Effects of acute hypoxic exposure in extraterrestrial habitats on work performance and biomechanical parameters of manual material handling

NASA has proposed long-duration lunar and Mars habitats operate at 8.0 psia / 32 % O₂ atmosphere (the equivalent air altitude [EAA] = 1213 m) nominally with an optional depress to 7.6 psia / 32 % O₂ (EAA = 2100 m). To investigate the design extension of atmosphere for emergency scenarios and the biomechanical responses of astronauts performing physical tasks in hypobaric hypoxia, this study analyzed the work performance, upper limb muscles activation and kinematics of ten male participants during repetitive manual material handling (MMH) of 25 kg boxes to fatigue at normobaric normoxia (NN, FiO₂ = 20.9 %) and acute hypobaric moderate (MH, FiO₂ = 13.6 %) and severe (SH, FiO₂ = 11.8 %) hypoxic exposure. The results indicated a significant work performance decrement for per five MMH repetitions at SH (mean ± SD: 76.49 ± 17.47 s) compared to NN (53.09 ± 14.84 s) (P < 0.01). The normalized root mean square (RMS, %MVC) of brachioradialis and erector spinae at fatigue states was significantly higher than those during the starting stage at NN and MH (P < 0.05). The mean power frequency (MPF) of brachioradialis was significantly higher in MH and SH than that in NN (P < 0.01). Both MPF and zero crossing rate (ZCR) of brachioradialis and erector spinae muscles post-MMH were significantly reduced compared to pre-MMH (P < 0.05). Elbow flexion and upper limb acceleration remained unaffected by changes in oxygen levels and fatigue state (P > 0.05). This study provides valuable insights for the design of hypoxic atmospheres in extraterrestrial habitats, as well as for astronaut physical fatigue monitoring and safety protection.