The Metabolic Cost of Walking in Simulated Martian Gravity and its Implications.

Lower body positive pressure (LBPP) is an effective way of simulating hypogravity. This study measured the submaximal VO₂, VCO₂ and heart rate when walking on an LBPP treadmill at 1G and simulated Martian gravity (0.38G). Twelve healthy subjects with a mean age ± SD of 22.75 ± 5.38 yrs took part in this study with full consent. The LBPP box used was designed and built by the Microgravity Center. The subjects walked for 8 min at a control of 1G and then for another 8 min in simulated 0.38G 2 wks later. VO₂ was 1.00 ± 0.61 L·min^-1 at 1G and 0.68 ± 0.33 L·min^-1 in the simulated 0.38G (P<0.05). Average caloric expenditure was significantly reduced at simulated Martian gravity (4.79 ± 2.80 kcal·min^-1) when compared to the control (3.37 ± 1.49 Kcal·min^-1) (P<0.05). The subjects' HR was reduced from 118.49 ± 15.07 beats·min^-1 at 1G to 106.20 ± 11.17 beats·min^-1 at simulated 0.38G (P<0.05). The average respiratory exchange ratio was significantly increased from 0.83 ± 0.13 to 1.14 ± 0.19 in simulated 0.38G (P<0.05), with no significant difference seen in VCO₂. Energy consumption was significantly decreased when walking in LBPP simulated hypogravity. Further research into LBPP physiology can be used to calibrate EVA suits and advise on exercise regimes for future astronauts. [ABSTRACT FROM AUTHOR]