The Influence of HIIT Versus MCT on Cardiorespiratory Fitness in PPMS

Endurance training revealed to be an effective means to increase cardiorespiratory fitness in persons with Multiple Sclerosis (MS), considered relevant to health-related quality of life in this population. Moreover, endurance training improves MS-related symptoms, such as reduced walking capacity, fatigue, depression, and cognitive impairment. Owing to these benefits, endurance training has evolved as an integral part of MS rehabilitation, anchored in current treatment guidelines. In recent years, High-Intensity Interval training (HIIT) evolved as a time-efficient and safe alternative to standard care in MS rehabilitation that is Moderate Continuous Training (MCT). Indeed, HIIT has already been proven superior to MCT in improving cardiorespiratory fitness, MS-related symptoms (e.g. cognitive impairment) and, beyond, seems to elicit disease-modifying effects on MS-pathophysiology (i.e. alleviated neuroinflammation and neurodegeneration). However, current evidence is restricted to clinical trials that include samples with mixed MS disease courses, in which persons with primary progressive MS (PPMS) are underrepresented due to comparatively low prevalence rates. Distinct pathophysiological mechanisms and symptom constellations prohibit the generalisation of previous findings to persons with PPMS. In this population, however, evidence-based rehabilitative strategies are urgently needed, as disability progression in PPMS is poorly responsive to pharmacotherapy. This study, aims to validate previous findings on the superior effect of HIIT compared to MCT on improving cardiorespiratory fitness, MS-related symptoms and MS pathophysiology in persons with PPMS, contributing to the development of specific recommendations to maximize the effects of exercise as a potent non-pharmacological treatment adjuvant.