Self-Powered Microgravity Resistance Exercise with Soft Pneumatic Exoskeletons

As preparations continue towards sending humans on a 3-year mission to Mars, space programs must find solutions to combat muscular atrophy experienced by astronauts during extended time in microgravity. One method currently used to combat muscle deterioration is daily resistance training sessions using an apparatus like the ARED or CEVIS exercise devices, but these daily exercise sessions are not expected to be enough to protect the muscles during longer missions. To help combat muscular atrophy, we propose self-resistance outside of the daily exercise sessions implemented through soft pneumatic exoskeletons that could be integrated into astronauts' suits, augmenting the formal exercise regimen to improve astronaut health during lengthy missions. To test the effects of self- resistance on muscle activity, we developed an elbow-elbow soft exoskeleton which we pressurized with air and connected to a closed fluid circuit so that as the user flexed their elbows, they were forced to work against themselves (self-resistance) via this column of air. In order to determine the effect of self-resistance, bicep muscle activity (obtained via surface electromyography) was recorded during horizontal motions with self-resistance and during both vertical and horizontal motions without self- resistance. Peak muscle activity and its variability both increased when self-resistance was applied, and correspondence between peak muscle activity and pressure indicates that the level of resistance could be tuned to achieve loads comparable to gravity. This soft pneumatic exoskeleton has the potential for easy integration into astronauts' suits and could reduce muscle deterioration in microgravity by engaging the muscles more consistently via self-resistance during daily tasks rather than only during specific exercise sessions.