Comparison of Mechanical Force of Manually Assisted Chiropractic Adjusting Instruments
Received 9 September 2003; received in revised form 4 November 2003 and 2 April 2005
Abstract
Objective
To quantify the force-time and force-delivery characteristics of six commonly used handheld chiropractic adjusting devices.
Methods
Four spring-loaded instruments, the Activator Adjusting Instrument; Activator II Adjusting Instrument, Activator III Adjusting Instrument, and Activator IV Adjusting Instrument, and two electromechanical devices, the Harrison Handheld Adjusting Instrument and Neuromechanical Impulse Adjusting Instrument, were applied to a dynamic load cell. A total of 10 force-time histories were obtained at each of three force excursion settings (minimum to maximum) for each of the six adjusting instruments at preload of approximately 20 N.
Results
The minimum-to-maximum force excursion settings for the spring-loaded mechanical adjusting instruments produced similar minimum-to-maximum peak forces that were not appreciably different for most excursion settings. The electromechanical adjusting instruments produced short duration (∼2-4 ms), with more linear minimum-to-maximum peak forces. The force-time profile of the electromechanical devices resulted in a more uniform and greater energy dynamic frequency response in comparison to the spring-loaded mechanical adjusting instruments.
Conclusions
The handheld, electromechanical instruments produced substantially larger peak forces and ranges of forces in comparison to the handheld, spring-loaded mechanical devices. The electromechanical instruments produced greater dynamic frequency area ratios than their mechanical counterparts. Knowledge of the force-time history and force-frequency response characteristics of spinal manipulative instruments may provide basic benchmarks and may assist in understanding mechanical responses in the clinical setting.
aPresident, Neuromechanical Innovations, L.L.C.; State of the Art Chiropractic Center, P.C., Phoenix, Ariz; and Biomechanics Laboratory, Exercise and Sport Science Research Institute, Department of Kinesiology, Arizona State University, Tempe, Ariz
bDepartment of Mechanical Engineering, and Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington, Vt
cBiomechanics Laboratory, Department of Sciences of Physical Activity, Universite du Quebec a Trois-Rivieres, Trois-Rivieres, Quebec, Canada
dBiomechanics Laboratory, Department of Sciences and Physical Activity, Universite du Quebec a Trois-Rivieres, Trois-Rivieres, Quebec, Canada
ePresident, Chiropractic Biophysics, Ruby Mountain Chiropractic Center, Elko, Nev
fBiomechanics Laboratory, Department of Sciences and Physical Activity, Universite du Quebec a Trois-Rivieres, Trois-Rivieres, Quebec, Canada
Submit requests for reprints to: Christopher J. Colloca, DC, State of the Art Chiropractic Center, P.C., 11011 S. 48th St., Suite 220, Phoenix, AZ 85044.
This research was presented, in part, at the 6th Biennial Congress of the World Federation of Chiropractic, Palais des Congrès, Paris, France, May 24-26, 2001.
ABSTRACT