Do Sex Differences in Physiology Confer a Female Advantage in Ultra-Endurance Sport?

Abstract

Ultra-endurance has been defined as any exercise bout that exceeds 6 h. A number of exceptional, record-breaking performances by female athletes in ultra-endurance sport has roused speculation that they might be predisposed to success in such events. Indeed, while the male-to-female performance gap in traditional endurance sport (e.g., marathon) remains at ~10%, the disparity in ultra-endurance competition has been reported as low as 4% despite the markedly lower number of female participants. Moreover, females generally outperform males in extreme-endurance swimming. The issue is complex, however, with many sportsspecific considerations and caveats. This review summarizes the sex-based differences in physiological functions and draws attention to those which likely determine success in extreme exercise endeavors. The aim is to provide a balanced discussion of the female versus male predisposition to ultra-endurance sport. Herein, we discuss sex-based differences in muscle morphology and fatigability, respiratory-neuromechanical function, substrate utilization, oxygen utilization, gastrointestinal structure and function, and hormonal control. The literature indicates that while females exhibit numerous phenotypes that would be expected to confer an advantage in ultra-endurance competition (e.g., greater fatigue-resistance, greater substrate efficiency, and lower energetic requirements), they also exhibit several characteristics that unequivocally impinge on performance (e.g., lower O2-carrying capacity, increased prevalence of GI distress, and sex-hormone effects on cellular function/ injury risk).Crucially, the advantageous traits may only manifest as ergogenic in the extreme endurance events which, paradoxically, are the races that females less often contest. The title question should be revisited in the coming years when/if the number of female participants increases. KEY POINTS• Females exhibit numerous physiological characteristics that would be expected to confer an advantage in ultra-endurance competition. However, these traits may only manifest in the extreme distance events that females less often contest• Several aspects of female physiology unequivocally inhibit performance making it unlikely that the fastest females will surpass the fastest males in this sport• More direct physiological comparisons between male and female ultra-endurance athletes are needed, particularly when/if female participation numbers increase

Pulmonary and Inspiratory Muscle Function Response to a Mountain Ultramarathon

“…Vernillo et al (2015) also reported a greater decline in inspiratory function compared to expiratory function and a correlation between respiratory muscle endurance (i.e., MVV12, maximum voluntary ventilation in 12 s) and performance; while our group showed that respiratory function decline was larger following a 107-km MUM as compared with a 65-km MUM (Martinez-Navarro et al, 2020b). Nevertheless, although respiratory muscle fatigue has been suggested as a potential factor conferring females a physiological advantage in ultra-endurance sport (Tiller et al 2021), no studies have yet evaluated whether sex differences exist regarding pulmonary and inspiratory muscle function after a MUM. Previous studies have supported the notion of a better fatigue resistance in the female respiratory muscles (Gonzales and Scheuermann 2006;Guenette et al, 2010).…”

Sex Differences in Supplement Intake in Recreational Endurance Runners—Results from the NURMI Study (Step 2)

“…Sex-based differences in sports and exercise nutrition have been considered an important area of debate, particularly during the recent two decades [ 1 , 2 ]. It has been well-established that even the minor differences between female and male athletes in physical, physiological, and psychological characteristics could result in considerable alterations in their nutritional needs [ 2 , 3 , 4 ]. Recent scientific advancements in sex-specific differences as well as an understanding of endurance athletes’ nutritional requirements have led to a remarkable progression of female endurance runners (4%) than males (1.8%) in the world records from 1985 to 2004 [ 5 ].…”

Effect of Advanced Shoe Technology on the Evolution of Road Race Times in Male and Female Elite Runners

“…This would suggest that this technology benefits female athletes more than males. As women, when compared with men, show greater fatigue resistance, greater substrate efficiency, and lower energetic demands during endurance events (Hunter, 2016;Tiller et al, 2021), the female lower body mass and/or a smaller shoes sizes could represent a possible explanation for this gender difference. It could be hypothesized that smaller shoe size is associated with a shorter but stiffer rigid plate in the AFT (Hoogkamer et al, 2017), and/or a higher midsole thickness/body mass ratio, facilitating a higher percentage of energy return in female runners (Hoogkamer et al, 2018).…”