To test systematically if spinal manipulative treatments (SMT) and the audible release associated with SMT cause activation of spinal muscles.
Experimental pilot study.
Human Performance Laboratory, The University of Calgary.
One male and one female asymptomatic volunteer.
Slow and fast SMTs to the left transverse process of thoracic vertebrae using a reinforced hypothenar contact. The treatment forces were directed in a posterior-to-anterior direction with the subjects in a prone position.
Main Outcome Measures:
Forces applied by the chiropractor during SMT. Measurements of the audible release using skin-mounted accelerometers. Electromyographical activity of selected spinal muscles.
Electromyographical (EMG) activity was observed consistently 50-100 msec after the onset of each of the fast SMTs, whether the treatment resulted in an audible release or not; for slow SMTs, there was never any visible electromyographical activity of the target muscles, whether the treatment resulted in an audible release or not.
The results of this study suggest that fast treatment thrusts elicit muscle activation, whereas slow force application does not. The timing of the onset of the EMG response suggests that activation may be produced by a reflex response originating in the muscle spindles. It also appears that the audible release does not (by itself) evoke muscle activation or a joint proprioceptive reflex response as has been speculated in the literature.
J Manipulative Physiol Ther. 1995 May;18(4):233-6. [PMID:7636413]
Author information: W. Herzog, PhD.; P.J. Conway, DC; Y.T. Zhang, PhD.; J. Gal, PhD; A.C.S. Guimaraes. Faculty of Physical Education, University of Calgary, Alberta, Canada.
Subject: The Activator Adjusting Instrument – Biomechanical
Reference: Tony S. Keller; J.B. Lehneman…Musculoskeletal Research Lab, February 1994: pp.1-16
Introduction: The Activator Adjusting Instrument (AAI) is a devise used for chiropractic manipulations. The device is intended to produce repeatable impacts (manipulations) at various force settings. The force is easily adjusted by turning the small knob on the lower part of the device.
Objective: The purpose of this study is to determine the effect of the force setting, and preload on the actual force delivered by the AAi to the impact surface.
To date, the diagnosis of whiplash injuries has been very difficult and largely based on subjective, clinical assessment. The work by Winters and Peles Multiple Muscle Systems–Biomechanics and Movement Organization. Springer, New York (1990) suggests that the use of finite helical axes (FHAs) in the neck may provide an objective assessment tool for neck mobility. Thus, the position of FHA describing head-trunk motion may allow discrimination between normal and pathological cases such as decreased mobility in particular cervical joints. For noisy, unsmoothed data, the FHAs must be taken over rather than large angular intervals if the FHAs are to be reconstructed with sufficient accuracy; in the Winters and Peles study, these intervals were approximately 10 degrees.
In order to study the movements’ microstructure, the present investigation uses instantaneous helical axes (IHAs) estimated from low-pass smoothed video data. Here, the small-step noise sensitivity of the FHA no longer applies, and proper low-pass filtering allows estimation of the IHA even small rotation velocity omega of the moving neck. For marker clusters mounted on the head and trunk, technical system validation showed that the IHAs direction dispersions were on the order of one degree, while their position dispersions were on the order of 1 mm, for low-pass cut-off frequencies of a few Hz (the dispersions were calculated from omega-weighted errors, in order to account for the adverse effects of vanishing omega).
Various simple, planar models relating the instantaneous, 2-D centre of rotation with the geometry and kinematics of a multi-joint neck model are derived, in order to gauge the utility of the FHA and IHA approaches.
Some preliminary results on asymptomatic and pathological subjects are provided, in terms of the ‘ruled surface’ formed by sampled IHAs and of their piercing points through the mid-sagittal plane during a prescribed flexion-extension movement of the neck.
J Biomechanics. 1994; 27(12):1415-32.
Author information: Woltring HJ, Long K, Osterbauer PJ, Fuhr AW. Whiplash Analysis, Inc. Phoenix, AZ.