Mechanisms underlying the energy optimization of human walking

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For many people, walking is something done every day, without much thought and with relative ease. People can gracefully adapt their gait to changing terrains, task demands, and constraints on their body. Yet, how the nervous system navigate the expanse of all possible movements, to rapidly arrive at what appears to be an optimal coordination strategy, is largely unknown. We have recently determined that an important objective in the real-time selection of our gait is energy minimization-people tend to walk in ways that minimize their metabolic energy expenditure. Here, we are interested in understanding how this energy optimization is accomplished by the nervous system. To do so, we will combine human walking experiments with a computational reinforcement learning model, to systematically investigate the energy optimization process. Specifically, we will investigate how three factors can facilitate or disrupt one's ability to optimize their gait, including i) variability in gait (i.e. the stride to stride changes in walking coordination); ii) saliency of the energetic consequences of gait (i.e. the ease with which one can sense changes in energy expenditure); and iii) constancy of the energetic consequences of gait (i.e. how frequently the energetic consequences of walking are changing). In each case, we will perturb the walking person or environment to exaggerate one of these factors and then study how rapidly, or if at all, the walking person can converge on the energy optimal gait. Finally, we will build a system that leverages this understanding to augment a walking persons optimization process-prescribing changes to gait that will allow them to more rapidly converge on the energy optimal solution. The proposed research will provide a basic and foundational understanding of how the human nervous system so elegantly performs energy optimization during walking. This has a number of broad implications for Canadian research and innovation, including: understanding gait adaptations that accompany ageing or injury; designing rehabilitation programs that consider the nervous systems internal objectives; designing assistive technologies that work in concert with the user to augment movement; and expediating locomotor skill learning. In addition, this research program will provide a rich training environment for cross-disciplinary undergraduate and graduate students, equally prepared to benefit the future of Canadian research and innovation through careers in either academia or industry.