How Exercising in the Heat Affects Women on Birth Control

By Alyssa Bialowas

Exercising in hot conditions is commonplace for both recreational and competitive athletes, and training can be more uncomfortable for women during various times of the month. Training in hot climates while menstruating can add pain to this uncomfortable state, and studies have looked more closely at how heat and exercise effect the immune response of women menstruating. Exercising in the heat stimulates the production of the stress hormone cortisol, which can lead to immune disturbances that contribute to the pathology of heat stroke, effecting an athletes ability to train and compete.

The ingestion of oral contraceptives impacts the body’s hormonal balance, and relatively little research has investigated how oral contraceptives effect immune function during exercise. It has been demonstrated that oral contraceptives improve inflammatory status in untrained women and stated that this greater anti-inflammatory environment is likely related to the lower concentration of endogenous estrogen when compared to normally-menstruating women.

A research team from Queensland, Australia investigated the immunoendocrine response to exercise in the heat in women taking oral contraceptives compared to normally-menstruating women.

They investigated –

The study included nine women taking oral contraceptives, and nine women normally menstruating who do not use oral contraceptives. Their immune and stress responses were studied in temperate conditions and hot conditions.
All participants performed a cycling trial in three stages at varying degrees of intensity in both conditions.
C-reactive protein (a biomarker of inflammation and tissue damage) and immune cell counts were measured at rest between the conditions, and salivary cortisol was evaluated before and after exercise in both conditions.

What they found?

Resting c-reactive protein was three times higher in women taking the oral contraceptives.
There were no differences stress cortisol, or in resting immune cell counts between the two groups.

In conclusion, women using oral contraceptives exhibit similar immune function to naturally menstruating women while exercising in temperate and hot conditions. The increased levels in c-reactive protein in women taking oral contraceptives could be indicative of inflammation, however, whether this effects performance is unclear. Further studies should investigate if this level of increased inflammation induced from taking oral contraceptives influences women’s athletic performance.

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