Human walking is remarkably adaptable on short and long timescales. We can immediately transition between directions and gait patterns, and we can adaptively learn accurate calibrations for different walking contexts. Here we studied the degree to which different motor patterns can adapt independently. We used a split-belt treadmill to adapt the right and left legs to different speeds and in different directions (forward versus backward). To our surprise, adults could easily walk with their legs moving in opposite directions. Analysis of aftereffects showed that walking adaptations are stored independently for each leg and do not transfer across directions. Thus, there are separate functional networks controlling forward and backward walking in humans, and the circuits controlling the right and left legs can be trained individually. Such training could provide a new therapeutic approach for correcting various walking asymmetries.
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Thanks to D. Reisman, S. Morton, J. Bastian and E. Connor for thoughtful discussions and input about these studies, and to A. Torrie for help with testing. This work was supported by US National Institutes of Health R01HD048740 and C06RR15488.
The authors declare no competing financial interests.
Animation of experiment I: test of transfer from forward to backward walking. (MOV 1208 kb)
Animation of experiment II: test of transfer from backward to forward walking. (MOV 1344 kb)
Animation of experiment III: test of dual adaptation in backward and forward walking. (MOV 1919 kb)
Animation of hybrid adaptation: hybrid-walking adaptation. (MOV 819 kb)
Animation of experiment IV: test of transfer from hybrid walking to forward and backward walking. (MOV 1843 kb)
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Choi, J., Bastian, A. Adaptation reveals independent control networks for human walking. Nat Neurosci 10, 1055–1062 (2007). https://doi.org/10.1038/nn1930
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