Unwrapping the ?black box? of balance training in people with multiple sclerosis-A descriptive systematic review of intervention components, progression, and intensity

Background: Delineating the specific components of the existing balance training interventions in people with multiple sclerosis (PwMS) may contribute to a framework for future design and reporting of such interventions. Thus, we aimed to systematically synthesize how balance training frequency, intensity, time, type, duration, and progression are reported in balance training interventions for PwMS.Methods: A systematic literature search was conducted in Medline, Embase, Web of Science, and Cinahl. Search terms were MS, postural balance, walking, gait, and randomized/quasi-randomized controlled or clinical trials. Articles including ambulatory PwMS and interventions designed to challenge the balance control system were eligible. Two investigators screened, selected, and extracted data independently. Data on study characteristics such as design, population, and balance training content were extracted. Categorization of balance training based on balance control components was performed.Results: We included 40 studies grouped under five balance training categories. Balance interventions were well described regarding frequency, session time, and duration, but only two interventions described training intensity, and no systematic, gradual progression approach was reported for balance training adaptation over time. However, the balance training interventions included many sensory and motor components of the balance control system. Still, little focus was on reactive motor strategies, vestibular sense, and cognitive dual-tasking.Conclusions: Existing balance training interventions in PwMS primarily consist of practicing sensory and motor strategies. Future balance training interventions are encouraged to systematically monitor individual advancements in balance training adaptations and to apply the progressive overload principle (i.e. continuous increase in balance exercise stimulus over time). Furthermore, we suggest that balance training in PwMS is performed with high intensity near an individual's balance capacity limits. Finally, individualized balance training is recommended to cover all relevant components of balance control using the proposed framework.