title: Mechanical stimulation of the foot sole in a supine position for ground reaction force simulation.
abstract: BACKGROUND
  To promote early rehabilitation of walking, gait training can start even when patients are on bed rest. Supine stepping in the early phase after injury is proposed to maximise the beneficial effects of gait restoration. In this training paradigm, mechanical loading on the sole of the foot is required to mimic the ground reaction forces that occur during overground walking. A pneumatic shoe platform was developed to produce adjustable forces on the heel and the forefoot with an adaptable timing. This study aimed to investigate the stimulation parameters of the shoe platform to generate walking-like loading on the foot sole, while avoiding strong reflexes.
  
  
  METHODS
  This study evaluated this platform in ten able-bodied subjects in a supine position. The platform firstly produced single-pulse stimulation on the heel or on the forefoot to determine suitable stimulation parameters, then it produced cyclic stimulation on the heel and the forefoot to simulate the ground reaction forces that occur at different walking speeds. The ankle angle and electromyography (EMG) in the tibialis anterior (TA) and soleus (SOL) muscles were recorded. User feedback was collected.
  
  
  RESULTS
  When the forefoot or/and the heel were stimulated, reflexes were observed in the lower leg muscles, and the amplitude increased with force. Single-pulse stimulation showed that a fast-rising force significantly increased the reflex amplitudes, with the possibility of inducing ankle perturbation. Therefore a slow-rising force pattern was adopted during cyclic stimulation for walking. The supine subjects perceived loading sensation on the foot sole which was felt to be similar to the ground reaction forces during upright walking. The EMG generally increased with force amplitude, but no reflex-induced ankle perturbations were observed. The mean change in the ankle joint induced by the stimulation was about 1°.
  
  
  CONCLUSIONS
  The rate of force increase should be carefully adjusted for simulation of walking-like loading on the foot sole. It is concluded that the dynamic shoe platform provides adjustable mechanical stimulation on the heel and the forefoot in a supine position and has technical potential for simulation of ground reaction forces that occur during walking.
authors.affiliation: Institute for Rehabilitation and Performance Technology, Division of Mechanical Engineering, Department of Engineering and Information Technology, Bern University of Applied Sciences, 3400 Burgdorf, Switzerland. juanfang_jane84@126.com.
authors.forename: Juan
authors.initials: J
authors.lastname: Fang
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Vuckovic
authors.forename: Sujay
authors.initials: S
authors.lastname: Galen
authors.forename: Bernard A
authors.initials: BA
authors.lastname: Conway
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Hunt
mesh_terms: D000328:Adult; D004576:Electromyography; D005260:Female; D005528:Foot / Q000502:physiology*; D061826:Foot Orthoses; D005684:Gait / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010812:Physical Stimulation / Q000379:methods*; D012046:Rehabilitation / Q000295:instrumentation / Q000379:methods*; D012775:Shoes; D016683:Supine Position; D016138:Walking / Q000502:physiology