded single-leg RDL (95% CI = 283-405 N). The tier 1 exercises for gluteus minimus were loaded single-leg RDL (95% CI = 267-389 N) and body weight side plank (95% CI = 272-382 N). Peak gluteal muscle forces increased by 28-150 N when exercises were performed with 12RM external resistance compared with body weight only. Peak muscle force coincided with maximum fiber length for most exercises.

CONCLUSIONS

Gluteal muscle forces were exercise specific, and peak muscle forces increased by varying amounts when adding a 12RM external resistance. These findings may inform exercise selection by facilitating the targeting of individual gluteal muscles and optimization of mechanical loads to match performance, injury prevention, or rehabilitation training goals.

Extracellular matrix content and remodeling markers do not differ in college-aged men classified as higher and lower responders to resistance training

We determined if skeletal muscle extracellular matrix (ECM) content and remodeling markers adapted with resistance training or were associated with hypertrophic outcomes. Thirty-eight untrained males (21 ± 3 yr) participated in whole body resistance training (10 wk, 2 × weekly). Participants completed testing [ultrasound, peripheral quantitative computed tomography (pQCT)] and donated a vastus lateralis (VL) biopsy 1 wk before training and 72 h following the last training bout. Higher responders (HR, n = 10) and lower responders (LR, n = 10) were stratified based on a composite score considering changes in pQCT-derived mid-thigh cross-sectional area (mCSA), ultrasound-derived VL thickness, and mean fiber cross-sectional area (fCSA). In all participants, training reduced matrix metalloprotease (MMP)-14 protein (P < 0.001) and increased satellite cell abundance (P < 0.001); however, VL fascial thickness, ECM protein content per myofiber, MMP-2/-9 protein content, tissue inhibitor of metalloproteinase (TIMP)-1/-2 protein content, collagen-1/-4 protein content, macrophage abundance, or fibroadipogenic progenitor cell abundance were not altered. Regarding responder analysis, MMP-14 exhibited an interaction (P = 0.007), and post hoc analysis revealed higher protein content in HR versus LR before training (P = 0.026) and a significant decrease from pre to posttraining in HR only (P = 0.002). In summary, basal skeletal muscle ECM markers are minimally affected with 10 wk of resistance training, and these findings could be related to not capturing more dynamic alterations in the assayed markers earlier in training. However, the downregulation in MMP-14 in college-aged men classified as HR is a novel finding and warrants continued investigation, and further research is needed to delineate muscle connective tissue strength attributes between HR and LR.NEW & NOTEWORTHY Although past studies have examined aspects of extracellular matrix remodeling in relation to mechanical overload or resistance training, this study serves to expand our knowledge on a multitude of extracellular matrix markers and whether these markers adapt to resistance training or are associated with differential hypertrophic responses.

Current evidence shows no influence of women's menstrual cycle phase on acute strength performance or adaptations to resistance exercise training

Introduction

The bias towards excluding women from exercise science research is often due to the assumption that cyclical fluctuations in reproductive hormones influence resistance exercise performance and exercise-induced adaptations.

Methods

Hence, the purpose of this umbrella review was to examine and critically evaluate the evidence from meta-analyses and systematic reviews on the influence of menstrual cycle phase on acute performance and chronic adaptations to resistance exercise training (RET).

Results

We observed highly variable findings among the published reviews on the ostensible effects of female sex hormones on relevant RET-induced outcomes, including strength, exercise performance, and hypertrophy.

Discussion

We highlight the importance of comprehensive menstrual cycle verification methods, as we noted a pattern of poor and inconsistent methodological practices in the literature. In our opinion, it is premature to conclude that short-term fluctuations in reproductive hormones appreciably influence acute exercise performance or longer-term strength or hypertrophic adaptations to RET.

Regular exercise combined with ferulic acid exhibits antiobesity effect and regulates metabolic profiles in high-fat diet-induced mice

Exercise (Ex) has been recognized as an effective way of obesity prevention, but it shows a dual effect on the body's antioxidant system. Ferulic acid (FA) is a kind of phenolic acid with well-known antioxidant capacity and numerous health benefits. Therefore, the aim of the study was to compare the antiobesity effect of Ex, FA, and Ex combined with FA (Ex-FA) in vivo and to illustrate the potential mechanisms. Mice were fed a high-fat diet (HFD) with or without administration of Ex, FA, and Ex-FA for 13 weeks. The body weight, antioxidant ability, Ex performance, and lipid profiles in the serum, liver, and skeletal muscle were compared among the groups, and serum metabolomics analysis was conducted. The results showed that Ex, FA, and Ex-FA exhibited a similar effect on body weight management. Ex had a more beneficial function by alleviating HFD-induced dyslipidemia than FA, while FA exerted a more efficient effect in mitigating lipid deposition in the liver and skeletal muscle. Ex-FA showed comprehensive effects in the regulation of the lipid contents in serum, liver, and skeletal muscle, and provoked enhancement effects on antioxidant ability and Ex capacity. Mice administered with Ex, FA, and Ex-FA showed different metabolic profiles, which might be achieved through different metabolic pathways. The findings of this research implied that Ex coupled with FA could become an effective and safe remedy for the management of dietary-induced obesity.