Koryak Y
Department of Neurophysiology, Institute of Biomedical Problems, Moscow, Russia.
Eur J Appl Physiol Occup Physiol. 1999 Jan;79(2):168-75. doi: 10.1007/s004210050491.
The effects are reported of prolonged exposure to simulated microgravity (strict bed rest in an antiorthostatic position -6 degrees head-down tilt, HDT) on voluntary and electrically evoked contractions of the triceps surae muscle in men (n = 6) and women (n = 4). The subjects served as their own controls. Bed rest is a model that has commonly been used to simulate spaceflight. Measurements made in the control condition (10-8 days before the beginning of HDT) and after 120-days of HDT (on the 3rd day after it ended) included examination of the properties of isometric maximal voluntary contractions (MVC), isometric twitch contractions (Pt) and tetanic contractions (Po). After HDT, the MVC decreased by means of 44% and 33%, P, by means of 36% and 11%, Po by means of 34% and 24%, in the men and the women, respectively. The difference between Po and MVC, expressed as a percentage of Po and referred to as force deficiency (FD), has also been calculated. The FD increased by means of 60% and 28.8% in the men and the women, respectively. Time-to-peak tension of the triceps surae muscle increased by means of 12% and 14% in the men and the women, respectively, but half-relaxation time decreased by means of 9% and 19%. Total contraction time increased by a mean of 23% in the men and decreased by a mean of 17% in the women. Force-velocity of properties of the triceps surae muscle calculated according to a relative scale of voluntary contraction development significantly decreased more in the women than the men. The calculations of the same properties of electrically evoked contraction development did not differ substantially from the initial physiological state. It can be concluded that not only were the contractile properties of the triceps surae muscle significantly different in the men and the women, but that the effects of exposure to simulated microgravity on these properties were also different. These differences may be explained by sex differences in the muscle tissue itself and in its maximal neural activation.
报告了长时间暴露于模拟微重力环境（以抗直立姿势 -6 度头低位卧床休息，HDT）对男性（n = 6）和女性（n = 4）腓肠肌自愿收缩和电诱发收缩的影响。受试者以自身作为对照。卧床休息是一种常用于模拟太空飞行的模型。在对照条件下（HDT 开始前 10 - 8 天）以及 HDT 120 天后（结束后第 3 天）进行的测量包括对等长最大自愿收缩（MVC）、等长单收缩（Pt）和强直收缩（Po）特性的检查。HDT 后，男性的 MVC 分别下降了 44%和 33%，Pt 分别下降了 36%和 11%，Po 分别下降了 34%和 24%；女性的 MVC 分别下降了 44%和 33%，Pt 分别下降了 36%和 11%，Po 分别下降了 34%和 24%。还计算了 Po 与 MVC 的差值，以 Po 的百分比表示，称为力量不足（FD）。男性和女性的 FD 分别增加了 60%和 28.8%。男性和女性腓肠肌的峰值张力时间分别增加了 12%和 14%，但半松弛时间分别减少了 9%和 19%。男性的总收缩时间平均增加了 23%，女性的总收缩时间平均减少了 17%。根据自愿收缩发展的相对尺度计算的腓肠肌力量 - 速度特性在女性中比男性显著下降得更多。电诱发收缩发展的相同特性计算结果与初始生理状态相比没有实质性差异。可以得出结论，不仅男性和女性腓肠肌 的收缩特性存在显著差异，而且暴露于模拟微重力对这些特性的影响也不同。这些差异可能由肌肉组织本身及其最大神经激活的性别差异来解释。
