Space Cadet

For astronauts, space travel can be demanding both mentally and physically. The human body undergoes several changes in zero gravity. As you can imagine, a person's sense of balance would be the first thing to go. This combined with the lack of pressure on any of the muscles is disorienting. Because the muscles are not needed as much, the body atrophies. The bones get weaker, too. The legs in particular get thinner. The heart usually relies on gravity to help pump blood into the legs, and without gravity, the legs get less blood flow. The upper body and head get extra blood, making the face puffy and the veins bulge. Some astronauts get sinus congestion, or they get headaches. The spine lengthens since there is no weight to compress it. This decompression sometimes causes backaches.

Still, it would have to be pretty cool to go into outer space.