ABSTRACT
Muscle is the second component of the locomotion system. As was found to be the case for bone, it is not surprising to discover that weightlessness induces alterations when the weight of the astronaut’s body and surrounding objects disappears in the absence of gravity. Hence the amusing scene where an astronaut is performing a series of push-ups perfectly effortlessly! However, joke aside, the space environment results in such reduced activity that a space mission leads to significant changes in muscle mass and functional properties. As in the case of bone tissue, it seems useful to give a short overview of muscle structure and physiology in order to have a better understanding of the effects of microgravity on the muscle system.
