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In microgravity, without the continuous load of Earth\u2019s gravity, the tissues that make up bones reshape themselves. Bone cells readjust their behaviors\u2014the cells that build new bone slow down, while the cells that break down old or damaged bone tissue keep operating at their normal pace so that breakdown outpaces growth, producing weaker and more brittle bones. For every month in space, astronauts\u2019 weight-bearing bones become roughly 1% less dense if they don\u2019t take precautions<\/a> to counter this loss.\u00a0 Muscles, usually activated by simply moving around on Earth, also weaken because they no longer need to work as hard. This loss of bone and muscle is called atrophy.<\/p>\n Atrophy has serious implications for astronaut health. On Earth, muscle and bone loss or atrophy also occur from normal aging, sedentary lifestyles, and illnesses. This may cause serious health issues from injuries due to falls, osteoporosis, or many other medical problems.<\/p>\n While researchers understand broad causes of atrophy, they continue to investigate the fundamental mechanisms and contributing factors of microgravity-induced muscle and bone atrophy. Much research focuses on determining the right combination of diet, exercise, and medication to keep astronauts healthy during missions and when they return to Earth or set foot on the Moon or Mars.<\/p>\nExercise & Forces<\/strong><\/h2>\n
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