Being an astronaut is very physically demanding; the radiation and irregular blood circulation followed by fatigue because of the unnatural day and night cycles. Not to mention that up in space with miniscule gravity causes the muscles and bones to work less. Prolonged time in space causes those muscles to deteriorate. Astronauts up in the International Space Station (ISS) exercise daily to counter the effect using specialized equipment because lifting regular weights would not work. The sweat produced by the body will evaporate, ventilated and then turned into edible water by separating the salts.
