Study on head protective device for judo by two-link model

Abstract

Judo has been compulsory at junior high school in Japan since 2012. However, judo has a higher mortality rate than other sports, and countermeasures are urgently required. The main cause of death accidents in judo is acute subdural hematoma (ASDH). ASDH is caused by the brain moving in the cranium due to a strong impact on the head and rupture of the bridging vein connecting the brain and skull. The purpose of this study is to examine the head protective equipment which can suppress the variation range of the head angular velocity at the time of head collision, paying attention to the head angular velocity from the viewpoint of suppressing the rotation of the cranium. As a result of changing the spring constant and the damping coefficient of the protection material, the variation range of the head angular velocity became the minimum in (k , c) = (10⁴ N/m , 10³ N ∙ s/m). Furthermore, as a result of fixing the spring constant to 10⁴ N/m and optimizing the damping coefficient, at c = 179.47 N ∙ s/m, the variation range of the head angular velocity became the minimum. Therefore, the optimum combination of spring and damping coefficients is (k , c) = (10⁴ N/m , 179.47 N ∙ s/m).