The lack of gravity in space reduces the mechanical loading seen by both the muscles and bones of the body, especially those related to standing and moving. The body adapts to reduced loading by losing bone mass and muscle mass. In long duration space flights this leads to "disuse atrophy" which requires rehabilitation once the astronauts return to earth. An astronaut may lose as much as 20% of their bone mass in a single year in space. A countermeasure therapy using passive vibration for neuromusculoskeletal stimulation was originally designed by Dr. Jeff Leismer, to enable longer space flights by reducing atrophy. The therapy is now being used to help terrestrial patients with impaired mobility to regain strength and function.