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April 29, 2025
In a striking shift from long-held beliefs about athletic performance, new research suggests that women are not only closing the gap with men in extreme endurance sports but, in some cases, are even outperforming them. The findings, published in Frontiers in Physiology, challenge traditional assumptions about sex differences in physical capabilities, particularly under the harshest conditions.
A History of Barriers-and Breakthroughs
For much of the 20th century, women faced significant barriers to participation in endurance sports. In 1967, Katherine Switzer famously became the first woman to officially run the Boston Marathon, despite attempts by race officials to physically remove her from the course. At the time, prevailing wisdom held that women were not capable of such feats-a belief that has been steadily eroded by decades of progress and performance.
While men still hold the fastest marathon times-Kenyan runner Kelvin Kiptum set the men’s world record at 2:00:35 in 2023, with Ruth Chepng’etich holding the women’s record at 2:09:56-the gap between elite male and female athletes is shrinking, especially as race distances and durations increase.
The Science of Endurance: Metabolic Efficiency in Women
The new study goes beyond laboratory settings, analyzing real-world data from some of the world’s most grueling events, including the Alaska Mountain Wilderness Ski Classic and the Yukon Arctic Ultra. Using advanced methods to measure energy expenditure, researchers found that women demonstrated greater metabolic efficiency than men during prolonged, unsupported expeditions in extreme cold.
Despite men’s generally higher muscle mass and strength, women’s bodies appear to be better adapted for endurance under extreme physiological stress. Notably, the study observed that women’s bodies activate cold-induced thermogenesis at lower temperatures, potentially reducing metabolic demands and enhancing resilience in freezing environments.
Real-World Results: Ultra-Endurance and Military Scenarios
The trend extends beyond sporting events. In simulated military operations-such as multi-week backcountry hunting expeditions in Alaska-female participants carried heavier loads relative to their body weight but matched men in resilience and energy efficiency.
The study also highlights remarkable performances by female athletes in ultramarathons, such as Pamela Reed and Hiroko Okiyama, who have outpaced male competitors in some of the world’s toughest races. Over the past four decades, the performance gap in ultra-endurance events has narrowed by approximately 3%, and when participation rates between men and women are similar, the gap shrinks even further.
What’s Next?
Researchers are now delving deeper into the biological mechanisms behind these findings, analyzing tissue samples to uncover how women’s bodies maintain resilience and efficiency under extreme stress. The results could have implications not only for sports but also for military training and survival strategies in harsh environments.
Disclaimer:
This article is based on a peer-reviewed study published in Frontiers in Physiology and summarized by Medical Xpress. While the findings reflect current scientific understanding, ongoing research may provide further insights. The information provided is for general knowledge and should not be interpreted as medical or performance advice. For more details, refer to the original publication: “Sex-specific energy expenditure during the Alaska Mountain Wilderness ski classic; insights from an Arctic winter expedition”.
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