
"The findings are important because they provide evidence that different channels of delivery can provide equally effective results," said lead author Bess Marcus, professor of psychiatry and human behaviour at Brown Medical School.
"Non face-to-face methods, such as the mail and the internet, can reduce potential barriers, such as lack of access to fitness facilities and time constraints."
Marcus and her team decided to study the effectiveness of web-based channels because of their potential to be available to larger populations at minimal cost.
They studied 249 healthy, sedentary US adults. Participants were randomly assigned one of three physical activity intervention programs: tailored internet, standard internet and tailored print.
Those in the tailored internet group were asked to log-on to a website designed by the researchers that included educational materials, tips for adopting and maintaining physical activity, and goal setting functions.
They completed daily physical activity logs online, were emailed monthly questionnaires, and received immediate feedback according to their responses.
Individuals in the tailored print group received the same information as those in the tailored internet group, but the materials, including feedback, were delivered through the post.
Participants in the standard internet group were provided links to six pre-selected physical activity websites available to the general public, but not customised by the researchers.
They were asked to complete physical activity logs and monthly questionnaires online, but did not receive tailored feedback reports.
After six months, participants in the tailored internet group reported approximately 120 minutes of physical activity per week, the tailored print group 112.5 minutes per week, and the standard internet group 90 minutes.
But after 12 months weekly activity reported was 90, 90 and 80 minutes respectively, showing no significant difference between the programs over time.
"We found that the online interventions worked just as well as the more expensive printed materials," said Marcus.