High Intensity Exercise in Multiple Sclerosis: Effects on Muscle Contractile Characteristics and Exercise Capacity, a Randomised Controlled Trial

INTRODUCTION Low-to-moderate intensity exercise improves muscle contractile properties and endurance capacity in multiple sclerosis (MS). The impact of high intensity exercise remains unknown. METHODS Thirty-four MS patients were randomized into a sedentary control group (SED, n = 11) and 2 exercise groups that performed 12 weeks of a high intensity interval (HITR, n = 12) or high intensity continuous cardiovascular training (HCTR, n = 11), both in combination with resistance training. M.vastus lateralis fiber cross sectional area (CSA) and proportion, knee-flexor/extensor strength, body composition, maximal endurance capacity and self-reported physical activity levels were assessed before and after 12 weeks. RESULTS Compared to SED, 12 weeks of high intensity exercise increased mean fiber CSA (HITR: +21 ± 7%, HCTR: +23 ± 5%). Furthermore, fiber type I CSA increased in HCTR (+29 ± 6%), whereas type II (+23 ± 7%) and IIa (+23 ± 6%,) CSA increased in HITR. Muscle strength improved in HITR and HCTR (between +13 ± 7% and +45 ± 20%) and body fat percentage tended to decrease (HITR: -3.9 ± 2.0% and HCTR: -2.5 ± 1.2%). Furthermore, endurance capacity (Wmax +21 ± 4%, time to exhaustion +24 ± 5%, VO2max +17 ± 5%) and lean tissue mass (+1.4 ± 0.5%) only increased in HITR. Finally self-reported physical activity levels increased 73 ± 19% and 86 ± 27% in HCTR and HITR, respectively. CONCLUSION High intensity cardiovascular exercise combined with resistance training was safe, well tolerated and improved muscle contractile characteristics and endurance capacity in MS. TRIAL REGISTRATION ClinicalTrials.gov NCT01845896.