Biomechanical Analysis Of Head And Neck Motions In Thrown Person By Judo Technique, Seoi-nage.

Abstract

PURPOSE: Severe head and neck injuries have occasionally occurred in judo, an athletic event in the Olympic Games. Because the pattern and severity of these injuries strongly depend on the kinematic motion of the thrown person, it is indispensable to clarify biomechanically the mechanisms of head and neck injuries, in regard to various throwing techniques. The purpose of this study was to investigate the mechanical impact on head and neck when person was thrown by seoi-nage, one of the most popular skills. METHODS: Anthropomorphic test device (ATD), a model of the human body that is typically used in vehicle crash testing, was thrown by a male judo expert for 5 times using seoi-nage. A 3-axis accelerometer was mounted at the ATD head’s center of the gravity. Linear and angular accelerations of the head were measured by the accelerometers. Furthermore, we utilized 6-axis load cells to detect load and moment of the neck. To evaluate the impact on the neck, the neck injury criterion (Nij) was calculated. ATD kinematics data were also obtained using a high-speed digital video camera. RESULTS: When seoi-nage was performed, the dummy fell frontwards with the parietal area of the skull contacting the mat. Time courses for linear and angular accelerations were corresponded to the kinematics data of the ATD obtained by video camera. For linear head acceleration, peak resultant values ranged from 9.1 to 30.8 G (20.3±4.4 G, mean±S.E.). Angular peak resultant accelerations of the head ranged from 641.3 to 3195.4 rad/s2 (1890.1±515.1 rad/s2). These accelerations were considerably lower than those in our previous report where other throwing technique (e.g. osoto-gari) was examined (p<0.05, respectively). On the other hand, the Nij value was 1.03±0.19, implying that the impact on the neck by seoi-nage might exceed the neck injury threshold Nij 1. CONCLUSIONS: The acceleration shock of the head thrown by seoi-nage with the direct parietal region contact against the mat was smaller than those by other throwing skills. However, our results of Nij raised the possibility that the impact on the neck in thrown person by seoi-nage caused serious cervical damages.