Kubo K, Akima H, Ushiyama J, Tabata I, Fukuoka H, Kanehisa H, Fukunaga T
Department of Life Science, University of Tokyo, Meguro, Tokyo, Japan.
Br J Sports Med. 2004 Jun;38(3):324-30. doi: 10.1136/bjsm.2003.005595.
The purpose of this study was to investigate the effects of 20 days' bed rest on the viscoelastic properties of human tendon structures in knee extensor and plantar flexor muscles in vivo.
Eight healthy men (age: 24+/-4 years, height: 172+/-9 m, body mass: 69+/-13 kg) carried out a 6 degrees head-down bed rest for 20 days. Before and after bed rest, elongation (L) of the tendon and aponeurosis of vastus lateralis (VL) and medial gastrocnemius muscles (MG) during isometric knee extension and plantar flexion, respectively, were determined using real-time ultrasonic apparatus, while the subjects performed ramp isometric contraction up to the voluntary maximum, followed by ramp relaxation. The relationship between estimated muscle force (Fm) and tendon elongation (L) was fitted to a linear regression, the slope of which was defined as stiffness. The hysteresis was calculated as the ratio of the area within the Fm-L loop to the area beneath the load portion of the curve.
L values above 100 N were significantly greater after bed rest for VL, while there were no significant differences in L values between before and after for MG. The stiffness decreased after bed rest for VL (70.3+/-27.4 v 50.1+/-24.8 N/mm, before and after bed rest, respectively; p = 0.003) and MG (29.4+/-7.5 v 25.6+/-7.8 N/mm, before and after bed rest, respectively; p = 0.054). In addition, hysteresis increased after bed rest for VL (16.5+/-7.1% v 28.2+/-12.9%, before and after bed rest, respectively; p = 0.017), but not for MG (17.4+/-4.4% v 17.7+/-6.1%, before and after bed rest, respectively; p = 0.925).
These results suggested that bed rest decreased the stiffness of human tendon structures and increased their hysteresis, and that these changes were found in knee extensors, but not the plantar flexors.
本研究旨在调查20天卧床休息对人体膝关节伸肌和跖屈肌肌腱结构体内粘弹性特性的影响。
八名健康男性（年龄：24±4岁，身高：172±9厘米，体重：69±13千克）进行了为期20天的6度头低位卧床休息。在卧床休息前后，分别使用实时超声设备测定股外侧肌（VL）和腓肠肌内侧头（MG）肌腱和腱膜在等长膝关节伸展和跖屈过程中的伸长（L），同时受试者进行逐渐增加负荷的等长收缩直至自愿最大收缩，随后进行逐渐放松。将估计的肌肉力量（Fm）与肌腱伸长（L）之间的关系拟合为线性回归，其斜率定义为刚度。滞后现象通过Fm-L环内的面积与曲线负荷部分下方的面积之比来计算。
VL在卧床休息后的L值在100 N以上显著增加，而MG在卧床休息前后的L值无显著差异。VL在卧床休息后的刚度降低（卧床休息前后分别为70.3±27.4和50.1±24.8 N/mm；p = 0.003），MG也有降低趋势（卧床休息前后分别为29.4±7.5和25.6±7.8 N/mm；p = 0.054）。此外，VL在卧床休息后的滞后现象增加（卧床休息前后分别为16.5±7.1%和28.2±12.9%；p = 0.017），而MG则无变化（卧床休息前后分别为17.4±4.4%和17.7±6.1%；p = 0.925）。
这些结果表明，卧床休息降低了人体肌腱结构的刚度并增加了其滞后现象，且这些变化出现在膝关节伸肌中，而非跖屈肌中。
