NASA seeks an effective aerobic and resistive exercise device for the Constellation vehicles, in a small footprint and with minimal impact to the vehicle resources. Constellation mission scenarios will require crewmembers to transit in microgravity and live and work in partial gravity for extended periods of time, initially with missions of approximately 14 days to missions on the order of months (and years with respect to Mars). Returning ISS crewmembers continue to exhibit losses in bone density, cardiovascular capacity, and muscle strength despite the prescribed exercise prescriptions to target these losses. In order to maintain these physiological capabilities so that Constellation crewmembers can perform their mission tasks and return home safely, the device has been allocated 20 lb for mass, stowed in approximately 1 cubic foot of space, and prohibits the device from drawing electricity from the vehicle. Along with these physical limitations on the device, the vehicle's environmental control and life support system will limit aerobic and resistive exercise to 1 hour total per day for each of the 4 crewmembers.