Exercise-induced Pain Intensity Predicted by Pre-exercise Fear of Pain and Pain Sensitivity

Objectives: Our primary goals were to determine whether preexisting fear of pain and pain sensitivity contributed to post-exercise pain intensity. Methods: Delayed-onset muscle pain was induced in the trunk extensors of 60 healthy volunteers using an exercise paradigm. Levels of fear of pain and experimental pain sensitivity were measured before exercise. Pain intensity in the low back was collected at 24 and 48 hours post-exercise. Participants were grouped based on pain intensity. Group membership was used as the dependent variable in separate regression models for 24 and 48 hours. Predictor variables included fear, pain sensitivity, torque lost during the exercise protocol, and demographic variables. Results: The final models predicting whether a participant reported clinically meaningful pain intensity at 24 hours only included baseline fear of pain at each level of pain intensity tested. The final model at 48 hours included average baseline pain sensitivity and the loss of muscle performance during the exercise protocol for 1 level of pain intensity tested (greater than 35mm of 100 mm). Discussion: Combined, these findings suggest that the initial reports of pain after injury may be more strongly influenced by fear whereas the inflammatory process and pain sensitivity may play a larger role for later pain intensity reports.