Leeds Beckett University - City Campus,
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Centre for Human Performance
The research examines the effects of the extreme physical and mental endeavour of crossing Antarctica on women. The study explored three key hormonal areas: stress, reproductive function and bone health.
The female reproductive system and stress responses are reportedly more sensitive to the negative effects of extreme physical activity. There is some evidence that arduous physical activity can suppress normal female reproductive hormone activity, impair bone strength and elevate stress hormone levels to a greater extent than in men. However, the reasons underlying these reported gender differences in response to extreme endurance exercise remain poorly understood.
How this army team made history in Antarctica Six women from the British Army, known as the 'Ice Maidens' became the largest all-female group to cross Antarctica, completing their coast-to-coast expedition in just 61 days.
The approach
We examined the effects of extreme exercise on hormone levels and the health of six women participating in Expedition Ice Maiden, the first all-female Transantarctic expedition. We monitored several markers of their health before and after the successful expedition. These included indicators of stress, reproductive and metabolic hormone levels, body weight and bone strength.
The six women completed a 1000-mile expedition, each hauling over 80kg in sledges. They became the first all-female team, the largest team of any sex and the first team of novices to complete the continental crossing unassisted.
Studying the team was extremely challenging, since the duration of the expedition wasn’t known beforehand. They completed 15 days ahead of schedule, so post-expedition study visits had to be planned with great flexibility in the UK and, meeting them straight after the expedition, in the Southern tip of Chile.
Before and after the expedition, the participants underwent direct assessment of metabolism over 36 hours in a direct calorimetry chamber in the Human Metabolic Research Unit at University Hospitals Coventry and Warwickshire NHS Trust. While in the chamber the participants were required to do two short step tests and limit activity as much as possible, something hard for an active group of women. On completion of two nights in the chamber, participants completed a maximal oxygen uptake test at sea level and 3000m.
The impact
While the women lost significant amounts of fat during the expedition (on average 10 kg), their lean mass and reproductive axis function were unaffected. Two weeks after the expedition, we found that the HPG axis had improved to near normal levels – indicating that it was suppressed before the expedition. Although average cortisol levels were high during the expedition, there was no change in the cortisol response to stress. Their bone strength was unaffected, and although some blood tests suggested one breakdown straight after the expedition, this resolved after two weeks.
Metabolic and maximal oxygen uptake was remarkably preserved or indeed increased efficiency of substrate utilisation, and increased fitness, despite the arduous conditions and weight loss experienced during the expedition.
The findings indicated not only that markers of reproductive function and bone strength were preserved, but that some markers showed evidence of delayed, exercise-related benefit to their physical fitness two weeks after the expedition. The study contains some myth-busting data on the impact of extreme physical activity on women. We have shown that with appropriate training and preparation, many of the previously reported negative health effects can be avoided.
Although the Ice Maiden team consisted of just six women and it was not possible to account for confounding factors such as age or ethnicity, these findings do suggest adherence to a comprehensive training schedule may have mitigated any negative health effects. We now plan to further investigate how different types of activities can contribute to negative effects on stress and energy balance caused by physical exertion, which may help in the generation of transferable strategies that prevent them in future.
These findings could have important relevance for men and women in arduous or stressful employment, where there is concern that they are damaging their health. If an appropriate training and nutritional regime is followed, their health may be protected.
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