The Gravity Loading Countermeasure Skinsuit

The Gravity Loading Countermeasure Skinsuit (GLCS or “Skinsuit”) is an intravehicular activity suit for astronauts that has been developed to simulate some of the effects of Earth gravity. The GLCS produces a static load from the shoulders to the feet with elastic material in the form of a skin-tight wearable suit [1],[2]. This wearable system is intended to supplement exercise during future missions to the moon and Mars (where current exercise equipment may be too large and bulky for the small spacecraft) and to further attenuate microgravity-induced physiological effects in current ISS mission scenarios. 

 The GLCS targets multiple physiological systems, with proposed applications in mitigating bone loss, muscle loss, and spinal elongation. Several GLCS versions have been developed over the past decade with various design modifications (Figure 2). Previous GLCS experiments, including ground experiments, parabolic flights, and ISS flights (Expeditions 43-44, 49-52) [3], have primarily studied operational feasibility, loading magnitude, and spinal elongation attenuation [4]. Current work aims to investigate the GLCS as a countermeasure for muscle atrophy and sensorimotor deterioration [5]. The goal of this project is to use the microgravity afforded by a parabolic flight to explore a research question: How does GLCS loading affect muscle activity in postural muscles during short-term activities in 1G and reduced gravity, compared to unsuited conditions?  In the 2022 Zero-G Flight, we will more specifically explore how the GLCS affects (electromyography) EMG activity in postural muscles during resistance exercise in microgravity, compared to unsuited conditions. 

The investigation of sensorimotor effects and microgravity EMG patterns associated with the GLCS is novel (prior to ongoing research at MIT). The sensorimotor effects of microgravity are difficult to simulate on Earth, even in bed rest analogs or body-weight suspension, due to the constant force of gravity on the body and body-load receptors. Microgravity unloading affects body-load receptors, such as mechanoreceptors in the skin and muscles. In combination with adaptations in the vestibular system, sensorimotor adaptations may affect posture, locomotion, balance, and proprioception upon return to Earth [7]. Our hypothesis is that GLCS loading (including axial body load and foot pressure) will cause an increase in postural muscle activity in reduced gravity environments, partially restoring the muscle activity levels typically seen in 1G. If the hypothesis is supported in short-term analogs such as parabolic flight, this will provide an indication of potential GLCS applications in mitigating muscle atrophy due to disuse and maintaining sensorimotor function. By maintaining typical 1G motor control strategies in parallel to microgravity adaptations, we aim to move toward dual adaptation to different gravity levels, allowing astronauts to more rapidly adjust to 1G upon return to Earth.

The experimental protocol for the 2021 Zero-G flight was developed in the Fall 2020 semester in the MAS.838 course. During the flight, one participant performed arm movements (known to promote postural muscle activation), In parallel to developing an experimental protocol to answer questions about physiology, we also designed and fabricated the next-generation GLCS [5] (Figure 1). For the 2022 Zero-G, two participants performed resistive exercise, including split squats, using simple resistive exercise equipment. For both studies, experiment measurables included electromyography (EMG) and foot pressure, and the participants completed the task with and without the GLCS for comparison to typical 1-G muscle activation patterns and postural control strategies. A 1-G control condition was also collected in the lab at MIT.

This work aims to characterize the function and physiological effects of the GLCS and may elucidate short-term changes in human sensorimotor function in microgravity. Overall, the proposed work would support the goal of the GLCS project in enabling humans to adapt to multiple levels of gravity, bringing us one step closer to long-term space habitation.

[1] Waldie, J. M., & Newman, D. J. (2011). A gravity loading countermeasure skinsuit. Acta Astronautica, 68, 722–730. https://doi.org/10.1016/j.actaastro.2010.07.022

[2] Waldie, J. M., & Newman, D. J. (2014). Gravity-Loading Body Suit.

[3] D. A. Green, J. Attias, P. Carvil, P. W. Carvil, H. Rosado, J. Scott, D. Kendrick, J. Waldie, F. D. Jong, and A. Physiological, “Skinsuit - Operational and Technical Evaluation of Gravity Loading Countermeasure Skinsuit,” tech. rep., 2017. Publication Title: Erasmus Experiment Archive.

[4] R. Bellisle and D. Newman, “Countermeasure suits for spaceflight,” 2020, [Online]. Available: https://ttu-ir.tdl.org/handle/2346/86259.

[5] R. Bellisle, A. Porter, J. Waldie, C. Ortiz, A. Harvey, and D. Newman, “The Mk-7 Gravity Loading Countermeasure Skinsuit: Evaluation and Preliminary Results,” 2022 IEEE Aerospace Conference, 2022.

[6] D. P. Kendrick, The gravity loading countermeasure skinsuit: a passive countermeasure garment for preventing musculoskeletal deconditioning during long-duration spaceflight. PhD thesis, Massachusetts Institute of Technology, Cambridge, MA, 2016.

[7] English, K. L., Bloomberg, J. J., Mulavara, A. P., & Ploutz-Snyder, L. L. (2020). Exercise Countermeasures to Neuromuscular Deconditioning in Spaceflight. Comprehensive Physiology, 10, 171–196. https://doi.org/10.1002/cphy.c190005