title: The effects of circumferential air-splint pressure on flexor carpi radialis H-reflex in subjects without neurological deficits.
abstract: The purposes of this study were to investigate the effects of circumferential pressure on flexor carpi radialis (FCR) H-reflex in subjects without neuromuscular deficits and to evaluate the skin's contribution to this effect. FCR H-reflex was assessed in 43 subjects by measuring the peak-to-peak amplitude change before, during, and after circumferential pressure was applied to the forearm. Twelve H-reflexes (H/M ratio: M = 25%, SD = 14) were recorded before pressure application to obtain a baseline value (H(baseline)) to which all data were compared. A pneumatic 15 to 20-cm air splint inflated to 51-60 mmHg provided the pressure around the forearm. H-reflex recordings were taken at 1, 3, and 5 min. during (H(pressure)) and after pressure application. A second smaller study (placebo), in which the air splint was inflated to 0 mmHg, was conducted in 5 subjects to ensure that changes in reflex amplitudes were not a result of cutaneous effects. Two types of responses were observed in the FCR H-reflex following pressure application. One group of subjects significantly increased in H-reflex amplitude while another group decreased in H-reflex amplitude when compared to H(baseline). Regression analysis found that H(max) explained 37.2% of the variance when controlling for H(baseline). Subjects with larger H(max) showed an increase in H(pressure) while subjects with lower H(max) showed decreases in H(pressure) The placebo study revealed no differences in H-reflex amplitude from baseline values, implying that skin stimulation from the air splint has no role in the effects observed. The dichotomous result indicates that pressure influences the upper extremity differently than it does the lower extremity in certain individuals. Clinicians, using circumferential pressure as a therapeutic modality to lower muscle activity of the upper extremity, need to be cognizant that pressure may have contrasting effects on their patients.
authors.affiliation: Physical Therapy Program, University of Rhode Island, 25 West Independence Way, Kingston, RI 02881, USA. gusser@uri.edu
authors.forename: James
authors.initials: J
authors.lastname: Agostinucci
authors.forename: Ashley
authors.initials: A
authors.lastname: Holmberg
authors.forename: Marileen
authors.initials: M
authors.lastname: Mushen
authors.forename: Jennifer
authors.initials: J
authors.lastname: Plisko
authors.forename: Magdalina
authors.initials: M
authors.lastname: Gofman
mesh_terms: D000328:Adult; D004550:Elbow / Q000294:innervation; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation*; D009433:Neural Inhibition / Q000502:physiology; D011312:Pressure; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D012867:Skin / Q000294:innervation*; D013165:Splints; D014953:Wrist / Q000294:innervation