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Sex differences in sports performances continue to attract considerable scientific and public attention, driven in part by high profile cases of: 1) biological male (XY) athletes who seek to compete in the female category after gender transition, and 2) XY athletes with medical syndromes collectively known as disorders or differences of sex development (DSDs). In this perspective, we highlight scientific evidence that informs eligibility criteria and applicable regulations for sex categories in sports. There are profound sex differences in human performance in athletic events determined by strength, speed, power, endurance, and body size such that males outperform females. These sex differences in athletic performance exist before puberty and increase dramatically as puberty progresses. The profound sex differences in sports performance are primarily attributable to the direct and indirect effects of sex-steroid hormones and provide a compelling framework to consider for policy decisions to safeguard fairness and inclusion in sports. [ABSTRACT FROM AUTHOR]

The cellular causes of the age‐related loss in power output and increased fatigability are unresolved. We previously observed that the depressive effects of hydrogen (H+) (pH 6.2) and inorganic phosphate (Pi) (30 mm) did not differ in muscle fibres from young and older men. However, the effects may have been saturated in the severe fatigue‐mimicking condition, potentially masking age differences in the sensitivity of the cross‐bridge to these metabolites. Thus, we compared the contractile mechanics of muscle fibres from the vastus lateralis of 13 young (20–32 years, seven women) and 12 older adults (70–90 years, six women) in conditions mimicking quiescent muscle and a range of elevated H+ (pH 6.8–6.6–6.2) and Pi (12–20–30 mm). The older adult knee extensor muscles showed hallmark signs of ageing, including 19% lower thigh lean mass, 60% lower power and a greater fatigability compared to young adult muscles. Progressively increasing concentrations of H+ and Pi in the chemically‐permeabilized fibre experiments caused a linear decrease in fibre force, velocity and power; however, the effects did not differ with age or sex. Fast fibre cross‐sectional area was 41% smaller in older compared to young adults, which corresponded with lower absolute power. Size‐specific power was greater in fibres from older compared to young adults, indicating the age‐related decline in absolute power was explained by differences in fibre size. These data suggest the age‐related loss in power is determined primarily by fast fibre atrophy in men and women, but the age‐related increase in fatigability cannot be explained by an increased sensitivity of the cross‐bridge to H+ and Pi. Key points: The causes of the age‐related loss in muscle power output and the increase in fatigability during dynamic exercise remain elusive.We show that progressively increasing concentrations of hydrogen (H+) and inorganic phosphate (Pi) causes a linear decrease in muscle fibre force, velocity and power, but the depressive effects of these metabolites on cross‐bridge function did not differ in fibres from older compared to young adults across a range of fatigue‐mimicking conditions.We also found peak absolute power did not differ in slow fibres from young and older adults but it was ∼33% lower in older adult fast fibres, which was explained entirely by age differences in fibre size.These data suggest that fast fibre atrophy is a major factor contributing to the loss in power of older men and women, but that the age‐related increase in fatigability cannot be explained by an increased sensitivity of the cross‐bridge to H+ and Pi. [ABSTRACT FROM AUTHOR]

Objective: To understand the biopsychosocial dimensions of university health sciences students' experiences during the COVID-19 pandemic. Participants: Health sciences students (n = 297) from two universities in July and August 2020. Methods: Participants completed a Web-based survey asking about depression, anxiety, physical activity, coronavirus threat, and career commitment. Results: Moderate or severe depression and anxiety were reported by 28.6% and 31.3% of respondents, respectively. Depression and anxiety were positively correlated with perceived coronavirus threat and negatively correlated with career commitment and strenuous physical activity. A change in career commitment interests during the COVID-19 pandemic was reported by 11% of respondents. Conclusions: Identified factors that could be targeted by universities to support their students and secure career commitment include online learning challenges, ability to secure clinical placements, mental health (anxiety and depression), financial challenges, family pressure, and promotion of physical activity. [ABSTRACT FROM AUTHOR]

The mechanisms for the loss in limb muscle power output in old (60–79 yr) and very old (≥80 yr) adults and whether the mechanisms differ between men and women are not well understood. We compared maximal peak power of the knee extensor muscles between young, old, and very old men and women and identified the neural and muscular factors contributing to the age-related differences in power. Thirty-one young (22.9 ± 3.0 yr, 15 women), 82 old (70.3 ± 4.9 yr, 38 women), and 16 very old adults (85.8 ± 4.2 yr, 9 women) performed maximal isokinetic contractions at 14 different velocities (30–450°/s) to identify peak power. Voluntary activation (VA) and contractile properties were assessed with transcranial magnetic stimulation to the motor cortex and electrical stimulation of the femoral nerve. The age-related loss in peak power was ∼6.5 W·yr−1 for men (R2 = 0.62, P < 0.001), which was a greater rate of decline (P = 0.002) than the ∼4.2 W·yr−1 for women (R2 = 0.77, P < 0.001). Contractile properties were the most closely associated variables with peak power for both sexes, such as the rate of torque development of the potentiated twitch (men: R2 = 0.69, P < 0.001; women: R2 = 0.57, P < 0.001). VA was weakly associated with power in women (R2 = 0.13, P = 0.012) but not in men (P = 0.191). Similarly, neuromuscular activation [rates of electromyography (EMG) rise] during the maximal power contraction was associated with power in women (R2 = 0.07, P = 0.042) but not in men (P = 0.456). These data suggest that the age-related differences in maximal peak power of the knee extensor muscles are due primarily to factors within the muscle for both sexes, although neural factors may play a minor role in older women. NEW & NOTEWORTHY: The greater age-related loss in power relative to the loss in muscle mass of the knee extensors was primarily due to factors altering the contractile properties of the muscle for both old and very old (≥80 yr) adults. The mechanisms for the decrements in power with aging appear largely similar for men and women, although neural factors may play more of a role in older women. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

High-level athletic performances may be a proxy for the trajectory of optimal function of human biology with advanced aging and the differences between males and females. Males are faster, stronger, and more powerful than females and these physical attributes decline dramatically with advanced aging for both sexes. Experimental mechanistic studies determine the physiological mechanisms for these sex and age differences in human physical performance. The assumption however, that real-world performances solely reflect the biological and physiological differences between the sexes and with advanced aging, even among elite athletes, is not complete. This review presents evidence that an integrated approach encompassing analysis of real-world data and experimental mechanistic studies is necessary to determine the biological and sociocultural factors attributed to the limits of performance with aging and between males and females. First, experimental studies are presented that focus on the sex and age differences in performance fatigability that determine the physiological mechanisms of absolute and relative exercise performance. Second, analysis of current and historical real-world data including world records, and performances of elite, collegiate, and competitive age-group athletes are highlighted. These data illustrate that the upper limits of physical performance that have changed historically, and other factors such as sociocultural influences, explain the widening of the sex and age gaps in human performance observed in real-world data even in present-day performances. These approaches have broader significance when applied to understanding the impact of the historically low representation of females and minority groups in biomedical research on health outcomes. [ABSTRACT FROM AUTHOR]

Females demonstrate greater fatigue resistance compared to males in tasks ranging from single-limb contractions to whole-body exercise, including running. Many of the studies investigating sex differences in fatigability following running, however, occur after long duration, low-intensity tasks and it is unknown whether there is a sex difference in fatigability following high-intensity running. This study compared fatigability and recovery following a 5 km running time trial in young males and females. Sixteen recreationally active participants (8 males, 8 females, age: 23 ± 4 years) completed a familiarisation and experimental trial. Knee-extensor maximal voluntary contractions (MVCs) were performed before and up to 30 min after a 5 km time trial on a treadmill. Heart rate and rating of perceived exertion (RPE) were recorded after every kilometre during the time trial. Although not significantly different, males completed the 5 km time trial 15% faster than females (p= 0.095). Heart rate (p = 0.843) and RPE (p = 0.784) were similar between the sexes during the trial. Prior to running, males had larger MVCs (p = 0.014). The relative decrease in MVC force was less in females than males immediately post-exercise (-4.6 ± 2.4% vs. -15.1 ± 3.0%, p < 0.001) and at 10-minutes post-exercise (p = 0.018). At 20- and 30-minutes recovery, however, relative MVC force was not different between the sexes (p = 0.129). These data demonstrate that females experienced less fatigability of the knee extensors than males following a high-intensity 5 km running time trial. The findings highlight the need to understand responses to exercise in both sexes and have implications for recovery from training and exercise prescription. [ABSTRACT FROM AUTHOR]