Proper Breakfall Skill Significantly Decreased The Head Impact Value In Judo Seoi-nage Throwing Technique

PURPOSE: Although the judo is an official Olympic event that played all over the world, serious head injuries, especially acute subdural hematomas (ASDHs) have occasionally occurred during judo competition or practice in Japan. The acceleration at the head impact is considered as one of the major influencing factors in serious head injuries. On the other hand, the break-fall technique called “ukemi” has been developed in judo to prevent head collision against the judo-floor (mat) and to minimize its impairments. However, the head acceleration-decreasing effect of ukemi on thrown person has not been fully understood. The purpose of this study was to evaluate head injury criterion (HIC) value as a level of head injury risk by the linear head accelerations and to compare it with the values previously obtained from an anthropomorphic test device (ATD) experiment without ukemi. METHODS: One male judo expert (thrower) repeatedly threw another male judo expert (faller) for 4 times by judo technique called Seoi-nagethat has been linked to the occurrence of ASDHs in judo. The faller took ukemi adequately without head collision against mat in all trials. The head axial linear acceleration was measured by a tri-axial accelerometer mounted on the forehead of the faller’s head in each trial. In order to evaluate the magnitude of faller's impact of the head, we calculated the HIC value from the head linear accelerations. Kinematic data of the faller’s head were also recorded during trials using digital video cameras. The HIC values of ATD thrown by the same judo expert were obtained from our previous study (Murayama et al., 2020). RESULTS: Kinematic data showed that the faller fell forwards without any head collisions against the mat in throwing technique Seoi-nage. In all trials, a large acceleration appeared at the body contact phase to the mat. The peak resultant linear acceleration values of faller ranged from 8.36 to 9.30 G and 9.11 to 30.83 G in ATD. The HIC values of faller (2.08 ± 0.22) were significantly lower than those observed in ATD (24.68 ± 21.23, p < 0.05). CONCLUSIONS: According to the findings, mastering proper ukemi technique could significantly decrease the HIC value of head impact and the likelihood of severe head injuries in judo.