Multiple sclerosis (MS) is an immune-mediated disease characterized by demyelination, axon transection, and lesion formation in the central nervous system (Guicciardi et al., 2019; Dobson and Giovannoni, 2019). MS has a prevalence of nearly 1 million adults in the United States and 2.8 million adults worldwide (The Multiple Sclerosis International Federation, 2020), and is usually diagnosed in early adulthood, typically between ages of 20 and 40 years (Ligouri et al., 2000). Persons with MS have an average life expectancy of 75.9 years based on early treatment, rehabilitation, and management of comorbid conditions (Marrie et al., 2015; Giovannoni, 2018). This highlights the crucial role of early intervention in slowing MS progression, preventing long-term disability, and enhancing health-related quality of life (HRQOL) (Burks, 2008; Cerqueira et al., 2018).

Physical activity (PA) offers multiple benefits for disease modification, rehabilitation, and symptom and comorbidity management in MS (Dalgas et al., 2019; Halabchi et al., 2017). The benefits of PA include reducing relapse rate and disability progression, as well as improving walking, balance, cognition, fatigue, depression, and HRQOL (Halabchi et al., 2017; Motl et al., 2017; Marck et al., 2014; Dalgas et al., 2010). However, persons with MS are not sufficiently active for accruing health benefits, including those newly diagnosed with MS (Motl et al., 2005; Casey et al., 2018; Kinnett-Hopkins et al., 2017), and PA is seldom promoted early in the disease (Huynh et al., 2021). By comparison, disease-modifying therapies (DMTs) are initiated early after diagnosis, yet PA promotion research has not focused on persons newly diagnosed with MS (Huynh et al., 2021). Indeed, one systematic review on theory-based behavior change interventions for promoting physical activity in persons with MS indicated that the shortest mean disease duration of participants across those studies was 7 years, and the majority of studies enrolled participants with a mean duration of 10 years or longer (Huynh et al., 2021). This underscores a salient opportunity for developing and delivering PA behavior change interventions in early MS for maximizing long-term benefits of PA along with DMTs.

Theory should be applied when developing and delivering PA behavior change interventions, as theoretical frameworks provide an extensive understanding of behavior and targets for its change (U.S. Department of Health and Human Services – National Institudes of Health, 2018; Bluethmann et al., 2016). The Capability-Opportunity-Motivation-Behavior (COM-B) model and the Behavior Change Wheel (BCW) (Michie et al., 2014) represent a comprehensive approach for developing behavior change interventions. The COM-B model provides an in-depth understanding of behavior through capability-opportunity-motivation interactions, and the BCW identifies fundamental tools (i.e., Intervention Functions and Behavior Change Techniques [BCTs]) for intervention design (Michie et al., 2011). The COM-B model has recently been applied for understanding PA behavior among adults with MS (Riemann-Lorenz et al., 2019; Riemann-Lorenz et al., 2020), including those newly diagnosed with MS (i.e., disease duration ≤2 years) (Huynh et al., 2023; Huynh et al., 2023). The COM-B-based PA determinants among persons newly diagnosed with MS and the links with the BCW domains could inform the design of PA intervention for this MS subpopulation.

Feasibility study designs should be applied in the early stage of intervention development and delivery for understanding study design parameters, potential problems, and practicality of an intervention before engaging in efficacy and effectiveness research (Adamson et al., 2016). Feasibility designs provide information on four essential metrics: process, resource, management, and scientific metrics (Learmonth and Motl, 2018). Process metrics evaluate recruitment methods, as well as retention and adherence rates. Resource metrics involve the time and cost of the intervention. Management metrics assess data management and safety reporting procedures for potential issues and alterations. Scientific metrics evaluate the safety, burden, and intervention effects. Collectively, these metrics provide foundational insights for developing and delivery future randomized control trials of PA behavior change interventions in persons newly diagnosed with MS.

This study examined the feasibility and initial efficacy of a 12-week remote COM-B-based behavior change intervention targeting lifestyle PA in persons newly diagnosed with MS. We anticipated the proposed intervention would be feasible based on four feasibility metrics, particularly ≥80 % retention rate and adherence rates to coaching calls and reviewing newsletters. We further hypothesized that the intervention would increase PA levels, reduce fatigue, and enhance HRQOL. If our hypotheses are supported, the results will provide novel evidence on feasibility and initial efficacy of a COM-B-based PA behavior change intervention in persons newly diagnosed with MS.