Exposure to microgravity often leads to disorientation and decreased neuromuscular coordination upon return from prolonged missions. Immediately after landing, astronauts may have problems standing up, stabilizing their gaze, walking and turning. I've done some digging and found out. In space, astronauts lose fluid volume including up to 22% of their blood volume. Why? Because it has less blood to pump, the heart will atrophy. When gravity is taken away or reduced during space exploration, the blood tends to collect in the upper body instead, resulting in facial edema and other unwelcome side effects. This is pretty scary to think you can suffer later on in life from having exposure to microgravity.