Effects of walking, running, and skipping under simulated reduced gravity using the NASA Active Response Gravity Offload System (ARGOS)

Past research efforts have focused on the energy difference between altered locomotion methods in reduced gravity at different speeds, suggesting that skipping is energetically more efficient than walking and running in these environments. While skipping may be more beneficial from an energy standpoint, the full range of reasons behind the gait transition and locomotion selection have not been researched. This includes damage to the leg muscles, which is partially prevented by a transition from walking to running locomotion methods known as the walk-run transition. In a space environment, these factors will play a role in astronaut health and injury prevention. Participants walked, ran, and skipped on a treadmill for this study while being supported by an analog for activity on other planets called the Active Response Gravity Offload System (ARGOS). These intervals were performed under 1g, then under simulated 0.38g, and 0.17g conditions to simulate gravity conditions on Mars and the Moon. Electromyography was used to monitor muscle activation, along with the Vicon motion capture system for 3D motion analysis. Results show that there are significant changes (p < 0.05) in activation of the TA and MG under simulated Martian and Lunar gravity conditions, as well as significant changes (p < 0.05) in dorsiflexion and plantar flexion under several conditions. These findings suggest that there are fundamental changes in the way humans move in these reduced gravity environments and that the effect these changes have on the body should be included in the development of astronaut training regimen and equipment development. These changes may affect safety issues associated with locomotion, including increased trip and fall risks. Additionally, the reduction of energy expenditure demonstrated in this study, as well as detrimental effects from gait asymmetry on muscle growth, may prove to be counterproductive to efforts meant to reduce muscle and bone degradation in reduced gravity environments. The efficacy of running or skipping as preferred methods of locomotion in reduced gravity environments are yet to be sufficiently supported by gait analysis.