Two-dimensional kinematic and dynamic analysis of a karate straight punch

The mechanical effect of punches performed in martial arts or boxing sports has been studied on different ways: the impact force was either directly measured with sensors fixed on rigid frames [5, 6] or indirectly estimated from the mechanical features of materials broken during strike tests [2, 3]. A few authors developed experimental devices for measuring this force in actual fighting conditions [1] or on a punching bag [4]. Among the studies that analyzed the kinematics of the striking segments [2, 3, 5], only one [2] related kinematic and dynamic data through the linear momentum. According to this approach, a straight punch struck by a karateka (1.68 m, 68 kg, 3rd dan black belt) on a training instrument traditionally used in karate (makiwara) was analyzed in two dimensions. The peak force was two to three times lower than the maximum values (4000 to 6000 N) reported in previous studies [1, 5, 6], which could be explained by the makiwara flexibility. The large difference between the variation of the karateka's linear momentum and the linear impulse of the target-block pointed out the limitation of a 2-D analysis of this movement, which cannot take into account the angular momenta of the trunk and the upper limbs around the vertical axis.