Neutral body posture
The neutral body posture is the posture the human body naturally assumes in microgravity. Adopting any other posture while floating requires muscular effort. In the 1980s, NASA developed the Man-System Integration Standards, a set of guidelines based on anthropometry and biomechanics, which included a definition of an average typical NBP created from measurements of crew members in the microgravity environment onboard Skylab.
Later work by NASA based on research aboard Space Shuttle mission STS-57 found greater individual variations between crew members' neutral body positions than originally suggested by the earlier Skylab study. In general, three main postures were exhibited by the crew as a whole. These constituted an almost standing posture, a slightly pitched forward posture with an extreme bend at the knees, and an elongated posture with a straight neck. Differences in posture exhibited in this study could be a result of the athletic bearing of the participants or the type of exercise, or both, and the amount of exercise regularly performed. Other differences may also stem from past physical injuries such as bone breaks and knee or shoulder injuries, and from gender differences such as center of gravity. No single crew member exhibited the typical NBP called out in the MSIS standard.
