Menstrual and Oral Contraceptive Phases Do Not Influence Submaximal and Maximal Responses to Exercise or Vascular Responsiveness at Rest
Date
2020-04-20
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Abstract
Endogenous and exogenous female reproductive hormones fluctuate across the respective menstrual and oral contraceptive cycle phases. Importantly, estrogen and progesterone are known to have numerous physiological effects, which are likely to have an impact on exercise outcomes. Current literature exploring the effects of the menstrual and oral contraceptive cycles on exercise responses is limited and remains inconclusive (1). Moreover, no previous studies have examined the within-cycle effects on muscle microvascular function at rest, which may provide important insight into the changes in oxygen delivery to active tissues during exercise across the cycle phases. Therefore, the objective of this thesis was to examine whether the menstrual or monophasic oral contraceptive cycle phases affect a wide variety of submaximal (oxygen uptake (V̇O2) kinetics, maximal lactate steady-state (MLSS)) and maximal (maximal oxygen uptake (V̇O2max), time-to-exhaustion (TTE)) responses to exercise, and vascular responsiveness of the lower limb microvasculature at rest in healthy, active women. During the follicular or inactive-pill phase and the luteal or active-pill phase of the menstrual or oral contraceptive cycle, respectively, 15 non-oral contraceptive users and 15 monophasic oral contraceptive users underwent a lower limb vascular occlusion test and performed one V̇O2 kinetics test; one ramp-incremental test to exhaustion; two to three 30-min constant-load cycling trials to determine the power output corresponding to MLSS, followed by a TTE trial. Menstrual cycle phases were verified using an ovulation test. Vascular responsiveness was assessed by calculating the near-infrared spectroscopy-derived muscle oxygen saturation (StO2) reperfusion slope and the post-occlusion StO2 area under the curve of the tibialis anterior muscle. The results suggest that the fluctuations of natural or synthetic hormones between the phases of the menstrual or oral contraceptive cycle, respectively, had no detectable effects on submaximal (V̇O2 kinetics, MLSS) and maximal (V̇O2max, TTE) exercise performance and lower limb microvascular reperfusion responses. Future research studies evaluating exercise performance or microvascular reperfusion should not avoid testing women solely based on the idea that the cycle phases may act as a confounding variable for their outcome measures.
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Keywords
Exercise Physiology, Oxygen Uptake, Menstrual Cycle, Oral Contraceptives, Vascular Responsiveness
Citation
Mattu, A. T. (2020). Menstrual and Oral Contraceptive Phases Do Not Influence Submaximal and Maximal Responses to Exercise or Vascular Responsiveness at Rest (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.