Lunar and Mars simulated extravehicular activity evoked physiological responses (882.7)

Abstract

It is currently unclear what physiological measurements from astronauts performing EVAs best indicate impending task failure. To date 7 subjects have completed a treadmill test for determination of maximal O2 uptake (V̇O2max) and two simulated EVAs at governed paces to evoke Lunar (V̇O2 ~20 ml/kg/min) and Mars (V̇O2 ~30 ml/kg/min) intensities, which have previously been reported for these environments. Subjects were separated into two groups based upon completion (COM) or failure (FAIL) of the Mars EVA. There were no significant (p > 0.05) differences between V̇O2 (Lunar COM 19.6 ± 1.3 ml/kg/min vs. FAIL 20.2 ± 0.9 ml/kg/min; Mars COM 29.9 ± 2.4 ml/kg/min vs. FAIL 30.0 ± 1.8 ml/kg/min), while FAIL %V̇O2max was significantly (p < 0.05) higher (Lunar COM 42.1 ± 3.9 % vs. FAIL 55.9 ± 1.3%; Mars COM 64.5 ± 8.5% vs. FAIL 83.1 ± 7.1%). FAIL V̇O2 rose throughout the Mars EVA until failure, while steady‐states were achieved in both groups for all other EVAs. Vastus lateralis muscle oxygenation and electromyographic data were not significantly (p > 0.05) different. These results indicate that global systemic measurements of EVA intensity are more informative of impending EVA failure than peripheral. The V̇O2 responses are characteristic of activities performed above & below critical power/speed. Thus critical speed may be vital to know for an astronaut prior to and during a mission, as EVA intensities above these will lead to task failure.Grant Funding Source: Supported by NASA Grant NNX10AK60G