Abstract des Autors

Some differences in step rate-running economy relationship between male and female runners were reported in our previous paper. The aim of the present study was to verify the possibility of contribution of running form as a cause of the sex difference. Five male and five female runners underwent treadmill running and cycling at a step rate from 150 to 200 per minute with a given step length of 80 or 100 cm in the former and a given load of 0.5 kp in the latter. Measurements of Vo2 and heart-rate were made in a steady state of each bout of exercise. At a lower step rate (below 170 steps/min), no difference in step rate-economy relationship was observed between men and women. The economy dropped with decreasing step rate in running, but not in cycling. At a higher step rate (above 180 steps/min), the same sex difference in step rate-economy relationship was found in both running and cycling. In men, the drop in economy was observed as step rate increased, but in women, no change was found at any step rate. During cycling, there is little change in center of gravity and movements of limbs with changing step rate. With this in mind, the results suggest that the sex difference in step rate-running economy relationship is due to not running form but other factors.