Maximal and submaximal forces of slow fibers in human soleus after bed rest.
Maximal and submaximal forces of slow fibers in human soleus after bed rest.
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卧床休息后人类比目鱼肌慢纤维的最大和次最大力。
DOI：
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发表时间：
2001
影响因子：
3.3
通讯作者：
T. Yoshioka
中科院分区：
文献类型：
--
作者：
K. Yamashita;R. Okuyama;M. Honda;K. Kawasaki;K. Fujita;T. Yamada;I. Nonaka;Y. Ohira;T. Yoshioka
观察了卧床2个月和4个月对人体比目鱼肌慢纤维收缩特性的影响。卧床2个月和4个月后，平均纤维直径分别比卧床前小8%和36%。卧床2个月和4个月后，最大强直力(P(O))、单位面积最大激活力(F(Max))和半最大激活所需的游离钙离子浓度的公共对数值(PCA(50))也降低。卧床2个月和4个月后，最大无负荷短轴缩短率(V(O))增大。恢复1mo后，纤维直径、P(O)、F(Max)/CsA(P>；0.05)和PCA(50)增加，V(O)降低，接近卧床前水平。在卧床2mo时，观察每天穿着抗荷企鹅服10h进行伸膝/屈膝训练的效果，以及在放置弹性载荷元件(企鹅1号)和不放置弹性载荷元件(企鹅2号)的情况下对足底屈肌的加载和卸载效果。在企鹅1号组，卧床前后的平均纤维直径、每CSA的P(O)、F(Max)、V(O)和PCA(50)相似。然而，企鹅2号组的纤维大小和收缩性能对卧床休息的反应并未被阻止，尽管这种变化的程度小于卧床休息而没有任何对策。这些结果表明，长期卧床会导致比目鱼肌慢纤维的纤维尺寸、力量产生能力和对Ca(2+)的敏感性减小，缩短速度加快。这些数据表明，对肌肉进行持续的机械负荷，如肌肉的拉伸，是防止肌肉对重力卸载适应的有效对策。
The effects of 2 and 4 mo of bed rest, with or without exercise countermeasures, on the contractile properties of slow fibers in the human soleus muscle were examined. Mean fiber diameters were 8 and 36% smaller after 2 and 4 mo of bed rest, respectively, than the pre-bed rest level. Maximum tetanic force (P(o)), maximum activated force (F(max)) per cross-sectional area (CSA), and the common-logarithm value of free Ca(2+) concentration required for half-maximal activation (pCa(50)) also decreased after 2 and 4 mo of bed rest. In contrast, maximum unloaded shortening velocity (V(o)) was increased after 2 and 4 mo of bed rest. After 1 mo of recovery, fiber diameters, P(o), F(max) per CSA (P > 0.05), and pCa(50) were increased and V(o) decreased toward pre-bed rest levels. Effects of knee extension/flexion exercise by wearing an anti-G Penguin suit for 10 h daily, and the effects of loading or unloading of the plantar flexors with (Penguin-1) or without (Penguin-2) placing the elastic loading elements of the suit, respectively, were investigated during ~2 mo of bed rest. In the Penguin-1 group, mean fiber diameter, P(o), F(max) per CSA, V(o), and pCa(50) were similar before and after bed rest. However, the responses of fiber size and contractile properties to bed rest were not prevented in the Penguin-2 group, although the degree of the changes was less than those induced by bed rest without any countermeasure. These results indicate that long-term bed rest results in reductions of fiber size, force-generation capacity, and Ca(2+) sensitivity, and enhancement of shortening velocity in slow fibers of the soleus. The data indicate that continuous mechanical loading on muscle, such as stretching of muscle, is an effective countermeasure for the prevention of muscular adaptations to gravitational unloading.
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