Changes in running speeds in a 100 km ultra-marathon race

The purpose of this study was to determine if runners who completed a 100 km ultramarathon race in the fastest times changed their running speeds differently compared to those runners who ran an overall slower race. Times were taken from the race results of the 1995 100 km IAU World Challenge in Winschoten, Netherlands. Race times and 10 km split times were analyzed. Runners (n = 67) were divided into groups of ten with the last group consisting of seven runners. The mean running speed for each 10 km segment was calculated using each runner's 10 km split times. Mean running speed was calculated using each runner's race time. The first 10 km split time was normalized to 100, with all subsequent times adjusted accordingly. The mean running speed for each group at each 10 km split was then calculated. The faster runners started at a faster running speed, finished the race within 15% of their starting speed, and maintained their starting speed for longer (approximately 50 km) before slowing. The slower runners showed a greater percentage decrease in their mean running speed, and were unable to maintain their initial pace for as long. It is concluded that the faster runners: 1) ran with fewer changes in speed, 2) started the race at a faster running speed than the slower runners, and 3) were able to maintain their initial speed for a longer distance before slowing.