When is Running More Efficient Than Walking in a Space Suit?

In unsuited locomotion, running is more energy efficient than walking, per unit distance and mass, when gravity is less than 0.5g. We analyzed past energetics studies to evaluate whether this finding also applies to locomotion in space suits. We found least-squares fits for cost of transport [J·kg⁻¹ · m⁻¹], C, as a function of gravity. Suited C was lower for running at all gravity levels (Earth, Lunar). High suited C during walking likely results from high space suit joint torques; space suit legs, acting as springs during running, achieve low C by improving recovery. Walk-back constraints for planetary extravehicular activity are probably overly conservative and can be reduced to reflect the relative efficiency of running in space suits.