Modulation of the tibial nerve H-reflex by mechanical stimulation of afferents in the lumbar spine.
The purpose of this study was to describe the convergence of afferent discharges from the ligament-muscular system of the lumbar spine to the segmentally-related gastrocnemius muscle. The subjects were 32 healthy, young volunteers recruited from a college student population. Afferent discharges from the ligament-muscular system of the lumbar spine were evoked by manually moving the trunk into either flexion (n = 16) or left lateral bending (n = 16) using a multi-directional adjustable treatment table (Zenith Cox Flexion Table). Using linear potentiometers affixed to the treatment table and interfaced with a computer data acquisition system, manual movements of the table were visually guided to generate passive trunk movements at velocities of 10 degrees, 20 degrees, and 40 degrees per second. Tibial nerve H-reflex responses were recorded from the right gastrocnemius muscle as the trunk approached its end range of motion. Regardless of velocity for the flexion movement, the H/M(Max) ratio significantly decreased from 28.0% to 20.9% (p < .05). During lateral bending, the H/M(Max) ratio significantly decreased from 27.4% to 24.0% at velocities of 10 degrees and 20 degrees per second (p < .05) with a subsequent decrease to 20.5% at a velocity of 40 degrees per second (p < .05). The nature of these decreases in the H/M(Max) ratios across the different velocities during lateral bending significantly departed from linearity (p < .05). These data provide sufficient evidence to suggest that heteronymous conditioning effects from the ligament-muscular system of the lumbar spine during passive trunk movements attenuate alpha motoneuronal activity of the segmentally-related gastrocnemius muscle.
Burke
J R
JR
New York Chiropractic College, Biodynamics Laboratory, 2360 State Route 89, Seneca Falls, NY 13148, USA. jburke@nyccc.edu
Bulbulian
R
R
D000328:Adult; D000344:Afferent Pathways; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000294:innervation*; D008159:Lumbar Vertebrae; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D009068:Movement; D016059:Range of Motion, Articular; D013979:Tibial Nerve / Q000502:physiology*