Sex-Based Effects on Muscle Oxygenation During Repeated Maximal Intermittent Handgrip Exercise

This investigation aimed to examine sex-based differences in deoxy[heme] (HHb), tissue saturation (StO₂), and force-deoxygenation ratio (FD) of the forearm flexor muscles during a maximal-effort intermittent fatiguing handgrip protocol.

Thirty-three healthy males (n = 15) and females (n = 18) completed a fatiguing handgrip protocol consisting of 60 4 s contractions separated by a 1 s rest. Near-infrared spectroscopy was used to measure muscle oxygenation before, during, and after the protocol.

Sex differences in HHb (p = 0.033) and StO₂ (p = 0.021) were observed with significantly greater values for females (HHb: 110.204 ± 12.626% of baseline; StO₂: 72.091 ± 5.812%) in comparison to males (HHb: 101.153 ± 12.847% of baseline; StO₂: 66.978 ± 7.799%). Females (0.199 ± 0.081 AU) also demonstrated significantly (p = 0.001) lower FD in comparison to males (0.216 ± 0.094 AU). However, males (b = -0.023 ± 0.008 AU) demonstrated a significantly (p < 0.001) greater rate of decline in FD in comparison to females (b = -0.017 ± 0.006 AU).

Prior to, during, and after a maximal-effort intermittent fatiguing handgrip fatiguing protocol, males demonstrate significantly lower StO₂ than females and a faster rate of decline in FD. Moreover, females demonstrate greater HHb values than males when assessed relative to a resting baseline.