Long-duration spaceflight poses many hazards to the health of a space exploration crew, including physiological deconditioning of the musculoskeletal and cardiovascular systems due to prolonged exposure to microgravity. To combat these adverse physical changes, the crew is required to perform both aerobic and resistive exercises. Onboard the International Space Station (ISS), the crew has access to the Advanced Resistive Exercise Device (ARED), the Combined Operational Load Bearing External Resistance Treadmill (T2), and the Cycle Ergometer with Vibration Isolation and Stabilization System (CEVIS). These devices provide the crew with the capability to perform a wide variety of exercises.
The ability for the crew to exercise is even more important for those missions that will extend beyond low-earth orbit (LEO). Since the mission times will be lengthy, the physiologic degradation that the crew will experience is also anticipated to increase. Un fortunately, the vehicle architecture is expected to be more limiting than the ISS in terms of mass, power, and volume available for equipment, thereby eliminating the possibility of using the current ISS exercise suite for long-duration travel. The overall goal of the Advanced Exercise Concept Project is to identify possible exercise hardware suitable for long-duration space travel in severely resource-constrained environments.
Currently, there are many candidate exercise technologies and design reference missions being considered by NASA. New exercise devices are needed that can perform resistive exercise (high loads, low stroke frequency), aerobic exercise (low loads, high stroke frequency), or both with a minimization of mass and volume. The project currently is exploring ideas for power-regenerating components to take advantage of the work being performed by the operator during exercise. The minimum exercises able to be performed include squats, dead lifts, leg presses, and heel raises. Other desired exercises include hip abductions, hip adductions, narrow stance squats, leg curls, bent-over rows, upright rows, shoulder raises, shoulder presses, biceps curls, triceps extensions, and wrist curls.
For resistance exercise devices, the device should provide a high enough resistance to maintain musculoskeletal health. For traditional devices (axial loading, e.g. free-weights, weight bar), the project has been using 600-lb. loads for heel raise exercises and 500-lb. loads for squat exercises as guidelines. For aerobic exercise, the device should allow the user to sustain 75% maximum heart rate for 30 minutes, or 90% maximum heart rate for 30-second intervals.
The project team has evaluated a number of technologies, including concepts using servomotors, pneumatic cylinders, and flywheels. Novel concepts and modes of operation that do not conform to the traditional requirements stated above are encouraged.