Effects of different unstable sole construction on kinematics and muscle activity of lower limb

Unstable sole construction can change biomechanics of lower extremity as highlighted by some previous studies, which could potentially help developing special training or rehabilitation schemes. In this study, unstable elements are fixed in heel and forefoot zone to exert unstable perturbations, and the position changes (medial, neutral and lateral) of unstable elements in forefoot coronal plane are adjusted to analyze changes of lower extremity kinematics and muscle activities. Twenty-two healthy male subjects participated in the test, walking with control shoes and experimental shoes randomly under self-selected speed. Kinematics and surface electromyography measurements were carried out simultaneously. It is found that experimental shoes can lead to the reduction of knee abduction and internal rotation and hip internal rotation, with p<.05. Ankle inversion and internal rotation amplitude were also reduced, which are associated with significantly increased activation levels of muscles (TA-tibialis anterior, PL-peroneus longus, LG-lateral gastrocnemius) in order to compensate perturbations. It is suggested that a training equipment incorporating unstable elements would enhance postural control by adjusting lower extremity kinematics and reorganizing muscle activity. More research can be conducted to testify the feasibility of unstable shoes construction on human postural control and gait, even guide training regime design, injury prevention and rehabilitation.