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Determining the Stabilizing Role of Individual Torso Muscles During Rehabilitation Exercises

Kavcic, Natasa, MSc; Grenier, Sylvain, PhD; McGill, Stuart M., PhD

Occupational Health/Ergonomics
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Study Design. A systematic biomechanical analysis involving an artificial perturbation applied to individual lumbar muscles in order to assess their potential stabilizing role.

Objectives. To identify which torso muscles stabilize the spine during different loading conditions and to identify possible mechanisms of function.

Summary of Background Data. Stabilization exercises are thought to train muscle patterns that ensure spine stability; however, little quantification and no consensus exists as to which muscles contribute to stability.

Methods. Spine kinematics, external forces, and 14 channels of torso electromyography were recorded for seven stabilization exercises in order to capture the individual motor control strategies adopted by different people. Data were input into a detailed model of the lumbar spine to quantify spine joint forces and stability. The EMG signal for a particular muscle was replaced either unilaterally or bilaterally by a sinusoid, and the resultant change in the stability index was quantified.

Results. A direction-dependent-stabilizing role was noticed in the larger, multisegmental muscles, whereas a specific subtle efficiency to generate stability was observed for the smaller, intersegmental spinal muscles.

Conclusions. No single muscle dominated in the enhancement of spine stability, and their individual roles were continuously changing across tasks. Clinically, if the goal is to train for stability, enhancing motor patterns that incorporate many muscles rather than targeting just a few is justifiable.

The stabilizing role of individual lumbar muscles was quantified. No single muscle dominated in the enhancement of spine stability; furthermore, their individual roles continuously changed across tasks. Clinically, if the goal is to train for stability, enhancing motor patterns that incorporate many muscles rather than targeting a few is justifiable.

From the University of Waterloo, Faculty of Applied Health Sciences, Waterloo, Ontario, Canada.

Acknowledgment date: May 21, 2003. First revision date: June 26, 2003. Acceptance date: August 6, 2003.

Supported by the National Science and Engineering Research Council of Canada.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Federal funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Address correspondence to Stuart M. McGill, PhD, Faculty of Applied Health Science, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1; E-mail: mcgill@healthy.uwaterloo.ca

© 2004 Lippincott Williams & Wilkins, Inc.