Suzuki Y, Murakami T, Haruna Y, Kawakubo K, Goto S, Makita Y, Ikawa S, Gunji A
Department of Health Administration, Faculty of Medicine, University of Tokyo, Japan.
Acta Physiol Scand Suppl. 1994;616:5-18.
Sedentary voluntary students were exposed to 10 (n = 8) and 20 (n = 14) days bed rest to study effects of prolonged bed rest on isometric strength of knee extension and flexion, total leg strength, right hand grip and elbow flexion using different dynamometers. Further, muscle mass of right leg and arm was measured by dual energy X-ray absorptiometry, and cross sectional area of right thigh by X-ray computed tomography before and after bed rest and after 4 or 8 weeks of recovery. After 10 days bed rest, these variables tended to decrease except for the muscle mass of right arm which increased. After 20 days of bed rest, a similar trend was observed, but at a statistically significant level of p < 0.05. However, no correlation was observed between the decrease in knee extensor strength and cross sectional area of the thigh. Nor was a correlation observed between the sum total of isometric strength of the leg and the total muscle mass measured. The 24h urinary excretion of N2 and creatinine was not changed through the experiments. During recovery, the variables measured had reached the initial levels after 4 or 8 weeks. These changes were not affected by mild supine exercise training. The results suggest that isometric muscle strength was decreased in non-antigravity muscles as well as antigravity muscles by prolonged bed rest, but the rate of changes did not correlate to the corresponding changes in muscle mass. The decreases in maximum voluntary strength are probably not only due to the decrease in muscle mass but also due to reductions of neuromuscular function.
让久坐不动的学生分别接受10天（n = 8）和20天（n = 14）的卧床休息，以研究长期卧床休息对使用不同测力计测量的膝关节伸展和屈曲等长力量、腿部总力量、右手握力和肘部屈曲的影响。此外，在卧床休息前后以及恢复4周或8周后，通过双能X线吸收法测量右腿和右臂的肌肉质量，通过X线计算机断层扫描测量右大腿的横截面积。卧床休息10天后，除右臂肌肉质量增加外，这些变量均呈下降趋势。卧床休息20天后，观察到类似趋势，但在统计学上具有显著意义，p < 0.05。然而，未观察到膝关节伸肌力量下降与大腿横截面积之间的相关性。腿部等长力量总和与测量的总肌肉质量之间也未观察到相关性。实验期间，N2和肌酐的24小时尿排泄量未发生变化。在恢复过程中，测量的变量在4周或8周后达到初始水平。这些变化不受轻度仰卧位运动训练的影响。结果表明，长期卧床休息会使非抗重力肌肉和抗重力肌肉的等长肌力均下降，但变化率与肌肉质量的相应变化无关。最大随意力量的下降可能不仅是由于肌肉质量的减少，还由于神经肌肉功能的降低。
