Age group performances in 100 km and 100 miles ultra-marathons.

Improved performance has been reported for master runners (i.e. athletes older than 40 years) in both single marathons and single ultra-marathons. This study investigated performance trends of age group ultra-marathoners competing in all 100 km and 100 miles races held worldwide between 1971 and 2013. Changes in running speeds across years were investigated for the annual ten fastest 5-year age group finishers using linear, non-linear and multi-level regression analyses. In 100 km, running speed remained unchanged in women in 25-29 years, increased non-linearly in 30-34 to 55-59 years, and linearly in 60-64 years. In men, running speed increased non-linearly in 18-24 to 60-64 years and linearly in 65-69 to 75-79 years. In 100 miles, running speed increased in women linearly in 25-29 and 30-34 years, non-linearly in 35-39 to 45-49 years, and linearly in 50-54 and 55-59 years. For men, running speed increased linearly in 18-24 years, non-linearly in 25-29 to 45-49 years, and linearly in 50-54 to 65-69 years. Overall, the faster race times over the last 30 years are a result of all top ten finishers getting faster. These findings suggest that athletes in younger to middle age groups (i.e. 25-35 to 50-65 years depending upon sex and distance) have reached their limits due to a non-linear increase in running speed whereas runners in very young (i.e. younger than 25-35 years) and older age groups (i.e. older than 50-65 years) depending upon sex and distance might still improve their performance due to a linear increase in running speed.