Lower body adynamia as a factor to reduce the risk of hypobaric decompression sickness

Background: We define lower body adynamia (LEA) as restricted lower body mo vement, particularly walking, during both the denitrogenation phase at site pressure and during the exercise phase while at altitude. Hypothesis: Our null hypothesis is that subjects who are adynamic in the lower body but do upper body exercise will be at similar risk of decompression sickness (DCS) and venous gas emboli (VGE) as subjects who randomly walk but do no planne d exercise while at altitude. Methods: We selected a data set that containe d 1401 attitude exposures with the following conditions: a) walking was par t of the exercise at altitude; or b) there was no planned exercise done at altitude but walking was not restricted; or c) LBA was inforced, but upper body exercise was done at altitude. We used logistic regression (LR) on ail 1401 exposures, a fog logistic survival analysis (SA) on a subset of data from "a" and "c" (n = 234), and estimated a model for how the incidence of VGE changes through time. Results: The estimated probabilities of DCS and V GE with 95% confidence intervals (CIs) from the LR with a simulation of a 3 -h oxygen prebreathe, a 4-h exposure to 4.3 psia in a male, and exercise an d LBA conditions as described above are: [GRAPHICS] Conclusion: LBA that includes upper body exercise appears to be as protecti ve against DCS and VGE as random walking by subjects who did no prescribed exercise while at altitude, and is more protective than exercise that inclu ded walking. Our conclusions are based on an assumption that we have adequa tely controlled, through our data selection process and the use of multivar iable models, important variables in tests that were not done at the Johnso n Space Center.