The exercise power-duration relationship is equally reproducible in eumenorrheic female and male humans

Abstract

Purpose: To investigate the effect of the menstrual cycle (MC) on exercise performance across the power-duration relationship (PDR). We hypothesized females would exhibit greater variability in the PDR across the MC than males across a similar timespan, with critical power (CP) and Work-prime (W') being lower during the early follicular phase than the late follicular and mid-luteal phases. Methods: Seven eumenorrheic, endurance-trained female adults performed multiple constant-load-to-task-failure and maximum-power tests at three time points across the MC (early follicular, late follicular, mid-luteal phases). Ten endurance-trained male adults performed the same tests approximately 10 days apart. Results: No differences across the PDR were observed between MC phases (CP: 186.74 ± 31.00 W, P = 0.955, CV = 0.81 ± 0.65 %) (W': 7,961.81 ± 2,537.68 J, P = 0.476, CV = 10.48 ± 3.06 %). CP was similar for male and female subjects (11.82 ± 1.42 W • kg−1 vs. 11.56 ± 1.51 W • kg−1, respectively) when controlling for leg lean mass. However, W' was larger (P = 0.047) for male subjects (617.28 ± 130.10 J • kg−1) than female subjects (490.03 ± 136.70 J • kg−1) when controlling for leg lean mass. Conclusion: MC phase does not need to be controlled when conducting aerobic endurance performance research on eumenorrheic female subjects without menstrual dysfunction. Nevertheless, several sex differences in the power-duration relationship exist, even after normalizing for body composition. Therefore, previous studies describing the physiology of exercise performance in male subjects may not perfectly describe that of female subjects.

The influence of skeletal muscle mitochondria and sex on critical torque and performance fatiguability in humans

“…The similar R 2 values for the intensity–duration relationship during CT determination, the similar CT‐10% test–retest ICC values for performance fatiguability indices between males and females, as well as similar overall findings from the first and second CT‐10% trials performed ∼10 days apart, suggest minimal influence from hormonal fluctuations and counter the belief that females’ data are more variable than males’ data (Shansky & Murphy, 2021). These results agree with a recent study of CP for cycling in eumenorrhoeic females (James et al., 2023) and support our use of a broader and more generalizable female population; however, we cannot rule out the possibility that males and females may differ in performance fatiguability under certain sex hormone conditions. Thirdly, CT determination has limitations, as CT represents a ‘phase transition’ between the heavy‐ and severe‐intensity exercise domains and not a fixed threshold (Pethick et al., 2020), indicating that, aside from statistical uncertainty, CT cannot be precisely determined.…”

Vascular dysfunction and the age‐related decline in critical power

“…In other words, male subjects exhibited a greater impact of age on W′ than female subjects. Additional studies designed to investigate sex differences are needed to confirm or reject these findings in our small sample; nevertheless, the differences in W′ between young males and young females are consistent with previous studies showing sex differences in W′ or D′ during cycling exercise (Collins et al, 2022;James et al, 2023) and running exercise (Gifford & Collins, 2021). Like CP, the deficit in W′ is exacerbated when considering total body mass, to the point that the younger subjects were able to perform ∼35% more work per kilogram than the older subjects (P = 0.028).…”

The Biological Basis of Sex Differences in Athletic Performance: Consensus Statement for the American College of Sports Medicine

“…Sex differences in the power of limb muscles are even larger than the differences in maximal isometric strength (93,128) possibly because maximal contraction velocity is typically slower in females for a given load (92). Peak power during cycling and knee extensor single limb exercise of females, for example, was 63% to 67% that of males (93,137,138). This sex difference in strength and limb power persists into very old age (92,93).…”

“…Individual responses to menstrual cycle related symptoms among females can be quite varied. Although hormonal fluctuations across the menstrual cycle can alter physiological responses in some females, the average effect on performance is likely small relative to the large differences in athletic performance between males and females (10,138) and other environmental factors that affect both males and females. Key questions on the influence of the menstrual cycle and conditions affecting menstruation on athletic performance remain and certainly deserve more detailed analysis and reviews.…”