預防跌倒可以說是現代生活中非常重要的健康課題之一，面對跌倒時跨步恢復平衡更扮演著重要的角色。目前有不少對於跨步恢復平衡的研究，但是針對跨步恢復平衡時上肢的影響僅有極少數的研究。本研究的目的是希望透過生物力學的角度，了解上肢在參與跨步恢復平衡時對於平衡恢復的影響。本研究共招募12名健康男性，利用繩索釋放系統分別在12.5ﾟ、15ﾟ、17.5ﾟ時無預警釋放繩索模擬失去平衡的情況，受試者動作分為手臂自由與手臂限制兩種情況。參數包含有恢復平衡時間、跨步參數、地面反作用力等參數。結果發現，受試者在手臂自由時可以有較長的重心轉移時間與跨步時間。雖然步長、地面反作用力與平均負荷率並沒有達顯著差異，以平均值而言手臂限制時有較短步長且地面反作用力與平均負荷率有高於手臂自由時的趨勢。此外，手臂限制時地面作用力與負荷率隨傾斜角度增加的現象並沒有出現在手臂自由的情況。因此從本研究可得知，手臂參與跨步恢復平衡時可以有較長的反應時間並有充裕的時間執行跨步動作。雖然手臂對於跨出較長的步長及降低地面反作用力的幫助並不明顯，但似乎可以有較好的平衡調節機制，所以即使在傾斜角度變大時地面反作用力並不會顯著增加。由此可以證實上肢對於跨步恢復平衡動作是有幫助的。

Injuries caused by falling have become a serious concern in an aging society. Balance recovery techniques are useful not only in preventing falls but also in many sports activities. The step strategy plays an important role especially under violent balance perturbations. However, relatively little is known about the effect of arm swing on stepping balance recovery although considerable arm motions have been observed. To investigate how the arms influence balance recovery, 12 young male adults were released from forward-lean postures with single step balance recovery under arm swing (AS) and arm constrained (AC) conditions. It was found that unconstrained arm motions did allow more time in preparation for taking the step. The actual stepping time and distance could also be lengthened. Furthermore, it seemed that arm swing assisted in body coordination for reducing ground reaction forces and loading rate on the stepping foot. Future studies are required to investigate the optimal strategy for the arms to coordinate with the trunk and lower body in balance recovery.

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