The Effect of Chronic Low Back Pain on Trunk Accuracy in a Multidirectional Isometric Tracking Task

Study Design. A cross-sectional study to quantify trunk motor control during multidirectional isometric tracking tasks. Objective. To investigate the effect of chronic low back pain (LBP) on trunk neuromuscular performance while participants performed isometric exertions of trunk muscles to track targets in different angles with various magnitudes. Summary of Background Data. Tracking tasks especially in multidirectional activities are among the common research methods to quantify human motor control in different conditions. However, little information is available on trunk motor control during these tasks. There is no study investigating trunk accuracy during multidirectional isometric tracking tasks in patients with LBP. Materials and Methods. Twelve patients with chronic LBP and 16 asymptomatic participants performed isometric target tracking tasks in 12 different directions with varying magnitude, from 0% to 80% of individual maximum voluntary exertion, in upright standing posture. The tracking system included a moving target object that moved on a straight line in a predefined angle with the rate of 6% maximum voluntary exertion/s. Trunk accuracy was quantified by computing constant error and variable error during each trial. A mixed model repeated measure analysis of variance was conducted to assess statistical analysis. Results. Patients with chronic LBP track the target object with higher error compared with healthy controls across almost all of the target angles (P < 0.01). Trunk accuracy decreased significantly in higher level of exertions (P < 0.01). Conclusion. The results provided additional evidence of a change in trunk control strategies in patients with chronic LBP. Decreased accuracy of trunk during isometric tracking tasks especially in higher levels of asymmetric exertions may explain higher risk of low back injuries in these activities. Level of Evidence: 4