Effects of Anthropometric Variability and Dimensional Change Due to Posture on Orthostatic Intolerance Garments
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Orthostatic intolerance garments (OIG) (e.g., the anti-gravity suit (AGS) worn by astronauts during earth reentry) produce therapeutic pressures on the body through inflation or through pattern reduction (i.e., undersized knit garments that stretch when donned). While pneumatic garments (AGS) are currently employed by NASA, skin-tight OIGs allow for increased mobility and could improve astronaut safety in the event of an off-nominal event. Undersized OIGs have been explored as alternatives to inflatable systems; however, they are static and designed from a series of limb circumferences taken from the standing position. Lower body radii are not fixed dimensions - but rather dynamic dimensions dependent on body posture, composition, and topography; therefore, functional pressures exerted on the body in a seated posture (i.e. during earth reentry) are unpredictable and could produce unanticipated blood pooling if radii increase. This paper serves as an investigation of the variability and dynamics of the human body in relation to OIGs. To quantify body variability due to posture change, anthropometrics from 1264 North American women were gathered from the Civilian American & European Surface Anthropometry Resource (CAESAR) database. Four circumferential measurements were collected from a sample of the CAESAR population (n=80) at the ankle, calf, knee, and thigh. A paired t-test was conducted to determine the difference between standing and sitting mean circumferences for each region of the leg. Descriptive statistics were calculated to determine the range of percentage change within the sample statistics. The study concludes that leg radii are complex and fluctuate non-uniformly from the thigh to the ankle between body postures (i.e. standing to sitting). Future OIG design will require an incorporation of anthropometric analysis to account for dimensional variability to maintain effective and predictable medically therapeutic pressure on the body.