Effects of unexpectedness on the risk of head injuries in judo novices and experts

Abstract

Problem Statement: Serious judo accidents in Japan have been reported worldwide since 2012. Currently, the number of serious judo-induced head injuries, such as acute subdural hematomas, is significantly reduced in Japan, indicating that the safety measures taken by the All Japan Judo Federation have been successful. However, head injuries such as concussions are still being reported, and the risk of serious head injuries remains. When a judo athlete is unexpectedly attacked, such as using a feint, Ukemi techniques to protect the head are often delayed. Thus, head injuries are more likely to occur when being thrown unexpectedly. Purpose: The present study clarifies the effects of unexpected conditions on the incidence of head injury in novice and expert judokas among junior high school, senior high school, and university students and elucidates the relationship between cervical muscle strength and the risk of head injury. Approach: Participants included 20 junior high school students (11 judo novices, 9 judo experts), 20 senior high school students (5 judo novices, 15 judo experts), and 15 university students (5 judo novices, 10 judo experts). Participants performed backward breakfalls after being pushed with a constant force under unexpected (while performing a mental addition task) and expected (not performing this task) conditions. Results: Among junior high school student judo novices, the maximum head angular accelerations during backward breakfalls were significantly different between the unexpected and expected conditions. The results showed that junior high school judo novices were at an extremely high risk of head injury under unexpected conditions. In the entire study population, no correlation was found between cervical muscle strength (anterior flexion) and angular acceleration of the head. Conclusions: To prevent head injuries, unexpected attacks, such as feints, should be avoided among junior high school judo novices.