Posture and ground reaction force related influences on Tai Chi pushing movement

The goal of this study was to investigate the differences in ground reaction force during a Tai Chi Chuan (TCC) pushing movement between those with and without TCC experience through a detailed 3D dynamic analysis of the lower extremities. Seven TCC practitioners who had practiced the TCC push-hands movement for 6.0 ± 4.8 years and eight males without any TCC experience were recruited in this study. An eight-camera Expert Vision Eagle motion analysis system and two Kistler force plates were used to collect kinematic data (100 Hz) and the ground reaction force (1000 Hz). About 34 retro-reflective markers were placed on anatomical significant locations that determine embedded axes for segments. Results showed that the angular motions of the knee joint were different between the two groups, both in pattern and magnitude. Compared with the TCC group, the non-TCC group had significantly smaller peak abduction angles at the ankle joint (p < 0.05). The magnitude of the vertical force of the TCC group was greater, whereas the medial and posterior shear forces were smaller. The significant difference in vertical force (p < 0.05) and fraction opponent force of vertical force were found significantly different (p < 0.05) between the two groups. The patterns of the anteroposterior component of the ground reaction force during pushing were different, but those for the other two components were similar. Different lower-limb kinematics and kinetics were found between those with and those without TCC experience during TCC pushing movement and it was also found that the TCC practitioners could generate more effective force transfer than the group with no prior TCC experience. It was further concluded that vertical force plays an important role in a pushing movement, and posterior force exerted from the opponent was absorbed and transformed into anterior force to help the TCC practitioners remain stable.