Astronauts who are selected for spaceflights are generally healthy, but they may face a variety of medical issues during their missions, starting with motion sickness as they get used to a lack of gravity, says Michael Barratt, MD. He is one of the nation's few specialists who is dually trained and certified in both internal medicine and aerospace medicine, and he has participated in two spaceflights. Barratt, who works at the Johnson Space Center in Houston as an active astronaut, speaks  about common medical issues of space travel, which include back pain, foreign bodies in the eye, headaches and sleep difficulty. Barratt, who holds an honorary doctorate from Upstate, also discusses the short- and long-term effects of space travel.