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

Abstract

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. 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 (HIIT_1:1: 10 × 60 s work/60 s rest; HIIT_2:1: 20 × 20 s work/10 s 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 min recovery using near-infrared spectroscopy. Data were analyzed as repeated measures ANOVA. During HIIT_1:1, TSI desaturation was greater in LHP (-8.30 ± 3.30%) compared to HHP (-6.77 ± 4.55%; MC phase p < 0.001). During HIIT_2:1, TSI desaturation was greater in HHP (-6.98 ± 3.54%) compared to LHP (-6.71 ± 3.61%; MC phase p < 0.001). During HIIT_2:1, 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 HIIT_1:1, THb was greater in LHP (16.25 ± 6.32 µmol/L) compared to HHP (15.91 ± 6.46 µmol/L; MC phase p = 0.039). During HIIT_2:1 recovery, THb was higher in HHP (15.92 ± 5.47 µmol/L) compared to LHP (14.08 ± 5.05 µmol/L; MC phase p = 0.039). During HIIT_2:1, HC demonstrated greater TSI desaturation and resaturation in HHP compared to LHP (p < 0.001). These data suggest MC influences SMO during HIIT, with HHP favoring longer work/rest intervals (HIIT_1:1), while recovery remains unaffected; HC demonstrated greater SMO fluctuations during HIIT_2:1 in HHP.

Keywords: endogenous hormones; exercise; female physiology; hemoglobin dynamics; recovery kinetics.