Koryak Y A
Department of Neurophysiology, Institute of Biomedical Problems, Moscow, Russia.
Aviat Space Environ Med. 1998 Aug;69(8):766-70.
The effect of a 120-d 6 degrees head-down tilt bed rest on the functional properties of the human triceps surae muscle have been studied in a group of male volunteers (n = 6), mean age 38 +/- 2 yr. According to tendometry measurements, maximum voluntary contraction and maximum strength in response to a nerve stimulation at a frequency of 150 impulses s(-1) after head-down tilt decreased by 45.5% and 33.7%, respectively (p < 0.05-0.01), and maximal twitch declined by 36.7% (p < 0.05). The magnitude of force deficiency increased by 60.2% (p < 0.001). Time to peak tension, half-relaxation time and total contraction time of twitch increased (p < 0.05-0.001); the maximum rate of rise of isometric tetanic tension as absolute tension exerted by the triceps surae muscle in response to an electrical stimulation of the motor nerve and during voluntary contraction performed on command to contract quickly and strongly decreased. With force expressed as a percentage of the maximum developed, the force-time curves did not alter significantly. A post head-down tilt fatigability index of the triceps surae muscle was to 0.61 +/- 0.02 as opposed to 0.80 +/- 0.03 prior to an exposure (p < 0.05). It is postulated that changes of contractile properties of the triceps surae muscle head-down tilt are linked to the atrophic processes, alterations of muscle length and the state of sarcoplasmic reticulum on the one hand, and to the altered state of the central nervous system, on the other.
在一组平均年龄为38±2岁的男性志愿者（n = 6）中，研究了120天6°头低位卧床休息对人小腿三头肌功能特性的影响。根据张力测定结果，头低位倾斜后，最大自主收缩以及对频率为150次/秒的神经刺激产生的最大力量分别下降了45.5%和33.7%（p<0.05 - 0.01），最大单收缩下降了36.7%（p<0.05）。力量不足的幅度增加了60.2%（p<0.001）。单收缩的峰值张力时间、半松弛时间和总收缩时间增加（p<0.05 - 0.001）；小腿三头肌在运动神经电刺激和快速强力自主收缩指令下产生的等长强直张力的最大上升速率作为绝对张力下降。以最大发力的百分比表示力量时，力量 - 时间曲线没有显著变化。小腿三头肌头低位倾斜后的疲劳指数为0.61±0.02，而暴露前为0.80±0.03（p<0.05）。据推测，小腿三头肌头低位倾斜时收缩特性的变化一方面与萎缩过程、肌肉长度改变和肌浆网状态有关，另一方面与中枢神经系统状态改变有关。
