你是否思考過為什么走路時會擺臂,，而且不是同手同腳,？
擺臂看起來是一個“成本昂貴”的習慣,，它不僅需要肩部運動，而且浪費力氣,。但是一項最新研究成果顯示,，行走時擺臂可以讓你更省力，也讓行走更有效率,。
為解開行走擺臂之謎，美國和荷蘭的3名研究人員招募10名志愿者,，讓他們行走時使用不同的擺臂方式,，如同手同腳、手臂靜止不動和正常的擺臂方式,。研究人員測量不同擺臂方式所需的能量,，即新陳代謝率和肩部運動所需力量。
結(jié)果顯示,，無論何種擺臂方式只需少量肩部運動,，但各自能量消耗差別較大。
研究報告29日發(fā)表在英國皇家學會的《皇家學會生物學分會學報》上,。
研究負責人,、美國芝加哥大學生物力學專家史蒂文·柯林斯介紹說，保持手臂靜止不動行走時比正常行走時的代謝率高12％,，相當于其他條件相同時行走速度加快20％或行走時身背重10千克的背包,。
他在接受《宇宙雜志》采訪時說：“擺臂并非受肩膀運動驅(qū)使，而是受人們行走時身體的自然動力驅(qū)使,。”
同樣是擺臂,，同手同腳的擺臂方式和“鐘擺式”擺臂，即正常的擺臂方式對行走的影響大不相同,。
研究人員發(fā)現(xiàn),，若強行以同手同腳的方式擺臂，步行者就得讓腳花費兩倍的力量防止身體旋轉(zhuǎn),。
“當你跨出一步時,，你的身體實際上正圍繞一根豎軸旋轉(zhuǎn)……就像芭蕾女演員跳舞那樣，”柯林斯解釋說,。
研究發(fā)現(xiàn),，“鐘擺式”擺臂可以抵消驅(qū)使身體旋轉(zhuǎn)的力，幫助分擔腳的一部分負擔,。而同手同腳走路時,，驅(qū)使身體旋轉(zhuǎn)的力量翻倍，意味著步行者的腳得花兩倍的力量讓身體保持平衡。在這個過程中,，新陳代謝率隨之上升25％,。 （生物谷Bioon.com）
生物谷推薦原始出處：
Proc. R. Soc. B July 29, 2009, doi: 10.1098/rspb.2009.0664
Dynamic arm swinging in human walking
Steven H. Collins1,2,3,*, Peter G. Adamczyk1,2 and Arthur D. Kuo1,2
1Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA
2Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA
3Department of Biomechanical Engineering, Delft University of Technology, NL-2628 CD Delft, The Netherlands
Humans tend to swing their arms when they walk, a curious behaviour since the arms play no obvious role in bipedal gait. It might be costly to use muscles to swing the arms, and it is unclear whether potential benefits elsewhere in the body would justify such costs. To examine these costs and benefits, we developed a passive dynamic walking model with free-swinging arms. Even with no torques driving the arms or legs, the model produced walking gaits with arm swinging similar to humans. Passive gaits with arm phasing opposite to normal were also found, but these induced a much greater reaction moment from the ground, which could require muscular effort in humans. We therefore hypothesized that the reduction of this moment may explain the physiological benefit of arm swinging. Experimental measurements of humans (n = 10) showed that normal arm swinging required minimal shoulder torque, while volitionally holding the arms still required 12 per cent more metabolic energy. Among measures of gait mechanics, vertical ground reaction moment was most affected by arm swinging and increased by 63 per cent without it. Walking with opposite-to-normal arm phasing required minimal shoulder effort but magnified the ground reaction moment, causing metabolic rate to increase by 26 per cent. Passive dynamics appear to make arm swinging easy, while indirect benefits from reduced vertical moments make it worthwhile overall.
