Abstract As a direct consequence of exposure to microgravity, astronauts experience a set of physiological changes which can have serious medical implications when they return to earth. Most immediate and significant are the headward shift of body fluids and the removal of gravitational loading from bone and muscles, which lead to progressive changes in the cardiovascular and musculoskeletal systems. Cardiovascular adaptations result in an increased incidence of orthostatic intolerance (fainting) following flight, decreased cardiac output, and reduced capacity for exercise. Changes in the musculoskeletal system contribute significantly to impaired function experienced in the post-flight period. The underlying factor producing these changes is the absence of gravity, and countermeasures are therefore designed primarily to simulate earthlike movements, stresses, and system interactions. Exercise is one approach that has had wide operational use and acceptance in both the US and Russian space programmes, and it has enabled humans to stay relatively healthy in space for well over a year. Although it remains the most effective countermeasure currently available, significant physiological degradation still occurs. The development of other countermeasures will be necessary for missions of longer duration, for example for human exploration of Mars.

中文翻译：

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在太空中锻炼的重要性

摘要 作为暴露于微重力的直接后果，宇航员在返回地球时会经历一系列生理变化，这些变化可能会产生严重的医学影响。最直接和重要的是体液的向前移动和骨骼和肌肉的重力负荷的消除，这导致心血管和肌肉骨骼系统的逐渐变化。心血管适应导致飞行后直立不耐受（昏厥）的发生率增加、心输出量减少和运动能力降低。肌肉骨骼系统的变化显着导致飞行后时期的功能受损。产生这些变化的潜在因素是重力的缺失，因此，对策主要是为了模拟地球运动、压力和系统相互作用。锻炼是一种在美国和俄罗斯太空计划中已被广泛使用和接受的方法，它使人类能够在一年多的时间里在太空中保持相对健康。尽管它仍然是目前可用的最有效的对策，但仍然会发生显着的生理退化。对于持续时间较长的任务，例如人类对火星的探索，需要开发其他对策。尽管它仍然是目前可用的最有效的对策，但仍然会发生显着的生理退化。对于持续时间较长的任务，例如人类对火星的探索，需要开发其他对策。尽管它仍然是目前可用的最有效的对策，但仍然会发生显着的生理退化。对于持续时间较长的任务，例如人类对火星的探索，需要开发其他对策。