Zero gravity does have problems, but, there is a solution. A tourniquet will keep blood flowing in the limbs. It can be any color, and is printed in any stretchy and flexible material, like rubber or flexible nylon. It is a long and narrow rectangle, that is ⅛ inches thick. When an astronaut comes back to Earth after having almost no blood in their limbs, the muscles are less healthy and weaker. Keeping blood flow in them will keep them strong and healthy. Astronauts have invented cuffs to keep blood down with, but they are uncomfortable. This will be soft and stretchy. It is less than 6 inches, so it will need to be tied to other ones. It can not be worn for more than 4 hours. Take it off for 10-15 minutes, then you can put it back on but in a different place. Doctors say that leaving it on for more than four hours will damage the tissue it is pushing on. The best way to put it on is to get blood circulating in the limb, then have a fellow astronaut attach the tourniquet for you.