Non-paretic leg movements can facilitate cortical drive to the paretic leg in individuals post stroke with severe motor impairment: Implications for motor priming.

Cross-education, a phenomenon where unilateral strength (or skill) training enhances strength (or skill) in the contralateral untrained limb, has been well studied in able-bodied individuals. Cross-education effect accompanies bilateral changes of corticomotor activity in the motor cortex (M1). Recent reports demonstrated greater cross-education effect in stroke survivors compared to healthy individuals, however, corticomotor responses to cross-education in stroke remains unclear. This study aimed to determine the effects of non-paretic leg movements on corticomotor excitability (CME) and reaction time of the paretic leg in severely impaired stroke survivors. Seventeen post stroke individuals with severe leg motor impairment (Fugl-Meyer lower extremity score less than 21 and absence of motor evoked potential in the paretic leg) performed three 20-min motor trainings using their non-paretic ankle: skill (targeted dynamic movements), strength (isometric resistance) and sham (sub-threshold electrical nerve stimulation). During training, verbal instructions were given to the participants to limit their movement to the non-paretic leg and this was confirmed with visual observation of the paretic leg. Transcranial magnetic stimulation measured CME of the contralateral pathways from the non-lesioned M1 to the non-paretic tibialis anterior (TA) muscle, ipsilateral pathways to the paretic TA and transcallosal inhibition (TCI) from the non-lesioned to lesioned M1. Paretic ankle reaction time was measured using a reaction time paradigm. All outcomes were measured before, immediately post, 30-min post and 60-min post priming. CME of the non-paretic TA increased after skill (.08 ± .10 mV) and strength (.06 ± .05 mV) training (p < .01). Ipsilateral CME of the paretic TA (.02 ± .01 mV) and TCI (.01 ± .01 s, ipsilateral silent period; more inhibition to the lesioned M1) increased after skill (p < .05) but not strength training. Reaction time of the paretic ankle improved after skill and strength training (-.11 ± .2 and -.13 ± .20 s, respectively; p < .05) and was sustained at 60 min. No changes were observed during the sham condition. Our findings may inform future studies for using non-paretic leg movements as a priming modality, especially for those who are contraindicated to other priming paradigms (e.g., brain stimulation) or unable to perform paretic leg movements. Conclusion: Non-paretic leg movements can be used as a priming modality, especially for those who are contraindicated to other priming paradigms (e.g., brain stimulation) or unable to perform paretic leg movements.

Game-based movement facilitates acute priming effect in stroke.

OBJECTIVE: Cortical priming is an emerging strategy to enhance motor recovery after stroke, however, limited information exists on the neuromodulatory effects of lower limb movement-based priming to facilitate corticomotor excitability after stroke. In this study, we investigated the feasibility and effectiveness of game-based ankle movement priming using the DIG-I-PRIME™ on corticomotor excitability and motor performance in chronic stroke survivors. METHODS: Nineteen stroke survivors participated in a 20-min session of game-based priming. A period of rest served as a control for the priming condition. Transcranial magnetic stimulation (TMS) was used to measure corticomotor excitability of the paretic and non-paretic tibialis anterior (TA) muscle representations. Motor performance was quantified by assessing the accuracy to track a sinusoidal target wave with paretic dorsiflexion and plantarflexion. RESULTS: Ipsilesional corticomotor excitability increased by 25% after game-based movement priming (p = 0.02) while changes were not observed after the control condition. No change in motor performance was noted. CONCLUSION: Game-based ankle movement priming demonstrated a significant acute priming effect on the ipsilesional lower limb M1. These data provide preliminary evidence for the potential benefits of game-based priming to promote functional recovery after stroke.

Cortical priming strategies for gait training after stroke: a controlled, stratified trial.

BACKGROUND: Stroke survivors experience chronic gait impairments, so rehabilitation has focused on restoring ambulatory capacity. High-intensity speed-based treadmill training (HISTT) is one form of walking rehabilitation that can improve walking, but its effectiveness has not been thoroughly investigated. Additionally, cortical priming with transcranial direct current stimulation (tDCS) and movement may enhance HISTT-induced improvements in walking, but there have been no systematic investigations. The objective of this study was to determine if motor priming can augment the effects of HISTT on walking in chronic stroke survivors. METHODS: Eighty-one chronic stroke survivors participated in a controlled trial with stratification into four groups: 1) control-15 min of rest (n = 20), 2) tDCS-15 min of stimulation-based priming with transcranial direct current stimulation (n = 21), 3) ankle motor tracking (AMT)-15 min of movement-based priming with targeted movements of the ankle and sham tDCS (n = 20), and 4) tDCS+AMT-15 min of concurrent tDCS and AMT (n = 20). Participants performed 12 sessions of HISTT (40 min/day, 3 days/week, 4 weeks). Primary outcome measure was walking speed. Secondary outcome measures included corticomotor excitability (CME). Outcomes were measured at pre, post, and 3-month follow-up assessments. RESULTS: HISTT improved walking speed for all groups, which was partially maintained 3 months after training. No significant difference in walking speed was seen between groups. The tDCS+AMT group demonstrated greater changes in CME than other groups. Individuals who demonstrated up-regulation of CME after tDCS increased walking speed more than down-regulators. CONCLUSIONS: Our results support the effectiveness of HISTT to improve walking; however, motor priming did not lead to additional improvements. Upregulation of CME in the tDCS+AMT group supports a potential role for priming in enhancing neural plasticity. Greater changes in walking were seen in tDCS up-regulators, suggesting that responsiveness to tDCS might play an important role in determining the capacity to respond to priming and HISTT. TRIAL REGISTRATION: ClinicalTrials.gov , NCT03492229. Registered 10 April 2018 - retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03492229 .

Cardiorespiratory Responses to Pool Floor Walking in People Poststroke.

OBJECTIVE: To compare cardiorespiratory responses between pool floor walking and overground walking (OW) in people poststroke. DESIGN: Cross-sectional study. SETTING: University-based therapeutic exercise facility. PARTICIPANTS: Participants (N=28) were comprised of 14 community-dwelling individuals poststroke (5.57±3.57y poststroke) and 14 age- and sex-matched healthy adults (mean age, 58.00±15.51y; male/female ratio, 9:5). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: A telemetric metabolic system was used to collect cardiorespiratory variables, including oxygen consumption (V˙o2), energy expenditure (EE), and expired volume per unit time (V˙e), during 6-minute walking sessions in chest-depth water and on land at a matched speed, determined by average of maximum walking speed in water. RESULTS: Individuals poststroke elicited no significant differences in cardiorespiratory responses between pool floor walking and OW. However, healthy controls showed significant increases in mean V˙o2 values by 94%, EE values by 109%, and V˙e values by 94% (all P<.05) during pool floor walking compared with OW. A 2×2 mixed model analysis of variance revealed a significant group × condition interaction in V˙o2, in which the control group increased V˙o2 from OW to pool floor walking, whereas the stroke group did not. CONCLUSIONS: Our results indicate that people poststroke, unlike healthy adults, do not increase EE while walking in water compared with on land. Unlike stationary walking on an aquatic treadmill, forward locomotion during pool floor walking at faster speeds may have increased drag force, which requires greater EE from healthy adults. Without demanding excessive EE, walking in water may offer a naturally supportive environment for gait training in the early stages of rehabilitation.

Effects of Cross-Education on Neural Adaptations Following Non-Paretic Limb Training in Stroke: A Scoping Review with Implications for Neurorehabilitation.

Current stroke rehabilitation interventions focus on intensive task specific training of the paretic limb, which may not be feasible for individuals with higher levels of impairment or in the early phase of stroke. Cross-education, a mechanism that improves strength or skill of the untrained limb following unilateral motor training, has high clinical relevance for stroke rehabilitation. Despite its potential benefits, our knowledge on the application and efficacy of cross-education in stroke is limited. We performed a scoping review to synthesize the current evidence regarding neurophysiological and motor effects of cross-education training in stroke. Low to strong evidence from five studies demonstrated strength gains ranging from 31-200% in the untrained paretic limb following non-paretic muscle training. Neurophysiological mechanisms underlying cross-education were unclear as the three studies that used transcranial magnetic stimulation to probe functional connectivity demonstrated mixed results in low sample size. Our review suggests that cross-education is a promising clinical approach in stroke, however high quality studies focusing on neurophysiological mechanisms are required to establish the efficacy and underlying mechanisms of cross-education in stroke. Recommendations regarding future directions and clinical utility are provided.

Functional connectivity of proximal and distal lower limb muscles and impact on gait variability in stroke.

BACKGROUND: Higher gait variability after stroke increases risk of falls and compromises safe community ambulation. Corticomotor connectivity plays an important role in walking after stroke, however, its relation to gait variability remains unknown. RESEARCH QUESTION: Do corticomotor characteristics of the proximal and distal lower limb muscles predict gait variability in individuals with chronic stroke? METHODS: Retrospective analysis of data from 30 individuals with chronic stroke was conducted. Corticomotor characteristics were measured in the paretic and non-paretic tibialis anterior (TA, distal muscle) and rectus femoris (RF, proximal muscle) using transcranial magnetic stimulation. We calculated corticomotor excitability ratio of paretic TA and RF (CMETA/RF), corticomotor excitability symmetry (CMEsym) between hemispheres for the TA and RF, and ipsilateral corticomotor excitability (ICE) of the paretic TA. Gait variability was quantified as the coefficient of variation of the paretic step length (spatial) and step time (temporal) during comfortable walking. Relations between corticomotor characteristics and gait variability were tested with multiple linear regression. RESULTS: CMETA/RF and CMEsym of RF were significant predictors of spatial gait variability. Greater corticomotor input to the paretic RF compared to the paretic TA and greater symmetry of RF were related to higher spatial gait variability. There were no significant predictors of temporal gait variability. SIGNIFICANCE: Corticomotor inputs to the proximal RF may be important for spatial gait variability, reflecting a compensatory role of RF in walking after stroke. Stroke survivors with relatively greater corticomotor input to the paretic RF may adopt compensatory strategy to enhance propulsion and achieve foot clearance, but it may also increase spatial gait variability, particularly when combined with impaired motor control of the paretic TA. These findings may provide novel rehabilitative targets to decrease gait variability and promote safe ambulation in individuals with stroke.

Design and Implementation of a Portable Knee Actuator for the Improvement of Crouch Gait in Children with Cerebral Palsy.

Common manifestation of spastic Cerebral Palsy (CP) are abnormal gait pathologies. These conditions require greater energy expenditure to successfully ambulate and are linked with significant deterioration in joint health and childhood musculoskeletal development. Crouch gait presents with knee hyperflexion throughout stance due to extensor muscle weakness and spasticity in flexor muscles stemming from neurological damage. The goal of this study was to develop a wearable cable-driven robotic system that applies controlled perturbation to the knee joint during overground walking in children with CP. Two children with spastic CP were recruited in this pilot study. They were tested in two conditions, i.e., applying knee resistance vs. knee assistance during overground walking. Kinematic and EMG data were recorded during overground walking. Data indicated that it was feasible to apply controlled knee perturbation torque during overground walking in children with crouch and preliminary results showed an improvement in crouch gait pattern in children with CP after one session of walking with the robotic system.Clinical Relevance- This study might have a potential clinical significance modifying neuromuscular control of CP patients with Crouch Gait.

Feasibility and Acceptability of Game-Based Cortical Priming and Functional Lower Limb Training in a Remotely Supervised Home Setting for Chronic Stroke: A Case Series.

Background: Movement-based priming has been increasingly investigated to accelerate the effects of subsequent motor training. The feasibility and acceptability of this approach at home has not been studied. We developed a game-based priming system (DIG-I-PRIMETM) that engages the user in repeated ankle movements using serious games. We aimed to determine the feasibility, acceptability, and preliminary motor benefits of an 8-week remotely supervised telerehabilitation program utilizing game-based movement priming combined with functional lower limb motor training in chronic stroke survivors. Methods: Three individuals with stroke participated in a telerehabilitation program consisting of 20-min movement-based priming using the DIG-I-PRIMETM system followed by 30-min of lower limb motor training focusing on strength and balance. We evaluated feasibility using reported adverse events and compliance, and acceptability by assessing participant perception of the game-based training. Motor gains were assessed using the 10-m walk test and Functional Gait Assessment. Results: All participants completed 24 remotely supervised training sessions without any adverse events. Participants reported high acceptability of the DIG-I-PRIMETM system, reflected by high scores on satisfaction, enjoyment, user-friendliness, and challenge aspects of the system. Participants reported overall satisfaction with our program. Post-training changes in the 10-m walk test (0.10-0.31 m/s) and Functional Gait Assessment (4-7 points) exceeded the minimal clinically important difference. Conclusion: Our results indicate that a remotely supervised game-based priming and functional lower limb exercise program is feasible and acceptable for stroke survivors to perform at home. Also, improved walking provides preliminary evidence of game-based priming to be beneficial as a telerehabilitation strategy for stroke motor recovery.

Differential corticomotor mechanisms of ankle motor control in post stroke individuals with and without motor evoked potentials.

OBJECTIVE: Deficits in ankle motor control has been identified as a significant contributor to impaired walking after stroke. Corticomotor excitability has been related to impaired upper limb motor control and poor recovery in stroke, however contributions to lower limb function are still unclear. This study used transcranial magnetic stimulation (TMS) to determine the influence of corticomotor characteristics on lower limb motor control in chronic stroke survivors. METHODS: This retrospective study assessed 28 individuals with post stroke hemiparesis. Motor evoked potentials (MEP) measured from the paretic and non-paretic tibialis anterior (TA) muscles were used to calculate corticomotor excitability symmetry (CMEsym) and relative ipsilateral corticomotor excitability (ICE). Participants were assigned to MEP+ and MEP- groups depending on the presence (+) or absence (-) of MEPs. Ankle motor control was quantified by the ability of participants to track a sinusoidal target using dorsiflexion-plantarflexion movements of the paretic ankle and tracking error was calculated using root mean square error (RMSE). RESULTS: Multiple linear regression model for all participants revealed only CMEsym and FMLE (p < 0.01) to significantly predict RMSE. In the MEP+ group, CMEsym significantly predicted RMSE (p = 0.03) while FMLE (p = 0.02) was a significant predictor for the MEP-. CONCLUSION: Our results indicate that CMEsym between the ipsilesional and contralesional hemispheres does not necessarily translate to better paretic ankle motor control in chronic stroke. Presence or absence of a MEP in the TA muscle did not affect the ankle tracking performance, however, it was noted that different strategies maybe used by those with and without a MEP.

The influence of water depth on kinematic and spatiotemporal gait parameters during aquatic treadmill walking.

The purpose of this study was to investigate kinematic and spatiotemporal variables of aquatic treadmill walking at three different water depths. A total of 15 healthy individuals completed three two-minute walking trials at three different water depths. The aquatic treadmill walking was conducted at waist-depth, chest-depth and neck-depth, while a customised 3-D underwater motion analysis system captured their walking. Each participant's self-selected walking speed at the waist level was used as a reference speed, which was applied to the remaining two test conditions. A repeated measures ANOVA showed statistically significant differences among the three walking conditions in stride length, cadence, peak hip extension, hip range of motion (ROM), peak ankle plantar flexion and ankle ROM (All p values < 0.05). The participants walked with increased stride length and decreased cadence during neck level as compared to waist and chest level. They also showed increased ankle ROM and decreased hip ROM as the water depth rose from waist and chest to the neck level. However, our study found no significant difference between waist and chest level water in all variables. Hydrodynamics, such as buoyancy and drag force, in response to changes in water depths, can affect gait patterns during aquatic treadmill walking.

Effects of high intensity speed-based treadmill training on ambulatory function in people with chronic stroke: A preliminary study with long-term follow-up.

High intensity treadmill training has shown to be beneficial for stroke survivors, yet the feasibility and long-term effects remain unclear. In this study, we aimed to determine whether a 4-week high intensity speed-based treadmill training (HISTT) is feasible for chronic stroke survivors, and we examined its effects on ambulatory function, and long-term retention. Sixteen individuals post-stroke participated in 40 minutes of HISTT for four weeks at a frequency of three sessions per week. Gait speed was measured using the 10-meter walk test, endurance was measured using the 6-minute walk test, and quality of life was assessed using the Stroke Impact Scale (SIS) at baseline, post-training, and at 3-month follow-up. All participants successfully completed the training without any serious adverse events. Participants significantly increased fastest walking speed by 19%, self-selected walking speed by 18%, and walking endurance by 12% after the training. These improvements were maintained for 3 months after the intervention. Our results indicate that this modified speed-based high intensity walking program has the potential to be a feasible and effective method of gait training for stroke survivors. However, the small sample size and lack of a control group warrant caution in interpretation of results. Further studies are recommended to better understand effectiveness of this protocol in combination with other physical therapy interventions for functional recovery after stroke.

Influence of water depth on energy expenditure during aquatic walking in people post stroke.

BACKGROUND AND PURPOSE: This study aimed to investigate the metabolic cost during aquatic walking at various depths in people post stroke. The secondary purpose was to examine the differences in metabolic cost between aquatic walking and land walking among individuals post stroke. DESIGN: A cross-sectional research design is used. METHODS: Twelve participants post stroke (aged 55.5 ± 13.3 years) completed 6 min of walking in 4 different conditions: chest-depth, waist-depth, and thigh-depth water, and land. Data were collected on 4 separate visits with at least 48 hr in between. On the first visit, all participants were asked to walk in chest-depth water at their fastest speed. The walking speed was used as a reference speed, which was applied to the remaining 3 walking conditions. The order of remaining walking conditions was randomized. Energy expenditure (EE), oxygen consumption (VO2 ), and minute ventilation (VE ) were measured with a telemetric metabolic system. RESULTS: Our findings showed statistically significant differences in EE, VO2 , and VE among the 4 different walking conditions: chest-depth, waist-depth, and thigh-depth water, and land (all p < .05). The participants demonstrated reduction in all variables as the water depth increased from thigh depth to chest depth. Significantly higher values in EE and VO2 were found when the water depth increased from waist depth to chest depth. However, no significant difference was found in all variables between thigh-depth and waist-depth walking. Only thigh-depth walking revealed significant differences when compared with land walking in all variables. CONCLUSIONS: People post stroke consume less energy in chest-depth water, which may allow them to perform prolonged duration of training. Thigh-depth water demonstrated greater EE compared with other water depths; thus, it can be recommended for time-efficient cardiovascular exercise. Waist-depth water showed similar EE to land walking, which may have been contributed by the countervailing effects of buoyancy and water resistance.