The relationship between performance and trunk movement during change of direction

The purpose of this study was to obtain the trunk kinematics data during a change-of-direction task and to determine the relationship between trunk kinematics and the change-ofdirection performance. the design of this investigation was a descriptive laboratory study. twelve healthy male collegiate soccer players (age: 21.3 ± 1.0 yrs,body mass: 67.7 ± 6.7 kg,and height: 1.75 ± 0.05 m) participated in this study. participants performed a shuttle run cutting task with a 180 degree pivot as quickly as possible. the shuttle run cutting time,ground contact time during a change-of-direction,and trunk inclination angle were measured. the shuttle run cutting time tends to correlate positively with ground contact time. during the change-ofdirection task,the trunk forward inclination angle gradually increased during the first 50% of the stance phase and decreased subsequently whereas the trunk flexed,maintaining a left inclination during the first 40% of the stance phase and changing exponentially in the opposite direction. forward angular displacement of the trunk between foot-contact and maximum trunk inclination correlated positively with the shuttle run cutting time (r = 0.61,p < 0.05) and ground contact time (r = 0.65,p < 0.05). these findings suggest that the change-of-direction performance could be related to the small angular displacement of the trunk during a change of direction. moreover,it was considered that there might be optimal inclination angles related to change-of-direction performance. therefore,coaches in field sports should check body posture and trunk movements during changes of direction. © journal of sports science and medicine.