Abstract: Objective To investigate the characteristic of vastus lateralis (VL) and vastus medialis (VMO) during the Taijiquan exercise with surface electromyography (EMG). Methods 15 healthy adults were collected their median frequency (MF), mean power frequency (MPF), zero crossing rate (ZCR), averaged EMG (AEMG) of bilateral VL and VMO when they maintained 5 Taijiquan typical posture. Results The differences were not significant in all those indexes between VL and VMO during the postures of Baihe Liangchi and Jinji Duli, and were significant during the postures of Louxi Aobu, Shizi Tui, Pubu (P<0.05), the VL's indexes were less. Compared with the maximum voluntary contraction, Taijiquan was the lower loaded, and more slow muscle fibers could be recruited. Conclusion Taijiquan is a lower loaded exercise, and more slow muscle fibers can be recruited, especially in the VMO in some actions.

Key words: Taijiquan, surface electromyography, vastus medialis (VMO), vastus lateralis (VL)