Sex differences in fatigability and recovery following a 5 km running time trial in recreationally active adults.

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 minutes 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.