title: Soleus H-reflex modulation in response to change in percentage of leg loading in standing after incomplete spinal cord injury.
abstract: Body weight support (BWS) is frequently used to retrain standing and walking in persons post spinal cord injury (SCI), but the effects of leg unloading using BWS on H-reflex excitability in this population are unknown. The purpose of the study was to assess the effect of two different loading conditions on soleus H-reflex while standing in persons with motor incomplete SCI (i-SCI) and non-injured persons. Eight persons with motor i-SCI (mean age 50.25 years) and five non-injured persons (mean age 48.6 years) participated in the study. Specific control of the loading conditions was achieved using a BWS system. To compare reflex modulation at 40% versus 0% BWS, soleus H-reflexes were evoked during standing and normalized to the maximum M wave amplitude. These studies revealed that (1) H-reflex excitability is significantly greater after SCI and is exhibited even during quiet standing; and (2) no significant modulation in reflex excitability was observed by change in loading conditions in either the non-injured or the i-SCI subjects. These findings suggest that non-injured persons and persons with i-SCI respond similarly to bilateral limb unloading during standing with no change in H-reflex amplitude. Our results suggest that BWS of up to 40% does not produce detectable changes in the excitability of the soleus H-reflex in persons with i-SCI.
authors.affiliation: Department of Physical Therapy, University of Florida, P.O. Box 100154, Gainesville, USA.
authors.forename: Chetan P
authors.initials: CP
authors.lastname: Phadke
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Wu
authors.forename: Floyd J
authors.initials: FJ
authors.lastname: Thompson
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Behrman
mesh_terms: D000328:Adult; D006181:H-Reflex; D006801:Humans; D007866:Leg / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D013124:Spinal Injuries / Q000503:physiopathology*; D016474:Weight-Bearing