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Shanghai, China

Liu Q.-G.,Shanghai Sports College | Huang Q.-M.,Shanghai Sports College
Yiyong Shengwu Lixue/Journal of Medical Biomechanics | Year: 2013

Objective: To analyze how the athletes control postural balance through observing their joint angular motion change, center of pressure (COP) change and EMG activities of lower extremities for both athletes and beginners when performing the movement of white crane spreads its wings in Tai Chi Quan. Methods: Twenty subjects were divided into 2 groups as 10 athletes and 10 beginners of Tai Chi Quan in each. When performing the movement of white crane spreads its wings, their EMG activities of 10 skeletal muscles, two-dimensional angular motion of 3 large joints in bilateral lower extremities, and COP displacements in lateral and anterior-posterior directions were recorded. Each performing trial took 8 seconds and repeated 5 times. All data were statistically processed for EMG, motion and balance analysis, and the EMG data were normalized to compare the differences between the athletes and beginners of Tai Chi Quan. Results: The EMG activities of tibialis anterior(Ta), biceps femur(bF), gluteus medium(Gm) in support leg of athletes were significantly greater than those of the ipsilateral muscles in support leg of beginners, and the same was the EMG activities of gastrocnemius (G) and rectus femur(rF) in virtual leg of athletes compared with the beginners. The maximal average angular motion of 3 large joints and the coxa joint motion of support leg in athletes were both significantly greater than that in beginners, but the anterior-posterior COP displacement in athletes was significantly smaller than that in beginners. Conclusions: When performing the movement of white crane spreads its wings in Tai Chi Quan, athletes could oppose the COP change by enhancing muscle activities to maintain the postural balance, while beginners couldn't make such active muscle activities against the uncontrolled anterior-posterior COP displacement. This may preliminarily explain the reason why Tai Chi Quan exercise can improve the muscle strength in lower extremities and enhance the ability of postural control. Source


Huang Q.-M.,Shanghai Sports College | Wang F.-H.,Shanghai Sports College | Fan S.,Shanghai Sports College
Yiyong Shengwu Lixue/Journal of Medical Biomechanics | Year: 2012

Objective: To observe the electromyography (EMG) activities and kinematic characteristics of the back, abdomen and hip muscles under the static symmetric loading and unloading with the flexion and extension posture. Methods: Six healthy male subjects stood on a specially designed testing platform, doing flexion/extension under symmetric loading and unloading, respectively. Each trial lasted 4 seconds and was repeated 3 times. The EMG activities of 10 muscles(rectus abdominis, obliquus externus abdominis, erector spinae, multifidus, gluteus Medius), the 3D angular movement, the plantar COP (center of pressure) were recorded during the trial. The normalized EMG, trunk angle and COP displacement were calculated, and statistical analyses of all data were made. ResultsSix healthy male subjects stood on a specially designed testing platform, doing flexion/extension under symmetric loading and unloading, respectively. Each trial lasted 4 seconds and was repeated 3 times. The EMG activities of 10 muscles(rectus abdominis, obliquus externus abdominis, erector spinae, multifidus, gluteus medius), the 3D angular movement, the plantar COP (center of pressure) were recorded during the trial. The normalized EMG, trunk angle and COP displacement were calculated, and statistical analyses of all data were made. Results: Muscle activities of the back were greater (10.47~16.94) with flexion both under loading and unloading. Muscle activities of the abdomen were greater with extension under unloading, and those of the back (3.70~17.95) and hip (6.64~11.52) were increasing under loading, with muscle activities of the abdomen decreasing (10.66~4.18). The flashing trunk numbers was increased with the increase of loading, especially 1.55-time increase in the trunk angle. The COP displacement in anterior-posterior direction was shifted greater than that in lateral direction, and this shift was more during flexion (14.60) than that during extension (7.65). Conclusions: Extension increases the activities of back muscles, especially for multifidus, and it also increases the torso angular displacement and flashing trunk numbers, especially under loading. Source

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