WHAT HAPPENS TO A PERSON TRAVELING IN SPACE? The zero-gravity environment of space offers many challenges to astronauts. One of them is bone and muscle loss. With no gravity to pull people down, there's no need to use muscles and bones to hold the body upright. Both systems weaken, which is why NASA established exercise programs for astronauts spending long periods of time in the International Space Station. Despite these efforts, astronauts still lose muscle strength and bone density, which is why they require physical therapy on Earth after lengthy stays in orbit.
DON'T STAY TOO LONG: The vastness of space may tempt scientists and space tourists alike to remain in space for months or longer, but that might not be a wise choice. Living in the weightless conditions of space can lead to atrophying muscles and bone loss. Engineers at NASA built an enhanced zero-gravity space station treadmill for their astronauts and continue to use earth-borne simulators to mimic the impact loads an astronaut would experience. Those efforts are intended to limit the muscle damage to astronauts and encourage them to stay active in space.