Intra-athlete changes in bent knee violations between yellow paddle and red card in race walking

In race walking, judges visually evaluate whether athletes’ legs are straightened from initial contact with the ground to the vertical upright position. Judges show a yellow paddle when the athlete is in danger of breaking the rules, and a red card when the infringement is clear. However, no study has examined the distinctions between these two judgement outcomes, particularly with respect to intra-athlete changes in walking motions. We aimed to clarify differences in knee joint motions between the yellow paddle and the red card conditions. The walking motions of 10 male athletes who received both a yellow paddle and a red card from national-level judges were analysed. Sagittal plane walking motions were recorded using a digital camera operating at 120 Hz. Step parameters (i.e., step length, step frequency and walking speed) and knee joint angle during the contact phase were analysed. Kinematic variables were compared between the yellow paddle and the red card conditions. No significant differences were observed in any kinematic parameters (step length: p = 0.684, d = 0.09, step frequency: p = 0.015, d = 0.42, walking speed: p = 0.245, d = 0.23). No obvious link was found between changes in step parameters and the award of a red card. Furthermore, there were no significant differences in knee joint angle during the contact phase. These findings suggest that athletes do not substantially adjust their knee joint angle during the contact phase after receiving a yellow paddle.