Sex differences in fatigability following exercise normalised to the power-duration relationship

Area of Science:

• Exercise Physiology
• Sports Science
• Human Performance

Background:

• Females generally display superior locomotor muscle fatigue resistance compared to males, particularly in single-limb and whole-body exercises.
• While females sustain higher relative intensities in single-limb exercise, research on sex differences in whole-body exercise fatigability, especially cycling, is limited.

Purpose of the Study:

• To establish the power-duration relationship during cycling in trained individuals.
• To assess exercise fatigability and its underlying mechanisms during critical power (CP)-matched cycling exercise in the heavy and severe intensity domains between sexes.

Main Methods:

• Determined the power-duration relationship and critical power (CP) in 18 trained participants (8 females).
• Conducted constant-load cycling exercise at CP-matched heavy and severe intensities.
• Assessed fatigability mechanisms using neurostimulation, near-infrared spectroscopy (NIRS), and pulmonary gas exchange.

Main Results:

• Relative CP and curvature constant of the power-duration relationship were similar between males and females.
• No significant sex differences were found in time to task failure during heavy or severe intensity cycling.
• Females exhibited less muscle de-oxygenation, reduced loss of knee-extensor contractile function, and smaller reductions in voluntary activation post-exercise compared to males.

Conclusions:

• The relative power-duration relationship during cycling is comparable between sexes.
• Despite similar performance in CP-matched exercise, the physiological mechanisms driving fatigue differ between males and females.
• Females appear to utilize more efficient metabolic pathways or possess greater intrinsic muscle resistance to fatigue during intense cycling.