Acute Effects of High-Intensity Interval Exercise on Physiological and Functional Outcomes in Multiple Sclerosis

Abstract

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system that results in physiological deconditioning and walking disability. High-intensity interval exercise (HIIE) has induced significant improvements in physiological conditioning in healthy and clinical populations. However, the effects of engaging in HIIE on cardiorespiratory functioning, gait, and walking performance in persons with MS who have mobility disability are relatively unknown. PURPOSE: To examine the effects of single sessions of recumbent stepping (HIIE) and continuous (CON) exercise on physiological and functional outcomes in persons with MS. METHODS: 5 participants with mild-to-moderate MS underwent HIIE and CON exercise bouts. The HIIE bout included 10 cycles of 1-min intervals at the wattage associated with 90% VO2peak followed by 1-min recovery intervals at 15W, totaling 20 min in length. The CON bout consisted of 20 min at the wattage associated with 50-60% VO2peak. Physiological measures were collected within session, and functional measures were collected pre-, immediately-post, and 10-minutes post-exercise. RESULTS: We observed significant differences between the CON and HIIE protocols for VO2 (t=-4.36, P=0.01), power output (t=-4.20, P=0.01), and RER (t=-7.24, P<0.01), with the HIIE condition inducing higher values than the CON condition. Heart rate approached a statistically significant difference between conditions (t=-2.61, P=0.06). There were no significant interaction effects or effects of time or condition on walking speed and gait kinematics (P>0.05). CONCLUSIONS: We determined that HIIE exercise taxes the cardiorespiratory system significantly more than CON exercise, yet without deleterious effects on walking and gait in persons with MS. This has important implications for informing an evidence-based exercise prescription in persons with MS who have walking impairments that is appropriate for improving physiological conditioning.