Do Social Cognitive Theory constructs explain response heterogeneity with a physical activity behavioral intervention in multiple sclerosis?

BACKGROUND: Behavioral interventions based on Social Cognitive Theory (SCT) are efficacious for increasing both objectively-measured and self-reported physical activity in people with multiple sclerosis (MS). PURPOSE: This study involved a secondary analysis of data focused on SCT constructs as correlates of individual-level changes (i.e., response heterogeneity) following a behavioral intervention. METHOD: Twenty-two persons with MS who completed a 6-month SCT-based behavioral intervention for increasing physical activity were included in analyses. The intervention consisted of two primary components, namely a dedicated Internet website and one-on-one video chats with a behavioral coach. Outcomes included objectively-measured moderate-vigorous physical activity (MVPA) using Actigraph model GT3X+ accelerometers and self-reported physical activity using the Godin Leisure-Time Exercise Questionnaire (GLTEQ) as well as SCT variables of exercise self-efficacy, barriers self-efficacy, outcome expectations, goal setting and planning and facilitators/impediments. RESULTS: There was individual variability in physical activity change following the intervention. For example, 4/22 participants demonstrated a reduction in MVPA, 1/22 participants had no change, 9/22 participants had less than 0.5 standard deviation (SD) increase in MVPA, and 8/22 participants had an increase in MVPA of more than 0.5 SD. Baseline SCT variables, particularly outcome expectations, goal setting, planning, and barriers self-efficacy, correlated with increased physical activity. CONCLUSIONS: This study indicates that SCT variables correlate with the response heterogeneity associated with physical activity behavioral interventions, and this might inform the delivery of interventions consistent with Bandura's stepwise implementation model for optimizing the “fit” of an intervention based on SCT for maximizing treatment efficacy in MS.