The Persuasive Power of Text Messages in Motivating Physical
Activity in Young Adults
The many benefits of physical activity are well established, yet 62% of U.S. young adults (ages
18-24) are not active at recommended levels, defined as 30 minutes or more of moderate
intensity activity everyday . The lack of physical activity among this population is of concern
because many adult behaviors are established during late adolescence and early adulthood ,
contributing to the increase in obesity and other chronic diseases later in life. In my dissertation,
I am investigating if text messages tailored to encourage physical activity among young adults
are an effective intervention. Specifically, I am interested in exploring the factors that might
affect the persuasive power of text messages in encouraging physical activity and suggest
guidelines for designing persuasive text-message based support systems.
1. Persuasion with Text Messages
Technology that is designed to change people’s attitude and/or behavior is termed Persuasive
Technology . The use of text messages as persuasive technology to motivate behavior change
is grounded in social cognitive theory  since text messages can be tailored to support personal
goals, enhancing motivation through increased self-efficacy . Text messaging has become
very popular over the years , making it a strong medium for intervention. Text messaging
can also be cost-effective by eliminating the need for “someone” to send the messages by
automating its delivery. However, we do not know if such a system will be accepted or effective
in encouraging physical activity.
Automated text messaging support-systems were useful in helping smokers to quit smoking 
and Type I diabetic adolescents to adhere to regular insulin therapy (Sweet Talk)  but it was
not effective in a bulimia nervosa aftercare program . In  participants thought the text
messages were “impersonal” and the program “too computerized.” On the other hand in another
study we conducted, free form text messages were exchanged among teenage girls to encourage
each other to walk more, showed potential but it was not completely effective . One of the
main reasons for its ineffectiveness was that the girls did not know what to say to motivate each
It is not clear from these studies what would make a text-messaging support system effective. In
my dissertation, I want to explore some of the factors that might have contributed to the success
and failure of these systems and suggest guidelines for designing persuasive text-message based
2. Factors Affecting Persuasion
Why did the automated text messaging support system succeed in the smoking cessation and
insulin adherence programs? Why were the automated messages in the bulimia nervosa aftercare
program “impersonal” and “computerized” when similar text messages were used successfully
for the other two programs? If automated messages are too impersonal and free-form text
messages are too unstructured for constructive messages, would customizable structured
messages from a friend be more effective? In my dissertation I am exploring these questions and
more by studying three factors that may contribute to the effect of text messages on motivating
physical activity: 1) the technology used to deliver the intervention which in this case is text
messaging 2) personal connection with the sender of the text message and 3) message tailoring to
the level of motivation of the person receiving the messages.
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