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Logistic Risk Model for the Unique Effects of Inherent Aerobic Capacity on (+)G(sub z) Tolerance Before and After Simulated WeightlessnessSmall sample size (n less than 1O) and inappropriate analysis of multivariate data have hindered previous attempts to describe which physiologic and demographic variables are most important in determining how long humans can tolerate acceleration. Data from previous centrifuge studies conducted at NASA/Ames Research Center, utilizing a 7-14 d bed rest protocol to simulate weightlessness, were included in the current investigation. After review, data on 25 women and 22 men were available for analysis. Study variables included gender, age, weight, height, percent body fat, resting heart rate, mean arterial pressure, Vo(sub 2)max and plasma volume. Since the dependent variable was time to greyout (failure), two contemporary biostatistical modeling procedures (proportional hazard and logistic discriminant function) were used to estimate risk, given a particular subject's profile. After adjusting for pro-bed-rest tolerance time, none of the profile variables remained in the risk equation for post-bed-rest tolerance greyout. However, prior to bed rest, risk of greyout could be predicted with 91% accuracy. All of the profile variables except weight, MAP, and those related to inherent aerobic capacity (Vo(sub 2)max, percent body fat, resting heart rate) entered the risk equation for pro-bed-rest greyout. A cross-validation using 24 new subjects indicated a very stable model for risk prediction, accurate within 5% of the original equation. The result for the inherent fitness variables is significant in that a consensus as to whether an increased aerobic capacity is beneficial or detrimental has not been satisfactorily established. We conclude that tolerance to +Gz acceleration before and after simulated weightlessness is independent of inherent aerobic fitness.
Document ID
19970023973
Document Type
Reprint (Version printed in journal)
Authors
Ludwig, David A.
(North Carolina Univ. Greensboro, NC United States)
Convertino, Victor A.
(Bionetics Corp. Cocoa Beach, FL United States)
Goldwater, Danielle J.
(NASA Kennedy Space Center Cocoa Beach, FL United States)
Sandler, Harold
(NASA Kennedy Space Center Cocoa Beach, FL United States)
Date Acquired
August 17, 2013
Publication Date
November 1, 1987
Publication Information
Publication: Aviation, Space, and Environmental Medicine
Subject Category
Aerospace Medicine
Report/Patent Number
NAS 1.15:112515
NASA-TM-112515
Distribution Limits
Public
Copyright
Public Use Permitted.
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