Ballet deep squat with legs rotated externally (grand plié) is a fundamental movement for dancers. However, performing this task is a challenge to ankle control, particularly for those with ankle injury. Thus, the purpose of this study was to investigate how ankle sprains affect the ability of postural and muscular control during grand plié in ballet dancers. Thirteen injured dancers and 20 uninjured dancers performed a 15 second grand plié consisting of lowering, squatting, and rising phases. The lower extremity motion patterns and muscle activities, pelvic orientation, and center of pressure (COP) excursion were measured. In addition, a principal component analysis was applied to analyze waveforms of muscle activity in bilateral medial gastrocnemius, peroneus longus, and tibialis anterior. Our findings showed that the injured dancers had smaller pelvic motions and COP excursions, greater maximum angles of knee flexion and ankle dorsiflexion as well as different temporal activation patterns of the medial gastrocnemius and tibialis anterior. These findings suggested that the injured dancers coped with postural challenges by changing lower extremity motions and temporal muscle activation patterns.
Chia-Wei Lin is with the Institute of Biomedical Engineering, College of Engineering, National Cheng Kung University, Tainan City, Taiwan. Fong-Chin Su is with the Institute of Biomedical Engineering, College of Engineering, and with the Medical Device Innovation Center, National Cheng Kung University, Tainan City, Taiwan. Cheng-Feng Lin (Corresponding Author) is with the Department of Physical Therapy, College of Medicine, and with the Medical Device Innovation Center, National Cheng Kung University, Tainan City, Taiwan.