The overall objective of the current study is to determine the efficacy of a 16-week remotely delivered lifestyle behavioral intervention compared with a control condition (i.e., waitlist control) in persons newly diagnosed with MS (disease duration ≤ 2 years).

Specific Aim 1: To evaluate the changes in self-report and device-measured physical activity after the 16-week remotely delivered physical activity behavior change intervention compared with a control condition (i.e., waitlist control) in persons who have diagnosed with MS within the past two years. The investigators hypothesize that the 16-week behavior change intervention will yield greater improvements in physical activity levels than the control condition immediately after the intervention.

Specific Aim 2: To investigate the efficacy of the 16-week, remotely delivered physical activity behavior change intervention compared with the control condition for improvements in fatigue, depression, anxiety, and QoL in persons newly diagnosed with MS. The investigators hypothesize that there will be beneficial effects on the symptoms and QoL outcomes immediately after the physical activity intervention compared with minimal changes in the control condition.

Multiple sclerosis (MS) is a prevalent neurological disease of the central nervous system that is the leading cause of neurological disability among young adults in the United States. This disease results in the progressive loss of walking, substantial worsening of cognition, symptoms of fatigue, as well as compromised quality of life (QoL). There is evidence that physical activity is beneficially associated with walking mobility, cognitive function, symptoms of fatigue, depression, anxiety, and pain in persons with MS. Nonetheless, this population is strikingly sedentary and physically inactive, including persons newly diagnosed with MS (diagnosed with MS for two years or less). Indeed, approximately 40% of persons with MS reported stopping physical activity after an MS diagnosis, and persons recently diagnosed with MS have not been included in physical activity intervention research. Yet, the early stage of MS represents an ideal time point for initiating physical activity for life-long benefits. There is further evidence that physical activity and exercises interventions delivered remotely can yield benefits in managing MS symptoms and comorbidities, and disability progression. To this end, the objective of this current study is to examine the efficacy of a 16-week remotely delivered behavioral intervention, compared with a control condition (i.e., waitlist control), for increasing physical activity and improving secondary outcomes in persons newly diagnosed with MS (disease duration ≤ 2 years). Participants will complete a series of assessments of physical activity, MS symptoms, and physical and cognitive function before and immediately after the 16-week program. The assessments involve the completion of a battery of questionnaires remotely over the Internet. The investigators will also ask that participants wear an accelerometer (like a pedometer) during the waking hours of the day for a 7-day period as an assessment of physical activity. The first assessments occur upon enrollment in the study (Baseline Assessment) and the second occurs right after the intervention (16- week Assessment). In this study, participants will be randomly assigned into 1 of 2 conditions: a physical activity condition (receive the intervention immediately after baseline assessment) or a waitlist condition (receive the intervention after the 16-week assessment). Participants in both conditions will receive access to an Internet delivered program for 16 weeks as well as one-on-one coaching through Zoom. The investigators will ask that participants in the physical activity condition wear a Fitbit (this is different from the accelerometer) for tracking physical activity daily during the 16- week period. The investigators will further ask that information from the Fitbit be recorded into a logbook daily.