Human subject evaluation of the controlled resistance exercise device (C-red) for spaceflight

Resistance exercise is an effective countermeasure to the muscle and bone atrophy associated with the unloading experienced during spaceflight. Long duration spaceflight will require compact exercise devices that are capable of delivering sufficient loading to prevent physiological losses while meeting strict mass and volume requirements. Accordingly, a controlled resistance exercise device (C-RED), developed as an advanced exercise concept for NASA, uses an electric motor for resistance and is programmed to simulate inertial loading based on barbell acceleration and desired resistance mass. The barbell acts as a movable pulley increasing efficiency by doubling the created load. Human subject testing of the functionality of the device was conducted in a laboratory at NASA’s Johnson Space Center. Subjects performed ten resistance exercises typically used by astronauts at three freely chosen load levels. The results indicate that subjects were able to perform all exercises with resistance loads that were typical to those used in the gymnasium with loads ranges of 4-1600 N, and bilateral symmetry of ground reaction force was quantified for the deadlift. A survey also was given to each subject to allow the users to express their opinions regarding the device. The subject questionnaire showed that the dumbbell attachment exercises were preferred to the barbell exercises. The positive preliminary results indicate promise for the device.