Between/within-session reliability of spinal kinematic and lumbar muscle activity measures in patients with chronic low back pain and asymptomatic individuals

Background: Longitudinal research is required to better understand the role of spinal movement alterations in chronic low back pain (CLBP). To this end, it is critical to assess the between-session reliability of spinal movement measures.Research question: What is the within/between-session reliability of spinal movement measures in patients with CLBP and asymptomatic controls?Methods: Spinal movement was recorded prospectively during two sessions, a week apart, for 20 patients with CLBP (60% male; 40.0 +/- 12.3 years old) and 20 asymptomatic individuals (55% male; 38.2 +/- 10.9 years old). Sagittal-plane angular amplitude and angular velocity at the lower lumbar, upper lumbar, lower thoracic and upper thoracic joints, as well as maximal erector spinae activity were measured during five daily-activity tasks. In addition, task-independent measures were obtained by averaging the measures across tasks. The Intraclass Correlation Coefficient (ICC 2,1) and the minimal detectable change (MDC) were calculated. Pearson correlation was used to compare task-independent and task-specific measures.Results: Between-session ICCs in patients with CLBP were mostly moderate to good for maximal angular amplitude and erector spinae activity measures. Lower ICCs were observed for range of angular motion and angular velocity measures (42% of ICCs < 0.5). Median MDCs were 9.6 degrees, 18.3 degrees /s and 1.0% for angular amplitude, angular velocity and erector spinae activity measures, respectively. The reliability of task-independent and task-specific measures was strongly correlated (r = 0.91, p < 0.001).Significance: Sagittal-plane maximal angular amplitude and erector spinae activity measures during various daily-activity tasks demonstrated mostly moderate to good between-session ICCs. However, relatively large MDCs suggested that important changes are needed to be detectable. Task-independent measures reported similarly acceptable ICCs than task-specific measures, supporting their use to describe spinal movement