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[\/vc_column_text][\/vc_column][vc_column width=”3\/4″][vc_column_text]The human body is uniquely designed to live in Earth\u2019s gravity. In space, the body begins to adapt to the microgravity environment.<\/p>\n
NSBRI\u2019s science and technology\u00a0program is addressing ways to reduce or eliminate many of the changes to the body that impact an astronaut\u2019s ability to perform well in space and that might impact their health after returning to Earth. The NSBRI program also looks at ways to enhance countermeasures already in place on long missions.<\/p>\n
Here\u2019s a quick introduction to how the body reacts to life in space.<\/p>\n
Bones<\/strong> Muscles<\/strong> Fluid Shift Cardiovascular System<\/strong> The Spine: Taller in Space<\/strong> Inner Ear and Balance System<\/strong> Sleep and Performance<\/strong>
\nIn microgravity, astronauts no longer walk to get to different parts of the spacecraft, they float. This means that the bones in the lower part of the body that typically bear weight \u2013 the legs, hips and spine \u2013 experience a significant decrease in load bearing. This reduction leads to bone breakdown and a release of calcium, leaving the bone more brittle and weak. The release of calcium can also increase the risk of kidney stone formation and bone fractures. To put it in perspective, postmenopausal women who are untreated for bone loss can lose 1 to 1.5 percent of bone mass in the hip in one year while an astronaut can lose the same amount of hip bone mass in a single month. On missions outside Earth\u2019s orbit, radiation exposure may also impact bone loss.<\/p>\n
\nExtended spaceflight results in less work for the legs and back. As a result, the muscles can begin to weaken or atrophy, and this could lead to fall-related injuries and accidents during exploration missions. Astronauts currently exercise to help maintain their muscle mass, but nutritional interventions designed to reduce the muscle loss may one day be added as a complement to the exercise program.<\/p>\n
\n<\/strong>In space, blood is redistributed with a little more in the upper part of the body and a little less in the lower extremities. While in space, astronauts often have a puffy face due to this fluid shift and legs that are smaller in circumference. The fluid shift to the head can also lead to a feeling of congestion.<\/p>\n
\nAlthough the cardiovascular system generally functions well in space, the heart doesn\u2019t have to work as hard in the microgravity environment. Over time, this could lead to deconditioning and a decrease in the size of the heart. There is also a concern that space radiation may affect endothelial cells, the lining of blood vessels, which might initiate or accelerate coronary heart disease.<\/p>\n
\nAstronauts get a bit taller in space. On Earth, the disks between the vertebrae of the spinal column are slightly compressed due to gravity. In space, that compression is no longer present causing the disks to expand. The result: the spine lengthens, and the astronaut is taller. One possible side effect is back pain that may be associated with the lengthening of the spine.<\/p>\n
\nOn Earth, a complex, integrated set of neural circuits allows humans to maintain balance, stabilize vision and understand body orientation in terms of location and direction. The brain receives and interprets information from numerous sense organs, particularly in the eyes, inner ear vestibular organs and the deep senses from muscles and joints. In space, this pattern of information is changed. The inner ear, which is sensitive to gravity, no longer functions as designed. Early in the mission, astronauts can experience disorientation, space motion sickness and a loss of sense of direction. Upon return to Earth, they must readjust to Earth\u2019s gravity and can experience problems standing up, stabilizing their gaze, walking and turning. These disturbances are more profound as the length of microgravity exposure increases. The changes can impact operational activities including approach and landing, docking, remote manipulation, extravehicular activity and post-landing normal and emergency egress.<\/p>\n
\nMany factors \u2013 the loss of a 24-hour day\/light cycle, a confined environment and work demands \u2013 can impact an astronaut\u2019s ability to work well in space. In addition, exploration crews will have to shift their \u201cbody clocks\u201d from the Earth day\/night cycle to that of their destination. Scientists hope to help the crew increase their alertness and reduce performance errors through improvements to spacecraft lighting, sleep schedules and the scheduling of work shifts.<\/p>\n