The Effect of Split-Belt Treadmill Interventions on Step Length Asymmetry in Individuals Poststroke: A Systematic Review With Meta-Analysis

Motor Learning Following Stroke: Mechanisms of Learning and Techniques to Augment Neuroplasticity

Sensorimotor impairments are common after stroke requiring stroke survivors to relearn lost motor skills or acquire new ones in order to engage in daily activities. Thus, motor skill learning is a cornerstone of stroke rehabilitation. This article provides an overview of motor control and learning theories that inform stroke rehabilitation interventions, discusses principles of neuroplasticity, and provides a summary of practice conditions and techniques that can be used to augment motor learning and neuroplasticity in stroke rehabilitation.

Reinforcement feedback impairs locomotor adaptation and retention

Introduction

Locomotor adaptation is a motor learning process used to alter spatiotemporal elements of walking that are driven by prediction errors, a discrepancy between the expected and actual outcomes of our actions. Sensory and reward prediction errors are two different types of prediction errors that can facilitate locomotor adaptation. Reward and punishment feedback generate reward prediction errors but have demonstrated mixed effects on upper extremity motor learning, with punishment enhancing adaptation, and reward supporting motor memory. However, an in-depth behavioral analysis of these distinct forms of feedback is sparse in locomotor tasks.

Methods

For this study, three groups of healthy young adults were divided into distinct feedback groups [Supervised, Reward, Punishment] and performed a novel locomotor adaptation task where each participant adapted their knee flexion to 30 degrees greater than baseline, guided by visual supervised or reinforcement feedback (Adaptation). Participants were then asked to recall the new walking pattern without feedback (Retention) and after a washout period with feedback restored (Savings).

Results

We found that all groups learned the adaptation task with external feedback. However, contrary to our initial hypothesis, enhancing sensory feedback with a visual representation of the knee angle (Supervised) accelerated the rate of learning and short-term retention in comparison to monetary reinforcement feedback. Reward and Punishment displayed similar rates of adaptation, short-term retention, and savings, suggesting both types of reinforcement feedback work similarly in locomotor adaptation. Moreover, all feedback enhanced the aftereffect of locomotor task indicating changes to implicit learning.

Discussion

These results demonstrate the multi-faceted nature of reinforcement feedback on locomotor adaptation and demonstrate the possible different neural substrates that underly reward and sensory prediction errors during different motor tasks.

Propulsive Force Modulation Drives Split-Belt Treadmill Adaptation in People with Multiple Sclerosis

Most people with multiple sclerosis (PwMS) experience significant gait asymmetries between their legs during walking, leading to an increased risk of falls. Split-belt treadmill training, where the speed of each limb is controlled independently, alters each leg's stepping pattern and can improve gait symmetry in PwMS. However, the biomechanical mechanisms of this adaptation in PwMS remain poorly understood. In this study, 32 PwMS underwent a 10 min split-belt treadmill adaptation paradigm with the more affected (MA) leg moving twice as fast as the less affected (LA) leg. The most noteworthy biomechanical adaptation observed was increased peak propulsion asymmetry between the limbs. A kinematic analysis revealed that peak dorsiflexion asymmetry and the onset of plantarflexion in the MA limb were the primary contributors to the observed increases in peak propulsion. In contrast, the joints in the LA limb underwent only immediate reactive adjustments without subsequent adaptation. These findings demonstrate that modulation during gait adaptation in PwMS occurs primarily via propulsive forces and joint motions that contribute to propulsive forces. Understanding these distinct biomechanical changes during adaptation enhances our grasp of the rehabilitative impact of split-belt treadmill training, providing insights for refining therapeutic interventions aimed at improving gait symmetry.

One-year retention of gait speed improvement in stroke survivors after treatment with a wearable home-use gait device

Background

Gait impairments after stroke are associated with numerous physical and psychological consequences. Treatment with the iStride® gait device has been shown to facilitate improvements to gait function, including gait speed, for chronic stroke survivors with hemiparesis. This study examines the long-term gait speed changes up to 12 months after treatment with the gait device.

Methods

Eighteen individuals at least one-year post-stroke completed a target of 12, 30-minute treatment sessions with the gait device in their home environment. Gait speed was measured at baseline and five follow-up sessions after the treatment period: one  week, one  month, three months, six months, and 12 months. Gait speed changes were analyzed using repeated-measures ANOVA from baseline to each follow-up time frame. Additional analysis included comparison to the minimal clinically important difference (MCID), evaluation of gait speed classification changes, and review of subjective questionnaires.

Results

Participants retained an average gait speed improvement >0.21 m/s compared to baseline at all post-treatment time frames. Additionally, 94% of participants improved their gait speed beyond the MCID during one or more post-treatment measurements, and 88% subjectively reported a gait speed improvement.

Conclusion

Treatment with the gait device may result in meaningful, long-term gait speed improvement for chronic stroke survivors with hemiparetic gait impairments.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT03649217, identifier NCT03649217.

Simple within-stride changes in treadmill speed can drive selective changes in human gait symmetry

Millions of people walk with asymmetric gait patterns, highlighting a need for customizable rehabilitation approaches that can flexibly target different aspects of gait asymmetry. Here, we studied how simple within-stride changes in treadmill speed could drive selective changes in gait symmetry. In Experiment 1, healthy adults (n = 10) walked on an instrumented treadmill with and without a closed-loop controller engaged. This controller changed the treadmill speed to 1.50 or 0.75 m/s depending on whether the right or left leg generated propulsive ground reaction forces, respectively. Participants walked asymmetrically when the controller was engaged: the leg that accelerated during propulsion (right) showed smaller leading limb angles, larger trailing limb angles, and smaller propulsive forces than the leg that decelerated (left). In Experiment 2, healthy adults (n = 10) walked on the treadmill with and without an open-loop controller engaged. This controller changed the treadmill speed to 1.50 or 0.75 m/s at a prescribed time interval while a metronome guided participants to step at different time points relative to the speed change. Different patterns of gait asymmetry emerged depending on the timing of the speed change: step times, leading limb angles, and peak propulsion were asymmetric when the speed changed early in stance while step lengths, step times, and propulsion impulses were asymmetric when the speed changed later in stance. In sum, we show that simple manipulations of treadmill speed can drive selective changes in gait symmetry. Future work will explore the potential for this technique to restore gait symmetry in clinical populations.

Split-Belt Treadmill Adaptation Improves Spatial and Temporal Gait Symmetry in People with Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease characterized by degradation of the myelin sheath resulting in impaired neural communication throughout the body. As a result, most people with MS (PwMS) experience gait asymmetries between their legs leading to an increased risk of falls. Recent work indicates that split-belt treadmill adaptation, where the speed of each leg is controlled independently, can decrease gait asymmetries for other neurodegenerative impairments. The purpose of this study was to test the efficacy of split-belt treadmill training to improve gait symmetry in PwMS. In this study, 35 PwMS underwent a 10 min split-belt treadmill adaptation paradigm, with the faster paced belt moving under the more affected limb. Step length asymmetry (SLA) and phase coordination index (PCI) were the primary outcome measures used to assess spatial and temporal gait symmetries, respectively. It was predicted that participants with a worse baseline symmetry would have a greater response to split-belt treadmill adaptation. Following this adaptation paradigm, PwMS experienced aftereffects that improved gait symmetry, with a significant difference between predicted responders and nonresponders in both SLA and PCI change (p < 0.001). Additionally, there was no correlation between SLA and PCI change. These findings suggest that PwMS retain the ability for gait adaptation, with those most asymmetrical at baseline demonstrating the greatest improvement, and that there may be separate neural mechanisms for spatial and temporal locomotor adjustments.

Asymmetric shoe height induces reactive changes in gait kinematics but not kinetics in healthy young adults

BACKGROUND

Footwear interventions are a potential avenue to correct walking asymmetry in neurologic populations, such as stroke. However, the motor learning mechanisms that underlie the changes in walking imposed by asymmetric footwear are unclear.

RESEARCH QUESTION

The objectives of this study were to examine symmetry changes during and after an asymmetric shoe height intervention in (1) vertical impulse and (2) spatiotemporal gait parameters and (3) joint kinematics, in healthy young adults METHODS: Eleven healthy young adults (3 males, 8 females; 21.2 ± 3.1 years old) participated in this study. Participants walked on an instrumented treadmill at 1.3 m/s for four conditions: (1) a 5-minute familiarization with equal shoe height, (2) a 5-minute baseline with equal shoe height, (3) a 10-minute intervention, where participants walked with asymmetric shoe height with a 10 mm shoe insert in one shoe, and (4) a 10-minute post-intervention, where participants walked with equal shoe height. Asymmetry in kinetics and kinematics were used to identify changes during intervention and aftereffects, a hallmark of feedforward adaptation RESULTS: Participants did not alter vertical impulse asymmetry (p = 0.667) nor stance time asymmetry (p = 0.228). During the intervention, step time asymmetry (p = 0.003) and double support asymmetry (p < 0.001) were greater compared to baseline. Leg joint asymmetry during stance (Ankle plantarflexion: p < 0.001; Knee flexion: p < 0.001; Hip extension: p = 0.011) was greater during the intervention compared to baseline. However, changes in spatiotemporal gait variables and joint mechanics did not demonstrate aftereffects.

SIGNIFICANCE

Our results show that healthy human adults change gait kinematics, but not weight-bearing symmetry with asymmetrical footwear. This suggests that healthy humans prioritize maintaining vertical impulse by changing their kinematics. Further, the changes in gait kinematics are short-lived, suggesting feedback-based control, and a lack of feedforward motor adaptations.

Exploring Temporospatial Gait Asymmetry, Dynamic Balance, and Locomotor Capacity After a 12-Week Split-Belt Treadmill Training in Adolescents with Unilateral Cerebral Palsy: A Randomized Clinical Study

AIM

To investigate the effects of a 12-week split-belt treadmill walking (Sb-TW) practice using an error augmentation strategy on temporospatial gait asymmetries, dynamic balance, and locomotor capacity in adolescents with unilateral cerebral palsy (ULCP).

METHODS

Fifty-two adolescents with ULCP (age: 10-16 years) were randomized into either the Sb-TW group (n = 26; underwent repeated Sb-TW practice, with exaggeration of the initial step-length asymmetry, three times/week, for 12 sequential weeks) or control group (n = 26; received equivalent dosages of traditional single-belt treadmill training). Step-length and swing-time asymmetries, directional (LoSdirectional) and overall (LoSoverall) limits of stability, and locomotor capacity [6-minute walk test (6-MWT), Timed Up and Down Stair test (TUDS), and 10-m Shuttle Run Test (10mSRT)] were assessed pre- and post-intervention.

RESULTS

The Sb-TW group demonstrated more favorable changes in step-length asymmetry (p < .001, η2partial = 0.27), LoSdirectional [affected side direction (p = .033, η2partial = 0.09), forward direction (p = .004, η2partial = 0.16), and backward direction (p = .01, η2partial = 0.12)], and LoSoverall (p < .001, η2partial = 0.31) than the control group. Also, the Sb-TW group showed significantly higher locomotor capacity [6-MWT (p < .001, η2partial = 0.38), TUDS (p = .032, η2partial = 0.09), 10mSRT (p = .021, η2partial = 0.10)] as compared to the control group.

CONCLUSION

The Sb-TW-induced adaptations can be capitalized on for remediating spatial gait asymmetry, dynamic balance deficits, and impaired locomotor performance in adolescents with ULCP.

Gait Classification with Gait Inherent Attribute Identification from Ankle's Kinematics

The human ankle joint interacts with the environment during ambulation to provide mobility and maintain stability. This association changes depending on the different gait patterns of day-to-day life. In this study, we investigated this interaction and extracted kinematic information to classify human walking mode into upstairs, downstairs, treadmill, overground and stationary in real-time using a single-DoF IMU axis. The proposed algorithm's uniqueness is twofold - it encompasses components of the ankle's biomechanics and subject-specificity through the extraction of inherent walking attributes and user calibration. The performance analysis with forty healthy participants (mean age: 26.8 ± 5.6 years yielded an accuracy of 89.57% and 87.55% in the left and right sensors, respectively. The study, also, portrays the implementation of heuristics to combine predictions from sensors at both feet to yield a single conclusive decision with better performance measures. The simplicity yet reliability of the algorithm in healthy participants and the observation of inherent multimodal walking features, similar to young adults, in elderly participants through a case study, demonstrate our proposed algorithm's potential as a high-level automatic switching framework in robotic gait interventions for multimodal walking.