# Sex-differences in Mountain Ultra-trail Performance: Look at the Scenery

## TL;DR

This paper explores why sex differences in ultra-trail running performance are larger in mountainous terrain due to factors like uphill running, altitude, and temperature changes.

## Contribution

The paper identifies three mountain-specific factors that amplify sex differences in ultra-distance running compared to flat terrain.

## Key findings

- Sex differences in uphill endurance performance are about twice as large as on flat terrain.
- Females show greater hypoxemia at altitude due to sex-sensitive ventilatory responses.
- Females face thermoregulatory challenges in cold mountain environments due to lower muscle mass and higher surface area-to-mass ratio.

## Abstract

There is a growing body of literature on sex-differences in human performance, particularly in the context of endurance sports. However, several mechanisms (e.g., higher type 1 fibres proportion; lesser neuromuscular fatigue; higher metabolic flexibility etc) have been previously proposed and suggest an advantage to females over ultra-endurance competitions on flat terrain. However, in mountain ultramarathon, the percent sex difference between male and female records appears to be larger than on various road/track running distances on flat terrain, suggesting that additional factors related to the specific mountainous conditions may be at play. In this Current Opinion, we point to three specific factors that are likely to influence and widen sex differences in ultra-distance running events performed in the mountains (i.e., uphill– downhill locomotion, altitude, and changes in extreme ambient temperatures).

First, the sex differences in uphill endurance performance are approximately two times larger than those in events primarily performed on flat terrain (i.e., 18–22% vs. 9–12%, respectively), mainly due to the detrimental influence of the lower lean mass to fat mass ratio and lower fast twitch/type II fibre type proportion in females).

At altitude, the ventilatory response to exercise emerges as one of the most sex-sensitive factors that may modify reactions to hypoxia. A diffusive mechanism appears to be involved in the larger hypoxemia commonly reported in females.

Finally, responses to cold environments are also sex-dependent, with females exhibiting lower muscle mass, which limits thermogenic heat production, a higher body surface area-to-mass ratio, and a greater prevalence of Raynaud’s phenomenon.

Altogether, these specific factors must be further understood when analyzing sex-differences in mountain ultra-trail performance. Don’t forget to look at the scenery!

1. Three specific factors are likely to widen sex differences in ultra-distance running events performed in the mountains, compared to ultra-endurance competitions on flat terrain (i.e., uphill– downhill locomotion, altitude, and changes in extreme ambient temperatures).

2. The sex differences in uphill endurance performance are approximately two times larger than those in events primarily performed on flat terrain.

3. At altitude, a reduced ventilatory response, an increased cost of breathing and a higher prevalence of exercise-induced hypoxemia in females, emerge as factors that may modify sex-differences in endurance performance in hypoxia.

4. Females experience thermoregulatory disadvantages in cold environments, exacerbated by simultaneous high altitude exposure and repeated transitions between cold and hot-dry conditions during mountain ultra-trail races.