Menstrual-cycle phase elevated resting minute ventilation in the mid-luteal phase but did not affect isocapnic hypoxic ventilatory response or sensitivity to chemical stimuli during rest or exercise.
Observational (n=20)
Does the menstrual cycle phase affect resting and exercise ventilatory chemosensitivity in healthy young females compared to males?
Naturally occurring changes in sex hormones across the menstrual cycle affect resting ventilation but do not significantly alter ventilatory chemosensitivity during rest or exercise.
We hypothesized that resting and exercise ventilatory chemosensitivity would be augmented in women when estrogen and progesterone levels are highest during the luteal phase of the menstrual cycle. Healthy, young females (n = 10; age = 23 ± 5 yrs) were assessed across one complete cycle: during early follicular (EF), late follicular (LF), early luteal, and mid-luteal (ML) phases. We measured urinary conjugates of estrogen and progesterone daily. To compare values of ventilatory chemosensitivity and day-to-day variability of measures between sexes, males (n = 10; age = 26 ± 7 yrs) were assessed on 5 nonconsecutive days during a 1-mo period. Resting ventilation was measured and hypoxic chemosensitivity assessed using an isocapnic hypoxic ventilatory response (iHVR) test. The hypercapnic ventilatory response was assessed using the Read rebreathing protocol and modified rebreathing tests. Participants completed submaximal cycle exercise in normoxia and hypoxia. We observed a significant effect of menstrual-cycle phase on resting minute ventilation, which was elevated in the ML phase relative to the EF and LF phases. Compared with males, resting end-tidal CO(2) was reduced in females during the EF and ML phases but not in the LF phase. We found that iHVR was unaffected by menstrual-cycle phase and was not different between males and females. The sensitivity to chemical stimuli was unaffected by menstrual-cycle phase, meaning that any hormone-mediated effect is of insufficient magnitude to exceed the inherent variation in these chemosensitivity measures. The ventilatory recruitment threshold for CO(2) was generally lower in women, which is suggestive of a hormonally related lowering of the ventilatory recruitment threshold. We detected no effect of menstrual-cycle phase on submaximal exercise ventilation and found that the ventilatory response to normoxic and hypoxic exercise was quantitatively similar between males and females. This suggests that feed-forward and feed-back influences during exercise over-ride the effects of naturally occurring changes in sex hormones.
MacNutt et al. (Fri,) conducted a observational in Healthy (n=20). Menstrual cycle phase vs. Different menstrual phases and male controls was evaluated on Resting and exercise ventilatory chemosensitivity. Menstrual-cycle phase elevated resting minute ventilation in the mid-luteal phase but did not affect isocapnic hypoxic ventilatory response or sensitivity to chemical stimuli during rest or exercise.