Menstrual cycle influences skeletal muscle oxygenation during high-intensity interval training: a work to rest evaluation

Abstract

Introduction: The menstrual cycle (MC), characterized by hormonal fluctuations, may impact skeletal muscle oxygenation (SMO) during high-intensity interval training (HIIT). SMO measured around HIIT in eumenorrheic (EUM) or hormonal contraceptive (HC) users can inform exercise and recovery practices.

Methods: Females who were EUM (no hormonal contraceptive n=21; copper intrauterine device n=5) or using HC (oral n=5; hormonal intrauterine n=6) completed two HIIT protocols (HIIT1:1: 10×60s work/60s rest; HIIT2:1: 20×20s work/10s rest) during both low-hormone (LHP) and high-hormone phases (HHP) of the MC, in randomized order. SMO (tissue saturation index [TSI] and total hemoglobin [THb] were measured at rest, during HIIT, and during 15-minute recovery using near-infrared spectroscopy. Data were analyzed as repeated measures ANOVA.

Results: During HIIT1:1, TSI desaturation was greater in LHP (-8.30±3.30%) compared to HHP (-6.77±4.55%; MC phase p<0.001). During HIIT2:1, TSI desaturation was greater in HHP (-6.98±3.54%) compared to LHP (-6.71±3.61%; MC phase p<0.001). During HIIT2:1, TSI resaturation was greater in LHP (-5.05±3.31%) compared to HHP (-5.33±3.31%; MC phase p=0.004). During recovery from HIIT1:1, THb was greater in LHP (16.25±6.32 µM) compared to HHP (15.91±6.46 µM; MC phase p=0.039). During HIIT2:1 recovery, THb was higher in HHP (15.92±5.47 µM) compared to LHP (14.08±5.05 µM; MC phase p=0.039). During HIIT2:1, HC demonstrated greater TSI desaturation and resaturation in HHP compared to LHP (p<0.001).

Conclusion: These data suggest MC influences SMO during HIIT, with HHP favoring longer work/rest intervals (HIIT1:1), while recovery remains unaffected; HC demonstrated greater SMO fluctuations during HIIT2:1 in HHP.