Larina I M, Tcheglova I A, Shenkman B S, Nemirovskaya T L
State Scientific Center for Russian Federation, Institute for Biomedical Problems, Moscow, Russia.
J Gravit Physiol. 1997 Jul;4(2):P121-2.
It is known, that exposures to real and simulated weightlessness results in pronounced reduction of the cross-sectional area (CSA) of slow-twitch(ST) and fast-twitch(FT) fibers of mammalian muscle. After space flights of various durations, head-down tilt bedrest, and 7-days of dry immersion sufficient [correction of isufficient] reductions of CSA of both fiber types were observed in man and in the majority of these cases the atrophy levels of ST and FT fibers were similar. It is well-known, that elevated contractile activities of muscle system attenuate muscle atrophy development. It remains still unclear which fiber type is more susceptible to training effects. Among physiological mechanisms involved in the process of microgravity-induced atrophy development which are supposed to be the most important are the profound decrease of a mechanical tension of muscle fibers in situ and alterations in hormonal control of muscle protein metabolism. But it is not known yet if the hormonal changes in the course of exposure to gravitational unloading match somehow the time-course of muscle fiber size reduction. The aim of the study was to investigate the time-course of muscle fiber atrophy development and changes in plasma hormone levels in the course of long-duration BR with and without high-intensity locomotor interval physical training.
众所周知，暴露于真实和模拟失重环境会导致哺乳动物肌肉慢肌纤维（ST）和快肌纤维（FT）的横截面积（CSA）显著减小。在进行不同时长的太空飞行、头低位卧床休息以及7天的干浸后，在人和大多数情况下都观察到这两种纤维类型的CSA有足够的[纠正“isufficient”为“sufficient”]减小，并且在大多数情况下，ST和FT纤维的萎缩程度相似。众所周知，肌肉系统收缩活动增强会减弱肌肉萎缩的发展。目前仍不清楚哪种纤维类型更容易受到训练效果的影响。在微重力诱导的萎缩发展过程中涉及的生理机制中，被认为最重要的是肌肉纤维原位机械张力的显著降低以及肌肉蛋白质代谢激素控制的改变。但目前尚不清楚在重力卸载过程中激素变化是否在某种程度上与肌肉纤维大小减小的时间进程相匹配。本研究的目的是调查在有和没有高强度运动间歇体育训练的长期卧床休息过程中肌肉纤维萎缩发展的时间进程以及血浆激素水平的变化。
