本研究目的為評估長期從事太極拳運動老年人在下階梯轉換的運動學、動力學與下肢主要肌群的肌電圖參數上的差異，以了解參與太極拳運動的老年人在功能性動作控制上產生的效果。本研究以長期從事太極拳運動與一般運動的老年人各18位作為研究對象，以十台Vicon紅外線攝影機、兩塊測力板與Noraxon無線肌電同步收集受試者下階梯著地與著地後前行的運動學、動力學與肌電參數進行分析探討。結果顯示，較年長之太極拳組老年人有較快之下階梯轉換質心速度、較大之髖關節活動度、較大的著地步長、COM-COP前後水平距離、踝關節蹠屈角度、推蹬力矩、推蹬功率與較短之股直肌肌肉延遲以及較低的脛骨前肌肌肉活動。透過本研究之結果，顯示長期規律從事太極拳運動的老年人，由於太極拳的運動型態與下肢肌群訓練的效果，在下階梯轉換時有較佳的速度表現與動態平衡能力，而髖關節與踝關節肌肉能力的增進也許與太極拳組較快質心速度息息相關。以下針對各分期進行更進一步說明：
一、下階梯期，太極拳組在著地時藉由踝關節維持較快速度下階梯時的穩定。一般組則以較接近地面的方式減緩可能的著地衝擊。
二、著地前行期，太極拳組以髖關節維持跨步時的穩定，並在踝關節往前推蹬上有較佳的效率。
三、與下階梯相比，兩組受試者在下階梯轉換過程皆呈現不同的下肢關節力矩分配、與皆著重於往前的質心運動，而太極拳組則有更明顯往前之質心運動。

The purpose of this study is to investigate the benefits of Tai Chi Exercise on functional abilities and balance control in elderly during stair-to-floor transition. Eighteen Tai Chi elder participants and 18 normal healthy elder ones would be volunteered. The kinematics, force data and EMG signals were obtained synchronously by ten Vicon high-speed cameras, a Kistler force plate and Noraxon system. Results revealed that the older Tai Chi group had faster center of mass velocity, greater hip range of motion, ground-step length, the horizontal distance before and after COM-COP, more propulsive joint moment, propulsive joint power of ankle during stair-to-floor transition, and greater plantarflexion angle, shorter quadriceps femoris latency and lower tibialis anterior while contact the ground. Conclusions shows that long-term practice of Tai Chi can still be performed with better ability of dynamic balance control and faster center of mass velocity. The improvement of muscular abilities in hip joint and ankle joint might be associated with faster center of mass velocity in Tai Chi elderly. More detail information showed as following:
First, while contacting the ground, ankle joint might be related to maintain stability while faster descending in Tai Chi group. Normal group showed lower body for decreasing the impact while contacting ground.
Secondly, more hip joint execution maintained stabilities while contralateral leg swings and more efficiency on propulsion of ankle joint in Tai Chi group during follow walking phase.
Thirdly, compared with stair descent, both groups would present more forward instead of downward COM motion and different joint execution during stair-to-floor transition. Tai Chi group showed faster forward COM velocity.

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