The Mk-7 Gravity Loading Countermeasure Skinsuit: Evaluation and Preliminary Results

The Gravity Loading Countermeasure Skinsuit (GLCS or “Skinsuit”) is a countermeasure garment for astronauts that provides axial loading on the body. The suit simulates some effects of Earth's gravity (1G) and aims to mitigate physiological deterioration due to the unloading ‘weightlessness’ condition experienced in the microgravity environment. The GLCS has been developed over several iterations in the past decade and has been tested in participant studies on Earth, partial gravity simulations, parabolic flights, and International Space Station (ISS) missions. Further GLCS studies observing neuromuscular activity are required to explore potential muscular benefits of the GLCS, including the mitigation of muscle atrophy and motor control changes due to reduced gravity environments. Additionally, several key improvements are necessary for future Skinsuit prototypes, primarily: greater axial loading magnitude and consistency. This paper discusses GLCS design requirements, the development of the Mk-7 GLCS, and a preliminary evaluation of the Mk-7 GLCS, including an initial consideration of effects on neuromuscular activity. While limited to one participant, these initial results are vital to 1) compiling design requirements for the next GLCS iteration, and 2) proposing design changes to support applications as a neuromuscular countermeasure. Notable recommendations resulting from this study include a redesign of the GLCS stirrups to improve comfort, load consistency, donning independence, and muscle activation in key antigravity muscles of the lower leg. The shoulder yoke design and loading material stiffness will also be modified in the next version of the GLCS to improve comfort and mobility. Lastly, the initial results of the pilot study provide encouraging evidence for GLCS applications as a neuromuscular countermeasure, prompting follow-up studies with more participants in simulated reduced gravity. By improving GLCS usability and exploring its impact on human health and performance, the GLCS aims to support human spaceflight in current mission scenarios on the ISS and aid in preparation for future missions to the Moon and Mars where non-exercise countermeasures will be highly valuable to reduce mass requirements on long-duration spacecraft.