Women are not affected by their menstrual cycle during exercise heat stress

November 29, 2016

Menstrual cycle phase does not affect a woman's autonomic heat responses (skin blood flow and sweating) at rest or during fixed intensity exercise.

That's according to a collaboration between Massey University, the University at Buffalo and the University of Otago. They also found that exercise performance was impaired by humid heat due to the reduced ability of the body to sweat effectively.

The research, published today in The Journal of Physiology, studied the effects of heat on ten well-trained women across their menstrual cycles. Each woman completed four trials comprising of resting and fixed-intensity cycling followed by a 30-minute variable-intensity performance trial. The trials were conducted in the early-follicular (days 3-6) and mid-luteal (days 18-21) phases of their menstrual cycle in dry and humid heat environments.

Dr Toby Mündel from Massey University and co-author of the study said "This study indicates that trained women self-pace to minimise autonomic differences (skin blood flow and sweating) but at the expense of their exercise performance under humid heat stress.

One in two competitive women believe that their menstrual cycle negatively impacts training and performance; however, these results question the assertion made by previous researchers that women should avoid competition or face a disadvantage when performing exercise with heat stress during their luteal phase."

Upcoming international events such as the 2018 Commonwealth Games will expose athletes to high levels of environmental heat making understanding how the body responds to these conditions of high interest and relevance. Of the limited studies that have investigated how females respond to such heat stress none can explain how a well-trained, competitive woman will respond and perform.

Due to the proportion of competitive women that take the oral contraceptive pill it remains to be investigated whether these athletes differ in their response and performance in hot and humid environments.
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Notes for Editors

1. Full Paper title: Influence of menstrual phase and arid vs. humid heat stress on autonomic and behavioural thermoregulation during exercise in well-trained women

2. The Journal of Physiology publishes advances in physiology that increase our understanding of how our bodies function in health and disease. http://jp.physoc.org

3. The Physiological Society brings together over 3,500 scientists from over 60 countries. The Society promotes physiology with the public and parliament alike. It supports physiologists by organizing world-class conferences and offering grants for research and also publishes the latest developments in the field in its three leading scientific journals, The Journal of Physiology, Experimental Physiology and Physiological Reports. http://www.physoc.org

4. Research limitations: The responses of women between early-follicular and mid-luteal phases were compared as this maximises the differences in ovarian hormones (oestrogen and progesterone) occurring naturally and is therefore applicable to competitive women experiencing their natural menstrual cycle and associated hormonal changes. The authors did not compare responses during the late-follicular (pre-ovulatory) phase, when oestrogen peaks. Additionally, women are in these phases (early-follicular and mid-luteal) for ?50% of their reproductive lives, and of course many female athletes take hormonal contraception that may well affect responses.

The Physiological Society

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