Narrative Review of Sex Differences in Muscle Strength, Endurance, Activation, Size, Fiber Type, and Strength Training Participation Rates, Preferences, Motivations, Injuries, and Neuromuscular Adaptations

Estimating repetitions in reserve through movement velocity: Applicability across bench press exercise modes and sexes

This study explored the accuracy of using the relationship between repetitions in reserve (RIR) and mean velocity (MV) to predict proximity to failure in bench press exercises across two modes (Smith machine and free-weight) and sexes (men and women). Twenty-eight recreationally trained individuals completed two sessions of each exercise mode, with sets performed to failure at 65% and 75% of one-repetition maximum. Individualized RIR-MV relationships showed a higher goodness-of-fit for the Smith machine compared to the free-weight bench press (R2 = 0.79-0.87 vs. 0.41-0.78), without significant sex differences (p = 0.880). MV values were mostly similar between exercise modes across different RIRs (p > 0.077), but men demonstrated higher MV values than women for RIR 5-1 (p ≤ 0.013). Individualized RIR-MV relationships were more accurate at estimating RIR 5 at 65%1RM in subsequent sessions than generalized RIR-MV relationships (absolute errors = 0.64-1.36 vs. 1.25-2.00 repetitions; p < 0.001), regardless of sex. However, the prediction accuracy was similar for both relationships at RIRs 2 and 0 (absolute errors ≤ 1 repetition; p ≥ 0.164). These results suggest that RIR-MV relationships can effectively estimate proximity to failure across exercise modes and sexes, with individualized relationships offering greater accuracy.

Does Maximum Strength Predict Rowing Performance in Elite Female Rowers?

PURPOSE

This study aimed to identify dynamic free-weight exercises for strength training and testing that are strong determinants of specific rowing ergometer performance measures in elite female rowers.

METHODS

A cross-sectional study examined the association between 1-repetition-maximum (1RM) power clean (PC1RM), 1RM bench row (BR1RM), 1RM back squat (SQ1RM), 1RM bench press (BP1RM), and 1RM deadlift (DL1RM) with peak stroke power (PSP) and 2000-m (P2000m) and 5000-m time-trial average power (P5000m) in 17 heavyweight elite female rowers.

RESULTS

Significant correlations were found between SQ1RM, DL1RM, and PC1RM with all rowing performance measures (r = .56-.86, all P < .05). BR1RM correlated significantly with PSP and P2000m (r = .52 and .55, P < .01 and .05), and BP1RM with PSP only (r = .55, P < .01). PC1RM and either DL1RM (R2 = 77%, P < .01) or SQ1RM (R2 = 76%, P < .01) were the greatest contributors to PSP. DL1RM and SQ1RM together provided the greatest explained variance for P2000m (R2 = 72%, P < .01) and P5000m (R2 = 60%, P < .05).

CONCLUSION

SQ1RM, DL1RM, and PC1RM were the strongest determinants of rowing ergometer performance in elite female rowers and are recommended for training and testing rowing-specific strength.

Sex Differences in Upper- and Lower-Limb Muscle Strength in Children and Adolescents: A Meta-Analysis

On average, adult men are physically stronger than adult women. The magnitude of this difference depends on the muscle tested, with larger sex differences observed in upper- than lower-limb muscles. Whether body region-specific sex differences in strength exist in children is unclear. The purpose of the current meta-analysis was to determine whether sex differences in muscle strength in children and adolescents differ between upper- and lower-limb muscles. Data were extracted from studies of participants aged ≤ 17 years who completed tests of maximal isometric or isokinetic strength of upper-limb muscles (e.g., elbow flexors and elbow extensors) or lower-limb muscles (e.g., knee extensors and ankle dorsiflexors). Participants were partitioned into three age groups: 5-10 years old, 11-13 years old, and 14-17 years old. The analysis included 299 effects from 34 studies. The total sample was 6634 (3497 boys and 3137 girls). Effect sizes of sex differences in upper- and lower-limb strength were g = 0.65 (95% confidence intervals (CI) [0.46, 0.84]) and 0.34 (95% CI [0.19, 0.50]) in 5-10-year-olds; g = 0.73 (95% CI [0.56, 0.91]) and 0.43 (95% CI [0.27, 0.59]) in 11-13-year olds; and g = 1.84 (95% CI [1.64, 2.03]) and 1.18 (95% CI [1.00, 1.37]) in 14-17-year-olds. Upper- and lower-limb strength were 17% and 8% greater in boys than girls when 5-10 years old, 18% and 10% greater when 11-13 years old, and 50% and 30% greater when 14-17 years old. Thus, boys are stronger than girls on average. This sex difference exists before puberty, increases markedly with male puberty, and is more pronounced in upper- than lower-limb muscles throughout development.

Sex-specific characteristics of special endurance and performance potential in female runners

OBJECTIVE

The coefficient of special endurance (KsA) is a metric that quantifies the relative pace loss between two consecutive distances (e.g., 100 m/200m). Here, we analyzed over 20,000 race times to determine KsA values for female runners across seven distance pairs from 100 m to 10,000 m. The data analyses are based on multiple official performance rankings at international to regional levels, exclusively compiled and processed for this study.

RESULTS

The KsA values obtained have remained stable for over four decades in national-level female runners and are applicable from world-class to regional levels. A sex-based analysis reveals that females undergo a more pronounced decrease in pace from 100 m to 1500 m in comparison to males. These sex differences in special endurance align with known variations in muscle fiber composition and fast-twitch type II fiber characteristics between males and females. In conclusion, we provide statistically valid KsA reference values for female runners from 100 m to 10,000 m. These values have practical implications for coaches and athletes seeking to assess runners' strengths, weaknesses, potential, and specific talents based on race times. Sex differences in KsA values may reflect muscle physiology and guide future research on KsA and muscle function.

A nationwide analysis of physical inactivity and sedentary behavior among stroke survivors in Korea

This study aimed to identify key predictors of physical inactivity and prolonged sedentary behavior among stroke survivors (SSs) using data from the 2016-2020 Korea National Health and Nutrition Surveys. Of the 28,146 participants, 633 had a history of stroke. The results showed that SSs were significantly more likely to be physically inactive and spend longer sedentary times than controls. Multivariate analysis identified that age ≥ 80 years (adjusted odds ratio [aOR] = 5.45, 95% confidence interval [CI] 1.96-15.15), lower education level (≤ 9 years) (aOR = 2.18, 95%CI 1.13-4.18), and living in rural areas (aOR = 1.91, 95%CI 1.11-3.29) were associated with aerobic physical inactivity. Female sex (aOR = 2.36, 95%CI 1.28-4.35) and lower education (aOR = 2.31, 95%CI 1.01-5.34) were linked to insufficient resistance exercises (≤ 1 day per week). Long sedentary time (≥ 8 h daily) was associated with being economically inactive (aOR = 1.90, 95%CI 1.21-2.96), single (aOR = 1.68, 95%CI 1.07-2.64), and perceiving oneself as unhealthy (aOR = 1.59, 95%CI 1.01-2.49). These findings highlight the need for targeted interventions, including community-based exercise programs and policy initiatives, to reduce sedentary behavior and promote physical activity among SSs. Implementing accessible and tailored rehabilitation strategies may help mitigate long-term health risks in this population.

Upper limb muscle strength and neuromuscular coordination and other factors as determinants of kinesiophobia in people with cervical and cervicothoracic spine dysfunction

The aim of this study was to analyze the incidence of neuromuscular coordination disorders and upper limb muscle strength in people with functional disorders of the cervical and cervicothoracic spine. A total of 407 participants took part in the study. The level of kinesiophobia was assessed using the Tampa scale. For cervical spine dysfunction, the pain was measured using the visual analogue scale (VAS) and the cervical disability index (NDI). Neuromuscular control was tested using the Deep Cervical Neck Flexor test with the Stabilizer device. Upper limb muscle strength was measured using a dynamometer test. The data obtained revealed a correlation between higher Tampa scale scores and most of the variables assessed. A positive correlation between age (rho = 0.27; p < 0.001), pain (rho = 0.43; p < 0.001), and NDI (rho = 0.43; p < 0.001) was registered. A negative relationship was found between neuromuscular coordination (rho = 0.41; p < 0.001) and muscle strength of most muscles(rho - 0.14 to -0.28, p < 0.01). Higher Tampa scale values correlate with poorer neuromuscular coordination, older age, pain, weaker NDI score, and strength of some upper limb muscles in the cervical and cervicothoracic spine functional impairment group. There is no correlation between kinesiophobia presence and gender.

The Relationship Between Motivation for Physical Activity, Physical Activity Level, and Body Mass Index for University Students

The object of the study was to identify the relationship between the motivation for physical activity, the physical activity index (PAI), and the body mass index (BMI) for a sample of university students, taking into consideration the gender difference. The study subjects were 813 (340 men and 473 women), and the age range of the participants varied between 18 and 25 years. The RM 4-FM (Motivation for Physical Activity and Exercise) and PAI online questionnaires were applied to measure the motivation and the physical activity level. The study's novelty focused on analyzing how intrinsic and extrinsic motivation interact and correlate BMI and physical activity levels (PAI). Regarding gender, we approached the identification of motivational differences and the level of physical activity of students from non-sports faculties to identify relevant aspects for promoting proactive behaviors. Results revealed significant gender differences: men had a higher PAI (53.48 ± 28.11) than women (36.67 ± 23.92, p < 0.01); BMI (23.25 vs. 21.69, p < 0.01). The Cohen's value of RAI of RM 4-FM, BMI, and PAI were > 0.5, indicating a large effect size. The analysis presents a unique perspective of the interactions between psychological factors, motivation, and physical characteristics, providing insight into developing strategies to improve and promote a proactive lifestyle.

Redefining Health-Related Fitness: The Adaptive Ability to Foster Survival Possibilities

Fitness has been dominantly defined in terms of physical conditioning components. Under such definition, males tend to outperform females in strength, speed, aerobic or anaerobic capacity when compared at the same age and training status. However, females have a higher life expectancy, which in humans is related to higher biological fitness. Using the paradox of sex differences in fitness-where males have higher physical fitness but do not have a higher life expectancy-the aim of this opinion paper is to (a) highlight the multidimensionality of fitness, and (b) redefine health-related fitness, drawing on key fitness goals in biology: adaptability and survival. The redefinition of health-related fitness as the "adaptive ability to foster survival possibilities" encompasses synergies across physical, mental, psychological, emotional, social and subjective dimensions, while embracing the diversity of human characteristics, including sex, gender, age, somatotype, vital state, disability, disease and wellbeing, among others.

Nutritional Strategies for Optimizing Health, Sports Performance, and Recovery for Female Athletes and Other Physically Active Women: A Systematic Review

CONTEXT

Despite the progress toward gender equality in events like the Olympic Games and other institutionalized competitions, and the rising number of women engaging in physical exercise programs, scientific studies focused on establishing specific nutritional recommendations for female athletes and other physically active women are scarce.

OBJECTIVE

This systematic review aimed to compile the scientific evidence available for addressing the question "What dietary strategies, including dietary and supplementation approaches, can improve sports performance, recovery, and health status in female athletes and other physically active women?"

DATA SOURCES

The Pubmed, Web of Science, and Scopus databases were searched.

DATA EXTRACTION

The review process involved a comprehensive search strategy using keywords connected by Boolean connectors. Data extracted from the selected studies included information on the number of participants and their characteristics related to sport practice, age, and menstrual function.

DATA ANALYSIS

A total of 71 studies were included in this review: 17 focused on the analysis of dietary manipulation, and 54 focused on the effects of dietary supplementation. The total sample size was 1654 participants (32.5% categorized as competitive athletes, 30.7% as highly/moderately trained, and 37.2% as physically active/recreational athletes). The risk of bias was considered moderate, mainly for reasons such as a lack of access to the study protocol, insufficient description of how the hormonal phase during the menstrual cycle was controlled for, inadequate dietary control during the intervention, or a lack of blinding of the researchers.

CONCLUSION

Diets with high carbohydrate (CHO) content enhance performance in activities that induce muscle glycogen depletion. In addition, pre-exercise meals with a high glycemic index or rich in CHOs increase CHO metabolism. Ingestion of 5-6 protein meals interspersed throughout the day, with each intake exceeding 25 g of protein favors anabolism of muscle proteins. Dietary supplements taken to enhance performance, such as caffeine, nitric oxide precursors, β-alanine, and certain sport foods supplements (such as CHOs, proteins, or their combination, and micronutrients in cases of nutritional deficiencies), may positively influence sports performance and/or the health status of female athletes and other physically active women.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD480674.

Sex Differences in Grip Strength From Birth to Age 16: A Meta-Analysis

In 1985, Thomas and French published results of a meta-analysis that examined sex differences in grip strength in children 5 years of age and older. Their analysis included results from only four studies, and no update has been published. The purpose of the current study was to use meta-analysis to examine sex differences in grip strength from birth to age 16. The analysis included 808 effects from 169 studies conducted in 45 countries between 1961 and 2023. The total sample was 353,676 (178,588 boys, 175,088 girls). From birth to 16 years of age, grip strength was consistently greater in boys than girls. Between 3 and 10 years old, the effect size was small-to-moderate, with female grip strength equaling 90% of male grip strength (Hedges g = 0.33-0.46). At age 11, the effect size decreased slightly, likely due to girls reaching puberty before boys (g = 0.29, 95% confidence intervals (CI) [0.22, 0.35]). At age 13, the effect size increased markedly likely due to male puberty (g = 0.63, 95% CIs [0.55, 0.70]). By age 16, the sex difference in grip strength was substantial, with female grip strength equaling 65% of male grip strength (g = 2.07, 95% CIs [1.86, 2.27]). Secondary analyses revealed that the sex difference in grip strength is broadly similar between countries and has been mostly stable since the 1960s, except for a narrowing of the difference among 5-10-year-olds after 2010. Various biological factors explain why, on average, boys are stronger than girls from birth onward.

Gender-Based Differences in Biomechanical Walking Patterns of Athletes Using Inertial Sensors

Background: Wearable inertial sensors are essential tools in biomechanics and sports science for assessing gait in real-world conditions. This study explored gender-based differences in biomechanical walking patterns among healthy Greek athletes using the BTS G-Walk system, focusing on key gait parameters to inform gender-specific training and rehabilitation strategies. Methods: Ninety-five healthy athletes (55 men, 40 women), aged 18 to 30 years, participated in this study. Each athlete performed a standardized 14 m walk while 17 biomechanical gait parameters were recorded using the BTS G-Walk inertial sensor. Statistical analyses were conducted using SPSS to assess gender differences and left-right foot symmetry. Results: No significant asymmetry was found between the left and right feet for most gait parameters. Men exhibited longer stride lengths (left: p = 0.005, Cohen's d = 0.61; right: p = 0.009, Cohen's d = 0.53) and longer stride and gait cycle durations (left: p = 0.025, Cohen's d = 0.52; right: p = 0.025, Cohen's d = 0.53). Women showed a higher cadence (p = 0.022, Cohen's d = -0.52) and greater propulsion index (left: p = 0.001, Cohen's d = -0.71; right: p = 0.001, Cohen's d = -0.73), as well as a higher percentage of first double support (p = 0.030, Cohen's d = -0.44). Conclusions: These findings highlight the impact of biological and biomechanical differences on walking patterns, emphasizing the need for gender-specific training and rehabilitation. The BTS G-Walk system proved reliable for gait analysis, with potential for optimizing performance, injury prevention, and rehabilitation in athletes. Future research should explore larger, more diverse populations with multi-sensor setups.

Match-play data according to playing categories in badminton: a systematic review

Introduction

This systematic review aimed to investigate differences in match-play data according to the five playing categories in badminton.

Materials and methods

The systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Searches were conducted on ScienceDirect, PubMed, Google Scholar, Scopus, Web of Science, and Cochrane Library databases. Studies assessing technical-tactical actions, activity profiles, or external and internal loads as match-play outcome measures according to the five playing categories in badminton were deemed eligible. Quality assessment was performed using a modified version of the AMSTAR-2 checklist to compare the outcome measures, effect sizes (ES) and associated 95% confidence intervals were calculated.

Results

Of the 12,967 studies that were identified, 34 met the eligibility criteria. Among these, 29 and five were rated as excellent and good quality, respectively. Some individual ESs of activity profiles showed up to large differences (ES ≤ 4.52) favouring the men's compared with the women's singles category. Some individual ESs of activity profiles showed up to large differences (ES ≤ -2.72) favouring the women's doubles category compared with other doubles categories. The overall ESs for the activity profiles were large (ES = -0.76 to -0.90), favouring the doubles over the singles categories in both sexes.

Discussion

There are up to large differences in match-play data according to the five playing categories in badminton, each category placing specific demands on the players. Thus, each category requires specific training and testing procedures, what should be considered by scientists and coaches.

The association between exercise, activities, and frailty in older Chinese adults: a cross-sectional study based on the Chinese Longitudinal Healthy Longevity Survey (CLHLS) data

OBJECTIVES

The purpose of this study was to evaluate the association between exercise/activities and frailty in older Chinese adults using the Chinese Longitudinal Healthy Longevity Survey (CLHLS).

METHODS

This cross-sectional study included 6862 participants aged 65 years or older from the CLHLS 2018. Frailty was assessed using a 38-variable frailty index (FI). Activities included Tai chi, square dance, garden work, raising animals/pets, playing cards/mah-jongg, social activity and housework. Multivariate logistic regression was used to assess the association between exercise/activities and frailty, adjusting for covariates such as gender, age, BMI, chronic diseases, residence, education, co-residence, economic status, smoking, drinking, physical labor history, and nutritional supplements.

RESULTS

The mean age of this study was 81.5 (SD = 10.3)years, with 3567 (52%) females. Frailty prevalence was 32.3%. The prevalence of exercise and daily activities was 31% and 78.6%, respectively. Multivariate logistic regression analysis showed that the likelihood of frailty increased with decreased exercise (OR = 1.85, 95% CI: 1.57, 2.18, P < 0.001) and activities (OR = 4.43, 95% CI: 3.74, 5.25, P < 0.001).

CONCLUSIONS

Participation in exercise/activities is associated with a lower likelihood of frailty. Regular housework may also contribute to reducing frailty risk.

Sex differences in absolute and relative changes in muscle size following resistance training in healthy adults: a systematic review with Bayesian meta-analysis

Background

Muscle hypertrophy may be influenced by biological differences between males and females. This meta-analysis investigated absolute and relative changes in muscle size following resistance training (RT) between males and females and whether measures of muscle size, body region assessed, muscle fibre type, and RT experience moderate the results.

Methods

Studies were included if male and female participants were healthy (18-45 years old) adults that completed the same RT intervention, and a measure of pre- to post-intervention changes in muscle size was included. Out of 2,720 screened studies, 29 studies were included in the statistical analysis. Bayesian methods were used to estimate a standardised mean difference (SMD), log response ratio (lnRR) with exponentiated percentage change (Exp. % Change of lnRR), and probability of direction (pd) for each outcome.

Results

Absolute increases in muscle size slightly favoured males compared to females (SMD = 0.19 (95% HDI: 0.11 to 0.28); pd = 100%), however, relative increases in muscle size were similar between sexes (Exp. % Change of lnRR = 0.69% (95% HDI: -1.50% to 2.88%)). Outcomes were minimally influenced by the measure of muscle size and not influenced by RT experience of participants. Absolute hypertrophy of upper-body but not lower-body regions was favoured in males. Type I muscle fibre hypertrophy slightly favoured males, but Type II muscle fibre hypertrophy was similar between sexes.

Conclusion

Our findings strengthen the understanding that females have a similar potential to induce muscle hypertrophy as males (particularly when considering relative increases in muscle size from baseline) and findings of our secondary analyses should inform future research that investigates sex differences in highly trained participants and muscle fibre type-specific hypertrophy.

Lifestyle Changes and Remission in Patients With New-Onset Type 2 Diabetes: A Nationwide Cohort Study

BACKGROUND

Lifestyle-related factors have been studied as a fundamental aspect in the onset and progression of type 2 diabetes mellitus. However, behavioral factors are easily overlooked in clinical practice. This study investigated whether lifestyle changes were associated with diabetes remission in newly diagnosed type 2 diabetes patients.

METHODS

We enrolled patients with new-onset type 2 diabetes from 2009 to 2012 using a health examination cohort from the Korean National Health Insurance Service (KNHIS). Remission was defined as a fasting glucose level less than 126 mg/dL at least once during a health examination after stopping medication. A self-administered questionnaire was used to investigate patients' lifestyles. We investigated smoking, alcohol consumption, and regular exercise before and after starting diabetes medication and the odds ratios (ORs) of logistic regression on remission to evaluate the associations.

RESULTS

A total of 138,211 patients diagnosed with type 2 diabetes from 2009 to 2012 were analyzed, and 8,192 (6.3%) reported remission during the follow-up period to 2017. Baseline fasting blood glucose level measured before starting diabetes medication was significantly higher in the non-remission group (180 mg/dL vs. 159 mg/dL, P < 0.001). In addition, the use rate of combined oral hypoglycemic agent treatment was higher in the non-remission group (15% vs. 8%, P < 0.001). Consistent smoking and drinking showed negative associations with remission (OR, 0.72; 95% confidence interval [CI], 0.67-0.77 and OR, 0.90; 95% CI, 0.84-0.95, respectively), and initiation of regular exercise presented a positive association with remission (OR, 1.54; 95% CI, 0.46-1.63). Abstinence from alcohol increased the likelihood of remission in the male population (OR, 1.20; 95% CI, 1.10-1.32). The association with smoking history or smoking cessation was not clear, but new smoking behavior interfered with remission in women (OR, 0.48; 95% CI, 0.28-0.81).

CONCLUSION

We confirmed associations between a healthy lifestyle and diabetic remission in new-onset type 2 diabetes patients. The results of this study suggest that improving lifestyle after diabetes diagnosis may contribute to disease remission.

Are There Differences Between Sexes in Performance-Related Variables During a Maximal Intermittent Flywheel Test?

BACKGROUND

Isometric and dynamic tasks of low-to-moderate intensities have been used to study sex differences in fatigability; however, maximal exertions with flywheel devices (FDs) have not been used. This study aimed to (1) detect sex differences in fatigue-related performance in a maximal intermittent fatiguing protocol on a FD, and (2) investigate the most sensitive dynamometric and mechanical variables for assessing fatigue in both sexes.

HYPOTHESIS

No sex differences should exist when performing this protocol on a FD.

STUDY DESIGN

Cohort observational study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A total of 34 young adults (17 female/17 male) performed 10 sets of 10 repetitions with 3 minutes of passive recovery of a half-squat exercise on a FD. Inter- and intraset analysis of force, power, velocity, work, and impulse, together with their relative change and slope, were calculated during concentric and eccentric phases. Raw data were also normalized to body mass in the interset analysis. The relative changes in each variable were compared.

RESULTS

Men showed greater and earlier decreases in performance throughout sets (P < .05; ηp2 ≥ 0.08), but these differences were not consistent after normalization for body mass (P > .05; ηp2 ≤ 0.05). Irrespective of sex and phase, the intraset analysis revealed that relative change was higher in the last set (P ≤ .03; ηp2 ≥ 0.14), with power being the most sensitive variable for detecting performance decline (P ≤ .04; ηp2 = 0.49).

CONCLUSION

Women experienced slower and delayed fatigue kinetics than men during a maximal intermittent fatiguing protocol with FD if body dimensionality is not considered. For training purposes, power seems to be the most sensitive and discriminative variable for detecting decreases in performance.

CLINICAL RELEVANCE

Body dimensionality is a key factor that must be considered when comparing both sexes in FDs.

Surface Electromyography Monitoring of Muscle Changes in Male Basketball Players During Isotonic Training

Physiological indicators are increasingly employed in sports training. However, studies on surface electromyography (sEMG) primarily focus on the analysis of isometric contraction. Research on sEMG related to isotonic contraction, which is more relevant to athletic performance, remains relatively limited. This paper examines the changes in the isotonic contraction performance of the male upper arm muscles resulting from long-term basketball training using the sEMG metrics. We recruited basketball physical education (B-PE) and non-PE majors to conduct a controlled isotonic contraction experiment to collect and analyze sEMG signals. The sample entropy event detection method was utilized to extract the epochs of active segments of data. Subsequently, statistical analysis methods were applied to extract the key sEMG time domain (TD) and frequency domain (FD) features of isotonic contraction that can differentiate between professional and amateur athletes. Machine learning methods were employed to perform ten-fold cross-validation and repeated experiments to verify the effectiveness of the features across the different groups. This paper investigates the key features and channels of interest for categorizing male participants from non-PE and B-PE backgrounds. The experimental results show that the F12B feature group consistently achieved an accuracy of between 80% and 90% with the SVM2 model, balancing both accuracy and efficiency, which can serve as evaluation indices for isotonic contraction performance of upper limb muscles during basketball training. This has practical significance for monitoring isotonic sEMG features in sports and training, as well as for providing individualized training regimens.

The Impact of Plant-Based Proteins on Muscle Mass and Strength Performance: A Comprehensive Review

PURPOSE OF REVIEW

Plant-based diets, which prioritize plant foods and limit or exclude animal-based products, have gained popularity due to their potential health and environmental benefits. While these diets are recognized as nutritionally adequate for all life stages, plant-based proteins have traditionally been considered less effective for muscle growth and athletic performance compared to animal-based proteins. This study aims to assess the quality of plant-based protein sources and their effects on muscle mass gain and strength performance.

RECENT FINDINGS

Although plant-based proteins may have lower digestibility and amino acid quality, combining protein sources and employing different processing techniques, such as cooking or fermentation, can improve their bioavailability. Animal protein supplementation has been associated with greater gains in lean mass and muscle strength. However, focusing exclusively on isolated protein supplementation fails to reflect the habitual dietary patterns, which typically involve consuming diverse protein sources throughout the day. Consequently, there is a growing interest in examining the broader impact of comprehensive dietary patterns on muscle mass and strength. Recent research suggests that when consumed in adequate amounts and with appropriate combinations, plant-based proteins can effectively support muscle protein synthesis and strength performance when consumed in adequate amounts and with appropriate combinations. When derived from diverse sources and consumed in sufficient quantities, plant-based proteins can effectively support muscle protein synthesis and promote strength development. Further research is needed to assess the impact of plant-based diets on muscle mass and strength in elite athletes and older adults, particularly those at risk of sarcopenia. Long-term studies are essential for a more comprehensive understanding of the sustained effects of plant-based nutrition on these outcomes.

Male mouse skeletal muscle lacking HuR shows enhanced glucose disposal at a young age

Introduction

Metabolic flexibility is the ability of a system to switch between metabolic substrates. Human and murine skeletal muscle tissues and cells with decreased activity of the regulatory RNA-binding protein, human antigen R (HuR), have decreased capacity for fat oxidation, and thus decreased metabolic flexibility. In this study, we aimed to assess the preference for carbohydrates in mice lacking HuR in skeletal muscle.

Methods

Experiments were performed on weight-matched control and HuR knockout mice of both sexes. Palmitate and pyruvate oxidation were performed in mouse muscle following the release of 14CO2. In vivo glucose and lipid uptake were assayed in mouse tissue following nonmetabolizable 3H-2-deoxyglucose or 14C-bromopalmitate injection. Transcriptomic analyses were performed in the skeletal muscle of all mice, followed by qPCR validation of select genes. Serum lactate and glucose levels were measured in mice via tail nick, and the muscle glycogen level was measured through colorimetric assay. Indirect calorimetry was used to measure respiratory exchange ratios.

Results

Male muscle-specific HuR knockout mice showed increased glucose uptake relative to controls, specifically in skeletal muscle, and have increased muscle glycogen content. These mice also displayed greater respiratory exchange ratios than controls. None of these differences were noted in females. Transcriptomics showed far more differences between male and female mice than between control and HuR knockout mice. However, differential gene expression between male and female mice was diminished by 50% following the removal of HuR. Male HuR knockout mouse skeletal muscle had increased glycolytic gene expression relative to controls but showed no difference relative to females of the same genotype. Both palmitate and pyruvate oxidation were decreased in the skeletal muscle of male HuR knockout mice relative to controls, and serum lactate levels were increased. No notable differences were seen in females between genotypes.

Discussion

The increase in the markers of glucose utilization with decreased HuR activity in male mice may indicate a switch toward glycolysis as compensation for decreased fat oxidation. These results continue to highlight a sex dependence on HuR as a driver of fat oxidation in mouse skeletal muscle while also indicating that muscle itself shows greater ambiguity between males and females following the removal of HuR.

Factors influencing regular exercise in young women: a survey study assessing the preferences and motivators for aerobic and muscle-strengthening exercise

Young adult women have unique barriers to exercise, but assessing the psychological and behavioral strategies of women who overcome these barriers may be beneficial for informing future exercise programs. This study assessed differences in motives and self-regulation by type (aerobic or muscle-strengthening) and frequency of exercise, along with preferences for exercise amongst young adult women who exercise regularly.

Methods

A survey assessed exercise frequency (International Physical Activity Questionnaire), intensity (Borg's scale), type, and social and physical preferences. The Exercise Motivations Inventory-2 measured motivators for exercise and the Physical Activity Self-Regulation Scale measured self-regulation. Characteristics and preferences for exercise were examined using descriptives and frequencies. MANOVAs assessed differences in motivators and self-regulation by frequency of exercise, and regression analyses assessed differences in exercise predictors by type.

Results

The sample consisted of 269 women ages 18-34 (66.5% White), of whom 80.3% met the national guidelines for aerobic exercise, 78.4% met the guidelines for muscle-strengthening exercise, and 32.3% identified resistance exercise as their preferred type of exercise. Weight management and self-regulation (p = .021, R2 = .073) were the strongest predictors of aerobic exercise. Positive health, strength and endurance, and self-regulation (p = .023, R2 = .161) were predictors of muscle-strengthening exercise. Women who participated in high amounts of aerobic exercise were motivated by interpersonal factors while psychological factors motivated high frequency of muscle-strengthening exercise.

Conclusions

Programs for young adult women should consider incorporating resistance exercise as this study shows it may evoke motivation that could lead to regular participation. Self-regulation strategies were associated with adherence to both aerobic and muscle-strengthening exercises, highlighting the potential importance for inclusion in future interventions.

Sex differences in anaerobic performance in CrossFit® athletes: a comparison of three different all-out tests

Background

Athletic performance can be influenced by various factors, including those related to biological sex. Various scientific disciplines have studied the observed differences in athletic performance between men and women. Moreover, anaerobic performance refers to the capacity of the human body to generate energy quickly and efficiently during high-intensity and short-duration activities. It is associated with the ability to perform explosive actions and the capacity for rapid recovery between repeated efforts. Anaerobic performance is a determining factor for performance in high-intensity sports and those with predominantly lower intensity but intermittent peaks of higher intensity. One high-intensity sport that has experienced exponential growth and attracts increasing numbers of participants yearly is commercially known as CrossFit® (CF). Therefore, the primary purpose of this study was to determine the anaerobic performance differences between sexes in CF athletes in terms of absolute and relative values.

Methods

A cross-sectional study was conducted over 2 weeks. Fifty CrossFit® athletes (25 men and 25 women) voluntarily participated in the study. They were subjected to body composition analysis and three maximal effort tests to measure anaerobic performance: a cycle ergometer test, a continuous jump test and a squat test.

Results

Significant differences were found in all the variables of absolute peak power and relative to body mass in the three tests. In values adjusted to lean and muscle mass, significant differences were only found in the cycle ergometer test but not in the other two. In mean power variables, significant differences were found in all the variables studied, except for the mean power adjusted to muscle mass in the squat test. In conclusion, this study's results indicate that differences between sexes in absolute and relative peak powers measured in all tests evaluated are explained by the amount of lean and muscle mass. However, mean powers show significant differences in all variables except for the one related to muscle mass in the squat test.

Does increasing the resistance-training volume lead to greater gains? The effects of weekly set progressions on muscular adaptations in females

We investigated the effect of increasing the number of sets per week every fortnight versus performing a constant set volume on muscular adaptations over 12 weeks. Thirty females (RT experience 2.1 ± 1.0 years) were randomly assigned to a constant group (CG, n = 9) that performed 22 sets per week, a two-set progression group (2SG, n = 11), or a four-set progression group (4SG, n = 10). Forty-five degree leg press one-repetition maximum (1RM), vastus lateralis cross-sectional area (VL-CSA), and the sum of proximal, middle and distal lateral thigh muscle thickness (∑MT) were assessed at baseline and after the intervention. We observed that the 4SG and 2SG conditions showed greater improvements in 1RM than the CG (p < 0.001, p = 0.032, respectively), with no differences between 4SG and 2SG (p = 0.118). Regarding VL-CSA, the 4SG group showed greater increases than the CG (p = 0.029) but not than the 2SG (p = 0.263), whereas no differences between the 2SG and CG (p = 0.443) were observed. There were no differences between groups for ∑MT (p = 0.783). While all groups demonstrated improvements in the measured outcomes, our findings suggest that increasing weekly sets may offer additional benefits for 1RM and vastus lateralis cross-sectional area. However, no additional benefits were observed for ∑MT.

Highly branched cyclic dextrin supplementation and resistance training: A randomized double-blinded crossover trial examining mechanical, metabolic, and perceptual responses

BACKGROUND & AIMS

The aim of this study was to investigate the potential ergogenic effects of intra-session supplementation of highly branched cyclic dextrin (HBCD) on mechanical (number of repetitions completed and repetition velocity), metabolic (lactate concentration), and perceptual (gastrointestinal complaints and ratings of perceived exertion [RPE]) responses to resistance training.

METHODS

This study used a randomized, double-blinded, placebo-controlled crossover study design. Thirty physically active individuals (15 men and 15 women) completed two experimental sessions that only differed in the supplement condition (placebo or HBCD). In each experimental session, subjects were prescribed five sets of eight repetitions with the 12-repetition maximum load during the bench press, bench pull, and squat exercises. During the sessions, participants consumed a total of 750 mL of the beverage, which either contained diluted 45 g of cyclic dextrin (HBCD condition) or only 2.5 g of the calorie-free excipients (placebo condition). The supplement (placebo or HBCD) was ingested during the inter-set rest periods (50 mL before each set).

RESULTS

The main findings indicated that intra-session HBCD supplementation (i) was well-tolerated without causing gastrointestinal complaints, (ii) led to improved repetition velocity during RT in men but not in women, (iii) tended to generate comparable or higher lactate values, and (iv) did not significantly influence the perception of fatigue.

CONCLUSIONS

These results suggest that HBCD can be considered an ergogenic supplement, particularly for enhancing mechanical performance in men, without noticeably affecting the perception of fatigue or discomfort.

Women Upward-Sex Differences in Uphill Performance in Speed Climbing, Ski Mountaineering, Trail Running, Cross-Country Skiing, and Cycling

INTRODUCTION

Women have generally lower body size and lean- to fat-mass ratio, lower maximal anaerobic power due to a lower muscle mass, and fewer fast-twitch fibers, although they can show higher resistance to fatigue or greater metabolic flexibility than men. These factors are well known and explain the sex differences in endurance sports such as distance running (10%-12%). Several of these factors-particularly the differences in body composition and skeletal-muscle characteristics-may directly impact vertical displacement and uphill performance. However, there is a lack of sex-difference reports in sports with uphill locomotion.

METHODS

The sex differences in world-level endurance performance over 10 years (2013-2022) in 6 different sports with uphill displacement (speed climbing, vertical race in ski mountaineering, vertical kilometer in mountain running, cycling, cross-country skiing, and ultratrail running) were calculated.

RESULTS

The sex differences are generally larger (18%-22%) than in endurance sports performed primarily on flat terrains. This may be due to the lower lean- to fat-mass ratio commonly reported in women. In shorter uphill events (eg, sport climbing, vertical kilometer, and short climb in cycling), the sex differences appear even more pronounced (28%-35%), potentially being explained by additional factors (eg, anaerobic capacity, muscle composition, and upper-body contribution).

CONCLUSION

This novel analysis over 10 years of elite endurance performance in different sports with uphill displacement shows that the sex differences are generally larger (18%-22%) than in endurance sports performed primarily on flat terrains.

Physiological Characteristics of Freestyle Snowboard and Freeski Athletes

PURPOSE

To investigate the physiological characteristics of freestyle snowboard and freeski athletes and explore potential differences between males and females.

METHODS

National-team athletes, snowboard (9 males, 21 [2.3] y; 8 females, 20 [4.1] y) and freeski (10 males, 21 [2.1] y; 8 females, 18 [2.2] y), underwent physiological assessments: maximal oxygen uptake (V˙O2max; indirect), countermovement-jump height, drop-jump (DJ) height, DJ contact time, reactive strength index, absolute peak force (PFabs), and relative peak force. Differences were analyzed using multivariate analyses of variance Wilks lambda (Λ) and magnitude with partial-eta squared (ηp2). Pairwise comparisons and the impact of sex and sport were analyzed with univariate tests, utilizing Cohen d.

RESULTS

No physiological differences were found between snowboard and freeski (Wilks Λ = 0.8, P > .251, ηp2 = .169). Sex differences were observed (Wilks Λ = 0.2, P < .001, ηp2=.79), without an interaction between sex and sport (Λ = 0.8, P > .449, ηp2=.120). For snowboard, sex differences included V˙O2max (P < .001, d = 1.04), countermovement-jump height (P < .001, d = 2.5), DJ height (P < .001, d = 1.45), DJ contact time (P < .001, d = 0.36), reactive strength index (P < .001, d = 1.36), front-limb PFabs (P < .001, d = 1.77), rear-limb PFabs (P < .001, d = 1.36), front-limb relative PF (P < .003, d = 0.88), and rear-limb relative PF (P < .021, d = 0.65). In freeski, differences included V˙O2max (P = .005, d = 0.81), countermovement-jump height (P < .001, d = 1.3), DJ height (P < .001, d = 1.17), DJ contact time (P < .040, d = 0.54), reactive strength index (P < .001, d = 1.0), left-limb PFabs (P < .001, d = 2.2), right-limb PFabs (P < .001, d = 1.88), left-limb relative PF (P < .001, d = 1.1), and right-limb relative PF (P < .001, d = 1.33).

CONCLUSIONS

Differences between the sexes, rather than between sports, explained the largest variance. A broad concurrent training approach with the aim of developing resilient athletes is likely warranted while acknowledging and adapting to individual needs.

Resisted sprint training with combined loads improve the maximum velocity in professional female soccer

We analysed the long-term adaptations of resisted sprint training (RST) with combined loads on the performance and kinematics of the maximal velocity (MV). One team women's professional soccer players performed a six-week training programme with progressive sled loading from 20% to 80% of body mass. Pre-training, post-training and detraining measures were obtained for sprint times for 0-20 m, 20-30 m and 0-30 m, while step length (SL), step rate (SR), step velocity, trunk, hip, thigh, knee, shank ankle, foot and centre of mass (CoM) angles were digitised with an 18-point human model. Two points were included: toe-off and touchdown, and both legs ipsilateral and contralateral. Sprint times were significantly reduced in the acceleration and MV phase, with a homogeneous individual response within the group. There were no significant alterations in the angles of the trunk, hip, thigh, knee, shank, ankle and foot across the different tests, nor in SR. Significant alterations in CoM-angle, step velocity and higher SL were observed. RST with progressive of combined loads effectively improved MV performance without causing changes that generated an adverse effect on sprint kinematics. The study offers an RST training programme to enhance sprint performance in professional female soccer.

Impact of exercise with blood flow restriction on muscle hypertrophy and performance outcomes in men and women

Blood flow restriction training (BFRT) has been previously studied as an alternative form of resistance training to gain lean mass and improve performance outcomes. However, in all exercise studies of BFRT, the proportion of female participants represents only 17-29% of all research participants. This highlights a strong underrepresentation of females and the need for more knowledge on the impact of BFRT and sex differences. The primary objective was to compare the impact of 6-week BFRT on lean mass, strength, and performance outcomes between males and females. A total of 38 adults [age, 25.3 ±  3.1 years; female, n = 19 (50%)] performed whole-body resistance training program with blood flow restriction three times per week. Exercises were performed at 30% of 1-repetition maximum (1-RM) and blood flow restriction cuffs were set to 60% of each individual's limb occlusion pressure. Body composition was assessed via dual-energy x-ray absorptiometry and strength was measured using 1-RM. A significant increase in lean mass was observed in males (p = 0.009) and females (p = 0.023) with no difference in the change between groups (p = 0.279). Both males and females increased 1-RM for upper- and lower-body exercises, with significant interaction effects (time x sex) for chest press (p = 0.003), seated row (p = 0.038), knee flexion (p = 0.043), and knee extension (p = 0.035), suggesting males increased 1-RM more for these exercises. Furthermore, peak power was improved in males (p < 0.001) and females (p = 0.002) during a vertical squat jump, but a significant interaction (time x sex) effect was observed (p = 0.039), suggesting males increased to a greater extent. Males and females significantly increased lean body mass, to a similar degree, following six weeks of resistance training in combination with blood flow restriction. Likewise, both males and females improved muscle strength following 6-week BFRT, however males may improve strength to a greater extent than females.

Comparison of the performance of instruments for screening sarcopenia in older adults

AIM

To compare the performance of the SARC-F and SARCCalf questionnaires in sarcopenia screening and their relationship with clinical and sociodemographic aspects of older adults.

METHODS

Analytical cross-sectional study carried out with 739 elderly people in the community. Clinical, sociodemographic, anthropometric data and screening for signs suggestive of sarcopenia were obtained using the SARC-F and SARCCalf.

RESULTS

Evaluation by method showed a difference in the proportion of positive results for the SARC-F regarding female sex (71.7; p = 0.001), among older adults who did not have a partner (49.7; p < 0.001), and osteoarticular diseases (13.4; p < 0.001). On the other hand, the SARCCalf identified a higher proportion of positive results among older adults at risk of malnutrition (12.2; p < 0.001).

CONCLUSION

The performance of the instruments varied according to the clinical and sociodemographic characteristics of the population, and it is up to professionals to consider these aspects when using them.

The fastest 24-hour ultramarathoners are from Eastern Europe

Ultramarathon running is of increasing popularity, where the time-limited 24-hour run is one of the most popular events. Although we have a high scientific knowledge about different topics for this specific race format, we do not know where the best 24-hour runners originate from and where the fastest races are held. The purpose of the present study was to investigate the origin of these runners and the fastest race locations. A machine learning model based on the XG Boost algorithm was built to predict running speed based on the athlete´s age, gender, country of origin and the country where the race takes place. Model explainability tools were used to investigate how each independent variable would influence the predicted running speed. A sample of 171,358 race records from 63,514 unique runners from 73 countries participating in 24-hour races held in 57 countries between 1807 and 2022 was analyzed. Most of the athletes originated from the USA, France, Germany, Great Britain, Italy, Japan, Russia, Australia, Austria, and Canada. Tunisian athletes achieved the fastest average running speed, followed by runners from Russia, Latvia, Lithuania, Island, Croatia, Slovenia, and Israel. Regarding the country of the event, the ranking looks quite similar to the participation by the athlete, suggesting a high correlation between the country of origin and the country of the event. The fastest 24-hour races are recorded in Israel, Romania, Korea, the Netherlands, Russia, and Taiwan. On average, men were 0.4 km/h faster than women, and the fastest runners belonged to age groups 35-39, 40-44, and 45-49 years. In summary, the 24-hour race format is spread over the world, and the fastest athletes mainly originate from Eastern Europe, while the fastest races were organized in European and Asian countries.

Effects of Different Loading Programs on Finger Strength in Rock Climbers

BACKGROUND

Climbing places high loads through the hands and fingers, and climbers may benefit from specific finger strength training (hangboarding) protocols. The purpose of this study was to evaluate the effect of a 10-minute low intensity hangboard finger strengthening protocol ("Abrahangs"), compared with the generally accepted Max Hangs protocol for training maximal grip strength.

METHODS

We retrospectively evaluated the change in grip strength and Strength: Weight following Max Hangs, Abrahangs, or the two protocols performed concurrently in rock climbers who used the Crimpd app to log their training. Users who had completed two finger strength tests within a 4-16-week period were included. Climbers were grouped by the number of training sessions into: "Climbing Only", "Abrahangs Only", "Max Hangs Only" and "Both" Max Hangs and Abrahangs.

RESULTS

Frequent low intensity finger loading was as effective at improving grip strength in climbers as training with maximal loads. Additionally, combining low intensity and maximal load training resulted in additive strength gains.

CONCLUSIONS

These results suggest that low-intensity long duration holds provide a promising training paradigm for training finger strength that is gentle enough to incorporate into existing training programs.

Beyond weakness: Exploring intramuscular fat and quadriceps atrophy in ACLR recovery

Muscle weakness following anterior cruciate ligament reconstruction (ACLR) increases the risk of posttraumatic osteoarthritis (OA). However, focusing solely on muscle weakness overlooks other aspects like muscle composition, which could hinder strength recovery. Intramuscular fat is a non-contractile element linked to joint degeneration in idiopathic OA, but its role post-ACLR has not been thoroughly investigated. To bridge this gap, we aimed to characterize quadriceps volume and intramuscular fat in participants with ACLR (male/female = 15/9, age = 22.8 ± 3.6 years, body mass index [BMI] = 23.2 ± 1.9, time since surgery = 3.3 ± 0.9 years) and in controls (male/female = 14/10, age = 22.0 ± 3.1 years, BMI = 23.3 ± 2.6) while also exploring the associations between intramuscular fat and muscle volume with isometric strength. Linear mixed effects models assessed (I) muscle volume, (II) intramuscular fat, and (III) strength between limbs (ACLR vs. contralateral vs. control). Regression analyses were run to determine if intramuscular fat or volume were associated with quadriceps strength. The ACLR limb was 8%-11% smaller than the contralateral limb (p < 0.05). No between-limb differences in intramuscular fat were observed (p = 0.091-0.997). Muscle volume but not intramuscular fat was associated with strength in the ACLR and control limbs (p < 0.001-0.002). We demonstrate that intramuscular fat does not appear to be an additional source of quadriceps dysfunction following ACLR and that muscle size only explains some of the variance in muscle strength.

Dynapenia and sarcopenia identify walking speed decline in women but not in men

OBJECTIVE

To determine the best indicator of mobility decline between dynapenia, low skeletal muscle mass index (SMMI), and sarcopenia defined by the EWGSOP2 using different cutoff points for grip strength.

METHODS

A longitudinal study was conducted with a follow-up of eight years, involving 2,680 individuals aged 60 and older who participated in the ELSA study with a walking speed greater than 0.8 m/s at baseline. Dynapenia was defined using different cutoff points for grip strength. SMMI was defined by the 20th percentile of the entire ELSA sample distribution and sarcopenia was defined based on the EWGSOP2, using different cutoff points for grip strength. Mobility was analysed using the walking speed test.

RESULTS

Over time, the greatest decline in walking speed occurred in dynapenic women with grip strength < 17 kg (-0.005 m/s per year; 95 % CI: -0.01 to -0.001) and < 20 kg (-0.007 m/s per year; 95 % CI: -0.01 to -0.001). With regards to sarcopenia, the greatest walking speed decline occurred in women with probable sarcopenia when defined by grip strength < 17 kg [(-0.006 m/s per year; 95 % CI: -0.01 to -0.001) or grip strength < 20 kg (-0.007 m/s per year; 95 % CI: -0.01 to -0.001)]. Dynapenia in men as well as low SMMI and sarcopenia in men and women did not enable identifying the risk of mobility decline.

CONCLUSION

Dynapenia and probable sarcopenia defined by grip strength < 17 kg and < 20 kg enabled identifying walking speed decline over time only in women.

Incidence of Elbow Injury Patterns in Japanese Adolescent Judo Players: Analysis from a Nationwide Insurance Database

Elbow injuries are common in judo, particularly among adolescents. This study investigated the incidence and patterns of three types of elbow injuries (sprain, dislocation, and fracture-dislocation) among Japanese adolescent judo players (12 to 18 years old) using data from a nationwide insurance database, covering the period from 2010 to 2019. A total of 4614 elbow injuries were recorded, with sprains being the most frequent (67.6% of cases). Female players had a 20% higher incidence of sprains than male players (6.8 vs. 5.4 per 1000 athlete-years). Severe injuries, such as dislocations and fracture-dislocations, were more common in high school players, with male middle school students exhibiting a higher rate of elbow fracture-dislocations (+15%) compared with female students. Elbow injuries frequently occurred during te-waza techniques, particularly seoi-nage, when players extended their arms to prevent being thrown. Peripheral nerve injuries, predominantly ulnar nerve injuries, accompanied elbow dislocations in 74% of the cases. This study highlights the importance of proper instruction in defensive and ukemi techniques, particularly those that discourage the use of hands to prevent falls during throws, to reduce the risk of elbow injuries.

Exercise, disease state and sex influence the beneficial effects of Fn14-depletion on survival and muscle pathology in the SOD1G93A amyotrophic lateral sclerosis (ALS) mouse model

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a devastating and incurable neurodegenerative disease. Accumulating evidence strongly suggests that intrinsic muscle defects exist and contribute to disease progression, including imbalances in whole-body metabolic homeostasis. We have previously reported that tumour necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) and fibroblast growth factor inducible 14 (Fn14) are significantly upregulated in skeletal muscle of the SOD1G93A ALS mouse model. While antagonising TWEAK did not impact survival, we did observe positive effects in skeletal muscle. Given that Fn14 has been proposed as the main effector of the TWEAK/Fn14 activity and that Fn14 can act independently from TWEAK in muscle, we suggest that manipulating Fn14 instead of TWEAK in the SOD1G93A ALS mice could lead to differential and potentially improved benefits.

METHODS

We thus investigated the contribution of Fn14 to disease phenotypes in the SOD1G93A ALS mice. To do so, Fn14 knockout mice (Fn14-/-) were crossed onto the SOD1G93A background to generate SOD1G93A;Fn14-/- mice. Investigations were performed on both unexercised and exercised (rotarod and/or grid test) animals (wild type (WT), Fn14-/-, SOD1G93A and SOD1G93A;Fn14-/-).

RESULTS

Here, we firstly confirm that the TWEAK/Fn14 pathway is dysregulated in skeletal muscle of SOD1G93A mice. We then show that Fn14-depleted SOD1G93A mice display increased lifespan, myofiber size, neuromuscular junction endplate area as well as altered expression of known molecular effectors of the TWEAK/Fn14 pathway, without an impact on motor function. Importantly, we also observe a complex interaction between exercise (rotarod and grid test), genotype, disease state and sex that influences the overall effects of Fn14 deletion on survival, expression of known molecular effectors of the TWEAK/Fn14 pathway, expression of myosin heavy chain isoforms and myofiber size.

CONCLUSIONS

Our study provides further insights on the different roles of the TWEAK/Fn14 pathway in pathological skeletal muscle and how they can be influenced by age, disease, sex and exercise. This is particularly relevant in the ALS field, where combinatorial therapies that include exercise regimens are currently being explored. As such, a better understanding and consideration of the interactions between treatments, muscle metabolism, sex and exercise will be of importance in future studies.

Analysis of combinatory effects of free weight resistance training and a high-protein diet on body composition and strength capacity in postmenopausal women - A 12-week randomized controlled trial

BACKGROUND

Menopause has a significant impact on the endocrine system of middle-aged women, resulting in a loss of skeletal muscle mass (SMM), changes in fat mass (FM) and a reduction in strength capacity. Resistance training (RT) and a high-protein diet (HPD) are effective methods for maintaining or increasing SMM. This study aims to determine the effects of HPD and RT on body composition, muscle thickness and strength capacity in postmenopausal women.

METHODS

In total 55 healthy postmenopausal women (age: 58.2 ± 5.6 years, weight 69.1 ± 9.6 kg, height 166.5 ± 6.5 cm) successfully participated in the study. The women were randomly assigned to either group: training + protein (2.5 g/kg fat-free mass (FFM)) (n = 15; TP); only training (n = 12; T); only protein (2.5 g/kg FFM) (n = 14; CP) or control (n = 14; C). TP and T performed RT for 12 weeks with three training sessions and five exercises each. CP and C were prohibited from training during the period. The main parameters analysed for body composition were FFM, SMM, FM, muscle thickness of the M. rectus femoris, M. biceps femoris, M. triceps brachii and M. biceps brachii muscles. Strength was tested using a dynamometer for grip strength and 1-RM in the squat (BBS) and deadlift (DL).

RESULTS

The SMM significantly increased by RT (TP: (Δ+1.4 ± 0.9 kg; p < 0.05; d = 0.4; T: Δ+1.2 ± 1.3kg; p < 0.05; d = 0.3) and FM could be reduced only in T: (Δ-2.4 ± 2.9 kg; p < 0.05; d = 0.3). In muscle thickness a significant increase in the M. biceps brachii in both training groups (TP: (Δ+0.4 ± 0.3 cm; p < 0.05; d = 1.6; T: (Δ+0.3 ± 0.3 cm; p < 0.05; d = 0.9) and in M. biceps femoris only in TP (Δ+0.3 ± 0.4 cm; p < 0.05; d = 0.9) were observed. HPD without training does not affect body composition, A significant increase in grip strength (TP: Δ+4.7 ± 2.4 kg; (p < 0.05; d = 1.5; T: (Δ+3.6 ± 3.0 kg; p < 0.05; d = 0.8), in BBS (TP: (Δ+30.0 ± 14.2 kg; p < 0.05; d = 1.5; T: (Δ+34.0 ± 12.0 kg; p < 0.05; d = 2.4) and in DL (TP: (Δ+20.8 ± 10.3 kg; p < 0.05; d = 1.6; T: (Δ+22.1 ± 7.6 kg; p < 0.05; d = 2.0) was observed in both training groups. The CP also recorded a significant increase in the BBS (Δ+7.5 ± 5.4 kg; p < 0.05; d = 0.4) and in DL (Δ+5.5 ± 7.7 kg; p < 0.05; d = 0.5). No significant differences were detected for TP and T for any of the parameters.

CONCLUSION

The results indicate that RT enhances body composition and strength capacity in postmenopausal women and is a preventive strategy against muscle atrophy. Besides HPD without training has a trivial significant effect on BBS and DL. HPD with RT has no clear additive effect on body composition and strength capacity. Further studies are needed to confirm these observations.

Are Ratings of Perceived Exertion during Endurance Tasks of Predictive Value? Findings in Trunk Muscles Require Special Attention

Background: Subjective rating scales of perceived exertion are often used to quantify effort levels during various endurance exercises, particularly submaximal tasks. The aim of the current study was to determine whether predictive conclusions can be drawn from perceived exertion levels surveyed at the start of defined submaximal endurance tasks. Methods: In this study, healthy participants performed a 10-min endurance task at 50% of their upper body weight, targeting either the back muscles (n = 47, 24 women) or abdominal muscles (n = 32, 17 women). At the end of each minute, participants were asked to rate their perceived exertion (RPE) using the 14-points Borg Scale. Based on their initial and final RPE levels, and for each muscle group separately, participants were divided into subgroups reflecting low (good start/good end) and high (bad start/bad end) strain levels. These values were then compared over the duration of the exercise. Comparisons of RPE levels between subgroups were made using the Mann-Whitney U-test for independent samples, with Bonferroni-Holm correction to account for multiple comparisons. Results: Overall, strain levels increased throughout the duration of the exercise. For the abdominal muscles, the difference between the two RPE groups remained constant over time: participants with good start/end ratings consistently showed different strain levels from those with bad start/end ratings, regardless of whether the grouping was based on initial or final exertion levels. In contrast, for the back muscles, the initial grouping showed a crossover in strain values: by the end of the task, participants in the good start group tended to report higher strain than those in the bad start group. No differences were found in initial RPE values when the grouping was based on final exertion levels. Conclusions: For endurance tasks involving the abdominal muscles, initial strain levels have strong predictive value, whereas this is not the case for the back muscles. Because back muscles are frequently loaded, continuous monitoring of RPE levels is necessary to prevent unexpected task failure, as initial RPE values are not predictive. In contrast, RPE values of 11 or higher on the 14-points Borg scale predict complete exhaustion or even premature task failure with high certainty for abdominal muscle exercises, while lower RPE levels indicate that exercise intensity can be increased.

Psychological needs, self-efficacy, motivation, and resistance training outcomes in a 16-week barbell training program for adults

Background

Despite extensive research on the relationship between psychological factors and aerobic training, there remains a gap in understanding these relationships within resistance training (RT), particularly barbell-based RT. This study aimed to examine the associations between basic psychological needs, behavioral regulation, self-efficacy, and a longitudinal barbell-based RT program for adults.

Methods

Forty-three adults (M age = 45.09 ± 10.72) were recruited from the Competitive Edge resistance training program at a medical fitness center in Northwest Montana. The study followed an 18-week schedule: 8 weeks of training, 1 week of active recovery, and 8 additional weeks of training.

Results

The results reveal several significant findings. First, the basic psychological need for competence significantly increased from baseline (M = 5.06) to post-program (M = 5.30), (p = 0.017). Second, the composite score of the BREQ-3 significantly predicting muscular strength improvements in the deadlift (β = 3.64, p = 0.039). Third, both mastery (p = 0.021) and resilience (p = 0.007) self-efficacy subscales increased from baseline to post-program. Fourth, exploratory analyses indicated that the reasons to exercise scale predicted increases in muscular endurance with the weight management (β = 10.016, p = 0.046) and solitude (β = 6.792, p = 0.037) subscales.

Conclusion

These findings highlight the importance of psychological factors in predicting strength outcomes and muscular endurance, suggesting that psychological interventions may complement physical training to maximize benefits. This research contributes valuable insights into how psychological factors influence training outcomes, potentially guiding future interventions and program designs to better support strength development and endurance in resistance training contexts.

Bigger Calves from Doing Higher Resistance Training Volume?

We compared the effects of different weekly calf training sets on muscle size changes. Sixty-one untrained young women performed a calf training program for 6 weeks, 3 d·wk-1, with differences in resistance training volume. The participants were randomly assigned to one of the three groups: 6-SET, 9-SET, and 12-SET weekly calf training sets. The calf raise exercise was performed in sets of 15-20 repetitions maximum. The muscle thickness measurements of medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (SOL) were taken via B-mode ultrasound. We used the sum of the three-muscle thickness as a proxy for the triceps surae (TSSUM). The 12-SET group elicited greater increases than the 6-SET in LG (6-SET=+ 8.1% vs. 12-SET=+ 14.3%; P=0.017), SOL (6-SET=+ 6.7% vs. 12-SET=+ 12.7%; P=0.024), and TSSUM (6-SET=+ 6.9% vs. 12-SET=+ 12.0%; P=0.005), but there was no significant difference in MG changes (6-SET=+ 6.6% vs. 12-SET=+ 9.9%; P=0.067). There were no significant differences when comparing 9-SET vs. 6-SET and 12-SET (P≥0.099). Although all groups experienced calf muscle hypertrophy, our results suggest that the higher dose range may optimize triceps surae muscle size gains.

Physical and technical attributes associated with on-water rowing performance in junior and elite rowers

On-water rowing performance consists of the integration of physical and technical attributes. This exploratory study aimed to describe key physical and technical variables for elite and junior rowers and examine the associations and predictive capacity of these variables with on-water rowing performance outcomes. Twenty-eight junior (16 females, 16 ± 0.8 years and 12 males, 17 ± 0.7 years) and 24 elite rowers (12 females, 24 ± 2.7 years and 12 males, 27 ± 2.6 years) completed an on-water, single sculling biomechanics assessment combined with a series of physical, strength and power tests. Elite men and women were superior in mean gate force, distance per stroke and recovery distance compared to junior groups as determined by independent t-tests and effect size appraisal (p < 0.017, d > 1.2). Large associations (p < 0.01) were evident between anthropometry, strength and power assessments with the on-water measures of catch angle, mean gate force, recovery distance and boat speed. Differences in ROM and flexibility attributes did not distinguish between elite and junior rowers. Linear discriminant analysis revealed that individual rowers can be appropriately categorised by sex and performance level based on their physical and technical attributes. This battery of testing with world-class athletes represents an excellent level of ecological validity for the assessment of rowers pertinent to on-water performance.

Leucine promotes energy metabolism and stimulates slow-twitch muscle fibers expression through AMPK/mTOR signaling in equine skeletal muscle satellite cells

Previous research has shown that leucine (Leu) can stimulate and enhance the proliferation of equine skeletal muscle satellite cells (SCs). The gene expression profile associated with Leu-induced proliferation of equine SCs has also been documented. However, the specific role of Leu in regulating the expression of slow-twitch muscle fibers (slow-MyHC) and mitochondrial function in equine SCs, as well as the underlying mechanism, remains unclear. During this investigation, equine SCs underwent culturing in differentiation medium and were subjected to varying concentrations of Leu (0 mM, 0.5 mM, 1 mM, 2 mM, 5 mM, and 10 mM) over a span of 3 days. AMP-activated protein kinase (AMPK) inhibitor Compound C and mammalian target of rapamycin complex (mTOR) inhibitor Rapamycin were utilized to explore its underlying mechanism. Here we showed that the expression of slow-MyHC at 2 mM Leu level was significantly higher than the concentration levels of 0 mM,0.5 mM and 10 mM (P <0.01), and there was no significant difference compared to other groups (P > 0.05); the basal respiration, maximum respiration, standby respiration and the expression of slow-MyHC, PGC-1α, Cytc, ND1, TFAM, and COX1 were significantly increased with Leu supplementation (P < 0.01). We also found that Leu up-regulated the expression of key proteins on AMPK and mTOR signaling pathways, including LKB1, p-LKB1, AMPK, p-AMPK, S6, p-S6, 4EBP1, p-4EBP1, mTOR and p-mTOR (P < 0.05 or P < 0.01). Notably, when we treated the equine SCs with the AMPK inhibitor Compound C and the mTOR inhibitor Rapamycin, we observed a reduction in the beneficial effects of Leu on the expression of genes related to slow-MyHC and signaling pathway-related gene expressions. This study provides novel evidence that Leu promotes slow-MyHC expression and enhances mitochondrial function in equine SCs through the AMPK/mTOR signaling pathways, shedding light on the underlying mechanisms involved in these processes for the first time.

Sex and Equipment Impact on Lifting Velocity and the Maximum Repetitions in Bench Press

This study investigated how equipment and sex affect the prediction accuracy of the maximum number of repetitions performed to failure (RTF) using the fastest mean velocity of the set (MVfastest). Sixteen men and twelve women completed four sessions (two using free-weight equipment and two sessions using the Smith machine). Each session involved three sets of repetitions to failure against the 65%, 75%, and 85% of the one-repetition maximum, interspersed by 10-min of rest. The goodness-of-fit of the individualized RTF-MVfastest relationships was comparable between both equipment types and sexes (P≥0.510). Moreover, there were not significant differences in the MVfastest associated with RTF between equipment types (P≥0.258). However, the MVfastest associated with RTF was higher for men than for women in repetitions 6 to 15 (P≤0.043; ES≥0.69). In addition, the absolute errors when predicting RTF showed no significant differences between equipment types and loads (P<0.444). Specifically, these RTF estimates were within an acceptable range for men (<2 repetitions), but not for women (≥2 repetitions) (main effect of sex: P≤0.018; ES≥0.58). These findings suggest that individualized RTF-MVfastest equations estimate the RTF with an acceptable precision in men during bench press exercises in both equipment types but exhibit lower precision for women.

Save Your Back: Comparison of the Compressive Force on the Lower Back Based on Differences in the Training Techniques

INTRODUCTION

Musculoskeletal injury prevention for nurses is aimed at removing the need to manually position patients. In the ED, this is not always possible or practical. The purpose of this study is to compare the calculated estimated compressive force on the lumbar spine between recommended lifting techniques and the SHAPE lifting method during the horizontal transfer of a patient.

METHODS

Twenty-one student nurses completed the horizontal transfer of a simulated patient while motion was collected using inertial measurement units. Motion data were analyzed to calculate an estimated compressive force on the lumbar spine while completing the movement based on current recommended lifting methods and while using the SHAPE lifting method.

RESULTS

A significant reduction in estimated peak and average compressive force at the lumbar spine was found during both the push and the pull portions (P < .001) of the horizontal transfer.

DISCUSSION

While the optimal way to limit musculoskeletal injury among nurses is to eliminate the need for manual handling of a patient, this is not always possible in the ED. It is critical that when emergency nurses must reposition a patient, they perform the movement in the most biomechanically sound method while using a friction reduction. These findings, coupled with the previous biomechanical risk factor reduction related to the SHAPE lifting intervention, gives promise to a safer lifting strategy for emergency nurses moving forward.

Sex differences in human performance

Sex as a biological variable is an underappreciated aspect of biomedical research, with its importance emerging in more recent years. This review assesses the current understanding of sex differences in human physical performance. Males outperform females in many physical capacities because they are faster, stronger and more powerful, particularly after male puberty. This review highlights key sex differences in physiological and anatomical systems (generally conferred via sex steroids and puberty) that contribute to these sex differences in human physical performance. Specifically, we address the effects of the primary sex steroids that affect human physical development, discuss insight gained from an observational study of 'real-world data' and elite athletes, and highlight the key physiological mechanisms that contribute to sex differences in several aspects of physical performance. Physiological mechanisms discussed include those for the varying magnitude of the sex differences in performance involving: (1) absolute muscular strength and power; (2) fatigability of limb muscles as a measure of relative performance; and (3) maximal aerobic power and endurance. The profound sex-based differences in human performance involving strength, power, speed and endurance, and that are largely attributable to the direct and indirect effects of sex-steroid hormones, sex chromosomes and epigenetics, provide a scientific rationale and framework for policy decisions on sex-based categories in sports during puberty and adulthood. Finally, we highlight the sex bias and problem in human performance research of insufficient studies and information on females across many areas of biology and physiology, creating knowledge gaps and opportunities for high-impact studies.

The effect of non-pathological neck pain on hand grip strength in healthcare practitioners across three different head positions: a cross-sectional study design

[Purpose] To determine how different head-neck positions (HNPs) influence the hand grip strength (HGS) of medical personnel with non-pathological neck pain (NPNP). [Participants and Methods] A cross-sectional study recruited 46 healthcare professionals: 21 (45.7%) with NPNP and 25 (54.3%) without. A dynamometer, cervical range of motion, and visual analogue scale measured HGS, HNPs, and NPNPs. Participants were instructed to squeeze the handgrip dynamometer handle in 90-degree elbow flexion as much as possible from a seated position to measure HGS from the neutral head position (NHP), 40° head neck flexion (HFP40°), and 30° head neck extension (HEP30°). [Results] The mean HGS for the dominant hand in NHP, HFP40°, and HEP30° was 29.27 kg (± 9.03), 27.24 kg (± 9.08), and 26.37 kg (± 9.32), while for the non-dominant hand it was 27.45 kg (± 9.62), 25.23 kg (± 9.36), and 24.61 kg (± 10.17). There was no significant correlation between HNPs and HGS. However, the only significant difference was between dominant HGS in the NHP and non-dominant HGS in the HEP30°. [Conclusion] NPNP had no significant influence on HGS in any of the three HNPs for either hand. Future studies should include other HNPs and other potential variables such as age, gender, weight, and pain intensity.

Automatic Quantitative Assessment of Muscle Strength Based on Deep Learning and Ultrasound

Skeletal muscle is a vital organ that promotes human movement and maintains posture. Accurate assessment of muscle strength is helpful to provide valuable insights for athletes' rehabilitation and strength training. However, traditional techniques rely heavily on the operator's expertise, which may affect the accuracy of the results. In this study, we propose an automated method to evaluate muscle strength using ultrasound and deep learning techniques. B-mode ultrasound data of biceps brachii of multiple athletes at different strength levels were collected and then used to train our deep learning model. To evaluate the effectiveness of this method, this study tested the contraction of the biceps brachii under different force levels. The classification accuracy of this method for grade 4 and grade 6 muscle strength reached 98% and 96%, respectively, and the overall average accuracy was 93% and 87%, respectively. The experimental results confirm that the innovative methods in this paper can accurately and effectively evaluate and classify muscle strength.

Plasma, Urinary, Erythrocyte and Platelet Zinc Concentrations in Soccer Players

Essential trace minerals are vital for general human health and athletic performance. Zinc (Zn) plays critical roles in several biochemical processes in exercise physiology, especially during intense physical exercise. This research aimed to analyze erythrocyte, platelet, plasma and urine Zn concentrations among men's and female soccer players over a sports season. A total of 22 male soccer players (20.61 ± 2.66 years; 71.50 ± 5.93 kg) and 24 female soccer players (23.37 ± 3.95 years; 59.58 ± 7.17 kg) participated in this longitudinal quasi-experimental study. Three assessments were carried out over the season: 1st evaluation: first week of training (August); 2nd assessment: middle of the season, between the end of the first and second round (January) and 3rd assessment: last week of training (May/June). In all evaluations extracellular (plasma and urine) and intracellular (erythrocytes and platelets) Zn concentrations were determined, as well as physical fitness and several blood parameters. Inductively coupled plasma mass spectrometry was used to measure Zn concentrations. Plasma and urinary concentrations were higher among male soccer players (p < 0.05) while erythrocyte and platelet Zn concentrations were higher in the female soccer players (p < 0.05). Additionally, variations in urinary and platelet Zn concentrations were observed over the season. The differences could be related to muscle mass, muscle damage or the specific sport's physical demands.

Transgender competition in combat sports: Position statement of the Association of ringside physicians

The Association of Ringside Physicians (ARP) is committed to the concept of fair competition. It advocates for two equally skilled and matched athletes to keep bouts fair, competitive, entertaining, and, most importantly, safe for all combatants. Numerous studies have proven that transgender women may have a competitive athletic advantage against otherwise matched cis-gender women. Likewise, transgender men may suffer a competitive disadvantage against cis-gender men. These differences - both anatomic and physiologic - persist despite normalization of sex hormone levels and create disparities in competitive abilities that are not compatible with the spirit of fair competition. More importantly, allowing transgender athletes to compete against cisgender athletes in combat sports, which already involve significant risk of serious injury, unnecessarily raises the risk of injury due to these differences. Hence the ARP does not support transgender athlete competition against cisgender athletes in combat sports.

Physical activity and fiber intake beneficial for muscle mass and strength preservation during aging: A comprehensive cross-sectional study in the UK biobank cohort

BACKGROUND

Aging triggers intricate physiological changes, particularly in whole-body fat-free mass (FFM) and handgrip strength, affecting overall health and independence. Despite existing research, the broader significance of how muscle health is affected by the intricate interplay of lifestyle factors simultaneously during aging needs more exploration. This study aims to examine how nutrition, physical activity, and sleep impact on FFM and handgrip strength in middle-aged men and women, facilitating future personalized recommendations for preserving muscle health.

METHODS

The cross-sectional analysis of the UK Biobank involved 45,984 individuals (54 % women) aged 40-70 years with a complete dataset. Multiple linear regression explored determinants of FFM and handgrip strength, considering traditional, socio-demographics, medication use and smoking as covariates, with sex and age (younger and older than 55 years) stratifications.

RESULTS

In older men and women, higher physical activity beneficially affect both FFM (respectively Β = 3.36 × 10-3, p-value = 1.66 × 10-3; Β = 2.52 × 10-3, p-value = 3.57 × 10-4) and handgrip strength (Β = 6.05 × 10-3, p-value = 7.99 × 10-5, Β = 8.98 × 10-3, p-value = 2.95 × 10-15). Similar results were found in fiber intake for FFM in older men and women (respectively B = 3.00 × 10-2, p-value = 2.76 × 10-5; B = 2.68 × 10-2, p-value = 1.78 × 10-9) and handgrip strength (Β = 3.27 × 10-2, p-value = 1.40 × 10-3; Β = 3.12 × 10-2, p-value = 1.34 × 10-5). Other lifestyle factors influence FFM and handgrip strength differently. Key determinants influencing handgrip strength included higher protein intake, lower water intake, higher alcohol intake, and extended sleep duration whereas mainly higher water intake is associated with higher FFM.

CONCLUSIONS

In both men and women, the main factors associated with FFM and handgrip strength are physical activity and fiber intake, which may underlie a connection between gut and muscle health. Given the observed complexity of muscle health in the age and sex strata, further longitudinal research is needed to provide personalized lifestyle recommendations.

Sex differences in ultramarathon performance in races with comparable numbers of males and females

There is a prominent sex-based difference in athletic performance such that males outperform females by 7%-14% in races from 100 m to marathon. In ultramarathons, the difference is often much smaller, leading to speculation that females are "built" for the sport. However, data are confounded by the low number of female participants; just 10%-30% in any given race. This study compared data from two ultramarathons where males and females competed in comparable numbers. There were 116 and 146 starters in the 50 mile and 100 mile races, respectively (52% female). Finish times were compared using t tests or Mann-Whitney U tests, a Chi-squared test of independence examined the relationship between sex and ranking, and multivariable linear regressions examined relationships between sex, age, and finish time. There were 96 finishers in the 50 mile race (46% female) and 91 finishers in the 100 mile race (45% female). The median finish time for 50 miles was 12.64 ± 2.11 h with no difference between sexes (1.2%, p = 0.441). However, the top-10 males finished the race ∼85 min faster than the top-10 females (13.8%, p = 0.045). The mean finish time for 100 miles was 31.58 ± 3.36 h with no difference between sexes (3.2%, p = 0.132) and no difference between the top-10 males and top-10 females (4.4%, p = 0.150). Linear and multivariable regression models using sex and age were unable to predict overall finish time in either race. In conclusion, the sex-based performance discrepancy shrinks to 1%-3% in ultramarathons when males and females compete in comparable numbers. Top-performing males still retain a considerable advantage over shorter distances.

Sex-related differences in corticospinal excitability outcome measures of the biceps brachii during a submaximal elbow flexor contraction

The purpose of this study was to investigate the effects of sex, muscle thickness, and subcutaneous fat thickness (SFT) on corticospinal excitability outcome measures of the biceps brachii. Eighteen participants (10 males and 8 females) completed this study. Ultrasound was used to assess biceps brachii muscle thickness and the overlying SFT. Transcranial magnetic stimulation (TMS) was used to determine corticospinal excitability by inducing motor-evoked potentials (MEPs) at eight different TMS intensities from 90% to 160% of active motor threshold (AMT) from the biceps brachii during an isometric contraction of the elbow flexors at 10% of maximum voluntary contraction (MVC). Biceps brachii maximal compound muscle action potential (Mmax) was also recorded prior to and after TMS. Males had higher (p < 0.001) biceps brachii muscle thickness and lower SFT, produced higher levels of MVC force and had, on average, higher (p < 0.001) MEP amplitudes at lower (p < 0.05) percentages of maximal stimulator output than females during the 10% elbow flexion MVC. Multiple linear regression modeling revealed that sex was not associated with any of the neurophysiological parameters examined, while SFT showed a positive association with the stimulation intensity required at AMT (p = 0.035) and a negative association with biceps brachii pre-stimulus electromyography (EMG) activity (p = 0.021). Additionally, there was a small positive association between muscle thickness and biceps brachii pre-stimulus EMG activity (p = 0.049). Overall, this study suggests that some measures of corticospinal excitability may be different between the sexes and influenced by SFT and muscle thickness.