Muscle contraction characteristics of the lower extremities during Tai Chi exercise

The objective of this study is to examine the muscle contraction characteristics of the lower extremities during Tai Chi exercise and to explain the beneficial effect of Tai Chi on the improvement of muscle strength.Sixteen experienced Tai Chi practitioners participated in this study.Five typical Tai Chi movements represented by stepping forward,backward,sideways,up-down and fixing were selected.The electromyographic activities of the rectus femoris,semitendinosus,gastrocnemius,and anterior tibialis muscles were recorded during the performance of five typical Tai Chi movements.The muscle contraction in terms of contraction amplitude,integrated electromyography,and onset contraction duration were calculated and analyzed.Results showed that muscle contraction amplitudes were varied in different Tai Chi movements.For integrated electromyography,the muscle contraction of rectus femoris(F=229.9,P=0.00),semitendinosus(F=190.8,P=0.00),gastrocnemius(F=263.5,P=0.00),and anterior tibialis(F=235.6,P=0.00),while for onset duration,the muscles contraction of rectus femoris(F=519.3,P=0.00),semitendinosus (F=585.5,P=0.00),gastrocnemius(F=844.5,P=0.00),and anterior tibialis(F=868.1,P=0.00) were significantly different when compared among five typical Tai Chi movements.It is speculated that the muscular contraction strategies,which required eccentric,concentric,and isometric muscle contractions,and combined with varied muscle loadings and contraction duration involved in Tai Chi may contribute to the muscle contraction coordination,muscle force fluctuation and muscle strength improvement.