title: Enhancement of arm and leg locomotor coupling with augmented cutaneous feedback from the hand.
abstract: Cutaneous feedback from the hand could assist with coordination between the arms and legs during locomotion. Previously we used a reduced walking model of combined arm and leg (ARM&LEG) cycling to examine the separate effects of rhythmic arm (ARM) and leg (LEG) movement. Here we use this same paradigm to test the modulation H-reflexes with and without interlimb cutaneous conditioning evoked by stimulating a nerve innervating the hand (superficial radial, SR). It was hypothesized that both ARM and LEG would contribute significantly to suppression of H-reflex amplitude during ARM&LEG. We also predicted a conservation of interlimb cutaneous conditioning during movement and an interaction between arm and leg rhythmic movement control. Subjects were seated in a recumbent ARM&LEG cycle ergometer and maintained a low-level soleus contraction for all tasks. H-reflex amplitude was facilitated by cutaneous conditioning evoked by stimulation of the SR nerve. H-reflex amplitudes were taken from recruitment curves and included modulation of 50% H max and H max. The suppressive effect of arm was less than that for LEG and ARM&LEG, while suppression during LEG and ARM&LEG were generally equivalent. For H-reflexes conditioned by cutaneous input, amplitudes during ARM&LEG instead were in between those for ARM and LEG modulation. Multiple regression analysis revealed a significant contribution for arm only in trials when SR stimulation was used to condition H-reflex amplitudes. We suggest that there is a measurable interaction between neural activity regulating arm and leg movement during locomotion that is specifically enhanced when cutaneous input from the hand is present.
authors.affiliation: Rehabilitation Neuroscience Laboratory, PO Box 3010 STN CSC, University of Victoria, Victoria, BC V8W 3P1, Canada. pzehr@uvic.ca
authors.forename: E Paul
authors.initials: EP
authors.lastname: Zehr
authors.forename: Marc
authors.initials: M
authors.lastname: Klimstra
authors.forename: Katie
authors.initials: K
authors.lastname: Dragert
authors.forename: Yasaman
authors.initials: Y
authors.lastname: Barzi
authors.forename: Mark G
authors.initials: MG
authors.lastname: Bowden
authors.forename: Bahar
authors.initials: B
authors.lastname: Javan
authors.forename: Chetan
authors.initials: C
authors.lastname: Phadke
mesh_terms: D000328:Adult; D001132:Arm / Q000294:innervation*; D005246:Feedback; D005260:Female; D006181:H-Reflex; D006225:Hand / Q000294:innervation*; D006801:Humans; D007866:Leg / Q000294:innervation*; D008124:Locomotion / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D009043:Motor Activity / Q000502:physiology*; D012867:Skin / Q000294:innervation*