Abstract
Background and Purpose—
The amount of task-specific stepping practice provided during rehabilitation poststroke can influence locomotor recovery and reflects one aspect of exercise dose that can affect the efficacy of specific interventions. Emerging data suggest that markedly increasing the intensity and variability of stepping practice may also be critical, although such strategies are discouraged during traditional rehabilitation. The goal of this study was to determine the individual and combined contributions of intensity and variability of stepping practice to improving walking speed and distance in individuals poststroke.
Methods—
This phase 2, randomized, blinded assessor clinical trial was performed between May 2015 and November 2018. Individuals between 18 and 85 years old with hemiparesis poststroke of >6 months duration were recruited. Of the 152 individuals screened, 97 were randomly assigned to 1 of 3 training groups, with 90 completing >10 sessions. Interventions consisted of either high-intensity stepping (70%–80% heart rate reserve) of variable, difficult stepping tasks (high variable), high-intensity stepping performing only forward walking (high forward), and low-intensity stepping in variable contexts at 30% to 40% heart rate reserve (low variable). Participants received up to 30 sessions over 2 months, with testing at baseline, post-training, and a 3-month follow-up. Primary outcomes included walking speeds and timed distance, with secondary measures of dynamic balance, transfers, spatiotemporal kinematics, and metabolic measures.
Results—
All walking gains were significantly greater following either high-intensity group versus low-variable training (all P<0.001) with significant correlations with stepping amount and rate (r=0.48–60; P<0.01). Additional gains in spatiotemporal symmetry were observed with high-intensity training, and balance confidence increased only following high-variable training in individuals with severe impairments.
Conclusions—
High-intensity stepping training resulted in greater improvements in walking ability and gait symmetry than low-intensity training in individuals with chronic stroke, with potential greater improvements in balance confidence.
Introduction
The increasing incidence1 and current survival rates of individuals who experience a stroke have resulted in a substantial patient population with neurological deficits that limit locomotor capacity and postural stability.2,3 In individuals with chronic (>6 months) stroke, mobility limitations4,5 lead to reduced cardiopulmonary capacity that can further exacerbate locomotor deficits.3 Previous work6,7 suggests specific exercise training parameters, including the frequency, intensity, time, and type, can influence changes in health and fitness in individuals with and without neurological injury.8 These parameters represent the dose of exercise interventions, although their contributions to locomotor recovery poststroke are uncertain. Early studies advocated that large amounts of stepping practice with focus on normalizing gait patterns was a critical determinant of improved mobility.9–11 Unfortunately, a multicenter trial using this strategy revealed limited gains beyond conventional approaches.12 Additional research indicates treadmill exercise at submaximal aerobic intensities determined during baseline testing can improve walking endurance poststroke,13–15 although changes in walking speed or other mobility outcomes (balance or transfers) are inconsistent or negligible. The combined findings imply that these dosage parameters may not be critical to locomotor recovery poststroke.
An alternative hypothesis is that specific training variables can influence locomotor recovery when their manipulation substantially challenges the physiological demands associated with functional mobility. In particular, pilot studies indicate stepping training at cardiovascular intensities that are oftentimes greater than those achieved during baseline testing can improve multiple measures of locomotor and cardiopulmonary function.16–18 In addition, increasing the variability and difficulty of stepping tasks (eg, multidirectional walking, stair climbing, overground walking on uneven, or compliant surfaces) requires increased neuromuscular coordination and postural control that may improve mobility and dynamic stability.16,17,19
Despite these findings, clinical implementation of high-intensity stepping training in variable contexts is limited. Specific concerns include the potential for cardiovascular events,20 despite data indicating no additional risks compared to standard interventions.21 Additional concerns include practice of abnormal kinematic strategies, particularly in those with severe neuromuscular impairments during difficult, variable tasks. Such training deviates considerably from traditional interventions that focus on correcting abnormal gait patterns,9,10,12 although available data suggest gait kinematics can improve with variable stepping training.16,17,22
The present study examined the relative contributions of stepping intensity and variability on mobility outcomes in ambulatory individuals with chronic stroke. Using a randomized, controlled trial design, we hypothesized that high-intensity stepping training in variable contexts would result in greater gains in locomotor outcomes as compared to more traditional training focused on forward walking or low-intensity training of variable stepping tasks. Additional outcomes included alterations in transfers, dynamic balance and balance confidence, spatiotemporal kinematics, peak metabolic capacity, and potential adverse events. Results from this trial could indicate the potential utility of high-intensity training of variable, difficult tasks to improve mobility poststroke.[…]
Source: https://www.ahajournals.org/doi/10.1161/STROKEAHA.119.026254
TBI Rehabilitation 