Design: A controlled study in which the PLM test was used repeatedly on patients with chronic low back pain and persons without back pain.
Subjects: Twelve patients with treatment-resistant chronic low back pain, selected by 2 orthopaedic spine surgeons and 12 age- and sex-matched individuals with no back pain history.
Methods: An optoelectronic camera and a computer were used to quantify the performance during a simple test in which subjects picked up an object from the floor and transported it up to a shelf, thereby forcing the body through postural, locomotor and manual movements. The outcome measures were: movement time, simultaneity index and phase times for postural, locomotion and arm movement phases. Statistical analyses regarding intra-individual agreement between the measurements (reliability analysis) and changes over time were carried out.
Results: The effect of test movement habituation was minimized when the lowest mean value of any of 3 consecutive measures (tri-average) was used. In the control group, variation between test occasions was small. In the group of patients with chronic low back pain there was a random measurement error before intervention (sensory motor learning). After intervention the PLM test had the same precision in both groups.
Conclusion: When the tri-average measure is used, the influence of test movement habituation is minimized and the optoelectronic PLM test is found to be reliable and responsive. It proved to be a useful tool to quantify dynamic performance in freely moving patients with chronic low back pain.