Exercise Equipment: Neutral Buoyancy

Axial skeletal loads coupled with muscle forces maintain bone in the spine and lower extremities during International Space Station (ISS) missions. Current exercise equipment on ISS has a mass of over 300 kg and cannot provide controlled eccentric loads equal to concentric loads. Astronauts working in pairs can act as motor and controller for low maintenance exercise equipment and provide loads with most effective higher eccentric loads on exploration missions. A ground test prototype verified the exercise frame concept. A lower mass and volume exercise frame for neutral buoyancy testing will demonstrate a configuration that minimizes exercise space requirements while effectively positioning exercisers so they do not strike or interfere with each other's range of motion. The design for this prototype will be useful for International Space Station testing and  musculoskeletal health maintenance during Orion missions.

Axial skeletal loads coupled with muscle torque forces maintain bone in microgravity. Muscles generate higher eccentric forces than concentric, and eccentric loads near maximum have proven more effective than concentric loads for bone and muscle strengthening. Exercise trainers and physical therapists routinely provide higher eccentric loads when training and rehabilitating clients and patients. The exercise equipment allows use of controlled eccentric overload and provides trunk support to reduce injury potential compared to risks with current ISS resistance exercises. Maintaining relative position of astronauts so they do not interfere with each other in a small exercise volume is achieved in the frame that utilizes a back to back inverted position uniquely possible in neutral buoyancy and in microgravity. A light weight frame securing astronauts back to back and inverted will be designed, produced, and made available for neutral buoyancy testing. Ropes will slide through conduits and guides to connect foot plates that two Neutral Buoyancy Laboratory divers or astronauts push to apply opposing forces. The ground based prototype tested in 2015 identified a need for fulcrums with adjustable positions to provide lever arms most advantageous to specific exercises and to avoid interference with joint motions. Exercises will include wide and narrow leg presses, heel raises, hip flexion, and hip extension. The frame will accommodate anthropometric ranges from 5^th percentile female through 95^th percentile male, with adjustable body positions within the frame. Goal for flight hardware is 5.4 kg mass. This prototype for neutral buyancy testing is anticipated to weigh about 12 kg.