Poster P17 - Effect of Center of Gravity (CoG) shift due to Simulated Exploration Extravehicular Mobility Unit (xEMU) on Center of Pressure (CoP) Balance Parameters

Introduction: Extravehicular activity is critical to human spaceflight and it requires astronauts to wear a cumbersome spacesuit. When donning the xEMU spacesuit, there is a superior shift of Center of Gravity (CoG) on one’s torso, however, there is limited information on this affect one’s balance, or balance studies in general. Previous suit studies have focused on ergonomics and the performance of isolated suit components (e.g., joints, bearings, and gloves). However, here we aimed to investigate the research question, of how the CoG shift when wearing a simulated xEMU spacesuit affect one’s balance, quantified in terms of their Center of Pressure (CoP). Our hypothesis was that the simulated xEMU spacesuit will decrease CoP parameters indicating decreased balance ability.

Materials and

Methods: Research experiments were conducted within the Center of Biomechanical & Rehabilitation Engineering at the University of the District of Columbia (IRB Protocol ID: 1837316-1) and the Anthropometry & Biomechanics Facility at the NASA Johnson Space Center. An overview of the study is shown in Figure 1. Twelve physically fit and healthy individuals (5 males and 7 females) aged 20–40 years old (26.91 ± 6.81 years old) participated. Using a Tekscan forceplate walkway, the CoG locations were determined as well as limits of stability. Further, balance assessments were performed during standing balance test conditions with wide or tandem stances with eyes open/closed. Test configurations included unsuited, weighted with an Extravehicular Mobility Unit (xEMU) vest, and xEMU hard upper body torso (HUT), as shown in Figure 2. The center of pressure (CoP) time series was examined in terms of displacement (root mean square distance, mean distance, and total excursion), mean velocity, and mean frequency measures.

Results, Conclusions, and Discussions: The xEMU Vest led to a significant increase in mediolateral root mean square and peak to peak displceament parameters when balancing with eyes-opened/wide stance, these observed increases may be an indication of decreased stability. Total excursion, mean velocity, and mean frequency were most affected when participants donned the xEMU vest or HUT. The HUT significantly increased these parameters, however, the xEMU vest led to decreases in these parameters compared to unsuited results. For example for the total excursion, the HUT introduced a significant increase while the participants attempt to balance with their eyes-open and eyes-closed compared to un-suited (eyes-open p = 0.04, eyes-closed p = 0.015) and compared to the xEMU Vest (eyes-open p = 0.0038, eyes-closed p = 0.00059). The HUT (and potentially the xEMU spacesuits) exaggerate the CoG shift compared to the HUT, introduce instability in terms of total excursion (sum of total displacements standing), the speed of these adjustments (mean velocity), and the rate of these adjustments (mean frequency). Spacesuits introducing some level of balance instability is intuitive; however, now we are beginning to understand exactly how balance is impacted. By quantifying CoG’s effect on balance, our results form the basis for future balance and posture studies of xEMU spacesuits, as well as for other professionals that have to don heavy auxiliary equipment (e.g., warfighters and firefighters).

Acknowledgements (Optional): This research was funded by the National Aeronautics and Space Administration (NASA) award #80NSSC21K206. This research was facilitated by the National Science Foundation (NSF) grants (Award Abstracts # 2229575, 1533479, 1654474, and 1700219) and our National Institutes of Health (NIH) grant (1R25AG067896).