Kinematic-specific proprioceptive stimulations to better understand sensory control of gait movements

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Complex movements of gait, i.e. gait kinematics, are associated with proprioceptive feedback coming from all muscles involved to produce these movements. This feedback, produced by self-generated movements, facilitates motor activity and is used to correct movements when it signals an error or a departure from intended movement. However, applying an artificial proprioceptive message in addition to the naturally occurring feedback did not up-to now change gait movements consistently or largely. Here, we propose that complex proprioceptive stimulation, inspired by gait kinematics, to better mimic error messages, could induce large changes of gait kinematics. We will use a unique system of multiple vibrators, developed in our lab, that can generate proprioceptive stimulations according to gait events, based on real-time kinematics and kinetics measurements. It can activate proprioception of up to 12 muscles, to reproduce sensory messages associated with complex movements such as gait. We will use it to generate a more intense proprioceptive activity with the pattern usually associated with steady-state gait, on the muscles that are lengthened or shortened during gait, on one joint or every lower-limb joints, or with a pattern inspired from kinematics a large gait perturbations such as a slip. These stimulations will be applied during steady-state gait and during unpredictable gait perturbation induced by changing the speed of one of the belts of a split-belt instrumented treadmill. We will measure and compare gait kinematics and balance and spatiotemporal parameters between conditions. We hypothesize that we will obtain the largest change in gait kinematics with stimulations reproducing more comprehensively actual proprioceptive patterns, i.e. applied on lengthening muscles of multiple joints, and during adaptive locomotion to complex gait situations such as gait perturbations. This innovative research program will help to understand the role of proprioceptive information in shaping gait movements. In the long term, we will make substantial contributions to the understanding of how proprioception can facilitate motor control and learning. It may also lead to the design of body-worn sensors and actuators for different purposes such as augmented/virtual reality, where we could change a movement at will according to the action that happens in the virtual scene, or to learn new motor skills with online movement correction, entertainment, performing arts, as well as for physical rehabilitation.