Pain-related fear, lumbar flexion, and dynamic EMG among persons with chronic musculoskeletal low back pain.

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Clin J Pain. 2004 Mar-Apr;20(2):61-9. Related Articles, Links

 

Pain-related fear, lumbar flexion, and dynamic EMG among persons with

chronic musculoskeletal low back pain.

Geisser ME, Haig AJ, Wallbom AS, Wiggert EA.

Spine Program, Department of Physical Medicine and Rehabilitation and dagger

Department of Surgery, University of Michigan, Health System, Ann Arbor,

48108, USA. mgeisser@...

OBJECTIVES: The purpose of this study was to examine the relationship

between pain-related fear, lumbar flexion, and dynamic EMG activity among

persons with chronic musculoskeletal low back pain. It was hypothesized that

pain-related fear would be significantly related to decreased lumbar flexion

and specific patterns of EMG activity during flexion and extension. STUDY

DESIGN: Data was obtained from subjects who, on a single day, completed

self-report measures of pain and pain-related fear, and were interviewed to

determine demographic and pain information. Subjects then underwent a

dynamic EMG evaluation for which they were asked to stand, then bend forward

as far as possible, stay fully flexed, and return to standing. Lumbar EMG

and angle of flexion were recorded during this time. A flexion-relaxation

ratio (FRR) was computed by comparing maximal EMG while flexing to the

average EMG in full flexion. SUBJECTS: Seventy-six persons with chronic

musculoskeletal low back pain. RESULTS: Zero-order correlations indicated

that pain-related fear was significantly related to reduced lumber flexion

(r = -0.55), maximum EMG during flexion (r = -0.38) and extension (r =

-0.51), and the FRR (r = -0.40). When controlling for pain and demographic

factors, pain-related fear continued to be related to reduced lumbar

flexion. Using a path-analytic model to examine whether angle of flexion

mediated the relationship between fear and EMG activity, the models

examining maximal EMG during flexion and extension supported the notion that

pain-related fear influences these measures indirectly through its

association with decreased range of motion. Conversely, pain-related fear

was independently related to higher average EMG in full flexion, while angle

of flexion was not significantly related. Pain-related fear was directly

related to a smaller FRR, as well as indirectly through angle of flexion.

CONCLUSIONS: Pain-related fear is significantly associated with reduced

lumbar flexion, greater EMG in full flexion, and a smaller FRR. The

relationship between pain-related fear and EMG during flexion and extension

appears to be mediated by reduced lumbar flexion. These results suggest that

pain-related fear is directly associated with musculoskeletal abnormalities

observed among persons with chronic low back pain, as well as indirectly

through limited lumbar flexion. These musculoskeletal abnormalities as well

as limited movement may be involved in the development and maintenance of

chronic low back pain. In addition, changes in musculoskeletal functioning

and flexion associated with pain-related fear may warrant greater attention

as part of treatment.

Publication Types:

* Clinical Trial

PMID: 14770044 [PubMed - indexed for MEDLINE]