Baseline predictors of treatment gains in peak propulsive force in individuals poststroke

Hsiao et al. Journal of NeuroEngineering and Rehabilitation (2016) 13:2 DOI 10.1186/s12984-016-0113-1 RESEARCH Open Access Baseline predictors of treatment gains in peak propulsive force in individuals poststroke HaoYuan Hsiao1,4*, Jill S. Higginson2 and Stuart A. Binder-Macleod3 Abstract Background: Current rehabilitation for individuals poststroke focuses on increasing walking speed because it is an indicator of community walking ability and quality of life. Propulsive force generated from the paretic limb is critical to walking speed and may reflect actual neural recovery that restores the affected neural systems. A wide variation across individuals in the improvements in paretic propulsive force was observed following an intervention that targeted paretic propulsive force. This study aimed to determine if specific baseline characteristics can be used to predict patients who would respond to the intervention. Methods: Participants (N = 19) with chronic poststroke hemiparesis walked at their self-selected and maximal walking speeds on a treadmill before and after a 12-week gait training program. Propulsive forces from the paretic limb were analyzed. Pearson correlation coefficient was used to determine the relationships between (1) treatment gains in walking speed and propulsive force following intervention, and (2) treatment gains in propulsive force and baseline propulsive forces. Results: Treatment gains in self-selected walking speed were correlated to treatment gains in paretic propulsive force following intervention. In addition, changes in paretic propulsive force between self-selected and maximal walking speeds at baseline were strongly correlated to treatment gains in paretic propulsive force. Conclusions: The capacity to modulate paretic propulsive force, rather than the absolute propulsive force during self-selected or maximal walking speed, predicted treatment gains in propulsive force following the intervention. Findings from this research could help to inform clinicians and researchers to target the appropriate patient population for rehabilitation interventions. Keywords: Stroke, Gait, Propulsion, Speed, Predictor, Ground reaction force Background Stroke is the leading cause of long term disability in the United States [1]. Current rehabilitation for individuals poststroke focuses on increasing walking speed because it is an indicator of community walking ability and quality of life [2–5]. Increases in walking speed can be achieved via neural recovery or the development of compensation strategies [6, 7]. Specifically, during walking, propulsive forces generated from both limbs contribute to the forward progression of the body center of mass. However, * Correspondence: 1 Biomechanics and Movement Science Program, University of Delaware, Newark, DE 19716, USA 4 540 S. College Avenue, Suite 201F, Newark, DE 19716, USA Full list of author information is available at the end of the article because of the reduced propulsive force generated from the paretic limb in individuals poststroke [8, 9], it was observed that more severely impaired stroke patients use the propulsive force generated from the non-paretic limb to compensate [10]. Indeed, previous intervention studies have found that subjects were likely to use compensatory strategies during training, leading to increases in walking speed due to promoting compensatory strategies rather than neural recovery [9, 11–13]. Thus, evaluating treatment gains in walking speed alone may be insufficient to represent neural recovery. In contrast, the propulsive force from the paretic extremity is a direct measure of the paretic limb’s contribution and, therefore, may reflect actual neural recovery that restores the affected neural systems. © 2016 Hsiao et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Hsiao et al. Journal of NeuroEngineering and Rehabilitation (2016) 13:2 Page 2 of 5 Thus, recent rehabilitation research has emphasized the importance of improving paretic propulsive ability [9, 14]. Our laboratory has designed an intervention that targets paretic propulsion in individuals poststroke to increase walking speed [14, 15]. Specifically, we hypothesized that an intervention combining treadmill gait training at maximal speed and functional electrical stimulation applied to the paretic ankle musculature (FastFES) would facilitate the translation of increased plantarflexor activity into forward propulsion, ultimately resulting in increased walking speed. Although a previous preliminary study from our laboratory has reported improvements in paretic propulsive force following 12-weeks of FastFES intervention [14], we observed a wide variation across individuals in the improvements in paretic propulsive force in response to the intervention. The primary purpose of this study was to determine if specific baseline characteristic can be used to predict patients who would respond to this intervention. We first examined the relationship between gains in walking speed and gains in paretic propulsive force following the FastFES intervention. Next, baseline propulsive forces were used in a linear regression model to predict gains in propulsive force following training. We hypothesized that baseline measurement of propulsive force may reflect those individuals most likely to increase propulsive force with FastFES training. Findings from this research would better inform clinicians and researchers to target the appropriate patient population for rehabilitation. participants provided written informed consent to participate in this study. Methods Participants A total of 19 participants (age, 60.3 ± 11.4 years; time since stroke, 6.3 ± 9.2 years; 5 female; 5 right hemiparetic; self-selected walking speed, 0.77 ± 0.32 m/s) with poststroke hemiparesis were included in this study. Participant inclusion criteria were a single cortical or subcortical stroke, a poststroke duration of at least 6 months, the ability to ambulate without the assistance of another individual, sufficient cognitive function to follow instruction and communicate with the investigators, the ability to walk for 6 min without orthotic support, sufficient passive dorsiflexion range of motion to position the ankle in a neutral position with the knee extended, and sufficient passive hip extension to extend the hip 10°. Individuals were excluded from participating if they had a history of multiple strokes, cerebella (...truncated)