Changing the demand on specific muscle groups affects the walk-run transition speed
Changing the demand on specific muscle groups affects the walk-run transition speed
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DOI：
10.1242/jeb.011932
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发表时间：
2008-04-15
影响因子：
2.8
通讯作者：
Kram, Rodger
中科院分区：
文献类型：
--
作者：
Bartlett, Jamie L.;Kram, Rodger
有人提出，肌肉特异性因素触发了人类行走-奔跑的转变。我们调查了改变触发肌肉的需求是否会改变首选的步行-跑步过渡速度。我们假设(1)减少对触发肌肉的需求会提高转换速度，(2)增加对触发肌肉的需求会降低转换速度。我们首先使用随机速度顺序的步进式方案确定了正常的首选步行-跑步转换速度(PTS)。然后，当受试者带着外部设备行走时，我们确定了PTS，这些设备减少或增加了对特定肌肉群的需求。我们同时测量了腿部五块肌肉(胫前肌、比目鱼肌、股直肌、腓肠肌内侧和外侧)在每个速度和状态下的肌电活动。在这项研究中，我们开发了一种背屈肌辅助装置，帮助背屈肌。腿摆动辅助装置在脚部施加向前拉力，从而在摆动过程中帮助髋屈肌。第三种装置在重心附近施加水平力，阻碍或帮助向前推进，从而使趾屈肌超负荷或减负。我们发现，当被测肌肉中的需求减少时，PTS显著增加。相反，当足底屈肌的肌肉需求增加时，PTS下降。然而，组合辅助设备并不能产生更快的PTS。我们的结论是，改变对特定肌肉的需求可以改变首选的步行-跑步过渡速度。然而，多个外部设备缺乏求和效应，这表明另一个潜在因素最终决定了首选的步行-跑步过渡速度。
It has been proposed that muscle-specific factors trigger the human walk-run transition. We investigated if changing the demand on trigger muscles alters the preferred walk-run transition speed. We hypothesized that ( 1) reducing the demand on trigger muscles would increase the transition speed and ( 2) increasing the demand on trigger muscles would decrease the transition speed. We first determined the normal preferred walk-run transition speed (PTS) using a step-wise protocol with a randomized speed order. We then determined PTS while subjects walked with external devices that decreased or increased the demand on specific muscle groups. We concurrently measured the electromyographic activity of five leg muscles ( tibialis anterior, soleus, rectus femoris, medial and lateral gastrocnemius) at each speed and condition. For this study, we developed a dorsiflexor assist device that aids the dorsiflexor muscles. A leg swing assist device applied forward pulling forces at the feet thus aiding the hip flexors during swing. A third device applied a horizontal force near the center of mass, which impedes or aids forward progression thus overloading or unloading the plantarflexor muscles. We found that when demand was decreased in the muscles measured, the PTS significantly increased. Conversely, when muscle demand was increased in the plantar flexors, the PTS decreased. However, combining assistive devices did not produce an even faster PTS. We conclude that altering the demand on specific muscles can change the preferred walk-run transition speed. However, the lack of a summation effect with multiple external devices, suggests that another underlying factor ultimately determines the preferred walk-run transition speed.