Appropriate Neck Flexion Without Head-hitting Decreases The Thrown Player’S Risk Of Brain Injury In Judo

Abstract

PURPOSE: Judo is one of the worldwide sports and its competitive athletic events have been held in Olympic Games. Serious brain injuries, however, have been occasionally noted in judo practices and/or competitions. Since the patterns and severities of brain injuries largely depend on the kinematics of the thrown players, it is essential to investigate the mechanism of brain injury from the biomechanical viewpoint in popular throwing techniques. The aim of this study is to evaluate the brain injury criterion (BrIC), an indicator of brain injury, with measuring the presence or absence of head-hitting on the anthropomorphic test device (ATD) in judo throwing technique Ouchi-gari. METHODS: A male judo expert (thrower) threw an ATD for 6 times by Ouchi-gari with or without head-hitting, respectively. The ATD with a straight neck component necessarily hit the occipital region on the mat, whereas an angled component was designed for preventing the ATD’s head-hitting. A 3-axis angular rate sensor, mounted in the gravity center of the ATD’s head, assessed head axial angular velocity in each trial. To evaluate the ATD’s head impact quantitatively, we calculated the BrIC from the head axial angular velocity. High-speed digital video cameras also recorded the kinematics of the ATD’s whole body during trials. RESULTS: In all trials, the largest angular velocities were recorded in the phase of the initial head (with head-hitting) or back (without head-hitting) contacting to the mat. The peak BrIC values of ATD ranged from 0.94 to 2.27 (with head-hitting) and 0.54 to 0.91 (without head-hitting). The average BrIC value with head-hitting (1.62 ± 0.22, mean ± S.E.) trials was significantly higher than those without head-hitting (0.73 ± 0.08) trials (p<0.05). Four out of six trials with head-hitting scored BrIC values larger than 1.0, which implies the human tolerance limit for serious brain injury. However, BrIC values were less than 1.0 in all other trials without head-hitting. CONCLUSIONS: These results suggested that thrown player’s break-fall technique, with appropriate neck flexion to avoid head-hitting, decreases the BrIC value effectively and the risk of serious brain injuries in judo.