Cardiopulmonary Responses During Clinical and Laboratory Gait Assessments in People With Chronic Stroke.

Background: The 6-Minute Walk Test (6MWT) is a common clinical assessment used to evaluate locomotor function in patients after stroke. Previous work suggests the 6MWT can estimate peak metabolic capacity (VO2peak) without cardiorespiratory assessments during graded exercise tests (GXTs), which may assist with exercise prescription. However, selected research also indicated increased heart rates (HRs) during 6MWTs beyond levels considered safe without GXTs. Objective: The goal of this study was to examine cardiorespiratory responses during 6MWTs and GXTs in individuals with chronic stroke and their associations with demographic or clinical characteristics. Design: The study used a cross-sectional observational design. Methods: Cardiorespiratory responses were assessed during 6MWTs at self-selected velocity (SSV) and fastest velocity (FV), and during GXTs. Secondary assessments included the lower extremity Fugl-Meyer Assessment, Functional Gait Assessment, gait speeds, and daily stepping activity. Correlation and regression analyses were used to evaluate associations between locomotor performance, cardiorespiratory responses, and clinical and demographic characteristics. Results: Average HRs during 6MWT-FV were 72% to 76% of the age-predicted maximum (HRmax), with 20% of participants exceeding 85% predicted HRmax. When normalized to HRs during GXTs, HRs during 6MWT-FV were 86% to 88% of observed HRmax. Primary predictors of increased HRs during 6MWTs were resting HR, body mass index, and daily stepping. Distance during 6MWT-FV was a significant predictor of VO2peak in combination with other variables. Electrocardiographic abnormalities were observed in >80% of participants at rest and 31% demonstrated distinct abnormalities during GXTs, which were not related to 6MWT or GXT performance. Limitations: In addition to sample size, a primary limitation involved the ability to accurately predict or measure HRmax in patients with motor dysfunction after stroke. Conclusions: Cardiac responses were higher than anticipated during 6MWTs and often exceeded recommended HR thresholds. Clinicians should closely monitor cardiorespiratory responses during 6MWTs.

Effects of Training Intensity on Locomotor Performance in Individuals With Chronic Spinal Cord Injury: A Randomized Crossover Study.

BACKGROUND: Many physical interventions can improve locomotor function in individuals with motor incomplete spinal cord injury (iSCI), although the training parameters that maximize recovery are not clear. Previous studies in individuals with other neurologic injuries suggest the intensity of locomotor training (LT) may positively influence walking outcomes. However, the effects of intensity during training of individuals with iSCI have not been tested. OBJECTIVE: The purpose of this pilot, blinded-assessor randomized trial was to evaluate the effects of LT intensity on walking outcomes in individuals with iSCI. METHODS: Using a crossover design, ambulatory participants with iSCI >1 year duration performed either high- or low-intensity LT for ≤20 sessions over 4 to 6 weeks. Four weeks following completion, the training interventions were alternated. Targeted intensities focused on achieving specific ranges of heart rate (HR) or ratings of perceived exertion (RPE), with intensity manipulated by increasing speeds or applying loads. RESULTS: Significantly greater increases in peak treadmill speeds (0.18 vs 0.02 m/s) and secondary measures of metabolic function and overground speed were observed following high- versus low-intensity training, with no effects of intervention order. Moderate to high correlations were observed between differences in walking speed or distances and differences in HRs or RPEs during high- versus low-intensity training. CONCLUSION: This pilot study provides the first evidence that the intensity of stepping practice may be an important determinant of LT outcomes in individuals with iSCI. Whether such training is feasible in larger patient populations and contributes to improved locomotor outcomes deserves further consideration.

Altered Sagittal- and Frontal-Plane Kinematics Following High-Intensity Stepping Training Versus Conventional Interventions in Subacute Stroke.

BACKGROUND: Common locomotor deficits observed in people poststroke include decreased speeds and abnormal kinematics, characterized by altered symmetry, reduced sagittal-plane joint excursions, and use of compensatory frontal-plane behaviors during the swing phase of gait. Conventional interventions utilized to mitigate these deficits often incorporate low-intensity, impairment-based or functional exercises focused on normalizing kinematics, although the efficacy of these strategies is unclear. Conversely, higher-intensity training protocols that provide only stepping practice and do not focus on kinematics have demonstrated gains in walking function, although minimal attention toward gait quality may be concerning and has not been assessed. OBJECTIVE: The present study evaluated changes in spatiotemporal and joint kinematics following experimental, high-intensity stepping training compared with conventional interventions. DESIGN: Kinematic data were combined from a randomized controlled trial comparing experimental and conventional training and from a pilot experimental training study. METHODS: Individuals with gait deficits 1 to 6 months poststroke received up to 40 sessions of either high-intensity stepping training in variable contexts or conventional lower-intensity interventions. Analyses focused on kinematic changes during graded treadmill testing before and following training. RESULTS: Significant improvements in speed, symmetry, and selected sagittal-plane kinematics favored experimental training over conventional training, although increases in compensatory strategies also were observed. Changes in many kinematic patterns were correlated with speed changes, and increased compensatory behaviors were associated with both stride length gains and baseline impairments. LIMITATIONS: Limitations include a small sample size and use of multiple statistical comparisons. CONCLUSIONS: Improved speeds and selected kinematics were observed following high-intensity training, although such training also resulted in increased use of compensatory strategies. Future studies should explore the consequences of utilizing these compensatory strategies despite the observed functional gains.

Alterations in Aerobic Exercise Performance and Gait Economy Following High-Intensity Dynamic Stepping Training in Persons With Subacute Stroke.

BACKGROUND AND PURPOSE: Impairments in metabolic capacity and economy (O2cost) are hallmark characteristics of locomotor dysfunction following stroke. High-intensity (aerobic) training has been shown to improve peak oxygen consumption in this population, with fewer reports of changes in O2cost. However, particularly in persons with subacute stroke, inconsistent gains in walking function are observed with minimal associations with gains in metabolic parameters. The purpose of this study was to evaluate changes in aerobic exercise performance in participants with subacute stroke following high-intensity variable stepping training as compared with conventional therapy. METHODS: A secondary analysis was performed on data from a randomized controlled trial comparing high-intensity training with conventional interventions, and from the pilot study that formed the basis for the randomized controlled trial. Participants 1 to 6 months poststroke received 40 or fewer sessions of high-intensity variable stepping training (n = 21) or conventional interventions (n = 12). Assessments were performed at baseline (BSL), posttraining, and 2- to 3-month follow-up and included changes in submaximal (Equation is included in full-text article.)O2 ((Equation is included in full-text article.)O2submax) and O2cost at fastest possible treadmill speeds and peak speeds at BSL testing. RESULTS: Significant improvements were observed in (Equation is included in full-text article.)O2submax with less consistent improvements in O2cost, although individual responses varied substantially. Combined changes in both (Equation is included in full-text article.)O2submax and (Equation is included in full-text article.)O2 at matched peak BSL speeds revealed stronger correlations to improvements in walking function as compared with either measure alone. DISCUSSION AND CONCLUSIONS: High-intensity stepping training may elicit significant improvements in (Equation is included in full-text article.)O2submax, whereas changes in both peak capacity and economy better reflect gains in walking function. Providing high-intensity training to improve locomotor and aerobic exercise performance may increase the efficiency of rehabilitation sessions.Video Abstract available for more insights from the authors (see Supplemental Digital Content, http://links.lww.com/JNPT/A142).

Variable Intensive Early Walking Poststroke (VIEWS): A Randomized Controlled Trial.

BACKGROUND: Converging evidence suggests that the amount of stepping practice is an important training parameter that influences locomotor recovery poststroke. More recent data suggest that stepping intensity and variability are also important, although such strategies are often discouraged early poststroke. OBJECTIVE: The present study examined the efficacy of high-intensity, variable stepping training on walking and nonwalking outcomes in individuals 1 to 6 months poststroke as compared with conventional interventions. Methods Individuals with unilateral stroke (mean duration = 101 days) were randomized to receive ≤40, 1-hour experimental or control training sessions over 10 weeks. Experimental interventions consisted only of stepping practice at high cardiovascular intensity (70%-80% heart rate reserve) in variable contexts (tasks or environments). Control interventions were determined by clinical physical therapists and supplemented using standardized conventional strategies. Blinded assessments were obtained at baseline, midtraining, and posttraining with a 2-month follow-up. Results A total of 32 individuals (15 experimental) received different training paradigms that varied in the amount, intensity, and types of tasks performed. Primary outcomes of walking speed (experimental, 0.27 ± 0.22 m/s vs control, 0.09 ± 0.09 m/s) and distances (119 ± 113 m vs 30 ± 32 m) were different between groups, with stepping amount and intensity related to these differences. Gains in temporal gait symmetry and self-reported participation scores were greater following experimental training, without differences in balance or sit-to-stand performance. Conclusion Variable intensive stepping training resulted in greater improvements in walking ability than conventional interventions early poststroke. Future studies should evaluate the relative contributions of these training parameters.

Effects of dynamic stepping training on nonlocomotor tasks in individuals poststroke.

BACKGROUND: During the physical rehabilitation of individuals poststroke, therapists are challenged to provide sufficient amounts of task-specific practice in order to maximize outcomes of multiple functional skills within limited visits. Basic and applied studies have suggested that training of one motor task may affect performance of biomechanically separate tasks that utilize overlapping neural circuits. However, few studies have explicitly investigated the impact of training one functional task on separate, nonpracticed tasks. OBJECTIVE: The purpose of this preliminary study was to investigate the potential gains in specific nonlocomotor assessments in individuals poststroke following only stepping training of variable, challenging tasks at high aerobic intensities. METHODS: Individuals with locomotor deficits following subacute and chronic stroke (n=22) completed a locomotor training paradigm using a repeated-measures design. Practice of multiple stepping tasks was provided in variable environments or contexts at high aerobic intensities for ≥40 sessions over 10 weeks. The primary outcome was timed Five-Times Sit-to-Stand Test (5XSTS) performance, with secondary measures of sit-to-stand kinematics and kinetics, clinical assessment of balance, and isometric lower limb strength. RESULTS: Participants improved their timed 5XSTS performance following stepping training, with changes in selected biomechanical measures. Statistical and clinically meaningful improvements in balance were observed, with more modest changes in paretic leg strength. CONCLUSIONS: The present data suggest that significant gains in selected nonlocomotor tasks can be achieved with high-intensity, variable stepping training. Improvements in nonpracticed tasks may minimize the need to practice multiple tasks within and across treatment sessions.