Sex differences in knee extensor torque control

Area of Science:

• Biomechanics
• Human Physiology
• Motor Control

Background:

• Evidence on sex-related differences in muscle force and torque control is currently equivocal.
• Understanding these differences is crucial for various applications, from rehabilitation to sports performance.

Purpose of the Study:

• To investigate sex differences in knee extensor muscle torque control.
• To analyze both magnitude- and complexity-based measures of torque control during typical daily living contraction intensities.

Main Methods:

• Fifty participants (25 male, 25 female) performed intermittent isometric knee extensor contractions at 10%, 20%, and 40% of maximal voluntary contraction (MVC).
• Torque was measured, and control was quantified using magnitude (standard deviation [SD], coefficient of variation [CV]) and complexity (approximate entropy [ApEn], detrended fluctuation analysis [DFA] α) of torque fluctuations.

Main Results:

• Males exhibited greater absolute torque fluctuations (SD) at all tested intensities (10%, 20%, 40% MVC).
• No sex differences were observed in normalized fluctuations (CV).
• Males showed lower complexity (lower ApEn, higher DFA α) at lower contraction intensities (10%, 20% MVC).

Conclusions:

• Significant sex differences exist in knee extensor muscle torque control strategies.
• These differences are evident in both the magnitude and complexity of torque fluctuations.
• Future research should consider both measures when examining sex differences in muscle force control.