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Session 14: Good Vibrations (SS) 10:30AM - Noon
Program Chairs: Leah Bent, PhD (University of Guelph) and Howard Hillstrom, PhD (HSS)
Conceptual, experimental and computational foot models rarely consider sensorimotor components beyond EMG and predictions of muscle force. An inability to stimulate and record responses from individual skin mechanoreceptors has significantly restricted our understanding of the link between foot sensation and foot biomechanics. However, recent developments in the motor control community demonstrate important contributions from skin sensation to gait and the potential to modify gait through sensory (e.g. vibration) rather than, or in addition to, mechanical means (e.g. orthoses). In parallel, there has been rapid growth in technologies that claim to stimulate feet for therapeutic benefit, often with minimal empirical support. It is therefore timely for the iFAB community to consider: (1) evidence to support a role for foot skin sensation in the control of foot biomechanics, balance and gait, and (2) opportunities to develop foot stimulation based interventions

Speaker 1: Dr Leah Bent (University of Guelph, Canada) will address the feasibility of foot sole skin to contribute to gait and balance; particularly the distribution and density of plantar mechanoreceptors. The physical location of mechanoreceptors and the physical characteristics of plantar skin (hardness, thickness) have implications on perceptual threshold and clinical testing techniques. The use of microneurography in parallel with other techniques weaves together the link between clinical measures of tactile and vibration thresholds and actual cutaneous afferent firing thresholds. She will aim to convince the audience that activation of foot sole mechanoreceptors really can play a role in whole body movement and control.

Speaker 2: Dr. Ryan Peters (University of Calgary, Canada) will review the relationship between plantar sensitivity, lower-limb cutaneous reflex strength, and standing balance stability in healthy adults and Parkinson’s disease patients. Given the importance of cutaneous feedback in standing balance control, a critical assessment of the effectiveness, feasibility, and physiological underpinnings of proposed therapeutic interventions is warranted. One approach are insoles that vibrate and supposedly enhance afferent sensitivity via the stochastic resonance phenomenon. Dr. Peters will finish his talk by discussing recent work examining the effect of stochastic resonance on plantar perceptual sensitivity and lower-limb cutaneous reflexes.

Speaker 3: Dr Paul Zehr (University of Victoria, Canada) will discuss evidence supporting the idea that feedback from plantar mechanoreceptors strongly influences gait parameters. In particular, cutaneous feedback from the plantar surface is an important contributor to neurorehabilitation and sensation from the dorsum is crucial to the stumbling corrective reaction. Stimulation of cutaneous nerves innervating the foot results in functionally relevant, phase- and nerve-dependent neuromechanical changes in walking parameters. Stimulation of discrete skin regions has revealed that neuromechanical responses are also topographically organized. Feedback from discrete regions of the feet contribute to ‘sensory steering’, which has implications in rehabilitation and athletic training.

Speaker 4: Dr Kristen Hollands (University of Salford, UK) will discuss her systematic review of the effects of sensory stimulating insoles in healthy older adults and neurologic patient groups. She will also present evidence for the way in which foot sensation is affected by brain injury and how impaired sensation relates to balance deficits and differences in foot biomechanics (e.g. plantar pressure, foot motion, muscle action). She will also consider how "sensory stimulating" insoles may (or may not) meet the needs of people with stroke and whether or not these devices meet the wishes of patients (gathered through qualitative patient studies).

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