The Influence of Robotic Assistance on Reducing Neuromuscular Effort And Fatigue During Extravehicular Activity Glove Use

The multi-layered, pressurized space suit glove worn by Extravehicular Activity (EVA) crew members during missions induces hand and forearm fatigue. The Spacesuit RoboGlove (SSRG), a Phase VI EVA glove modified with robotic grasp-assist capabilities, has been developed to improve endurance and reduce the risk of injury in astronauts by augmenting grip strength. The overall goals of this study were to i) quantify the neuromuscular modulations that occur in response to wearing a conventional Phase VI EVA glove (SSG) during a fatiguing task, and ii) determine the efficacy of Spacesuit RoboGlove (SSRG) in reversing undesirable modulations and restoring altered muscular activity to barehanded levels. Six subjects performed a fatigue sequence consisting of repetitive dynamic-gripping interspersed with isometric grip-holds under three conditions: barehanded, wearing pressurized SSG, and wearing pressurized SSRG. Surface electromyography (sEMG) from six forearm muscles and subjective fatigue ratings were collected during each condition. Trends in amplitude and spectral distributions of the sEMG signals were used to derive metrics quantifying neuromuscular effort and fatigue that were compared across the glove conditions. Results showed that the SSRG successfully reduced the neuromuscular effort needed to close the fingers of the space suit glove in more than half of subjects. However, the SSRG required more neuromuscular effort to extend the fingers compared to a conventional SSG in many subjects. Psychologically, the SSRG aided subjects in feeling less fatigued during short periods of intense work compared to the SSG. These results reveal the potential benefits of SSRG in improving astronaut performance and reducing the risk of injury by offsetting neuromuscular effort. Modifications to the experimental protocol are needed, however, to determine the effectiveness of SSRG in reducing astronaut fatigue. Nevertheless, these findings will enhance the understanding of astronaut-spacesuit interaction and help to improve the design of spacesuit gloves and robotic-assist devices, such as SSRG.