Physical activity in daily life in patients with chronic low back pain

Objectives: To evaluate disuse (ie, a decreased daily physical activity level) in patients with chronic low back pain (LBP) and to evaluate the construct validity of accelerometry for measuring physical activity in daily life. Design: Case-control study in a cross-sectional design; comparison of accelerometry to the criterion standard (doubly labeled water technique). Setting: Normal daily living (unrestricted by the measurement devices). Patients: Thirteen patients with chronic nonspecific LBP and 13 age- and gender-matched healthy controls. Main Outcome Measures: Physical activity in daily life, expressed as whole-body acceleration measured with a triaxial accelerometer (Tracmor), and as the ratio between average daily metabolic rate (ADMR), measured by the doubly labeled water technique, and resting metabolic rate (RMR), measured by the ventilated hood. Both techniques were used simultaneously for 14 days. Results: Mean physical activity level in patients and controls did not differ significantly. The correlation between the Tracmor and ADMR and RMR was .72 (p < .01). Conclusions: Decreased physical activity levels in this sample of chronic LBP patients was not confirmed. The Tracmor is a valid instrument for measuring daily activity in LBP patients. (C) 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.