BACKGROUND: Physical activity has been associated with improvements in walking mobility and quality of life in persons with multiple sclerosis (MS), and yet this population is largely sedentary and inactive compared with the general population.

OBJECTIVES: We conducted a pilot, randomized controlled trial (RCT) for examining the effect of an Internet intervention based on social cognitive theory (SCT) for favorably increasing physical activity among persons with MS. We further examined variables from SCT as possible mediators of the Internet intervention.

METHODS: We randomly allocated 54 persons with MS into either an Internet intervention condition or a waitlist control condition. The participants completed measures of physical activity, self-efficacy, outcome expectations, functional limitations, and goal setting before and after the 12-week period.

RESULTS: The intervention group reported a statistically significant (p = 0.01) and large increase in physical activity over time (d = 0.72), whereas the control group had a small (d = 0.04) and non-significant change in physical activity (p = 0.71). The intervention group further reported a statistically significant (p = 0.001) and large increase in goal setting over time (d = 0.97), whereas the control group had a small (d = -0.13) and non-significant change (p = 0.17). The change in goal setting over time mediated the effect of the Internet intervention on physical activity behavior.

CONCLUSIONS: This pilot study sets the stage for a subsequent RCT that includes a larger sample of persons with MS, longer intervention period along with a follow-up, objective measure of physical activity, and secondary outcomes of walking mobility and QOL.