Assessing Asymmetry in Exercise Intensity Domains between Lower Limbs in Persons with Multiple Sclerosis: A Pilot Study

Persons with multiple sclerosis (PwMS) experience a variety of physical impairments that can present in an asymmetrical pattern, resulting in significant differences between contralateral limbs (i.e., >10%). Asymmetries in PwMS have been associated with walking impairment and postural instability. Exercise intensity has been shown to influence the degree of asymmetry outcomes in healthy populations, and may have an impact on appropriate exercise prescriptions. The purpose of the current pilot study was to investigate the potential presence of asymmetry in metabolic events demarcating exercise intensity domains during single-leg cycling in PwMS. Five PwMS (Expanded Disability Status Scale range 2.0 to 4.5) completed a single leg incremental cycling test (SLICT) and a series of single-leg constant power time-to-exhaustion trials to determine gas exchange threshold (GET), peak oxygen consumption (VO2peak), peak power output (PPO), critical power (CP), and W’ (exercise tolerance above CP) for both lower limbs. Statistical analysis revealed no significant between-limb differences for VO2peak, GET, CP, PPO, and W’. Only W’ asymmetry score was significantly (49.5 ± 28.7 vs. 10.0, p = 0.04) greater than 10%. No significant differences between asymmetry scores at the GET, CP, and PPO were observed. Results from the current pilot investigation suggest that exercise intensity may not influence asymmetry outcomes in PwMS. Future studies with larger sample sizes and those with higher disability levels are required to fully understand the influence of exercise intensity on asymmetry in PwMS.