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A few years before Apollo Missions to Moon, locomotion physiologists promoted research and discussion about the potential adaptation of human body, the musculo-skeletal apparatus in particular, to an environment subject to a much smaller gravity acceleration than on Earth. Rodolfo Margaria and Giovanni Cavagna, who had just started investigating the fundamental mechanical paradigms of terrestrial locomotion, built a gravity-emulation facility in a 15 m tall vent shaft in Milano to study how jumping ability was affected by low-gravity. The combined knowledge led them to correctly predict that humans on the Moon would have walked at a very low pace and the alternative to an impaired running would have been a bouncing gait like hopping. Since then, other scientists around the world kept on researching on this subject, both experimentally and through mathematical models. Models based on ‘dynamic similarity’ (Froude Number) have confirmed that spontaneous locomotion adopted by astronauts was predictable. Recent biomechanical and metabolic experiments in the rebuilt emulation facility in Milano indicated that gaits with very different economy on Earth (running, skipping and hopping range from 2x to 10x, when compared to walking) progressively tend to have the same cost of transport when gravity decreases, and they are all alike at Moon gravity. This suggests that the energy devoted to sustain body weight represents a crucial determinant in the propulsion economy. Together with further biomechanical analysis, these data from emulated outer space are promising clues toward a better understanding of still unsolved mysteries of terrestrial locomotion (as the speed independence of metabolic cost of running).