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.

The purpose of this study was to clarify the energy source contribution in giant slalom (GSL) and slalom (SL) skiing. The subjects were five Japanese male varsity alpine ski racers, ranked in the semi-elite class in Japan. Maximal oxygen intake (〓 O₂ max), alactic power, and lactic power were measured in the laboratory. Aerobic and anaerobic metabolisms during and just after SL and GSL skiing were measured by oxygen intake (〓 O₂) and blood lactate concentration (LA), respectively. The results showed that the body dimension of the racers in this study were smaller, and that they had lower 〓 O₂ max and anaerobic power than the elite world class racers in the previous studies. The contribution of the three energy systems was estimated by measuring oxygen intake during SL and GSL skiing. Approximately 55% of total energy came from the alactic system, 20% from the lactic system and 25% from the aerobic system. Compared to the elite world-class racers in the previous study, our results showed that the racers in this study had less contribution to the lactic system, a higher oxygen expenditure and smaller lactate accumulation.