Residual torque depression (rTD) is the decrease in isometric (ISO) torque after active shortening of skeletal muscle compared with a purely ISO contraction performed at the same muscle length and level of activation. Performance fatigability is defined as any exercise-induced reduction in voluntary force or power, and females are typically more fatigue resistant than males at low-intensity ISO contractions.
This study investigated performance fatigability in males and females during ISO contractions and ISO contractions after active shortening (rTD).
Fourteen females (22 ± 2 yr) and 14 males (23 ± 2 yr) performed three baseline maximal voluntary contractions (MVCs) of the dorsiflexors
. The MVCs were used to determine a 30% submaximal torque target, which participants matched as steadily as possible until task failure. The ISO fatigue task was performed at 10° plantar flexion. In the rTD session, the participants’ ankle was rotated from 40° to 10° plantar flexion before performing the same fatigue task. MVCs were performed immediately after task failure, 30 s, and 1, 2, 3, 4, 5, 10, 20, and 30 min after task failure to track recovery.
The baseline MVC torque amplitude for males (32.1 ± 6.6 N·m) was 31% greater than that for females (22.3 ± 3.1 N·m; P
< 0.001, ηp2
= 0.490). Females’ time to task failure
was 44% longer than that of males in the ISO state (P
= 0.032, ηp2
= 0.164). However, there was no sex
difference in the rTD state (P
It seems that the sex
differences in fatigue resistance observed in a low-intensity ISO task are abolished in the ISO state after an active shortening contraction.