Differences in Feedforward Trunk Muscle Activity in Subgroups of Patients With Mechanical Low Back Pain
Presented in part to the American Physical Therapy Association, February 14, 2007, Boston, MA.
published online 08 June 2009.
Abstract
Silfies SP, Mehta R, Smith SS, Karduna AR. Differences in feedforward trunk muscle activity in subgroups of patients with mechanical low back pain.
Objective
To investigate alterations in trunk muscle timing patterns in subgroups of patients with mechanical low back pain (MLBP). Our hypothesis was that subjects with MLBP would demonstrate delayed muscle onset and have fewer muscles functioning in a feedforward manner than the control group. We further hypothesized that we would find differences between subgroups of our patients with MLBP, grouped according to diagnosis (segmental instability and noninstability).
Design
Case-control.
Setting
Laboratory.
Participants
Forty-three patients with chronic MLBP (25 instability, 18 noninstability) and 39 asymptomatic controls.
Interventions
Not applicable.
Main Outcome Measures
Surface electromyography was used to measure onset time of 10 trunk muscles during a self-perturbation task. Trunk muscle onset latency relative to the anterior deltoid was calculated and the number of muscles functioning in feedforward determined.
Results
Activation timing patterns (P<.01; η=.50; 1-β=.99) and number of muscles functioning in feedforward (P=.02; η=.30; 1-β=.83) were statistically different between patients with MLBP and controls. The control group activated the external oblique, lumbar multifidus, and erector spinae muscles in a feedforward manner. The heterogeneous MLBP group did not activate the trunk musculature in feedforward, but responded with significantly delayed activations. MLBP subgroups demonstrated significantly different timing patterns. The noninstability MLBP subgroup activated trunk extensors in a feedforward manner, similar to the control group, but significantly earlier than the instability subgroup.
Conclusions
Lack of feedforward activation of selected trunk musculature in patients with MLBP may result in a period of inefficient muscular stabilization. Activation timing was more impaired in the instability than the noninstability MLBP subgroup. Training specifically for recruitment timing may be an important component of the rehabilitation program.
aRehabilitation Sciences Research Laboratory, Drexel University, Philadelphia, PA
bDepartment of Human Physiology, University of Oregon, Eugene, OR
Reprint requests to Sheri P. Silfies, PT, PhD, Rehabilitation Sciences Research Laboratory, Drexel University, 245 N. 15th Street, MS 502, Philadelphia, PA 19102-1192
Supported in part by grants from Orthopaedic Section of the American Physical Therapy Association and the US Department of Education, National Institute on Disability and Rehabilitation Research (H133F030024).
No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.
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ABSTRACT