Female athletes: a state-of-the-art review of multiorgan influence of exercise training

Endurance sports have witnessed an increase in female participation, demanding a constant and evolving reassessment of the specific physiological and health implications of female athletes. In the present review, we analyze cardiovascular, hematological adaptations and anthropometry and hormonal fluctuations highlighting sex-specific differences in response to exercise, with estrogen playing a fundamental role in modulating body composition and metabolic processes. Nutritional aspects, in particular energy availability, macronutrient distribution and hydration, are fundamental in supporting training demands and menstrual function. Nevertheless, the repercussions of nutritional deficiencies, interacting in the female athlete triad - which also includes amenorrhea, osteoporosis and eating disorders - underline the importance of comprehensive management strategies. In addition, we comprehensively discuss the multiorgan effects of physical training, highlighting the intersections between sex-specific differences, nutritional needs, and cardiovascular adaptations. Cardiovascular remodeling in female endurance athletes reveals both morphological and functional adaptations, requiring a deep understanding of effective cardiovascular risk assessment and screening. The synthesis of current knowledge highlights the complexity of the physiological landscape of the female athlete practicing endurance sports, requiring ongoing exploration and tailored interventions. In conclusion, this review aims to support a gender-based approach to athletic training and health management and research, intending to optimize performance while safeguarding the well-being of female athletes.

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.

Resistance exercise-induced circulating factors influence the damaged skeletal muscle proteome in a sex-dependent manner

Muscle recovery after damage is mediated by circulating factors and intracellular signaling pathways. Our previous studies have demonstrated that resistance exercise (RE)-induced circulating factors elicited sex-differential responses in damaged muscle. However, the global effects of these circulating factors on damaged muscle are largely understudied. We examined the differential effects of RE-induced circulating factors and sex on the damaged muscle proteome. Damaged vastus lateralis muscle from 3 men and 3 women from a parent study were analyzed. Participants completed 2 identical bouts of unilateral eccentric knee extensions immediately followed by either upper body RE to induce circulating factors (EXE) or 20-min seated rest (CON). Muscle biopsies collected from the damaged leg at 24 h were used. 900 proteins were identified by LC-MS/MS analysis. Ingenuity Pathway Analysis was used to detect activation prediction using z-scores for functional and pathway analyses. In men, 79 proteins were downregulated and 15 were upregulated in EXE versus CON. These differentially expressed proteins were associated with immunological and inflammatory signaling pathways. Biological functions of the differentially expressed proteins in EXE vs. CON in men include inactivating acute inflammatory signaling, neutrophil extracellular trap signaling, ROS production, and activating IL-12 signaling. These results underline that RE-induced circulating factors have a sex-specific effect on the damaged muscle proteome, where immune signaling is altered in men but not women. Given that the immune response is critical for recovery from muscle damage, these results highlight the potential role of RE-induced circulating factors that could be essential in mediating muscle recovery.

Multimodal Adaptations to Expiratory Musculature-Targeted Resistance Training: A Preliminary Study in Healthy Young Adults

PURPOSE

Exercise-induced adaptations, including neuroplasticity, are well studied for physical exercise that targets skeletal muscles. However, little is known about the neuroplastic potential of targeted speech and swallowing exercises. The current study aimed to gather preliminary data on molecular and functional changes associated with the neuroplastic effects of 4-week expiratory musculature-targeted resistance training in healthy young adults.

METHOD

Five healthy young adult men aged between 19 and 35 years, M (SD) = 28.8 (2.68) years, underwent 4 weeks of expiratory muscle strength training (EMST). We measured changes in maximum expiratory pressure (MEP), serum brain-derived neurotrophic factor (BDNF), and insulin-like growth factor 1 (IGF-1) levels at baseline and posttraining conditions. Furthermore, functional and structural magnetic resonance images were obtained to investigate the neuroplastic effects of EMST. We analyzed the effects of training using a linear mixed model for each outcome, with fixed effects for baseline and posttraining.

RESULTS

MEP and serum BDNF levels significantly increased posttraining. However, this effect was not observed for IGF-1. A significant increase in functional activation in eight regions was also observed posttraining. However, we did not observe significant changes in the white matter microstructure.

CONCLUSIONS

Preliminary data from our study suggest targeted resistance training of expiratory muscles results in molecular and neuroplastic adaptations similar to exercise that targets skeletal muscles. Additionally, these results suggest that EMST could be a potential intervention to modulate (or prime) neurotrophic signaling pathways linked to functional strength gains and neuroplasticity.

Reference intervals of hematological parameters in the Chilean adult population and the Mapuche ethnic group

Objectives

Reference intervals (RI) are an essential tool to support clinical decisions. These may have intra- and inter-individual variations associated with genetic differences and environmental factors. Given that Chile is a multiethnic territory, studying these variables is even more relevant. The purpose of this study was to establish RI for various hematological parameters in the Chilean population and the Mapuche ethnic group.

Methods

A sample of 356 adult individuals (aged 18-65 years), of which 146 belonged to the Mapuche ethnic group, was selected using the indirect a posteriori method from the database of the UC Temuco Clinical Laboratory. The analysis was conducted by sex and ethnicity. The Tukey fences method was employed to detect outliers, and the RIs were established through the non-parametric method recommended by the IFCC.

Results

The median age for the overall sample of the general population was 35 years (female) and 36 years (male). Differences (p<0.05) were found by sex in parameters dependent on hemoglobin and platelets counts. In the analysis by ethnicity, the parameters of RBC, HGB and HCT presented significant differences (p<0.0001).

Conclusions

This study shows that hematological RI vary according to sex and ethnicity, which must be considered in a multiethnic population. This understanding enhances our comprehension of the individual characteristics of each person and facilitates more accurate clinical interpretation.

Intervalos de referencia de parámetros hematológicos en población chilena adulta y en la etnia mapuche

Objetivos

Los intervalos de referencia (IR) son una herramienta esencial para apoyar la toma de decisiones clínicas. Estos pueden presentar variaciones intra e interindividuales asociadas a diferencias genéticas y factores medioambientales. Dado que la población de Chile está compuesta por múltiples grupos étnicos, estas variables adquieren aún mayor relevancia. El objetivo del presente estudio es establecer IR para diferentes parámetros hematológicos en la población chilena y la etnia mapuche.

Métodos

Se seleccionó una muestra de 356 adultos (entre 18 y 65 años), de los cuales 146 pertenecían a la etnia mapuche, utilizando el método indirecto a posteriori a partir de la base de datos del laboratorio clínico UC Temuco. El análisis se realizó considerando el sexo y la etnia. Los valores atípicos se detectaron mediante la prueba de Tukey, mientras que los IR se establecieron aplicando el método no paramétrico recomendado por la IFCC.

Resultados

La mediana de edad de la muestra global de la población general fue de 35 años en mujeres y 36 años en hombres. Se observaron diferencias estadísticamente significativas (p<0,05) por sexo en los parámetros dependientes de la hemoglobina y del recuento de plaquetas. En el análisis por etnicidad, se observaron diferencias significativas en el recuento de glóbulos rojos, hemoglobina y hematocrito (p<0,0001).

Conclusiones

Este estudio demuestra que los intervalos de referencia hematológicos varían según el sexo y la etnicidad, lo cual debería ser considerado en una población multiétnica. Este hallazgo contribuye a un mejor conocimiento de las características individuales de cada persona, facilitando una interpretación clínica más precisa.

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.

A Personalized Muscle-Tendon Assessment and Exercise Prescription Concept Reduces Muscle-Tendon Imbalances in Female Adolescent Athletes

BACKGROUND

Imbalances between muscle strength and tendon stiffness influence the mechanical demand on the tendon (i.e., tendon strain) and may increase tendon injury risk. The purpose of this study was to identify muscle-tendon imbalances and to promote a more balanced musculotendinous adaptation through a personalized assessment and exercise prescription concept in female adolescent handball athletes (13-16 years).

METHODS

At four measurement time points during a competitive season, we used dynamometry and ultrasonography to assess knee extensor muscle strength, patellar tendon stiffness and strain. Tendon micromorphology was assessed with a peak spatial frequency (PSF) analysis of proximal tendon ultrasound images. Muscle-tendon imbalances were identified based on tendon strain during maximum voluntary contractions. A control group (n = 15) followed their usual training. In the intervention group, athletes with a deficit in tendon stiffness (strain ≥ 9%; n = 6) or no muscle-tendon imbalances (strain between 4.5% and 9%; n = 15) performed exercises (3x/week for 32 weeks) with a personalized load to reach ~ 6.2% tendon strain to predominantly promote tendon or both muscle and tendon adaptation. Individuals with a muscle strength deficit (strain ≤ 4.5%; n = 1) trained with submaximal loads to failure to promote muscle strength.

RESULTS

In the intervention group we found lower fluctuations of maximum tendon strain (p = 0.005) and a decrease in tendon strain over time (p = 0.010), which was more pronounced in individuals with initially high tendon strain. While there were no systematic changes in muscle strength or tendon stiffness at the group level (p > 0.05), the marked decrease in tendon strain in individuals with a deficit in tendon stiffness was caused by a predominant increase in tendon stiffness. Overall, the prevalence of muscle-tendon imbalances was reduced in the intervention group, while it temporarily increased in the control group. PSF did not differ between groups at baseline but decreased significantly in the intervention group (p = 0.013).

CONCLUSIONS

The findings suggest that the personalized concept is suitable to promote a more uniform adaptation of knee extensor muscle strength and patellar tendon stiffness and to reduce the prevalence of musculotendinous imbalances in female adolescent athletes, which may have important implications for tendon injury prevention.

TRIAL REGISTRATION

DRKS, DRKS00035110. Registered 20 September 2024-retrospectively registered, https://drks.de/search/de/trial/DRKS00035110 .

Hamstrings and Quadriceps Weaknesses Following Anterior Cruciate Ligament Reconstruction Persist Up to 6 Months After Return-to-Sport: An Angle-specific Strength Analysis

BACKGROUND

Hamstrings and quadriceps strength recovery and restoration of the hamstrings-to-quadriceps ratio (H/Q ratio) is a major concern after anterior cruciate ligament reconstruction (ACLR). Recently, moment-angle profiles and angle-specific H/Q ratios are receiving increasing interest.

PURPOSE

The first objective of this study was to investigate moment-angle profiles and angle-specific H/Q ratio profiles in athletes with ACLR at the time of RTS. The second objective of this study was to assess whether strength asymmetries identified at the time of RTS, persist after six months.

STUDY DESIGN

Case-Control study.

METHODS

Twenty athletes who had undergone ACLR performed isokinetic strength tests for concentric knee flexion and extension (60°/s) at RTS, and three and six months later. Twenty controls were tested once. T-tests were used to compare strength differences between 1) ACLR athletes and controls and 2) the injured and uninjured leg of the ACLR athletes. Finally, to assess strength deficits over time, two-way ANOVAs were used.

RESULTS

Angle-specific analyses and peak moments showed lower hamstrings strength in the injured leg of ACLR athletes compared to their uninjured leg at RTS. Furthermore, angle-specific analyses showed a lower hamstrings strength and H/Q ratio in the injured leg compared to controls at larger knee flexion angles. The latter deficit was not identified with a peak-based analysis. The asymmetries identified at RTS did not change over the six months following RTS.

CONCLUSIONS

Athletes with ACLR show strength deficits and asymmetries that persist even six months after RTS. As some asymmetries may go undetected by peak-based analyses, angle-specific analyses are recommended.

LEVEL OF EVIDENCE

Level 3b.

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.

Eight weeks of resistance exercise improves mood state and intestinal permeability in healthy adults: A randomized controlled trial

To explore a potential link between resistance exercise and the gut-brain axis, this study examined the impact of resistance exercise on intestinal permeability, as indicated by lipopolysaccharide binding protein (LBP), and mood state in healthy adults. Sedentary participants (n = 20; 39.5 ± 12.1 y; 27.4 ± 5.3 kg/m2) were randomly assigned to the resistance exercise (REX) or wait-listed control (CON) groups. REX participants strength trained 3× weekly (advancing from 45%-55% to 70%-80% 1RM for 3-4 sets over 8 weeks). Strength testing, evaluation of mood states, and collection of fasting blood occurred at baseline and weeks 4 and 8. At baseline, LBP concentrations were inversely correlated to all strength measures (r range: -0.48 to -0.57; p < 0.05). The gain in total strength [(split squat left + right)/2 + bench press] was 45% higher for REX versus CON participants (p = 0.019), and serum LBP concentrations fell 16% for REX participants and rose 9% in CON participants (p = 0.014). Mood was significantly improved by resistance training versus control (but this improvement was not related to changes in LBP; r = -0.001). These findings support a role for resistance exercise in improving mood state and intestinal barrier function, but more research is warranted to further explore the effects of resistance training on the gut-brain axis.

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.

Knowledge of gym goers on myths and truths in resistance training

Over the last decades, resistance training (RT) has experienced a surge in popularity, and compelling evidence underpins its beneficial effects on health, well-being, and performance. However, sports and exercise research findings may translate poorly into practice. This study investigated the knowledge of Austrian gym-goers regarding common myths and truths in RT. Based on topical systematic reviews (n = 45), a digital questionnaire with 14 statements on RT methods and practices, randomly phrased as myths or truths, was administered to Austrians exercising in local fitness centres. Chi-squared tests were used to check if a majority correctly identified true and false statements. A total of n = 721 (30.1 ± 14 years, 454 males) out of n = 790 contacted individuals completed the survey (response rate: 91.2 percent). Five out of fourteen statements (truth: protein augments strength and hypertrophy, creatine augments strength, superiority of full- vs. partial-ROM RT for hypertrophy; myth: RT reduces flexibility, low-load, high-volume RT is as effective as high-load RT with regard to maximal strength) were identified correctly by a majority (p < .01). The awareness of the scientific evidence on RT is low among gym-goers. Upcoming studies should be geared to improve science communication.

Sex-based differences in physical and psychological recovery, and return to sport, following anterior cruciate ligament reconstruction

BACKGROUND

A robust comparison of the recovery pathway between sexes after anterior cruciate ligament reconstruction (ACLR) is lacking. This study investigated sex-based differences in physical and psychological recovery, and return to sport (RTS), after ACLR.

METHODS

104 community-level patients underwent ACLR. Patients were evaluated at 6-, 12- and 24-months with the Anterior Cruciate Ligament Return to Sport after Injury Scale (ACL-RSI), International Knee Documentation Committee (IKDC) form and Tegner Activity Scale (TAS), a 4-hop test battery including the 6-meter timed hop (6MTH) and the single (SHD), triple (THD) and triple crossover (TCHD) hop tests for distance, and peak isokinetic knee extensor and flexor torque. Sex-based differences were assessed, while regression analysis modelled the relationship between patient characteristics and outcomes, with 24-month psychological readiness to RTS.

RESULTS

All PROMS improved (p < 0.05), with males reporting higher 24-month ACL-RSI (p = 0.002), IKDC (p = 0.007) and TAS (p = 0.005) scores. A greater percentage of males returned to pivoting sports at 24 months (p = 0.030, males 60.0%, females 40.8%). Males demonstrated higher knee extensor strength LSIs at 6 (p = 0.037) and 24 (p = 0.047) months, and higher knee flexor strength LSIs at 6 (p = 0.007) and 12 (p = 0.002) months. IKDC knee scores (β = 24.9; 95% CI, 10.8 to 35.0), male sex (β = 12.2; 95% CI, 3.9 to 20.4) and the 6MTH LSI (β = 1.31; 95% CI, 0.6 to 2.1) were associated with the ACL-RSI.

CONCLUSIONS

In community-level ACLR patients, females demonstrated lower physical performance recovery, subjective function and psychological readiness, as well as a lower rate of RTS.

Evaluation of rest interval following a series of tuck jumps on anaerobic performance

Background/objective

This study assessed the influence of rest interval duration after tuck jumps on 10-s Wingate outcomes and countermovement jump height.

Methods

Eighteen resistance trained individuals (males: n = 10, 21.3 ± 3.6 years; females: n = 8, 22.1 ± 2.2 years) volunteered to participate in four sessions: familiarization, 3-min rest interval with no jumps (CON), and two randomized experimental sessions with a rest interval of either 1-min (ER1) or 5-min (ER5) after a series of tuck jumps. Countermovement jump (CMJ) height was assessed at baseline (PRE) and after (POST) the CON, ER1, and ER5 conditions, and 10-s Wingate cycling testing. Wingate relative peak power (RPP) and mean peak power (RMP) were measured. Separate mixed-factorial repeated measures analyses of variance assessed changes across conditions and sex for the Wingate variables and conditions, sex, and time for CMJ height at an alpha of p ≤ 0.05.

Results

RPP and RMP were significantly greater than CON for ER1 by 0.92 ± 0.23 W kg-1 and 0.41 ± 0.14 W kg-1, respectively, and ER5 by 0.77 ± 0.23 W kg-1 and 0.36 ± 0.10 W kg-1, respectively. ER1 and ER5 RPP and RMP were similar (p > 0.05). For CMJ height, there was only a main effect for sex as males jumped higher than females by 31.3 % (p = 0.002).

Conclusion

Performing tuck jumps prior to anaerobic exercise may increase performance for up to 5-min.

Optimizing concurrent training programs: A review on factors that enhance muscle strength

The purpose of this study is to explore the factors that should be considered when designing concurrent training programs to minimize the "interference effect." This study provides a comprehensive summary of various perspectives from existing studies on factors such as the ability level of the target group, the frequency and intensity of concurrent training, the order and interval time of resistance and endurance training, nutritional arrangements during training, and gender differences in concurrent training. The results of this study suggest that the emergence of the "interference effect" in concurrent training is influenced by several factors, with a particular emphasis on the adaptation status of muscle fitness when compared to resistance training alone. However, it is important to note that the current understanding of this theory remains somewhat ambiguous. The ability level of participants plays a crucial role in training adaptation and the specificity of post-training skeletal muscle molecular responses. Therefore, the participant's capacity level is likely a key determinant of the extent of the interference effect in concurrent training. In addition to training-related factors such as frequency, duration, intensity, volume, training sequence, recovery time, and nutritional intake, non-training-related variables, including the methodology used to assess various metrics, also significantly impact the design of concurrent training programs. These factors collectively influence the overall outcomes and provide insight into the extent of the "interference effect" in concurrent training. Understanding these aspects is essential for comprehending the phenomenon of the "interference effect" in concurrent training.

The Strength and Power Profile of Junior and Senior Female Rugby League Athletes

ABSTRACT

Flannery, L, Secomb, JL, West, MA, Compton, HR, and Dascombe, BJ. The strength and power profile of junior and senior female rugby league athletes. J Strength Cond Res 38(12): 2129-2135, 2024-The purpose of this study was to compare the lower-body strength and power profiles of the various female rugby league (RL) competition levels, thereby establishing normative data for these athletes. Seventy-nine female RL athletes from 3 different competition levels: junior-state ( n = 45, age: 17.5 ± 0.6 years), senior-state ( n = 15, age: 24.3 ± 3.7 years), and senior-national ( n = 19, age: 25.4 ± 4.0 years) participated in this study. All testing was completed in a single session at the beginning of preseason, with the following assessments performed: countermovement jump (CMJ), isometric mid-thigh pull (IMTP), and bilateral and unilateral isometric hip adduction and abduction strength. One-way analyses of variance with Bonferroni post hoc analyses, revealed that junior-state athletes exhibited significantly lower IMTP peak force (PF) and relative PF (rPF), and CMJ height compared with the senior-state and senior-national athletes. Importantly, senior-national athletes demonstrated significantly greater body mass (80.9 ± 14.6 kg) than senior-state athletes (70.9 ± 8.1 kg), but no significant differences were identified between these athletes for any IMTP or CMJ measure. Finally, the senior-national athletes possessed significantly lower unilateral hip adduction rPF (0.13 ± 0.04 N·BW -1 ) and adduction to abduction strength ratio (0.92 ± 0.14) than senior-state athletes (0.17 ± 0.03 N·BW -1 and 1.04 ± 0.13, respectively), which may have implications for noncontact lower-body injury risk. This study highlights the importance of practitioners prescribing training to increase the lower-body strength and power of junior-state RL athletes. Whereas, for senior-state athletes progressing to senior-national levels, the focus should on maintaining or improving relative strength and power, while increasing their body mass to enhance preparedness for the greater contact demands at that level.

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.

Combined high-intensity interval and resistance training improves cardiorespiratory fitness more than high-intensity interval training in young women with overweight/obesity: a randomized controlled trial

Objective

This study aimed to compare the effects of high-intensity interval training (HIIT) combined with resistance training (RT) versus HIIT alone on body composition, cardiorespiratory fitness and glycolipid metabolism in young women with overweight/obesity.

Methods

This randomized controlled trial divided 40 subjects into an experimental group (HIIT+RT) and a control group (HIIT). Both groups underwent training three times per week for eight weeks. Body composition, cardiorespiratory fitness and glycolipid levels were assessed before and after the intervention.

Results

The results revealed that compared to baseline, both the experimental and control groups showed significant improvements in body weight, body mass index (BMI), Body fat, waist circumference (WC), waist-hip ratio (WHR), peak oxygen uptake (VO2peak), vital capacity (VC), oxygen pulse (VO2/HR), minute ventilation, resting heart rate, blood oxygen saturation, blood pressure, fasting blood glucose, triglycerides and high-density lipoprotein cholesterol (p<0.05). Additionally, a significant increase in muscle mass and a significant reduction in 2-hour postprandial glucose were observed in the experimental group (p<0.05). Muscle mass (mean difference: 2.75%), VO2peak (mean difference: 1.61 mL/min/kg), VC (mean difference: 334mL), and VO2/HR (mean difference: 0.51mL/beat) showed greater improvement in the HIIT+RT group compared to the HIIT group (p<0.05).

Conclusion

In conclusion, an 8-week regimen of either combined HIIT and RT or HIIT significantly improves body composition, cardiorespiratory fitness and glycolipid metabolism in women with overweight/obesity. However, the combined training appears to offer more benefits than HIIT alone. Further research is needed to evaluate the long-term effects and feasibility of combined training.

Trial registration

https://www.chictr.org.cn/, identifier ChiCTR2300075961.

Acute and Chronic Changes in Muscle Androgen Receptor Markers Are Not Associated with Muscle Hypertrophy in Women and Men

PURPOSE

Androgen receptor (AR) expression and signaling have been regarded as a mechanism for regulating muscle hypertrophy. However, little is known about the associations between acute and chronic changes in skeletal muscle total AR, cytoplasmic AR (cAR), nuclear AR (nAR), and AR DNA-binding (AR-DNA) induced by resistance training (RT) and hypertrophy outcomes in women and men. This study aimed to investigate the acute and chronic effects of RT on skeletal muscle total AR, cAR, and nAR contents and AR-DNA in women and men. In addition, we investigated whether these acute and chronic changes in these markers were associated with muscle hypertrophy in both sexes.

METHODS

Nineteen women and 19 men underwent 10 wk of RT. Muscle biopsies were performed at baseline, 24 h after the first RT session, and 96 h after the last session. AR, cAR, and nAR were analyzed using Western blotting, and AR-DNA using an ELISA-oligonucleotide assay. Fiber cross-sectional area (fCSA) was analyzed through immunohistochemistry and muscle cross-sectional area (mCSA) by ultrasound.

RESULTS

At baseline, men demonstrated greater nAR than women. Baseline cAR was significantly associated with type II fCSA hypertrophy in men. Acutely, both sexes decreased AR and cAR, whereas men demonstrated greater decreases in nAR. After 10 wk of RT, AR, and nAR remained unchanged, men demonstrated greater cAR compared with women, and both sexes decreased AR-DNA activity. Acute and chronic changes in AR markers did not correlate with muscle hypertrophy (type I/II fCSA and mCSA) in women or men.

CONCLUSIONS

Baseline cAR content may influence hypertrophy in men, whereas neither RT-induced acute nor chronic changes in AR, cAR, nAR, and AR-DNA are associated with muscle hypertrophy in women or men.

Importance of strength training for sustaining performance and health in military personnel

The physical capacity of male and female warfighters is challenged on the modern battlefield by heavy loads and high-intensity work. When designing training programmes for warfighters, approaches for developing strength and power alongside endurance must be considered. Strength training often requires facilities that may not be available during deployments while multiple stressors may impair or decrease overall performance. Understanding the effect of military environments on warfighter performance and acknowledging the variation in demands for individuals during field training and deployments, including possible sex differences, is essential to promote the development of adequate physical reserves (strength, power and endurance), attenuate risk for injury and promote health during and after military careers. The purpose of this narrative review is to discuss considerations for programming physical training in a military environment where 'one size does not fit all'. In addition, a brief description of physiological contributions (neural and muscular) to strength development is included.

Sex Differences in Effects of Exercise on Physical Function in Aging: A Systematic Review with Meta-Analysis

PURPOSE

Our objective was to synthesize and determine whether there are sex differences in physical function following exercise interventions in older adults.

MATERIALS AND METHODS

A systematic search was conducted in four databases from inception to July 8th, 2023 searching for prospective trials that conducted exercise interventions in older adults and results for physical function were reported by sex. Pooled standardized mean differences (SMDs) with their 95% confidence intervals (CIs) were estimated using a randomeffects method. The Sidik-Jonkman estimator was used to calculate the variance of heterogeneity (I²).

RESULTS

A total of 19 studies involving 20,133 older adults (mean age ≥60 years, 33.7% female) were included. After exercise interventions, males reported significantly greater pre-post changes compared to females for upper body strength (SMD=-0.40, 95% CI: -0.71 to -0.09; I²=75.6%; n=8), lower body strength (SMD=-0.32, 95% CI: -0.55 to -0.10; I²=52.0%; n=11), and cardiorespiratory fitness (SMD=-0.29, 95% CI: -0.48 to -0.10; I²=89.1%; n=12). Conversely, the pooled SMDs showed a significant effect favoring females for motor fitness (SMD=0.21, 95% CI: 0.03 to 0.39; I²=0%; n=7). Limited and inconsistent results were observed for flexibility.

CONCLUSIONS

Our study suggests the existence of sex-related differences on physical function after an exercise intervention in the older population.

Incretin-Based Weight Loss Pharmacotherapy: Can Resistance Exercise Optimize Changes in Body Composition?

This narrative review highlights the degree to which new antiobesity medications based on gut-derived nutrient-stimulated hormones (incretins) cause loss of lean mass, and the importance of resistance exercise to preserve muscle. Glucagon-like peptide 1 receptor agonists (GLP-1RA) induce substantial weight loss in randomized trials, effects that may be enhanced in combination with glucose-dependent insulinotropic polypeptide (GIP) receptor agonists. Liraglutide and semaglutide (GLP-1RA), tirzepatide (GLP-1 and GIP receptor dual agonist), and retatrutide (GLP-1, GIP, and glucagon receptor triple agonist) are peptides with incretin agonist activity that induce ∼15-24% weight loss in adults with overweight and obesity, alongside beneficial impacts on blood pressure, cholesterol, blood glucose, and insulin. However, these agents also cause rapid and significant loss of lean mass (∼10% or ∼6 kg), comparable to a decade or more of aging. Maintaining muscle mass and function as humans age is crucial to avoiding sarcopenia and frailty, which are strongly linked to morbidity and mortality. Studies indicate that supervised resistance exercise training interventions with a duration >10 weeks can elicit large increases in lean mass (∼3 kg) and strength (∼25%) in men and women. After a low-calorie diet, combining aerobic exercise with liraglutide improved weight loss maintenance compared with either alone. Retaining lean mass during incretin therapy could blunt body weight (and fat) regain on cessation of weight loss pharmacotherapy. We propose that tailored resistance exercise training be recommended as an adjunct to incretin therapy to optimize changes in body composition by preserving lean mass while achieving fat loss.

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.

The effect of home-based neuromuscular electrical stimulation-resistance training and protein supplementation on lean mass in persons with spinal cord injury: A pilot study

In persons with a spinal cord injury (SCI), resistance training using neuromuscular electrical stimulation (NMES-RT) increases lean mass in the lower limbs. However, whether protein supplementation in conjunction with NMES-RT further enhances this training effect is unknown. In this randomized controlled pilot trial, 15 individuals with chronic SCI engaged in 3 times/week NMES-RT, with (NMES+PRO, n = 8) or without protein supplementation (NMES, n = 7), for 12 weeks. Before and after the intervention, whole body and regional body composition (DXA) and fasting glucose and insulin concentrations were assessed in plasma. Adherence to the intervention components was ≥96%. Thigh lean mass was increased to a greater extent after NMES+PRO compared to NMES (0.3 (0.2, 0.4) kg; p < 0.001). Furthermore, fasting insulin concentration and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) were decreased similarly in both groups (fasting insulin: 1 [-9, 11] pmol∙L-1; HOMA-IR: 0.1 [-0.3, 0.5] AU; both p ≥ 0.617). Twelve weeks of home-based NMES-RT increased thigh lean mass, an effect that was potentiated by protein supplementation. In combination with the excellent adherence and apparent improvement in cardiometabolic health outcomes, these findings support further investigation through a full-scale randomized controlled trial.

Sex differences in the adaptations in maximal strength and anaerobic power to upper body plyometric training

This study aimed to compare the effects of a 6-week upper body plyometric training (UBPT) on maximal strength and anaerobic power performance of male and female subjects. Forty collegiate physically active male and female subjects participated in the study and were assigned to either UBPT group (M-UBPT, n = 10, F-UBPT, n = 10) or control group (M-CON, n = 10; F-CON, n = 10). The training groups performed 6 weeks of progressive overload UBPT three times per week using six exercises and were evaluated for upper-body anaerobic power and maximal strength, 3-kg medicine ball throw (MBT), push-up endurance, and reaction time at pre- and post-intervention. After the training intervention, the M-CON and F-CON groups did not show significant (p > 0.05) changes in the variables, while both the M-UBPT and F-UBPT groups demonstrated significant (p = 0.001) medium to very large improvements in their performance as follows: maximal strength (effect size [ES] = 0.55, 0.92), MBT (ES = 1.96, 0.89) peak power output (ES = 2.31, 1.52), mean power output (ES = 2.19, 1.11), push-up endurance (ES = 1.26, 0.70), and reaction time (ES =  - 2.16, - 1.56), respectively. Nevertheless, the male group experienced more significant improvements in the MBT (p = 0.001), peak (p = 0.001) and mean power output (p = 0.01), as well as reaction time (p = 0.01) compared to the female group when utilizing UBPT. In conclusion, it is imperative to take sex into account as a crucial factor when incorporating UBPT, particularly if the objective is to enhance anaerobic power output, muscular power, and reaction time.

Age, Sex, and Training Specific Effects on Cross-Education Training

An extensive number of publications have examined cross-education effects with adults, primarily investigating contralateral homologous (same) muscles. There are far fewer investigations on cross-education effects on contralateral heterologous (different) muscles and age (youth vs adult) and no studies investigating sex differences. Hence, the objective was to compare cross-education in female and male youth and young adults to contralateral homologous (chest press [CP], elbow flexors and extensors, handgrip isometric strength, and shot put) and heterologous (leg press, knee extension isometric strength, and countermovement jump) muscles. Twenty-eight female adults, 28 female youth, 28 male adults, and 28 male youth (total: 112) were examined before and after an 8-week (3 sessions/wk) unilateral, dominant arm, CP training program. Unilateral testing assessed dominant and nondominant leg press and CP 1-repetition maximum, knee extensors, elbow extensors, elbow flexors, and handgrip maximum voluntary isometric contraction (MVIC) strength, as well as shot put distance and countermovement jump height. Unilateral CP training induced training specific (CP 1-repetition maximum) and nonspecific (elbow extensors, elbow flexors, handgrip MVIC force, and shot put distance) improvements (P < .04, η2: .45-.85) but no significant lower body improvements. There was evidence for testing limb specificity as the dominant arm provided significantly (P < .021, η2: .17-.75) greater training gains than the nondominant arm. Youth's training adaptations exceeded with unilateral CP 1-repetition maximum, elbow extensors MVIC force, and shot put distance (P < .049, η2: .14-.49). No sex main effect differences were apparent. In conclusion, cross-education was training specific (greatest gains with upper body and dominant limbs) with greater benefits for youth and generally no sex differences with the exception of elbow extensors MVIC.

Sex Differences in Neuromuscular Adaptations Following 12 Weeks of Kettlebell Swing Training

The purpose of this study was to investigate whether there are sex differences in strength, power, and muscular endurance gains following a 12-week kettlebell swing protocol. Twenty-eight men (29.4 ± 7.3 years; 176.4 ± 6.2 cm; 80.1 ± 11.0 kg; 146.0 ± 22.3 kg in deadlift; 1.8 ± 0.2 kg/body mass deadlift relative strength) and 25 women (32.3 ± 5.5 years; 162.5 ± 7.5 cm; 66.2 ± 9.7 kg; 92.4 ± 17.3 kg in deadlift; 1.4 ± 0.2 kg/body mass deadlift relative strength) participated in this study. Measures of strength in the deadlift, power in the countermovement jump, muscular endurance in the deadlift, and workout of the day (WOD) were obtained before and following six and 12-week time points. Both sexes showed pre- to post-test differences in strength (p < 0.001; one repetition maximum (1RM) improvement of 12.6% for men and 11.7% for women), power (p < 0.001; jump height improvement of 12.9% for men and 6.8% for women), and muscular endurance deadlift test (p < 0.001; improvement in deadlift repetitions of 24.5% for men and 29.2 for women), and only men improved performance in DT WOD (p < 0.001; WOD improvement of 21.3% for men and 1.3% for women). Furthermore, men had greater gains in the power test (p = 0.02) and in the DT WOD endurance test (p = 0.04). Kettlebell training appears to be an effective strategy for increasing strength, power, and endurance in both men and women, but considering the lower responses in power and DT WOD, other strategies should also be considered to optimize women's results in these tests.

Sexual dimorphism in peri-articular tissue anatomy - More keys to understanding sex-differences in osteoarthritis?

Objective

Osteoarthritis prevalence differs between women and men; whether this is the result of differences in pre-morbid articular or peri-articular anatomical morphotypes remains enigmatic. Albeit sex within humans cannot be reduced to female/male, this review focusses to the sexual dimorphism of peri-articular tissues, given lack of literature on non-binary subjects.

Methods

Based on a Pubmed search and input from experts, we selected relevant articles based on the authors' judgement of relevance, interest, and quality; no "hard" bibliometric measures were used to evaluate the quality or importance of the work. Emphasis was on clinical studies, with most (imaging) data being available for the knee and thigh.

Results

The literature on sexual dimorphism of peri-articular tissues is reviewed: 1) bone size/shape, 2) subchondral/subarticular bone, 3) synovial membrane and infra-patellar fad-pad (IPFP), 4) muscle/adipose tissue, and 5) peri-articular tissue response to treatment.

Conclusions

Relevant sex-specific differences exist for 3D bone shape and IPFP size, even after normalization to body weight. Presence of effusion- and Hoffa-synovitis is associated with greater risk of incident knee osteoarthritis in overweight women, but not in men. When normalized to bone size, men exhibit greater muscle, and women greater adipose tissue measures relative to the opposite sex. Reduced thigh muscle specific strength is associated with incident knee osteoarthritis and knee replacement in women, but not in men. These observations may explain why women with muscle strength deficits have a poorer prognosis than men with similar deficits. A "one size/sex fits all" approach must be urgently abandoned in osteoarthritis research.

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.

Movement pattern definitions for resistance training behavior measurement in diabetes

Type 2 diabetes can result in debilitating vascular complications, and resistance training (RT) is an effective therapy for improving cardiovascular outcomes. However, only 10-30% of adults meet the public health guidance for RT. While current RT guidelines focus on targeting major muscle groups, guidance specific to simplified movement categorization may augment understanding of RT programming and improve uptake and outcomes. Current movement pattern definitions and descriptions lack clarity, accuracy, and consistency. This paper proposes movement definitions and descriptions to be used for RT intervention design and prescription, and includes the following categories: hip, knee, ankle, vertebral column, vertical push, horizontal push, vertical pull, and horizontal pull. These categories are intended to aid clinicians, researchers, and trainers in RT surveillance and RT intervention design for improving vascular complications in type 2 diabetes. Simplified RT program design using these categories may also facilitate greater RT program understanding and adherence for patients.

The Effects of Load, Crank Position, and Sex on the Biomechanics and Performance during an Upper Body Wingate Anaerobic Test

INTRODUCTION

The upper body Wingate Anaerobic Test (WAnT) is a 30-s maximal effort sprint against a set load (percentage of body mass). However, there is no consensus on the optimal load and no differential values for males and females, even when there are well-studied anatomical and physiological differences in muscle mass for the upper body. Our goal was to describe the effects of load, sex, and crank position on the kinetics, kinematics, and performance of the upper body WAnT.

METHODS

Eighteen participants (9 females) performed three WAnTs at 3%, 4%, and 5% of body mass. Arm crank forces, 2D kinematics, and performance variables were recorded during each WAnT.

RESULTS

Our results showed an increase of ~49% effective force, ~36% peak power, ~5° neck flexion, and ~30° shoulder flexion from 3% to 5% load ( P < 0.05). Mean power and anaerobic capacity decreased by 15%, with no changes in fatigue index ( P < 0.05). The positions of higher force efficiency were at 12 and 6 o'clock. The least force efficiency occurred at 3 o'clock ( P < 0.05). Sex differences showed that males produced 97% more effective force and 109% greater mean power than females, with 11.7% more force efficiency ( P < 0.001). Males had 16° more head/neck flexion than females, and females had greater elbow joint variability with 17° more wrist extension at higher loads. Males cycled ~32% faster at 3% versus 5% WAnT load with a 65% higher angular velocity than females. Grip strength, maximal voluntary isometric contraction, mass, and height positively correlated with peak and mean power ( P < 0.001).

CONCLUSIONS

In conclusion, load, sex, and crank position have a significant impact on performance of the WAnT. These factors should be considered when developing and implementing an upper body WAnT.

Sexual dimorphisms in skeletal muscle: current concepts and research horizons

The complex compositional and functional nature of skeletal muscle makes this organ an essential topic of study for biomedical researchers and clinicians. An additional layer of complexity is added with the consideration of sex as a biological variable. Recent research advances have revealed sexual dimorphisms in developmental biology, muscle homeostasis, adaptive responses, and disorders relating to skeletal muscle. Many of the observed sex differences have hormonal and molecular mechanistic underpinnings, whereas others have yet to be elucidated. Future research is needed to investigate the mechanisms dictating sex-based differences in the various aspects of skeletal muscle. As such, it is necessary that skeletal muscle biologists ensure that both female and male subjects are represented in biomedical and clinical studies to facilitate the successful testing and development of therapeutics for all patients.

"Male athletes play well to feel good, and female athletes feel good to play well": Attitudes, beliefs, and practices pertaining to perceived sex-related differences in communication and interpersonal approach of strength and conditioning coaches in international women's rugby union

Effective communication and rapport building with athletes are key tenets of coaching. As the majority of empirical evidence to date has adopted an androcentric view of strength and conditioning, a potential knowledge gap exists regarding sex-related differences in physical preparation and coaching approaches. Therefore, this study explored the attitudes, beliefs and practices of strength and conditioning coaches (n = 8; M/F, 6/2) in elite level (international) women's rugby union using semi-structured interviews (mean ±standard deviation duration 59 ± 15 min). The interviews explored differences in coaching practices for elite female rugby players compared to males, with a specific focus on the interpersonal aspects of the athlete-coach relationship. Reflexive thematic analysis was used to generate a rich qualitative dataset. The analysis resulted in the identification of higher order themes: athlete engagement, and interpersonal approach. The coaches in this study consistently perceived important differences between male and female players in factors related to engagement and interpersonal approach. Coaches adopted differing coaching practices for male and female athletes. This study provides important contextual evidence for the understanding of differences in the interpersonal relationships of female rugby players compared to male athletes from the perspective of elite-level strength coaches.

Effect of resistance training on quadriceps femoris muscle thickness obtained by ultrasound: A systematic review with meta-analysis

OBJECTIVE

The present study aimed to determine the magnitude and intervention time of resistance training required to generate adaptations in the muscle thickness of the quadriceps muscle obtained by ultrasound in healthy adults.

METHOD

A systematic review with meta-analysis was conducted on studies recovered from Pubmed, Web of Science, and Scopus databases up to March 2022. The study selection process was carried out by two independent researchers, with the presence of a third researcher in case of disagreements. The methodological quality of the studies was determined with the TESTEX scale, and the risk of bias analysis was determined using Cochrane's RoB 2.0 tool. The meta-analysis used the inverse of the variance with a fixed model, and the effect size was reported by the standardized mean difference (SMD) with a confidence interval of 95%.

RESULTS

Ten studies were included in a meta-analysis. The overall analysis of the studies demonstrated an SMD = 0.35 [95% CI: 0.13-0.56] (P = 0.002), with a low heterogeneity of I2 = 0% (P = 0.52). No publication bias was detected using a funnel plot followed by Egger's test (P = 0.06). The degree of certainty of the meta-analysis was high using the GRADE tool.

CONCLUSION

We found that resistance training can generate significant average increases of 16.6% in muscle thickness obtained by ultrasound in the quadriceps femoris muscles of healthy adults. However, the subgroup analysis showed that significant effect sizes were only observed after eight weeks of training.

Sex Differences in the Ergogenic Response of Acute Caffeine Intake on Muscular Strength, Power and Endurance Performance in Resistance-Trained Individuals: A Randomized Controlled Trial

BACKGROUND

This study assessed the impact of acute caffeine intake on muscular strength, power, and endurance performance between resistance-trained male and female individuals according to load in upper- and lower-body exercises.

METHODS

Here, 76 resistance-trained individuals (38 females, 38 males) participated in a study comparing caffeine and a placebo. Each received either 3 mg/kg of caffeine or a placebo 60 min before tests measuring muscular strength and power through bench press and back squat exercises at different intensities (25%, 50%, 75%, 90% 1RM). Muscular endurance at 65% 1RM was also assessed by performing reps until reaching task failure.

RESULTS

Compared to placebo, caffeine increased mean, peak and time to reach peak velocity and power output (p < 0.01, ηp2 = 0.242-0.293) in the muscular strength/power test in males and females. This effect was particularly observed in the back squat exercise at 50%, 75% and 90% 1RM (2.5-8.5%, p < 0.05, g = 1.0-2.4). For muscular endurance, caffeine increased the number of repetitions, mean velocity and power output (p < 0.001, ηp2 = 0.177-0.255) in both sexes and exercises (3.0-8.9%, p < 0.05, g = 0.15-0.33).

CONCLUSIONS

Acute caffeine intake resulted in a similar ergogenic effect on muscular strength, power, and endurance performance in upper- and lower-body exercises for male and female resistance-trained participants.

Sex Does Not Affect Changes in Body Composition and Insulin-Like Growth Factor-I During US Army Basic Combat Training

ABSTRACT

Roberts, BM, Staab, JS, Caldwell, AR, Sczuroski, CE, Staab, JE, Lutz, LJ, Reynoso, M, Geddis, AV, Taylor, KM, Guerriere, KI, Walker, LA, Hughes, JM, and Foulis, SA. Sex does not affect changes in body composition and insulin-like growth factor-I during US Army basic combat training. J Strength Cond Res 38(6): e304-e309, 2024-Insulin-like growth factor 1 (IGF-I) has been implicated as a biomarker of health and body composition. However, whether changes in body composition are associated with changes in IGF-I is unclear. Therefore, we examined the relationship between body composition changes (i.e., fat mass and lean mass) and total serum IGF-I levels in a large cohort of young men ( n = 809) and women ( n = 397) attending US Army basic combat training (BCT). We measured body composition using dual energy x-ray absorptiometry and total serum IGF-I levels during week 1 and week 9 of BCT. We found that pre-BCT lean mass ( r = 0.0504, p = 0.082) and fat mass ( r = 0.0458, p = 0.082) were not associated with pre-BCT IGF-I. Body mass, body mass index, body fat percentage, and fat mass decreased, and lean mass increased during BCT (all p < 0.001). Mean (± SD ) IGF-I increased from pre-BCT (176 ± 50 ng·ml -1 ) to post-BCT (200 ± 50 ng·ml -1 , p < 0.001). Inspection of the partial correlations indicated that even when considering the unique contributions of other variables, increases in IGF-I during BCT were associated with both increased lean mass ( r = 0.0769, p = 0.023) and increased fat mass ( r = 0.1055, p < 0.001) with no sex differences. Taken together, our data suggest that although changes in IGF-I weakly correlated with changes in body composition, IGF-I, in isolation, is not an adequate biomarker for predicting changes in body composition during BCT in US Army trainees.

Sex differences in muscle-quality recovery following one week of knee joint immobilization and subsequent retraining

This manuscript represents the second phase of a clinical trial designed to examine the effects of knee joint immobilization and retraining on muscle strength and mass. In Phase 2, we examined sex differences in the recovery of multiple indices of muscle quality after a resistance training-based rehabilitation program. Following 1 week of immobilization, 27 participants (16 males, 11 females) exhibiting weakness underwent twice weekly resistance training sessions designed to re-strengthen their left knee. Unilateral retraining sessions utilizing leg press, extension, and curl exercises were conducted until participants could reproduce their pre-immobilization knee extension isometric maximal voluntary contraction (MVC) peak torque. Post-immobilization, both sexes demonstrated impaired MVC peak torque (males = -10.8%, females = -15.2%), specific torque (-9.8% vs. -13.1%), echo intensity of the vastus lateralis (+6.9% vs. +5.9%) and rectus femoris (+5.9% vs. +2.1), and extracellular water/intracellular water ratio (+7.8% vs. +9.0%). The number of retraining sessions for peak torque to return to baseline for males (median = 1, mean = 2.13) versus females (median = 2, mean = 2.91) was not significantly different, though the disparity in recovery times may be clinically relevant. Following retraining, specific torque was the only muscle-quality indicator that improved along with MVC peak torque (males = 20.1%, females = 22.4%). Our findings indicate that measures of muscle quality demonstrate divergent recovery rates following immobilization, with muscle mass lagging behind improvements in strength. Greater immobilization-induced strength loss among females suggests that sex-specific rehabilitation efforts may be justified.

Comparison of resistance training using barbell half squats and trap bar deadlifts on maximal strength, power performance, and lean mass in recreationally active females: an eight-week randomised trial

BACKGROUND

The aim of this study was to investigate the effect of high load resistance training using barbell half squats compared with trap bar deadlifts on maximal strength, power performance, and lean mass in recreationally active females.

METHODS

Twenty-two recreationally active female participants (age: 26.9 ± 7.7 yrs.; height: 166.0 ± 5.1 cm; weight: 68.6 ± 9.9 kg) were randomly assigned to either a barbell half squat group (SG: n = 10) or trap bar deadlift group (DG: n = 12). Training consisted of twice-weekly sessions for eight weeks. Both groups completed one-repetition maximum (1RM) testing for both barbell half squat and trap bar deadlift groups. Countermovement jump (CMJ) and sprint performance were also assessed. Total body (TBLM) and leg lean mass (LLM) were measured with dual-energy x-ray absorptiometry. Between-group differences were analysed using analysis of covariance.

RESULTS

SG tended to improve 1RM half squat (21.0 ± 11.5 kg vs. 13.1 ± 7.5 kg) more than DG (mean difference (MD): 8.0 kg, 95% CI: -0.36 - 16.3 kg). A similar pattern in favour of DG (18.4 ± 11.2 vs. 11.7 ± 8.1 kg) compared to SG was observed (MD: 6.5 kg, 95% CI: -2.5 - 15.6 kg). No between-group differences for sprint, jump or lean body mass changes was observed. For groups combined, the following changes in CMJ (2.0 ± 2.4 cm), 5-m sprint (-0.020 ± 0.039 s), 15-m sprint (-0.055 ± 0.230 s), TBLM (0.84 ± 1.12 kg), and LLM (0.27 ± 0.59 kg) was observed.

CONCLUSIONS

An exercise intervention consisting of half squats or trap bar deadlift were associated with improved muscle strength, power, and lean mass. Our findings suggests that in recreationally active females, exercise selection is less of a concern provided that heavy loads are applied, and relevant muscle groups are targeted.

A comprehensive study of the academic benefits and practical recommendations to include resistance training programs in institutional education

The connection between physical activity and cognitive function has become a focus of attention in educational research in recent years. Regular exercise has been shown to have significant positive effects on physical health, but it also appears to have a significant impact on cognitive function and academic performance. Of all the exercise modalities, resistance training has drawn interest for its ability to improve cerebral abilities in addition to physical well-being. However, there is limited available knowledge exploring the relationship between resistance training regimens and academic performance. This narrative review aims to investigate the underlying mechanisms linking resistance training to academic performance. Firstly, we will examine the biological mechanisms and psychosocial links that potentially connect resistance training to academic performance to find and describe the different mechanisms by which resistance training improves academic performance. In the next part of the work, we delve into the existing observational and intervention studies that have explored the relationship between resistance training and academic performance. Lastly, we provide practical recommendations for including resistance training in institutional education settings, emphasizing the need of dispelling myths and addressing barriers to increase participation as well as the relevance of considering key training variables and adaptation of protocols to developmental stages, always guided by a properly trained professional. Overall, the available evidence supports that resistance training provides potential benefits to the academic performance of youth students with many biological and psychosocial factors that explain this relationship. However, most of the studies are observational, and broader interventional studies are needed to understand and maximize the benefits of this type of physical exercise.

Circulating extracellular vesicle characteristics differ between men and women following 12 weeks of concurrent exercise training

Concurrent resistance and endurance exercise training (CET) has well-studied benefits; however, inherent hormonal and genetic differences alter adaptive responses to exercise between sexes. Extracellular vesicles (EVs) are factors that contribute to adaptive signaling. Our purpose was to test if EV characteristics differ between men and women following CET. 18 young healthy participants underwent 12-weeks of CET. Prior to and following CET, subjects performed an acute bout of heavy resistance exercise (AHRET) consisting of 6 × 10 back squats at 75% 1RM. At rest and following AHRET, EVs were isolated from plasma and characteristics and miRNA contents were analyzed. AHRET elevated EV abundance in trained men only (+51%) and AHRET-induced changes were observed for muscle-derived EVs and microvesicles. There were considerable sex-specific effects of CET on EV miRNAs, highlighted by larger variation following the 12-week program in men compared to women at rest. Pathway analysis based on differentially expressed EV miRNAs predicted that AHRET and 12 weeks of CET in men positively regulates hypertrophy and growth pathways more so than in women. This report highlights sex-based differences in the EV response to resistance and concurrent exercise training and suggests that EVs may be important adaptive signaling factors altered by exercise training.

Impact of a 16-week strength training program on physical performance, body composition and cardiac remodeling in previously untrained women and men

Even if more and more women are involved in strength-training (ST) programs in fitness centers, studies on strength gain, body composition, and cardiac remodeling were mainly conducted in men and whether they are similar in women remains to be explored. In this context, the aim of our study was to assess the effect of a supervised ST program on strength gains, body composition, and cardiac remodeling in previously untrained women and men. 17 healthy and previously untrained young women and 17 young men participated in a supervised 16-week ST program built according to the recommendation of the American College of Sports Medicine in terms of intensity, and strictly using similar volume and intensity in both groups. Strength performance, body composition, and cardiac remodeling were evaluated every 4 weeks. Cardiac adaptations were assessed using resting echocardiography, including regional 2D-Strain analysis of the left atrium and ventricle (LA and LV, respectively). Despite lower values at baseline, women exhibited similar or even higher strength gains compared to men. ST induced a decrease of body and abdominal fat mass and an increase of lean body mass in both groups. Similar cardiac remodeling was observed in women, and women, including an early and progressive LV and LA enlargement throughout the ST program, without any alteration of LV diastolic and systolic functions. These findings underlie that ST programs are highly suitable for women to enhance their strength performance and their cardiovascular health.

Skeletal muscle adaptations to high-intensity, low-volume concurrent resistance and interval training in recreationally active men and women

This study compared the structural and cellular skeletal muscle factors underpinning adaptations in maximal strength, power, aerobic capacity, and lean body mass to a 12-week concurrent resistance and interval training program in men and women. Recreationally active women and men completed three training sessions per week consisting of high-intensity, low-volume resistance training followed by interval training performed using a variety upper and lower body exercises representative of military occupational tasks. Pre- and post-training vastus lateralis muscle biopsies were analyzed for changes in muscle fiber type, cross-sectional area, capillarization, and mitochondrial biogenesis marker content. Changes in maximal strength, aerobic capacity, and lean body mass (LBM) were also assessed. Training elicited hypertrophy of type I (12.9%; p = 0.016) and type IIa (12.7%; p = 0.007) muscle fibers in men only. In both sexes, training decreased type IIx fiber expression (1.9%; p = 0.046) and increased total PGC-1α (29.7%, p < 0.001) and citrate synthase (11.0%; p < 0.014) content, but had no effect on COX IV content or muscle capillarization. In both sexes, training increased maximal strength and LBM but not aerobic capacity. The concurrent training program was effective at increasing strength and LBM but not at improving aerobic capacity or skeletal muscle adaptations underpinning aerobic performance.

Sex Differences in Association of Physical Activity With All-Cause and Cardiovascular Mortality

BACKGROUND

Although physical activity is widely recommended for reducing cardiovascular and all-cause mortality risks, female individuals consistently lag behind male individuals in exercise engagement.

OBJECTIVES

The goal of this study was to evaluate whether physical activity derived health benefits may differ by sex.

METHODS

In a prospective study of 412,413 U.S. adults (55% female, age 44 ± 17 years) who provided survey data on leisure-time physical activity, we examined sex-specific multivariable-adjusted associations of physical activity measures (frequency, duration, intensity, type) with all-cause and cardiovascular mortality from 1997 through 2019.

RESULTS

During 4,911,178 person-years of follow-up, there were 39,935 all-cause deaths including 11,670 cardiovascular deaths. Regular leisure-time physical activity compared with inactivity was associated with 24% (HR: 0.76; 95% CI: 0.73-0.80) and 15% (HR: 0.85; 95% CI: 0.82-0.89) lower risk of all-cause mortality in women and men, respectively (Wald F = 12.0, sex interaction P < 0.001). Men reached their maximal survival benefit of HR 0.81 from 300 min/wk of moderate-to-vigorous physical activity, whereas women achieved similar benefit at 140 min/wk and then continued to reach a maximum survival benefit of HR 0.76 also at ∼300 min/wk. Sex-specific findings were similar for cardiovascular death (Wald F = 20.1, sex interaction P < 0.001) and consistent across all measures of aerobic activity as well as muscle strengthening activity (Wald F = 6.7, sex interaction P = 0.009).

CONCLUSIONS

Women compared with men derived greater gains in all-cause and cardiovascular mortality risk reduction from equivalent doses of leisure-time physical activity. These findings could enhance efforts to close the "gender gap" by motivating especially women to engage in any regular leisure-time physical activity.

Relationship between a body shape index and muscle strength index in Chinese university students: a cross-sectional survey

BACKGROUND

The problem of overweight obesity and decrease in muscle strength among university students has become an indisputable fact. In this study, a comprehensive index reflecting obesity degree a body shape index (ABSI) and a comprehensive index reflecting muscle strength muscle strength index (MSI) were studied to analyze the cross-sectional correlations existing between them.

METHODS

This study began recruiting participants and conducting the test survey in April 2022 and closed in July 2022. Basic condition, height, weight, waist circumference, grip strength, pull-up (boys), bent-leg sit-up (girls), and standing long jump were tested on 12,046 (boys: 6011, 49.90%) university students aged 19-22 years in China, and ABSI and MSI were calculated separately. ABSI was categorized into 5 groups according to age and sex, namely ABSI < 5th percentile (A), 5th ≤ ABSI < 25th percentile (B), 25th ≤ ABSI < 75th percentile (C), 75th ≤ ABSI < 95th percentile (D) and ABSI ≥ 95th percentile (E). The comparison of MSI between different ABSI groups was performed using effect size, and the association between them was performed by curve estimation analysis.

RESULTS

The association between ABSI and MSI of Chinese university students showed an inverted "U" curve. The effect of increased ABSI on MSI was greater in university girls compared to boys. The ABSI of boys was (0.080 ± 0.010) and MSI was (-0.005 ± 2.080); the ABSI of girls was (0.079 ± 0.008) and MSI was (-0.017 ± 1.867). Overall, university students ABSI was at a relatively high point for MSI between 0.050 and 0.100. The university students ABSI at 0.150 had an MSI of -1.229 for boys and - 2.779 for girls.

CONCLUSION

The ABSI of Chinese university students showed an inverted "U"-shaped curve relationship with MSI, and university students with low or high ABSI had lower MSI. The effect of increasing ABSI on the decrease of MSI was more obvious for girls than for boys.

Gender-Related Effectiveness of Personalized Post-COVID-19 Rehabilitation

Background: Post-COVID-19 syndrome (PCS) may affect a substantial proportion of patients who have had COVID-19. The rehabilitation program might improve the physical capacity, functioning of the cardiopulmonary system, and mental conditions of these patients. This study aimed to investigate the effectiveness of personalized rehabilitation in patients with PCS according to gender. Methods: Adults who underwent a 6-week personalized PCS rehabilitation program were enrolled in a prospective post-COVID-19 Rehabilitation (PCR-SIRIO 8) study. The initial visit and the final visit included the hand-grip strength test, the bioimpedance analysis of body composition, and the following scales: modified Borg's scale, Modified Fatigue Impact Scale (MFIS), Functioning in Chronic Illness Scale (FCIS), modified Medical Research Council (mMRC) dyspnea scale, and tests: 30 s chair stand test (30 CST), Six-Minute Walk Test (6MWT), Short Physical Performance Battery test (SPPB)e. Results: A total of 90 patients (54% female) underwent the rehabilitation program. Rehabilitation was associated with an increase in skeletal muscle mass (24.11 kg vs. 24.37 kg, p = 0.001) and phase angle (4.89° vs. 5.01°, p = 0.001) and with a reduction in abdominal fat tissue volume (3.03 L vs. 2.85 L, p = 0.01), waist circumference (0.96 m vs. 0.95 m, p = 0.001), and hydration level (83.54% vs. 82.72%, p = 0.001). A decrease in fat tissue volume and an increase in skeletal muscle mass were observed only in females, while an increase in grip strength was noticed selectively in males. Patients' fatigue (modified Borg's scale, MFIS), physical capacity (30 CST, 6MWT), balance (SPPB), dyspnea (mMRC), and functioning (FICS) were significantly improved after the rehabilitation regardless of gender. Conclusions: Personalized rehabilitation improved the body composition, muscle strength, and functioning of patients diagnosed with PCS. The beneficial effect of rehabilitation on body composition, hydration, and phase angle was observed regardless of gender.

Concurrent Strength and Endurance Training: A Systematic Review and Meta-Analysis on the Impact of Sex and Training Status

BACKGROUND

Many sports require maximal strength and endurance performance. Concurrent strength and endurance training can lead to suboptimal training adaptations. However, how adaptations differ between males and females is currently unknown. Additionally, current training status may affect training adaptations.

OBJECTIVE

We aimed to assess sex-specific differences in adaptations in strength, power, muscle hypertrophy, and maximal oxygen consumption ( V ˙ O2max) to concurrent strength and endurance training in healthy adults. Second, we investigated how training adaptations are influenced by strength and endurance training status.

METHODS

A systematic review and meta-analysis was conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, and a Cochrane risk of bias was evaluated. ISI Web of science, PubMed/MEDLINE, and SPORTDiscus databases were searched using the following inclusion criteria: healthy adults aged 18-50 years, intervention period of ≥ 4 weeks, and outcome measures were defined as upper- and lower-body strength, power, hypertrophy, and/or V ˙ O2max. A meta-analysis was performed using a random-effects model and reported in standardized mean differences.

RESULTS

In total, 59 studies with 1346 participants were included. Concurrent training showed blunted lower-body strength adaptations in males, but not in females (male: - 0.43, 95% confidence interval [- 0.64 to - 0.22], female: 0.08 [- 0.34 to 0.49], group difference: P = 0.03). No sex differences were observed for changes in upper-body strength (P = 0.67), power (P = 0.37), or V ˙ O2max (P = 0.13). Data on muscle hypertrophy were insufficient to draw any conclusions. For training status, untrained but not trained or highly trained endurance athletes displayed lower V ˙ O2max gains with concurrent training (P = 0.04). For other outcomes, no differences were found between untrained and trained individuals, both for strength and endurance training status.

CONCLUSIONS

Concurrent training results in small interference for lower-body strength adaptations in males, but not in females. Untrained, but not trained or highly trained endurance athletes demonstrated impaired improvements in V ˙ O2max following concurrent training. More studies on females and highly strength-trained and endurance-trained athletes are warranted.

CLINICAL TRIAL REGISTRATION

PROSPERO: CRD42022370894.

Similar muscle hypertrophy following eight weeks of resistance training to momentary muscular failure or with repetitions-in-reserve in resistance-trained individuals

This study examined the influence of resistance training (RT) proximity-to-failure, determined by repetitions-in-reserve (RIR), on quadriceps hypertrophy and neuromuscular fatigue. Resistance-trained males (n = 12) and females (n = 6) completed an 8-week intervention involving two RT sessions per week. Lower limbs were randomised to perform the leg press and leg extension exercises either to i) momentary muscular failure (FAIL), or ii) a perceived 2-RIR and 1-RIR, respectively (RIR). Muscle thickness of the quadriceps [rectus femoris (RF) and vastus lateralis (VL)] and acute neuromuscular fatigue (i.e., repetition and lifting velocity loss) were assessed. Data was analysed with Bayesian linear mixed-effect models. Increases in quadriceps thickness (average of RF and VL) from pre- to post-intervention were similar for FAIL [0.181 cm (HDI: 0.119 to 0.243)] and RIR [0.182 cm (HDI: 0.115 to 0.247)]. Between-protocol differences in RF thickness slightly favoured RIR [-0.036 cm (HDI: -0.113 to 0.047)], but VL thickness slightly favoured FAIL [0.033 cm (HDI: -0.046 to 0.116)]. Mean volume was similar across the RT intervention between FAIL and RIR. Lifting velocity and repetition loss were consistently greater for FAIL versus RIR, with the magnitude of difference influenced by the exercise and the stage of the RT intervention.

Sex differences in skeletal muscle fiber types: A meta-analysis

Biopsies have been acquired from living men and women to determine proportions of Type I (slow-twitch) and II (fast-twitch) skeletal muscle fibers since the 1970s. Sex differences have been assumed but the literature has not been submitted to meta-analysis. Here, the aim was to generate effect sizes of sex differences in muscle fiber cross-sectional areas, distribution percentages, and area percentages. Data from 2875 men and 2452 women, who participated in 110 studies, were analyzed. Myofibrillar adenosine triphosphatase histochemistry was used in 71.8% of studies to classify fibers as Type I, II, IIA, and/or IIX; immunohistochemistry, immunofluorescence, or sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used in 35.4% of studies to similarly classify myosin heavy chain (MHC) isoform content. Most studies involved biopsies from vastus lateralis (79.1%) in healthy individuals (92.7%) between 18 and 59 years old (80.9%). Men exhibited greater cross-sectional areas for all fiber types (g = 0.40-1.68); greater distribution percentages for Type II, MHC II, IIA, IIX fibers (g = 0.26-0.34); greater area percentages for Type II, IIA, MHC IIA, IIX fibers (g = 0.39-0.93); greater Type II/I and Type IIA/I fiber area ratios (g = 0.63, 0.94). Women exhibited greater Type I and MHC I distribution percentages (g = -0.13, -0.44); greater Type I and MHC I area percentages (g = -0.53, -0.69); greater Type I/II fiber area ratios (g = -1.24). These data, which represent the largest repository of comparative muscle fiber type data from living men and women, can inform discussions about biological sex and its impact on pathologies and sports performance (e.g., explaining sex differences in muscle strength and muscle endurance).