Astronauts are subject to many possible problems due to travel in a gravity free
environment. Muscles start to waste away. Bones get brittle and the heart and lungs start
to get deconditioned.
Exercise in space has not been able to help staff keep muscle strength and mass.
Treadmills with bungee cords have been tried but the harness is uncomfortable. A lower
body negative pressure chamber has been devised to help with this problem.
The chamber is a rectangle-shaped box that forms a vacuum around the lower body. It's sealed at the waist. A pecial saddle helps the legs stay relaxed while supported.
Pressure can be lowered to reduce the force on the joints equal to 20 percent of the person's body weight.
Using this idea might be helpful with patients who need to get up and moving but can't put weight on their leg. This could apply to patients with hip and knee surgeries, amputations, and even strokes. It's not available for commercial use yet. It's still being tested for patient use.