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

## TL;DR

This study found that males and females differ in muscle oxygenation and fatigue during repeated handgrip exercises.

## Contribution

The study identifies sex-based differences in muscle oxygenation and fatigue metrics during maximal intermittent handgrip exercise.

## Key findings

- Females showed higher deoxy[heme] and tissue saturation compared to males during the exercise.
- Males experienced a faster decline in the force-deoxygenation ratio than females.
- Sex differences in muscle oxygenation were observed before, during, and after the exercise protocol.

## Abstract

Background: 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. Methods: 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. Results: 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). Conclusions: 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.