Physical functioning: self-report and performance measures are related but distinct.
METHODS
Cross-sectional study of 63 patients with chronic low back pain (CLBP).


OBJECTIVE
To determine the relationship between the SF-36 physical functioning (PF) scale and physical performance on a modified symptom limited treadmill test, and to determine the effect of disability status and SF-36 mental health (MH) scores on self-reported physical functioning and on physical performance.


BACKGROUND
Patients with CLBP report low levels of physical functioning. Because self-report measures are influenced by psychosocial factors, such as disability and low MH, a common recommendation is to supplement self-report with objective or physical performance testing. Little information exists regarding whether performance testing is also influenced by disability and low MH.


METHODS
Patients completed the SF-36 and performed a maximal, symptom-limited, modified treadmill test. Total walking time and heart rate on the treadmill were registered. The effects of disability and low MH on self-report and performance testing were calculated by unpaired Student's t-testing and effect size estimation.


RESULTS
A strong relationship between the PF scale of the SF-36 and treadmill walking time was found, but there was little evidence of overlap between these physical functioning domains. Both disability status and low MH had a much larger effect on self-report measures than on physical performance.


CONCLUSIONS
Self-report measurements and performance-based assessments provide information about distinct, although related, domains of physical functioning. Disability and low MH are associated with lower SF-36 PF scores. Our results confirm that self-report measures require supplementation with objective performance testing to provide optimal assessment for patients with CLBP.
Wittink
Harriët
H
Department of Physical Therapy, VU Medical Center, De Boelelaan, Amsterdam.
Rogers
William
W
Sukiennik
Andrew
A
Carr
Daniel B
DB
D000203:Activities of Daily Living; D000328:Adult; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology* / Q000523:psychology; D008297:Male; D008603:Mental Health; D008875:Middle Aged; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires