Objectives: Several research groups established functional tests to obtain performance data for mobility-related activities in patients with low back pain (LBP). In our study we aimed to assess the construct validity and associations with other measures of a battery of functional tests in relationship to physical performance on the one hand and physical capacity and variables of pain, disability and psychological variables on the other.
Design: Eight physical performance tests of everyday activities such as climbing stairs, picking up an object from the floor, bending forward, and sitting up from supine position etc. were evaluated in 106 patients with LBP and 106 control subjects.
Results: Distribution of results in each test demonstrated a marked overlap in a number of tests between those with and those without back pain. In a factor analysis we found pronounced differences in the factorial structure of the data between patients and control subjects as well in the bivariate correlations between functional test results. There was a strong relationship between self-report disability rating (FFbH-R) and physical performance tests especially in patients whereas physical capacity tests had less relationship in patients and not at all in the control subjects.
Conclusion: In contrast to the past and present literature, our results suggest that physical performance tests have an inherent problem to sharply differentiate patients with back pain from healthy controls and problems with inter-rater reliability. Physical performance seems to be more a matter of patients' perception of generalized disability than of restricted function.
Keywords: Activity Limitation; Back Pain; Disability; Physical Capacity; Physical Performance.
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