Changes in muscular flexibility and performance during an ultra-marathon

The purpose of the present study was to examine the changes in muscle flexibility during an ultra-marathon race and to relate these changes to the performance of the runners. Twenty-two male runners were evaluated for lower back and hamstring flexibility by measuring knee range of motion from a free bending position at the beginning and at the end of a 250km race or as soon as they stopped running. Comparisons were made between the subjects who covered the longest (219.6 +/- 42.3km) and the shortest (102.8 +/- 37.8km) distance during the race (n=11 in each group) as well as between those who completed the race (250km, n = 7) and those who did not (119.7 +/- 43.2km, n= 15). Knee range of motion decreased after the race (pre: 167.2 +/- 15.8degrees vs. post: 155.5 +/- 19.2degrees, p<0.05) in all subjects. No differences were observed between groups in knee range of motion before or after the race (p>0.05). When the decrease in knee range of motion was normalised with the distance covered by each runner, the runners in long distance group and the runners who completed the race (0.05 +/- 0.05 and 0.05 +/- 0.04degrees/km, respectively) had a lower rate of decrease in knee range of motion compared to the runners in the short distance group as well with those who did not complete the race (0.14 +/- 0.11 and 0.12 +/- 0.11degrees/km, respectively; p<0.05). A negative correlation was observed between the distance covered by the runners who quit the race and the rate of decrease in knee range of motion (r=-0.73, p<0.05, n=15). The above results suggest that the loss of muscle flexibility impairs the performance of runners during an ultramarathon race so that runners who are able to preserve their muscle flexibility have a chance to perform better during the race.