Rio Olympics: Menstrual Cycle and Performance in Hot Weather

Gymnasts practicing in Rio New research from Massey University’s College of Health from New Zealand has shed light on the impact the female menstrual cycle has on exercise performance in hot environments, such as the potential conditions in Rio, for competitive and well-trained female athletes.

Many will have heard the saying ‘Horses sweat, men perspire, and women glow’. Senior lecturer in Sport and Exercise, Dr Toby Mündel says to some extent this is true, as women are more efficient in terms of losing body heat when challenged by exercising in hot conditions than men.

“Yet one in two women with a normal/regular menstrual cycle believe this negatively impacts their training and performance, and a female athlete’s body will operate up to half a degree warmer and start to sweat later during her second half [luteal phase] of the menstrual cycle, potentially putting them at greater risk of hyperthermia and impaired performance,” Dr Mündel says.

“When compared to less-trained women, well-trained females often display lower fluctuations in the reproductive hormones progesterone and estrogen, and have an enhanced sweating capacity to cool themselves.

“Their exercise performance in hot environments is less likely to be negatively affected across their menstrual cycle, although this has received very little attention previously,” Dr Mündel says.

Gymnasts practicing in Rio

Second-year PhD student Joe Lei was supervised by Dr Mündel as he carried out a study at Massey’s Manawatu campus. Participants were tested four times – twice in their early-follicular phase when both hormones are known to be low, and twice in their mid-luteal phase when hormones had risen.

During each menstrual phase they performed a 30-minute cycling time trial in hot-dry (desert) and hot-humid (tropical) conditions, to test whether each type of heat stress interacted with the menstrual phase.

The results showed that exercise performance was not affected by menstrual phase but was clearly impaired by the tropical compared to desert environment. Dr Mündel says this is the first time this has been demonstrated in well-trained women, and mirrors what has been observed in men.

“It makes it even more important for competitive women to realize that preparation, such as heat acclimation, is paramount when challenged by hot environments. Even more so as New Zealand-based athletes competing in Northern Hemisphere events will be competing in the opposite season,” Dr Mündel says.

Whilst too late for our Rio-bound athletes, these findings are of importance to the athletes and their support teams aiming for the 2018 Commonwealth Games on Australia’s Gold Coast.

In the second study towards his PhD, Mr Lei will be comparing the responses of women with a normal/regular menstrual cycle to those taking the oral contraceptive pill, as many athletes use these not only for contraception but also to negate pre-menstrual symptoms and cycle manipulation for travel, training and competition.

Originally from Taiwan, Mr Lei graduated with a Bachelor of Sport and Exercise from Massey in 2010. He received his Masters in Physical Education from the National Taiwan Sport University in 2013.

Having suffered heat exhaustion during his military service in Taiwan, Mr Lei was attracted back to Massey University by Dr Mündel’s expertise in thermoregulation. In 2014 he received a three-year Massey doctoral scholarship to further investigate the effects of heat stress on exercise performance and risk for health.

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