The goal of the joint USSR-Cuba experiment Support was to study the support properties of the foot arch in weightlessness-induced motor changes and their prevention with the help of the Cupula Sand-501 device. Comparison of the responses of the crewmembers shows that support simulation diminished the level of many of the adverse effects of zero-g in the Cuban pilot who used the prophylactic device. It is suggested that the efficiency of the device is due to its activation of the system of support reactions. The mechanisms of the effects of weightlessness on the structure and function of the bones and joints in humans are discussed.