The investigators are conducting a pilot study to examine the feasibility and efficacy of a technology-based behavior change intervention for reducing SB in African Americans with MS located in the United States. The intervention combines text message- and print-based approaches for behavior change based on Social Cognitive Theory (SCT). SCT-based content will be the active component for changing SB, while cellphone text messages and print newsletter will be the delivery mechanism. The use of cellphone to deliver the intervention content is based, in part, on the fact that cellphone is an ordinary form of communication in today's world, providing an optimal medium for reaching large groups of people remotely. The study will yield major advancement in identifying the feasibility and efficacy of interrupting and reducing SB via a technology-based intervention in African Americans with MS, a segment of the MS population that has been underrepresented in MS therapeutic management studies. If successful, this research will lay the foundation for applying the current strategy in large-scale interventions including African Americans and possibly other minority groups with MS.

The intervention will be 12 weeks and divided into two parts. Part 1: Weeks 1-6 will focus on interrupting long periods of SB. At the beginning of the first week, participants will receive a packet containing print material providing lay information on what constitutes SB and examples of such behavior, highlighting the importance of interrupting prolonged periods of SB and the associated health benefits. The aim of the packet is to provide the basis to introduce the key element (i.e., SCT-based instructional cellphone text-messages) of the intervention. This will occur during the following six weeks, wherein participants will receive two text-messages/day (i.e., morning and afternoon) on the importance and health benefits of interrupting SB hourly. The text-messages will prompt individuals to interrupt SB by standing still, standing while performing tasks, or walking around. The text-messages will include further tips and strategies for interrupting SB. The investigators have previously developed a computerized messaging system that will be used to send the text-messages twice a day in the proposed intervention. The investigators will supplement the text messaging by sending bi-weekly SCT-based newsletters to participants that highlight ways of overcoming difficulties in effectively interrupting SB. The SCT content for the messages and newsletter has been created in previous research and will be revised for the proposed intervention. Part 2: Weeks 7-12 will focus on replacing SB with light PA. On the first day of week 7, participants will receive a second packet of print material explaining the concept of light PA and emphasizing the importance of moving more daily. The print material will highlight the benefits of replacing SB with light PA and will contain instructions for goal setting (i.e., target number of steps/day) and self-monitoring of daily PA, including receive a pedometer and a log for recording total steps/day. Similar to part 1, the key element for intervention delivery will be the SCT-based instructional cellphone text-messages, which participants will receive during the second six-week intervention period. More specifically, they will receive two text-messages/day on the importance and health benefits of replacing SB with light PA. The text-messages will recommend participants to watch for prolonged periods of SB and try and substitute these for light PA, such as light intensity walking and light-intensity focal exercise (e.g., stationary walk, marching). The text-messages will also remind participants to use the pedometer to set incremental personal goals for steps/day and to gauge the replacement of SB with light PA by watching the pedometer readings. The investigators further will include tips and strategies for replacing SB with light PA based on common daily activities. Bi-weekly SCT-based newsletters will be used to supplement the stimulus from the text-messages, by reinforcing the importance of sitting less and moving more.