title: An electrohydraulic actuated ankle foot orthosis to generate force fields and to test proprioceptive reflexes during human walking.
abstract: The control of human walking can be temporarily modified by applying forces to the leg. To study the neural mechanisms underlying this adaptive capacity, a device delivering controlled forces and high-velocity displacements to the ankle was designed. A new solution, involving a closed circuit hydraulic system composed of two cylinders (master-slave) mutually connected by hoses and controlled by an electric motor was preferred over classical mechanical/electrical approaches. The slave cylinder delivers desired torques to the ankle using a light weight, custom-designed ankle-foot orthosis. This electrohydraulic orthosis (EHO) can produce several types of force fields during walking, including constant, position-dependent, and phase-dependent. With phase-dependent force fields, active torque cancellation maintains low-residual torques ( < or = 1.85 Nm root mean square) outside of the zone of force application for walking speeds ranging from 0.2 to 4.5 km/h. Rapid ankle stretches/unloads ( > 200 degrees/s) can also be produced alone or during force field application, and elicited proprioceptive reflexes in ankle muscles. In conclusion, the EHO is capable of delivering controlled force fields and of activating proprioceptive reflexes during human walking. It will provide the flexibility needed to test the adaptability of healthy and pathological gait control, and to address some of its underlying neural mechanisms.
authors.affiliation: Centre for Interdisciplinary Research in Rehabilitation and Social Integration (CIRRIS), Québec, QC, G1M 2S8 Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Noël
authors.forename: Benoit
authors.initials: B
authors.lastname: Cantin
authors.forename: Sébastien
authors.initials: S
authors.lastname: Lambert
authors.forename: Clément M
authors.initials: CM
authors.lastname: Gosselin
authors.forename: Laurent J
authors.initials: LJ
authors.lastname: Bouyer
mesh_terms: D000328:Adult; D000842:Ankle / Q000294:innervation* / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008875:Middle Aged; D009989:Orthotic Devices; D010808:Physical Examination / Q000295:instrumentation*; D010812:Physical Stimulation / Q000295:instrumentation; D011434:Proprioception / Q000502:physiology*; D013314:Stress, Mechanical; D016138:Walking / Q000502:physiology*