How many days of bed rest for acute low back pain? Objective assessment of trunk function.

Bed rest is usually considered an efficient treatment for acute low back pain. However, the optimal duration of bed rest is still being discussed. The recommended periods vary from 2 days to 2 weeks. The duration of optimum length is an important topic given the economical and physiological drawbacks of prolonged inactivity. The purpose of this work is to measure objectively the efficacy of two different durations of bed rest through a dynamometric measure of trunk function. Some 51 male patients, students or self-employed, being treated for acute low back pain were randomized into two groups. Group I was prescribed a bed rest period of 3 days and group II, a period of 7 days. We used a multi-axis isoinertial trunk testing dynamometric device (Isostation B200, Isotechnologies, USA). Patients were all assessed on day 1 and also on day 5 for group I or on day 9 for group II. The variables measured in the sagittal plane were isometric torques in flexion and extension, unresisted range of motion, average dynamic torques and average velocities. Patients were also asked to fill in a visual analogue pain scale on both assessment days. The improvement of all performance measures were important and highly significant (P < 0.001) in both groups. The results of the functional testing and the visual analogue pain scale showed no significant differences between the groups. In these relatively young and motivated patients, a duration of bed rest of 3 days resulted in the same objective functional improvement of trunk function and pain rating as a period of 7 days. This shorter duration should be considered as preferable, given the same objective results but important physiological and economical advantages.