Cardiorespiratory response to high-intensity interval exercise across the menstrual cycle and with oral contraceptive use in recreationally active females

Fluctuations in female sex hormones may influence the cardiorespiratory response to exercise. Cardiorespiratory response to high-intensity interval exercise (HIIE) across the menstrual cycle (MC) or with oral contraceptive (OC) use has limited data. Therefore, the influence of MC phase and OC use on cardiorespiratory response during HIIE was assessed. Twenty-five females (24.4 (3.6) years) were categorized by a natural MC (non-oral contraceptive users (NOC), <i>n</i> = 14) or OC use (<i>n</i> = 11). HIIE was four sets of four repetitions with 3 min rest between intervals on a cycle ergometer at a power output halfway between the ventilatory threshold and V̇O_2peak. An HIIE bout was performed during the early follicular and mid-luteal phases (days 2-7 and ∼21 of the MC) and during inactive (days 2-7) and active pill (third week) phases. Cardiorespiratory responses to HIIE were assessed via indirect calorimetry. No group or cycle phase differences were noted for relative and absolute VO₂, ventilatory exchange, heart rate, or rating of perceived exertion (<i>p</i> > 0.05). In NOC during the follicular phase, FEO₂ and V̇E/V̇O₂ during pre-exercise seated rest was lower compared to the luteal phase (<i>p</i> < 0.05). In NOC during the follicular phase, V̇E/CO₂, FEO₂, FECO_2, V̇E/V̇O₂, and V̇E/CO₂ during warmup was lower compared to the luteal phase (<i>p</i> < 0.05). Most cardiorespiratory variables assessed do not appear to be impacted by MC phase or OC use during HIIE.