Velocity-dependent transfer of adaptation in human running as revealed by split-belt treadmill adaptation.

Animal studies demonstrate that the neural mechanisms underlying locomotion are specific to the modes and/or speeds of locomotion. In line with animal results, human locomotor adaptation studies, particularly those focusing on walking, have revealed limited transfers of adaptation among movement contexts including different locomotion speeds. Running is another common gait that humans utilize in their daily lives and is distinct from walking in terms of the underlying neural mechanisms. The present study employed an adaptation paradigm on a split-belt treadmill to examine the possible independence of neural mechanisms mediating different running speeds. The adaptations learned with split-belt running resulted in aftereffects with magnitudes that varied in a speed-dependent matter. In the two components of the ground reaction force investigated, the anterior braking and posterior propulsive components exhibited different trends. The anterior braking component tended to show larger aftereffect under speeds near the slower side speed of the previously experienced split-belt in contrast to the posterior propulsive component in which the aftereffect size tended to be the largest at a speed that corresponded to the faster side speed of the split-belt. These results show that the neural mechanisms underlying different running speeds in humans may be independent, just as in human walking and animal studies.