Characteristics of leg motion that related to bent knee violation in race walking

Race walkers must have a straightened knee from first contact until the vertical upright position. This study aimed to identify the characteristic motions in which an athlete is judged to have a bent knee by verifying the accuracy of judges’ evaluation of a bent knee. Twenty athletes participated in this study and were categorised into two groups: those who received a red card (n = 10) and those who did not (n = 10). Their walking motions were captured using a digital video camera at 120 Hz. The step parameters (i.e., step frequency, step length, walking speed, and contact time) and knee joint angle were analysed during the stance phase. No significant differences were observed in any step parameter. The knee joints did not show significant differences during heel contact and immediately thereafter. However, compared with the no red card group, the red card group exhibited a significantly smaller knee joint angle during the mid-stance phase (22%–77%). Thus, athletes being conscious of keeping their knees extended even after the support leg is vertical may help avoid a red card.