Multiple sclerosis (MS) is an autoimmune disease characterized by chronic inflammation specifically targeting the central nervous system. 1 It is associated with destruction of the surrounding myelin sheaths leading to formation of plaques/lesions dispersed throughout the brain and spinal cord. 1 The prevalence of MS is nearly one million in the United States with the majority of diagnoses occurring between the ages of 20 and 50. 2 Though the precise etiology remains unknown, genetic and environmental factors have been linked to the cause and therefore MS is considered a multifactorial disease. 3 Hallmark signs of MS include progressive demyelination, oligodendrocyte damage, and ultimately axonal destruction. These adaptations occur due to an inflammatory response consisting of macrophages, microglia, T and B Cells, followed by an intense astrocyte reaction leading to glial scarring, a common characteristic of chronic MS lesions. 4 According to Lassmann 1, clinical deficits seen throughout the course of MS are more closely correlated to the degree of axonal loss as opposed to the amount of lesions or extent of demyelination. These include deficits in cognition, vision, bowel and bladder control, coordination, and loss of muscle strength. 5 Multiple Sclerosis has various subtypes making the clinical course heterogeneous among patients. 6 Subtypes include: clinically isolated syndrome (CIS), relapsing remitting MS (RRMS), primary progressive MS (PPMS), and secondary progressive MS (SPMS). 6 The variability of disease course for each individual subtype is extremely important, and should be taken into consideration for prognosis and intervention options. 3

Due to the aggressive, progressive, unpredictable nature of MS, lack of evidence for a cure, and the wide array of cognitive and physical symptoms, MS can detrimentally impact a patient's health and reduce overall quality of life. 7 Current research advocates for physical activity (PA) as an intervention to combat these effects. Physical activity is referred to here as low to moderate level exercise. 8 Some individuals with MS who incorporated long-term physical activity into their life demonstrated a decrease in the progression of the disease and a reduction in MS flare-ups. 9 In order to successfully implement PA based interventions for the management of MS one must first identify individual motivators for PA. 5 Motivators for physical activity include self-efficacy and internalized motivation which are derived from physical activity outcomes. 5Self-efficacy is "the belief that one can successfully cope with challenging conditions" 7 whereas self -determination refers to the origin of one's motivation. 8 Other researchers found that "those with MS who were more physically active had greater self-efficacy for function and control, and self-efficacy for function and control were associated with greater physical and psychological components of quality of life." 7 However, the vast majority of those diagnosed with MS avoid exerting themselves due to symptoms of muscle weakness and fatigue; this lack of PA is thought to exacerbate those symptoms which then leads to a perpetual cycle of inactivity and flare-ups. 8,9 Therefore, it has also been theorized that a program designed for MS patients which focuses on promoting self-efficacy could lead to long-term PA participation and thus result in increased quality of life. 8

One such form of physical activity that could provide physiological and psychological benefits for individuals diagnosed with MS is yoga. "Yoga is an ancient Indian, non-religious mind- body approach that has components centering on meditation, mindfulness, breathing, and activity or postures." 10 Exercise programs which involve these components have been found to improve the quality of life by addressing the biopsychosocial (BPS) model. The BPS model is composed of biological, psychological and social components which has been found to have a positive impact on an individual's health. 11 Therefore, it is hypothesized that by increasing muscular strength and flexibility while decreasing affective factors such as depression, stress and anxiety and improving social factors will improve an individual's overall well-being and allow them to cope with the symptoms associated with MS. 11,12 Numerous studies have found yoga to be beneficial in improving fatigue and other symptoms associated with MS. 13 For example, standing yoga poses can promote improved reactive balance through the use of stepping strategies. Yoga also has the potential to reduce cognitive and motor costs for individuals during dual tasks resulting in decreased interference and thus optimal functioning in more challenging conditions. 14 Previous research has demonstrated that yoga significantly improved "physical performance and mental function" and factors associated with quality of life in subjects with MS.15 Based on these findings, the investigators hypothesize that yoga will improve quality of life and self-efficacy for physical activity in people living with MS.