Leg adjustments during running across visible and camouflaged incidental changes in ground level
Leg adjustments during running across visible and camouflaged incidental changes in ground level
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DOI：
10.1242/jeb.072314
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发表时间：
2012-09-01
影响因子：
2.8
通讯作者：
Blickhan, Reinhard
中科院分区：
文献类型：
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作者：
Mueller, Roy;Ernst, Michael;Blickhan, Reinhard
在自然环境中跑步时，人类必须经常应对地面高度的各种不可预测的变化。为了防止摔倒，地面高度的变化，尤其是那些看不见的变化，需要运动系统在短时间内快速做出反应。我们对11名受试者在跨越可见（落差为0、5和10厘米）和伪装（落差为0和10厘米）的地面高度变化跑步时的两次连续触地进行了研究。对于这两种情况，我们发现他们在受干扰的第二次触地时，腿部参数和地面反作用力（GRF）存在显著差异，而且在未受干扰的第一次触地时（提前一步）也存在差异。在可见的第一次触地时，人类会线性地调整他们的地面反作用力以降低并平稳其质心。在伪装的情况下，地面反作用力也会降低，但似乎跑步者会预期有大约5 - 10厘米的落差。在可见的受干扰的第二次触地时，地面反作用力随着落差高度增加。在伪装的第二次触地时，地面反作用力与跨越类似可见落差时观察到的反应明显不同，而触地时间减少，初始冲击峰值增加。这种增加的冲击可以解释为应对该情况的一种纯机械作用。此外，我们观察到在两种情况下，攻角和腿长都随着落差高度增加。这与在鸟类跨越有意外落差的跑道时观察到的结果一致，并表明摆动腿回缩的适应性是在不平地面上跑步策略的一部分。
During running in a natural environment, humans must routinely negotiate varied and unpredictable changes in ground level. To prevent a fall, changes in ground level, especially those that are invisible, require a quick response of the movement system within a short time. For 11 subjects we investigated two consecutive contacts during running across visible (drop of 0, 5 and 10 cm) and camouflaged (drop of 0 and 10 cm) changes in ground level. For both situations, we found significant variances in their leg parameters and ground reaction forces (GRFs) during the perturbed second contact but also one step ahead, in the unperturbed first contact. At visible first contact, humans linearly adapt their GRF to lower and smooth their centre of mass. During the camouflaged situation, the GRF also decreased, but it seems that the runners anticipate a drop of approximately 5-10 cm. The GRF increased with drop height during the visible perturbed second contact. At the camouflaged second contact, GRFs differed noticeably from the observed reaction when crossing a similar visible drop, whereas the contact time decreased and the initial impact peak increased. This increased impact can be interpreted as a purely mechanical contribution to cope with the event. Furthermore, we observed an increased angle of attack and leg length with drop height for both situations. This is in accordance with results observed in birds running over a track with an unexpected drop, and suggests that adaptations in swing leg retraction form part of the strategy for running across uneven ground.