Ground reaction forces were commonly used as a means for evaluating dynamic function of running/jogging shoes. In the present study, we examined several methodological problems related to evaluation of running shoes using ground reaction force data. Twelve long-distance runners served as subjects, and they wore two types of running shoes for testing. The number of trails required to detect the difference between different cushioning properties of shoes is first examined. The results indicated that at least 22 trials par shoe were needed to detect a subtle difference in the parameters of shock absorption. Trial to trial variability of the shoes with different cushioning properties was then examined. There was no difference in trial-to-trial variability between these two types of running shoes. Inter- and intra-day variability of ground reaction force data was secondly examined. It was found that their inter-day variability was 4-times larger than the intra-day variability. The results suggested that data collection should be made within the same day. Thirdly, we examined adaptive changes ground reaction force when the runners wore a different cushioning property of running shoes. It was found that the runners adapted to the new shoes within approximately 10 running trials lasted less than 10 min. This quick adaptability of runners seems to mask the actual difference in physical properties of running shoes when evaluating with a running test. Kinematic data may better describe changes in this adaptation.

DESCENTE SPORTS SCIENCE Vol.25/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE