Sex Differences in Ultramarathon Performance in Races with Comparable Numbers of Males and Females.

INTRODUCTION: There is a prominent sex-based difference in athletic performance such that males outperform females by 7-14% in races from 100 m to marathon. In ultramarathons, the difference is often much smaller, leading to speculation that females are "built" for the sport. However, data are confounded by the low number of female participants; just 10-30% in any given race. This study compared data from two ultramarathons where males and females competed in comparable numbers.

METHODS: There were 116 and 146 starters in the 50-mile and 100-mile races, respectively (52% female). Finish times were compared using t-tests or Mann-Whitney U tests. A Chi-squared test of independence examined the relationship between sex and ranking. Multivariable linear regressions examined relationships between sex, age, and finish time.

RESULTS: There were 96 and 91 finishers in the 50-mile and 100-mile races, respectively (45-46% female). In 50 miles, the median finish time was 12.64±2.11 h with no difference between sexes (1.2%, p=0.441). However, the top-10 males finished the race ~85 min faster than the top-10 females (13.8%, p=0.045). In 100 miles, the mean finish time was 31.58±3.36 h with no difference between sexes (3.2%, p=0.132) and no difference between the top-10 males and top-10 females (4.4%, p=0.150). The regression model revealed that sex, age, and a multivariable regression failed to predict overall finish time in either race.

CONCLUSIONS: The sex-based performance discrepancy shrinks to 1-3% in ultramarathons when males and females compete in comparable numbers. Top-performing males still retain a considerable advantage over shorter distances.