Abstract
Objective: The mechanisms underlying the benefits of spinal manipulation are not well understood.
Neurophysiological mechanisms likely mediate its effects, at least in part, yet we
know little about how the nervous system is affected by spinal manipulation. The purpose
of the present study was to determine whether muscle spindles and Golgi tendon organs
in paraspinal muscles respond to a mechanical load whose force-time profile is similar
to that of a spinal manipulation. Methods: Experiments were performed on 10 anesthetized adult cats. The L6 dorsal root was
isolated for electrophysiological recordings while the L6-L7 vertebrae and associated
paraspinal tissues on one side of the vertebral column were left intact. Single unit
recordings were obtained from 5 muscle spindles, 4 Golgi tendon organs, and 1 presumed
Pacinian corpuscle afferent with receptive fields in paraspinal muscles. Loads were
applied at the spinous process of the L6 vertebra through use of an electronic feedback
control system. The load simulated the force-time profile of a spinal manipulation.
Loads were applied in compressive and distractive directions and at 2 different angles
(0 degrees and 45 degrees) with respect to the long axis of the vertebral column.
Results: Golgi tendon organ afferent discharge frequency increased more to the impulse than
to the preload during 13 of 15 spinal manipulations. Generally, the 4 Golgi tendon
organ afferents became silent immediately at the end of each impulse. Similarly, muscle
spindle discharge frequency increased more to the impulse than to the preload during
10 of 16 manipulations. Distractive manipulations loaded the spindles more effectively
than compressive manipulations. After 7 of these 10 manipulations, muscle spindles
became silent for 1.3 ± 0.6 seconds (range, 0.1-4.3 seconds). Six of the 16 manipulations
unloaded the muscle spindles. A presumed Pacinian corpuscle responded to the impulse
of a manipulative-like load but not to loads with a slower force-time profile. Conclusion: The data suggest that the high-velocity, short-duration load delivered during the
impulse of a spinal manipulation can stimulate muscle spindles and Golgi tendon organs
more than the preload. The physiologically relevant portion of the manipulation may
relate to its ability to increase as well as decrease the discharge of muscle proprioceptors.
In addition, the preload, even in the absence of the impulse, can change the discharge
of paraspinal muscle spindles. Loading of the vertebral column during a sham manipulation
may affect the discharge of paraspinal proprioceptors. (J Manipulative Physiol Ther
2001;24:2-11)
Keywords
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Article info
Publication history
Received in revised form:
March 9,
2000
Received:
January 4,
2000
Footnotes
*bPrivate practice, Manhattan, Kan.
**This project was funded by National Institute of Neurological Disease and Stroke (NINDS) grant NS35300 on behalf of the Office of Alternative Medicine and through a grant from the National Chiropractic Mutual Insurance Company (NCMIC) administered by the Foundation for Chiropractic Education and Research (FCER).
★Submit reprint requests to: Joel G. Pickar, Palmer Center for Chiropractic Research, 741 Brady Street, Davenport, IA 52803; [email protected]
★★J Manipulative Physiol Ther 2001;24:2-11
Identification
Copyright
© 2001 JMPT. Published by Elsevier Inc. All rights reserved.
