Physical functioning: self-report and performance measures are related but distinct

Spine (Phila Pa 1976). 2003 Oct 15;28(20):2407-13. doi: 10.1097/01.BRS.0000085304.01483.17.


Study design: Cross-sectional study of 63 patients with chronic low back pain (CLBP).

Objectives: 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.

Summary of background data: 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.

Materials and 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.

MeSH terms

  • Activities of Daily Living
  • Adult
  • Chronic Disease
  • Cross-Sectional Studies
  • Disability Evaluation
  • Exercise Test
  • Female
  • Heart Rate
  • Humans
  • Low Back Pain / physiopathology*
  • Low Back Pain / psychology
  • Male
  • Mental Health
  • Middle Aged
  • Quality of Life
  • Reproducibility of Results
  • Surveys and Questionnaires*