Biostereometric analysis of body form: the second manned Skylab mission.

Biostereometrics is the measurement and the mathematical description of the three-dimensional form of biological objects. Stereophotogrammetry was used to derive the Cartesian coordinates of numerous points on the body surface of the Skylab crewmen, both before and after flight, on all three Skylab missions. Mathematical analysis of the coordinate description allows the computation of surface area and volume of the body, as well as the volume of body segments, and the area and shape of cross sections. Loss of body weight in the first two Skylab flight crews was accompanied by comparable loss of volume and little change in density. Volume loss wad divided about equally between the trunk and the legs; however, because the volume of the legs is less than that of the trunk, this finding represented a greater proportional volume loss in the legs. Comparison of cross-sectional areas suggests that the calf undergoes shrinkage to a greater extent than does the thigh. The suggested interpretation of these changes is that, during flight, a reduction in bulk of many of the body tissues occurs. This reduction is probably caused, at least in part, by disuse atrophy of skeletal muscles in the absence of gravity. The atrophy is lessened to some extent by the in-flight exercise program. The stereoscopic images of the crewmen from a permanent archival record of body form on which more detailed measurements may be made in the future.