A new study suggests that healthy adults who get at least eight hours of sleep a night may be less likely to experience common exercise-related injuries. The study was based on information from over 7,500 United States soldiers in the Army’s Special Operations Forces. About 95 percent of the study subjects were men. The researchers found that soldiers who got no more than four to five hours of sleep a night were over two times as likely to report bone or muscle injury in the last year than those who slept eight hours or longer.