Sex differences in fatiguability during single-joint resistance exercise in a resistance-trained population

The primary aim of this study was to compare the fatiguability and acute recovery from a session of unilateral biceps curl exercise between habitually resistance-trained males and females. Twenty participants performed biceps curl one repetition maximum (1RM) and maximal voluntary contraction (MVC) testing of the elbow flexors. The exercise protocol consisted of four sets of unilateral biceps curls at 50% of the measured 1RM to volitional failure. MVC force and EMG activity of the elbow flexors were assessed following each set and during the recovery phase. The outcome variables compare the repetition volume, MVC strength loss, and EMG responses between males and females during the exercise and recovery phases. Across the exercise protocol, females completed significantly more repetitions compared to males (p < 0.01, d = 1.7) and lost significantly less strength across time (76% versus 69%, d = 0.48, p = 0.046). Additionally, females maintained a higher level of normalized EMG amplitude compared to males across the protocol (p = 0.035; d = 0.510). However, there were no sex differences in the strength (p = 0.562) or EMG (p = 0.607) responses during the recovery phase. In a resistance-trained population, females were able to perform a greater number of repetitions during the biceps curl exercise compared to their male counterparts at the same relative intensity of exercise. The ability of females to maintain a greater proportion of their maximal elbow flexor strength and muscle excitation during exercise suggests females can tolerate greater upper-body resistance exercise volume than males.