This study investigated the degree to which measures of spontaneous and movement-evoked pain accounted for shared or unique variation in functional disability related to whiplash injury. The study also addressed the role of fear of movement as a mediator or moderator of the relation between different indices of pain and functional disability. Measures of spontaneous pain, single-point movement-evoked pain, repetition-induced summation of activity-related pain (RISP), and fear of movement and disability were obtained on a sample of 142 individuals who had sustained whiplash injuries. Participants’ pain ratings, provided following their lifting of a weighted canister, were used as the index of single-point movement-evoked pain. RISP was computed as the increase in pain reported by participants over successive lifts of 18 weighted canisters. Measures of functional disability included physical lift tolerance and self-reported disability. Hierarchical regression analyses revealed that measures of single-point movement-evoked pain and RISP accounted for significant unique variance in self-reported disability, beyond the variance accounted for by the measure of spontaneous pain. Only RISP accounted for significant unique variation in lift tolerance. The results indicate that measures of movement-evoked pain represent a disability-relevant dimension of pain that is not captured by measures of spontaneous pain. The clinical and conceptual implications of the findings are discussed.
This study investigated the degree to which measures of spontaneous and movement-evoked pain accounted for shared or unique variance in functional disability related to whiplash injury. The findings indicate that approaches to the clinical evaluation of pain would be improved by the inclusion of measures of movement-evoked pain.