Menstrual cycle effects on cardiovascular drift and maximal oxygen uptake during exercise heat stress

Abstract

Aim

Compared to other modulators of physiological strain associated with exercise heat stress, hyperthermia results in the greatest magnitude of cardiovascular (CV) drift and associated decrements in maximal oxygen uptake ($\dot{V}{\text{O}}_{2\max }$).

Purpose

To determine if elevated core temperature in the luteal phase (LP) of the menstrual cycle results in greater CV drift and reductions in $\dot{V}{\text{O}}_{2\max }$ versus the follicular phase (FP).

Methods

Seven women performed 15- and 45-min cycling bouts on separate occasions (60% $\dot{V}{\text{O}}_{2\max }$, 35 °C) followed by a $\dot{V}{\text{O}}_{2\max }$ test during the FP and LP. CV drift was measured between 15 and 45 min during the 45-min bout, and the 15-min bout was for measuring $\dot{V}{\text{O}}_{2\max }$ over the same time interval that CV drift occurred.

Results

Core temperature during LP was ~ 0.3 °C higher than FP (P < 0.05), but changes from rest during exercise were similar between phases (all P > 0.05). Heart rate increased significantly over time but was not different between phases (P = 0.78). Stroke volume decreased more over time during LP compared to FP (P = 0.02), but the values were similar at the end of exercise between phases (both time points P > 0.05). $\dot{V}{\text{O}}_{2\max }$ decrements for FP (13%) and LP (16%) were also comparable (P = 0.97).

Conclusions

The LP–FP difference in core temperature in this study was not sufficient to amplify CV strain and decrements in $\dot{V}{\text{O}}_{2\max }$. Greater differences in core temperature may be required to independently modulate CV drift and accompanying decrements in $\dot{V}{\text{O}}_{2\max }$ during prolonged exercise heat stress.