Leg muscle fatigue by long distance running from the viewpoint of rebound jump

Abstract

Five healthy men who are engaged in jogging ran 43.2 km (5.4 km x 8 laps) at constant speed with a predetermined intensity of 2 mmol/l blood lactate level. During the running, subjects took 5 minutes rest every 1 lap completed. At that time, body weight (BW), blood lactate (LA) and ratings of perceived exertion (RPE) in the whole body and the leg were measured. In addition, subjects were instructed to perform five-rebound jumps (5 RJ), during which jumping height (JH), contact time (CT), 5 RJindex (= JH/CT), and absolute work in ankle, knee and hip joints were measured.

Results were summarized as follows ; (1) During the running, BW decreased significantly while RPE increased significantly. However, LA remained unchanged. (2) Although there was a tendency towards a decrease in JH and 5 RJindex of 5 RJ and an increase in CT of 5 RJ, these were not significant. Also, absolute work done by the ankle and knee joint, and percent absolute work (contribution to total work) done by knee joint during 5 RJ changed significantly. (3) There were significant relationships between percent change in JH and 5 RJindex of 5 RJ and percent change in RPE in the whole body, and percent change in CT of 5 RJ and percent change in RPE in the leg. Furthermore, the subject who decreased his running speed most among the subjects decreased percent absolute work done by the ankle.

These results suggest that 1) on average, the long distance running at a constant speed of moderate intensity did not decrease leg muscular power output to a great extent, but muscle fatigue may have occurred in muscles around the ankle and knee joint, and 2) individually observed, the enhancement of fatigue may have been related to the decrease in leg muscular power output, and the decrease in muscular power output in ankle joint may have caused the decrease in running speed during the long distance running.