Independent effects of weight and mass on plantar flexor activity during walking: implications for their contributions to body support and forward propulsion
Independent effects of weight and mass on plantar flexor activity during walking: implications for their contributions to body support and forward propulsion
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DOI：
10.1152/japplphysiol.90448.2008
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发表时间：
2008-08-01
影响因子：
3.3
通讯作者：
Kram, R.
中科院分区：
文献类型：
--
作者：
McGowan, C. P.;Neptune, R. R.;Kram, R.
踝跖屈肌，腓肠肌（Gas）和比目鱼肌（Sol），已被证明在人类行走过程中提供身体支撑和向前推进方面发挥重要作用。然而，关于气体和溶胶对这些功能任务的相对贡献一直存在分歧。在这项研究中，使用独立的操纵体重和身体质量，我们研究了相对贡献的个人跖屈肌的支持和推进。我们假设气体和溶胶有助于身体的支持，而溶胶是主要的贡献者向前躯干推进。我们通过测量肌肉活动来测试这一假设，同时通过以下方式实验性地控制体重和质量：1）使用重量支撑系统降低体重，2）使用相等的增加躯干负荷和重量支撑的组合单独增加体重，以及3）增加躯干负荷（增加体重和质量）。这项研究的基本原理是，提供身体支撑的肌肉对体重的变化敏感，而提供向前推进的肌肉对体重的变化敏感。气体活动增加，增加负荷和重量支持下降，但只有一个小的增加，相对于对照试验时，质量单独增加。溶胶活性表现出类似的增加，增加负荷和增加质量单独和下降，在早期的立场与重量支持。因此，我们接受了这样的假设，即溶胶和气体有助于身体的支持，而溶胶是主要的贡献者向前躯干推进。
The ankle plantar flexor muscles, gastrocnemius (Gas) and soleus (Sol), have been shown to play important roles in providing body support and forward propulsion during human walking. However, there has been disagreement about the relative contributions of Gas and Sol to these functional tasks. In this study, using independent manipulations of body weight and body mass, we examined the relative contribution of the individual plantar flexors to support and propulsion. We hypothesized that Gas and Sol contribute to body support, whereas Sol is the primary contributor to forward trunk propulsion. We tested this hypothesis by measuring muscle activity while experimentally manipulating body weight and mass by 1) decreasing body weight using a weight support system, 2) increasing body mass alone using a combination of equal added trunk load and weight support, and 3) increasing trunk loads (increasing body weight and mass). The rationale for this study was that muscles that provide body support would be sensitive to changes in body weight, whereas muscles that provide forward propulsion would be sensitive to changes in body mass. Gas activity increased with added loads and decreased with weight support but showed only a small increase relative to control trials when mass alone was increased. Sol activity showed a similar increase with added loads and with added mass alone and decreased in early stance with weight support. Therefore, we accepted the hypothesis that Sol and Gas contribute to body support, whereas Sol is the primary contributor to forward trunk propulsion.