Fitts R H, Brimmer C J
J Appl Physiol (1985). 1985 Sep;59(3):916-23. doi: 10.1152/jappl.1985.59.3.916.
Contractile properties of slow-twitch soleus (SOL), fast-twitch extensor digitorum longus (EDL), and fast-twitch superficial region of the vastus lateralis were determined in vitro (22 degrees C) in rats remobilized after prolonged (3 mo) hindlimb immobilization (IM). For all muscles the muscle-to-body weight ratio was significantly depressed by IM, and the ratios failed to completely recover even after 90 days. The contractile properties of the fast-twitch muscles were less affected by IM than the slow-twitch SOL. The IM shortened the SOL isometric twitch duration due to a reduced contraction and half-relaxation time. These parameters returned to control levels by the 14th day of recovery. Peak tetanic tension (Po, g/cm2) declined with IM by 46% in the SOL but showed no significant change in the fast-twitch muscles. After IM the SOL Po (g/cm2) recovered to control values by 28 days. The recovery of Po in absolute units (g) was considerably slower and did not return to control levels until 60 (SOL) to 90 (EDL) days. The maximum shortening velocity was not altered by IM in any of the muscles studied. These results demonstrate that both fast- and slow-twitch skeletal muscles possess the ability to completely recover normal contractile function following prolonged periods of hindlimb IM.
在体外（22摄氏度）测定了长期（3个月）后肢固定（IM）后再活动的大鼠的慢肌比目鱼肌（SOL）、快肌趾长伸肌（EDL）以及股外侧肌快肌表层区域的收缩特性。对于所有肌肉而言，肌肉与体重的比值因后肢固定而显著降低，即使在90天后这些比值也未能完全恢复。快肌的收缩特性受后肢固定的影响小于慢肌比目鱼肌。后肢固定使比目鱼肌等长收缩时的收缩时间和半松弛时间缩短，从而导致其等长收缩时的抽搐持续时间缩短。这些参数在恢复的第14天恢复到对照水平。比目鱼肌的强直收缩峰值张力（Po，g/cm²）因后肢固定而下降了46%，但快肌未出现显著变化。后肢固定后，比目鱼肌的Po（g/cm²）在28天时恢复到对照值。以绝对单位（g）表示的Po的恢复则相当缓慢，直到60天（比目鱼肌）至90天（趾长伸肌）才恢复到对照水平。在所研究的任何肌肉中，最大缩短速度均未因后肢固定而改变。这些结果表明，快肌和慢肌骨骼肌肉在长时间后肢固定后均具有完全恢复正常收缩功能的能力。
