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Allometry Allometry
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Balance and Perception Balance and Perception
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Bone and Muscle Bone and Muscle
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Weightlessness and the White Blood Cell Weightlessness and the White Blood Cell
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Cite
Abstract
This chapter discusses the physical effects of microgravity. Microgravity was originally predicted to have a major effect on balance and perception, given the spatial disorientation experienced by pilots of high-performance aircraft and airsickness in aircrews. However, the inner ear adapts surprisingly well to microgravity in a few days. The loss of bone and muscle is another concern. Measurements of the bone density of astronauts before and after visits to the International Space Station (ISS) have shown that the rate of bone loss in the pelvis and lower spine is about 1 to 1.5 percent per month. Bone loss is such a concern because of the higher risk of fractures after long missions. Astronauts also lose muscle mass during spaceflight, and this wasting or atrophy begins in just a few days. Without exercise, the wasting continues until the astronaut loses 30 to 50 percent of her muscle mass. The affected muscle groups are mainly the postural or antigravity muscles, which are involved in standing, walking, and lifting, especially in limb extension rather than flexion.
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