Relationship Between Supporting Leg Stiffness and Trunk Kinematics of the Kicking Leg During Soccer Kicking.

The stiffness of the supporting leg may alter the energy transfer to the trunk and lower extremities of the kicking leg, which may affect kick performance. This study aimed to clarify whether the stiffness of the supporting leg affects the trunk kinematics during kicking and kicking performance in soccer players. Twenty-two male collegiate soccer players participated in the study. The data for the stiffness properties of the supporting leg and trunk kinematics were obtained and calculated using a 3-dimensional motion analysis system. The results showed that a greater leg stiffness of the supporting leg was associated with a lower trunk rotation angle during kicking. There were no significant correlations between the maximum swing speed and the stiffness of the supporting leg (P < .05). These results suggest that stiffness of the supporting leg may restrain trunk rotation during the kicking motion. However, the lack of a relationship with swing speed indicates the need for further investigation into its effects on kicking performance.