Feasibility of a web-based randomised controlled trial for a tailored physical activity intervention

Abstract

active-online.ch is a freely available Internet-based physical ac-tivity counselling programme disseminated population-wide with a multimedia strategy. The feasibility of an Internet-based ran-domised controlled trial was tested in a small-scale study. Partici-pants were recruited using print advertisements, Internet banners and e-mail messages. After baseline assessment, they were ran-domised to the intervention programme active-online.ch or a con-trol website. Participants were re-contacted by e-mail after six weeks and six months for follow-up assessment. E-mail invitations in an administration unit and a print advertisement were most ef-fective for recruitment. After six weeks, complete data was avail-able from 76% of the original participants, after six month from 63%. 48% of the original subjects were women, 76% between 30 and 60 years old and 57% insufficiently active. At every stage of the study, the proportion of women in the trial decreased signifi-cantly. 35% of the participants in the intervention group completed the intervention programme. For future full-scale randomised tri-als using an Internet design, recruitment should be planned in view of the implementation strategy of the intervention. Expected adherence to both the study protocol and the physical activity in-tervention need to be considered when sample sizes are estimated.