Human sensitivity to gravity (on the problem of gravipreferendum)

Experiments were carried out in a centrifuge with an arm of 7.25 m, the cabin being equipped with a self-contained system of control. During an exposure to head-to-feet accelerations (+gz) of 2 g and an onset rate of 0.1 g s-1 the test subject controlled the centrifugation himself and selected the acceleration values he was instructed to attain. The subjects were shown to be capable of assessing integrally the value of accelerations and estimating it with an error of 0.1-0.12 g. During an exposure to chest-to-back accelerations (+gx) limited to a value of 12 g and a gradient of 0.3 g s-1 the ability to select actively the rate of an acceleration increase was studied. Repeated centrifugations resulted in the formation and strengthening of the skill of maintaining a physiologically optimal rate of an acceleration increase. Onset rates were determined for every level of acceleration. When calculated as a mean, physiologically optimal values of the onset rate for 12 g were 0.16-0.18 g s-1. The findings give insight into important properties of the physiological structure of "gravipreferendum", which is the capability of man to differentiate between gravity levels and to select actively optimal rates of an increase in acceleration.