Pierre Mark C, Genc Kerim O, Litow Micah, Humphreys Brad, Rice Andrea J, Maender Christian C, Cavanagh Peter R
Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
J Neuroeng Rehabil. 2006 Apr 13;3:8. doi: 10.1186/1743-0003-3-8.
Spaceflight has been shown to cause atrophy, reduced functional capacity, and increased fatigue in lower-limb skeletal muscles. The mechanisms of these losses are not fully understood but are thought to result, in part, from alteration in muscle usage.
Knee-joint angles and lower-extremity muscle activity were measured continually, via elecrogoniometry and surface electromyography respectively, from two subjects during entire working days of activity on Earth and onboard the International Space Station (ISS).
On Earth the distribution of angular positions of the knee was typically bimodal, with peaks of >75 degrees of flexion and in almost full extension (<15 degrees of flexion). However, on the ISS, a single peak in the mid-range of the available range of motion was seen. The knee joint was also moved through fewer excursions and the excursions were smaller in amplitude, resulting in a reduced span of angles traversed. The velocities of the excursions in space were lower than those used on Earth.
These results demonstrate that, in space, overall knee-joint motion is reduced, and there is a transformation in the type of muscle action compared to that seen on Earth, with more isometric action at the expense of concentric and particularly eccentric action.
航天飞行已被证明会导致下肢骨骼肌萎缩、功能能力下降和疲劳加剧。这些损耗的机制尚未完全了解，但部分原因被认为是肌肉使用方式的改变。
通过测角计和表面肌电图，分别对两名受试者在地球上和国际空间站（ISS）上整个工作日的活动过程中持续测量膝关节角度和下肢肌肉活动。
在地球上，膝关节角度位置的分布通常呈双峰模式，峰值出现在屈曲超过75度以及几乎完全伸展（屈曲小于15度）时。然而，在国际空间站上，在可用运动范围内出现了一个单一峰值。膝关节的活动次数也减少了，并且活动幅度更小，导致所经过的角度范围减小。在太空中活动的速度低于在地球上的速度。
这些结果表明，在太空中，膝关节的整体运动减少，与在地球上相比，肌肉动作类型发生了转变，等长动作增多，以向心动作尤其是离心动作减少为代价。
