Sex Differences in Prefrontal Oxygenation and Neuromuscular Fatigue to Incremental Cycling and Cognitive Testing Lead...

Cognitive-motor dual-task performance is prevalent in many sports and appears to be impaired during high-intensity exercise, in association with central fatigue and cerebral deoxygenation. However, the extent to which these responses differ between males and females remains unknown.

Forty-eight well-trained adults (16 females) performed an incremental cycling test with a sustained-attention Mackworth task. The protocol consisted of 3-min ramp stages (starting at 1 W·kg -1, +0.4 W·kg -1 per stage) until an "extremely strong" perceived exertion was achieved (Borg CR100, task-failure). At each stage, cognitive performance (Mackworth score), quadriceps isometric maximal voluntary contraction (IMVC), neuromuscular fatigue (peripheral: twitch force, Pt; central: voluntary activation, VA) and prefrontal oxygenation (near-infrared spectroscopy) was assessed.

Both sexes reached similar normalised power output (~3.3±0.5 W·kg -1) and heart rate (~175±7 bpm) at task-failure (all P≥0.25). Mackworth score declined at task-failure (P=0.014), with no sex differences (males: -9±28%; females: -4±28%; P=0.56). Prefrontal oxygenation was lower in females versus males (-3.0±2.6%; P=0.031), while females exhibited reduced prefrontal total-haemoglobin at task-failure (-9.1±4.4 ∆µmol; P=0.016). IMVC and Pt declined more in males (all P≤0.014), whereas VA decreased similarly in both sexes (P=0.62), concomitant with comparable increased perceived exertion (P=0.73).

Although high-intensity exercise similarly impaired sustained attention performance and VA, females conjointly exhibited reduced prefrontal total-haemoglobin and less peripheral fatigue for comparable perceived exertion. These results extend the understanding of women's reduced (primarily peripheral) fatigability to whole-body exercise under a challenging dual-task paradigm.