UC San Diego

Chronic pain, a disabling biopsychosocial condition, is increasingly addressed with cognitive behavioral interventions such as Acceptance and Commitment Therapy (ACT) and Cognitive Behavioral Therapy (CBT). Such interventions seek to maximize physical, social, and occupational functioning by changing how one manages pain via addressing pain-related thoughts, beliefs, and behaviors. The chronic pain literature is dominated by between-subject designs and self-report measures that lack ecological validity and may be subject to bias. Both pain and physical activity, a component of function, can be objectively measured in an ecologically valid way using ecological momentary assessment (EMA) and accelerometry, respectively. Prior research has indicated cross-sectionally a dynamic within-person pain-physical activity relationship, but statistical analytic approaches have lacked nuance, and this relationship has not been examined in an intervention context. This dissertation addressed gaps in the literature by 1) modelling the relationship between EMA-assessed pain and objective physical activity over a 7-day baseline period using parallel latent growth curve modelling; 2) using multigroup analysis to examine if the relationship between the growth trajectories of EMA pain and objective physical activity changed from baseline to post-intervention, and 3) qualitatively exploring how treatment impacts individuals’ function while having pain. These aims were pursued using data from a randomized controlled trial in Veterans with chronic pain (N = 116) randomly assigned to receive 8-week group ACT or CBT. Aim 1 identified a negative trend between the rate of change of pain and physical activity at baseline. Aim 2 did not find statistical support for a change in this relationship between pain and physical activity from baseline to post-intervention. Post-hoc analyses indicated substantial between-person variability and found that the pain-physical activity association changed from baseline to post-intervention for about half of participants, indicating this relationship is not static for all individuals. The Exploratory Aim qualitatively identified themes that supported the role of pain acceptance, activity pacing, and change in the pain-physical activity relationship. These findings suggest that the relationship between pain and physical activity is highly individualized and dynamic. Future studies should expand on these findings in larger samples and should apply idiographic approaches to better capture individualized patterns.