Assessment of activities of daily living with an ambulatory monitoring system: a comparative study in patients with chronic low back pain and nonsymptomatic controls

Objective: The aim of this study was twofold: (1) to investigate whether differences in activities of daily living exist between patients with chronic low back pain (CLBP) and nonsymptomatic controls; (2) to investigate the day-today variability in daily activities. Design: Physical activities were measured over a 24-hour period with an ambulant monitoring system. Setting: Measurements were carried out in the subject's own environment. Subjects: Forty-seven CLBP patients and 10 nonsymptomatic controls participated in this study. Results: On group level, CLBP patients show a lower activity pattern compared with controls, especially during the evening. This is reflected in a lower walking step frequency during the day and evening, more lying time during the day and a lower physical activity level, less standing time and more lying time during the evening. The day-to-day variability in activity pattern is high and similar for both the patient and control group. Conclusion: The lower activity level especially found during the evening might indicate that patients need all their capacity to perform the tasks imposed during the day and as a consequence have less capacity left for their leisure time, in general the evening. This suggests the existence of an imbalance between the patient's physical capacity and the imposed environmental load. The large but similar day-to-day variability in activity pattern, which does not support the clinical findings of 'bad days' in CLBP patients, suggests the need for repeated measures.