title: Effects of postural anxiety on the soleus H-reflex.
abstract: Previous research has proposed that spinal reflex modulation may mediate anxiety-related changes in postural control. This study investigated how soleus H-reflex amplitude was influenced by standing at heights that induced different levels of anxiety. H-reflexes were elicited in 15 participants standing at the center and edge of a platform raised from a low to a high height (with and without vision). Increased skin conductance confirmed the anxiety effect of elevated surface heights. When standing at the edge of the platform with vision, H-reflex amplitude was attenuated in the high compared to low height condition. Changes in background muscle activity could not explain observed H-reflex changes, suggesting the potential involvement of pre-synaptic inhibition or fusimotor drive on anxiety-related changes in reflex modulation. This study reveals that healthy participants reduce spinal reflex excitability in the presence of increased postural anxiety and a postural threat imposed by standing at the edge of a raised platform. These findings have implications for understanding control of standing balance in individuals with postural instability and/or fear of falling, such as the elderly or stroke.
authors.affiliation: University of Toronto, Toronto Rehabilitation Institute, 550 University Avenue Room 11019, Toronto, ON, Canada M5G 2A2. k.sibley@utoronto.ca
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Sibley
authors.forename: Mark G
authors.initials: MG
authors.lastname: Carpenter
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Perry
authors.forename: James S
authors.initials: JS
authors.lastname: Frank
mesh_terms: D000328:Adult; D001007:Anxiety; D004576:Electromyography; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D011187:Posture; D013131:Spine / Q000502:physiology*; D014785:Vision, Ocular