Sex differences in durability following heavy intensity cycling exercise in trained athletes

The ability to withstand impairments in key physiological variables during prolonged exercise, known as durability, is emerging as an important factor in cycling performance. While females possess physiological characteristics that could confer enhanced durability relative to males, little is known about potential sex differences. 32 trained cyclists (16 males and 16 females) performed an incremental exercise test to exhaustion in visit 1. In visit 2 they performed 90 minutes of heavy intensity cycling (HVY) at 110% of gas exchange threshold (GET), followed by another incremental test. During HVY, pulmonary gas exchange (VO2 and VCO2) ventilation (VE), heart rate (HR), rating of perceived exertion (RPE), near-infrared spectroscopy and electromyography were recorded, and blood lactate (BLa) was collected. Before and after HVY, maximal voluntary contraction (MVIC), voluntary activation (VA) and potentiated twitches (100Hz, 10Hz, Qtw.pot) of the knee extensors were assessed. Power at GET (-16±15% vs -2±13%) and respiratory compensation point (-13±10% vs -6±9%) decreased more in males than females (P≤0.049). All aspects of neuromuscular function decreased from pre to post (all P<0.001), without sex differences (P≥0.096). During HVY, HR, VO2 (%peak), relative energy expenditure increased more in males (P≤0.008), whereas respiratory exchange ratio decreased more in females (P=0.001). BLa was higher in males than females (P=0.030). Muscle oxygen extraction was lower (P=0.004) and tissue saturation index higher for females (P<0.001). The smaller reductions exhibited by females in submaximal thresholds, associated with lesser derangements to oxidative efficiency, highlight the need to consider sex-specific training prescription and pacing strategies for long duration events.