Sex differences in fatigability after ischemic preconditioning of non-exercising limbs

BACKGROUND: Ischemic preconditioning (IPC) is suggested to decrease fatigability in some individuals but not others. Sex differences in response to IPC may account for this variability and few studies systematically investigated the effects of IPC in men and women. The goal of this study was to determine if time to task failure, perception of pain, and neuromuscular mechanisms of fatigability were altered by IPC in men and women. METHODS: Ten women (29 ± 5 years old) and 10 men (28 ± 6 years old) performed isometric contractions with the plantar flexor muscles of the dominant leg at 20% of maximal voluntary contraction until task failure. We used a repeated measures design where each individual performed 3 randomized and counterbalanced test sessions: (A) IPC session, cuff inflation and deflation (5 min each repeated 3 times) performed before the exercise by inflating cuffs to the non-dominant leg and arm; (B) sham session, cuffs were inflated for a short period (1 min); and (C) control session, no cuffs were involved. RESULTS: Compared with control, IPC increased time to task failure in men (mean difference, 5 min; confidence interval (CI) of mean difference, 2.2; 7.8 min; P = 0.01) but not women (mean difference, − 0.6 min; CI of mean difference, − 3.5; 2.4 min; P = 0.51). In men, but not women, the IPC-induced increase in time to task failure was associated with lower response to pressure pain (r = − 0.79). IPC further exposed sex differences in arterial pressure during fatiguing contractions (session × sex: P < 0.05). Voluntary activation, estimated with the twitch interpolation technique, and presynaptic inhibition of leg Ia afferents were not altered after IPC for men and women. The tested variables were not altered with sham. CONCLUSIONS: The ergogenic effect of IPC on time to task failure was observed only in men and it was associated with reductions in the perception of pain. This pilot data suggest the previously reported inter-individual variability in exercise-induced fatigability after IPC could be a consequence of the sex and individual response to pain.