Physiological and comfort assessment of the gravity loading countermeasure skinsuit during exercise

The microgravity environment causes physiological deconditioning in astronauts due primarily to the absence of skeletal loading. The Gravity Loading Countermeasure Skinsuit (GLCS) is a proposed countermeasure for the musculoskeletal system. The suit provides the wearer with a static load regime replicating Earth's gravity by increasing the vertical load from the shoulders to the feet. A first prototype of the GLCS was developed, and a pilot study conducted during a parabolic flight campaign resulted in reasonable suit comfort and negligible impact of mobility during basic, low-metabolic movement. However, in order for the GLCS to serve as a countermeasure in future missions, it must also be unobtrusive and comfortable during active periods of intra-vehicular activity such as exercise. Hence, the purpose of this pilot study was to gain a better understanding of the physiological and comfort responses to wearing the GLCS during simulated exercise in microgravity, using a cyclometer in the supine position (6 degrees head down tilt) with the downstroke of the cycle perpendicular to direction of gravitational acceleration. Two subjects followed an exercise cyclometer protocol with and without the skinsuit. Heart rate and respiration chest pressure rate were measured in order to assess any physiological differences while exercising in the GLCS. In addition, force plates were mounted on the pedals to record the force in the Gz axis and validate previously measured loads imposed on the feet by the suit. Qualitative feedback regarding comfort and mobility was also collected after the trials. Preliminary results from the physiological measurements showed that the suit resulted in no significant difference from the unsuited condition in any of the parameters. Comfort results showed that subjects would be able to wear the suit for up to 16 hours with only minor discomfort. These preliminary results indicate that the GLCS may be wearable during exercise, thereby reinforcing the initial design philosophy of that suit that it could be worn for extended periods inside the spacecraft. Further, the combination of static skeletal loading provided by the suit with the aerobic exercise of cycling may serve as a combined future countermeasure to spaceflight deconditioning.