title: Cutaneous stimulation of discrete regions of the sole during locomotion produces "sensory steering" of the foot.
abstract: BACKGROUND
  While the neural and mechanical effects of whole nerve cutaneous stimulation on human locomotion have been previously studied, there is less information about effects evoked by activation of discrete skin regions on the sole of the foot. Electrical stimulation of discrete foot regions evokes position-modulated patterns of cutaneous reflexes in muscles acting at the ankle during standing but data during walking are lacking. Here, non-noxious electrical stimulation was delivered to five discrete locations on the sole of the foot (heel, and medial and lateral sites on the midfoot and forefoot) during treadmill walking. EMG activity from muscles acting at the hip, knee and ankle were recorded along with movement at these three joints. Additionally, 3 force sensing resistors measuring continuous force changes were placed at the heel, and the medial and lateral aspects of the right foot sole. All data were sorted based on stimulus occurrence in twelve step-cycle phases, before being averaged together within a phase for subsequent analysis.
  
  
  METHODS
  Non-noxious electrical stimulation was delivered to five discrete locations on the sole of the foot (heel, and medial and lateral sites on the midfoot and forefoot) during treadmill walking. EMG activity from muscles acting at the hip, knee and ankle were recorded along with movement at these three joints. Additionally, 3 force sensing resistors measuring continuous force changes were placed at the heel, and the medial and lateral aspects of the right foot sole. All data were sorted based on stimulus occurrence in twelve step-cycle phases, before being averaged together within a phase for subsequent analysis.
  
  
  RESULTS
  The results demonstrate statistically significant dynamic changes in reflex amplitudes, kinematics and foot sole pressures that are site-specific and phase-dependent. The general trends demonstrate responses producing decreased underfoot pressure at the site of stimulation.
  
  
  CONCLUSIONS
  The responses to stimulation of discrete locations on the foot sole evoke a kind of "sensory steering" that may promote balance and maintenance of locomotion through the modulation of limb loading and foot placement. These results have implications for using sensory stimulation as a therapeutic modality during gait retraining (e.g. after stroke) as well as for footwear design and implementation of foot sole contact surfaces during gait.
authors.affiliation: Rehabilitation Neuroscience Laboratory, University Victoria, PO Box 3010 STN CSC, Victoria, BC V8W 3P1, Canada ; Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada ; Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada ; Division of Medical Sciences, University of Victoria, Victoria, BC, Canada.
authors.forename: E Paul
authors.initials: EP
authors.lastname: Zehr
authors.affiliation: Department of Integrative Physiology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nakajima
authors.affiliation: Rehabilitation Neuroscience Laboratory, University Victoria, PO Box 3010 STN CSC, Victoria, BC V8W 3P1, Canada ; Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada ; Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada.
authors.forename: Trevor
authors.initials: T
authors.lastname: Barss
authors.affiliation: Rehabilitation Neuroscience Laboratory, University Victoria, PO Box 3010 STN CSC, Victoria, BC V8W 3P1, Canada ; Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada ; Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada.
authors.forename: Taryn
authors.initials: T
authors.lastname: Klarner
authors.affiliation: Rehabilitation Neuroscience Laboratory, University Victoria, PO Box 3010 STN CSC, Victoria, BC V8W 3P1, Canada.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Miklosovic
authors.affiliation: Laboratory of Signal Processing and Motor Control, College of Physical Education, University of Brasília, Brasília, Brazil ; Biomedical Engineering Laboratory, EPUSP, PTC, University of São Paulo, São Paulo, Brazil ; Department of Health and Sports Sciences, Faculty of Education, Chiba University, Chiba, Japan.
authors.forename: Rinaldo A
authors.initials: RA
authors.lastname: Mezzarane
authors.affiliation: Nike Sport Research Laboratory, Beaverton, OR, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Nurse
authors.affiliation: Department of Health and Sports Sciences, Faculty of Education, Chiba University, Chiba, Japan.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Komiyama