Ovarian Sex Hormones and Substrate Oxidation During a High-Intensity Interval Exercise: A Comparative Analysis Across...

To compare energy expenditure (EE), carbohydrate (CHOx), and fat oxidation (FatOx) during a high-intensity interval exercise across the early follicular, late follicular, and mid-luteal phases of the menstrual cycle (MC); the active pill (APP) and withdrawal (WP) phases of the oral contraceptive (OC) cycle; and in postmenopausal females (POS).

Twenty-four eumenorrheic females, 18 OC users and 13 POS completed a standardized high-intensity interval running protocol (8 × 3 min at 85% vVO2peak). Eumenorrheic participants were tested in the early follicular phase, late follicular phase, and mid-luteal phase; OC users in the APP and WP; and POS once. Hormonal phases were verified by circulating 17β-oestradiol and progesterone. EE, CHOx, and FatOx were quantified using indirect calorimetry.

EE and substrate oxidation did not differ across the MC phases (all P > .05). CHOx was slightly lower during APP than WP (P = .025; mean difference = 123 mg·min-1). FatOx was lower in POS compared with late follicular phase (P = .03; mean difference = 92 mg·min-1) and mid-luteal phase (P = .039; mean difference = 89 mg·min-1).

Hormonal fluctuations during the MC have minimal impact on EE or substrate oxidation during exercise, suggesting their measurements do not need to be adjusted according to MC phases. However, small but significant differences were found between phases of the OC cycle, with lower CHOx during the APP compared to the WP. Finally, POS exhibit lower FatOx than eumenorrheic females.