Activity-related summation of pain and functional disability in patients with whiplash injuries.

This study investigated the relation between repetition-induced summation of activity-related pain (RISP) and indicators of functional disability in a sample of 62 individuals who had sustained whiplash injuries. Participants completed measures of pain severity, pain catastrophizing, fear of movement and depression prior to lifting a series of 36 weighted canisters. An index of RISP was computed as the increase in pain reported by participants over successive lifts of the weighted canisters. Measures of functional disability included physical lifting tolerance, self-reported disability and perceived work demands. Regression analyses revealed that the index of RISP accounted for significant variance in measures of lifting tolerance and perceived work demands, even when controlling for age, sex and pain severity. The index of RISP was also significantly correlated with pain catastrophizing and pain duration. The discussion addresses the mechanisms by which physiological and psychological factors might contribute to increases in pain during repeated physical activity. Discussion also addresses whether RISP might represent a risk factor for problematic recovery outcomes following whiplash injury.