Late facilitation of the human soleus H reflex induced by sustained isometric maneuver

Am J Phys Med Rehabil. 1997 May-Jun;76(3):188-90. doi: 10.1097/00002060-199705000-00004.

Abstract

Studying the effect of spinal cord reinforcement maneuvers (SCRMs) on H reflex assists in understanding aspects of motor control. Our objective was as follows: (1) to elucidate the effects of four neck positions (neck resting at neutral position (control); passive hyperflexion of the neck; hyperextension of the neck with simultaneous abdominal contraction; and sustained active neck hyperflexion); (2) to evaluate the temporal changes of soleus H reflexes repeatedly evoked after a period of sustained neck flexion. We used a prospective, intrinsically controlled trial of the effects of these SCRMs on the H reflexes and M-responses in ten healthy volunteers. Pre- and postmaneuver measures included H reflex and M-response latencies and amplitudes, H/M maximum amplitude ratio, and H threshold. The four maneuvers showed no significant effect on the H reflex or M-response measures. To investigate temporal changes in the H reflex amplitude, H reflexes were repeatedly evoked at two-minute intervals after a one-minute period of active neck flexion. The amplitude of the H reflex was enhanced (P = 0.0356; analysis of variance), and the post hoc least significant difference test was significant at four minutes postmaneuver. Peak magnitude of the H reflex occurred at four minutes after relaxation, and the response returned to pretest baseline at eight minutes. The results of this study document the time course of repeated H reflexes after SCRM, and the timing of the H reflex was found to be a contributing variable that should be considered in future study designs.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Adaptation, Physiological
  • Adult
  • Female
  • H-Reflex / physiology*
  • Humans
  • Isometric Contraction / physiology*
  • Male
  • Motor Neurons / physiology
  • Muscle, Skeletal / innervation*
  • Neck / physiology*
  • Physical Stimulation
  • Posture / physiology*
  • Prospective Studies
  • Time Factors