Comparison of the Tibialis Anterior and Soleus Muscles Activities during the Sit-to-stand Movement with Hip Adduction and Hip Abduction in Elderly Females

[Purpose] The purpose of this study was to compare the activation of the tibialis anterior (TA) and soleus (SOL) muscles during the sit-to-stand (STS) task with hip adduction and hip abduction in elderly females. [Subjects] We recruited 16 healthy elderly females with no pain in the knee joint and no other orthopedic problems of the lower limbs. [Methods] The activities of the dominant lower extremity muscles were measured using a wireless electromyography (EMG) system. Subjects then performed a total of nine STS trials, including three trials each for hip adduction, hip abduction, and natural STS tasks. [Results] In the pre- thigh-off (TO) phase, the normalized EMG data of the TA muscle increased significantly when the STS task was performed with hip adduction compared with hip abduction. In the post-TO phase, the normalized EMG data of the TA muscle showed a significant increase during the STS task with hip adduction compared with hip abduction. Additionally, the normalized EMG data of the SOL muscle increased significantly when the STS task was performed with hip adduction compared with hip abduction. [Conclusion] Therefore, the STS movement with hip adduction poses a greater challenge for balance control, indicating that certain elderly individuals would have difficulty in executing an abrupt adjustment in their dynamic postural stability during the STS movement.