Residual torque depression (rTD) is the decrease in isometric torque following active shortening of skeletal muscle, compared to a purely isometric (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 isometric contractions.
This study investigated performance fatigability in males and females during ISO contractions and isometric contractions following active shortening (rTD).
14 females (22 ± 2 years) and 14 males (23 ± 2 years) performed three baseline maximum 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 prior to performing the same fatigue task. MVCs were performed immediately after task failure, 30-s, 1, 2, 3, 4, 5, 10, 20, and 30-mins after task failure to track recovery.
The baseline MVC torque amplitude for males (32.1 ± 6.6 N·m) was 31% greater than females (22.3 ± 3.1 N·m) (p
< 0.001, ηp2
= 0.490). Female’s time to task failure
was 44% longer than males in the ISO state (p
= 0.032, ηp2
= 0.164). However, there was no sex
-difference in the rTD state (p
It appears that the sex
-differences in fatigue resistance observed in a low intensity ISO task are abolished in the isometric state following an active shortening contraction.