High-intensity interval training after stroke: An opportunity to promote functional recovery, cardiovascular health, and neuroplasticity

Introduction. Stroke is the leading cause of adult disability. Individuals poststroke possess less than half of the cardiorespiratory fitness (CRF) as their nonstroke counterparts, leading to inactivity, deconditioning, and an increased risk of cardiovascular events. Preserving cardiovascular health is critical to lower stroke risk; however, stroke rehabilitation typically provides limited opportunity for cardiovascular exercise. Optimal cardiovascular training parameters to maximize recovery in stroke survivors also remains unknown. While stroke rehabilitation recommendations suggest the use of moderateintensity continuous exercise (MICE) to improve CRF, neither is it routinely implemented in clinical practice, nor is the intensity always sufficient to elicit a training effect. High-intensity interval training (HIIT) has emerged as a potentially effective alternative that encompasses brief high-intensity bursts of exercise interspersed with bouts of recovery, aiming to maximize cardiovascular exercise intensity in a time-efficient manner. HIIT may provide an alternative exercise intervention and invoke more pronounced benefits poststroke. Objectives. To provide an updated review of HIIT poststroke through (a) synthesizing current evidence; (b) proposing preliminary considerations of HIIT parameters to optimize benefit; (c) discussing potential mechanisms underlying changes in function, cardiovascular health, and neuroplasticity following HIIT; and (d) discussing clinical implications and directions for future research. Results. Preliminary evidence from 10 studies report HIIT-associated improvements in functional, cardiovascular, and neuroplastic outcomes poststroke; however, optimal HIIT parameters remain unknown. Conclusion. Larger randomized controlled trials are necessary to establish (a) effectiveness, safety, and optimal training parameters within more heterogeneous poststroke populations; (b) potential mechanisms of HIIT-associated improvements; and (c) adherence and psychosocial outcomes.