Comparison of the gluteus medius and rectus femoris muscle activities during natural sit-to-stand and sit-to-stand with hip abduction in young and older adults

[Purpose] The purpose of this study was to compare the relative levels of activation of the gluteus medius (Gmed) and rectus femoris (RF) muscles during natural (N) sit-to-stand (STS) and STS with hip abduction (ABD) in young and elderly females. [Subjects] We recruited 15 healthy young females and 15 healthy elderly females. [Methods] The activities of the dominant lower extremity gluteus medius (Gmed) and rectus femoris (RF) muscles were measured using a wireless electromyography (EMG) system for natural STS and STS with hip abduction. [Result] In the elderly subjects, the Gmed increased significantly and RF decreased significantly when STS was performed with hip ABD compared with when it was performed naturally. The Gmed in the elderly subjects was significantly increased during natural STS compared with in the young subjects. [Conclusion] These results indicate that the Gmed was recruited to compensate for weakened RF muscle function in the elderly adults.