Chronic Hemiparetic Stroke Survivors Research Articles

Normobaric Hypoxia Exposure During Treadmill Aerobic Exercise After Stroke: A Safety and Feasibility Study.

ObjectiveTo evaluate the safety and feasibility of performing treadmill aerobic exercise in moderate normobaric hypoxia among chronic hemiparetic stroke survivors.DesignObservational study using convenience sampling.SettingResearch laboratory in a tertiary rehabilitation hospital.ParticipantsChronic hemiparetic stroke survivors who could walk at least 10-m with or without assistance and had no absolute contraindications to exercise testing.InterventionParticipants (three male and four female) were asked to complete three normobaric hypoxia exposure protocols within a single session. First, they were passively exposed to normobaric hypoxia through gradual reductions in the fraction of inspired oxygen (FIO2 = 20.9, 17.0, and 15.0%) while seated (5-min at each level of FIO2). Participants were then exposed to the same reductions in FIO2 during constant-load exercise performed on a treadmill at 40% of heart rate reserve. Finally, participants completed 20-min of exercise while intermittently exposed to moderate normobaric hypoxia (5 × 2-min at FIO2 = 15.0%) interspaced with 2-min normoxia intervals (FIO2 = 20.9%).Outcome MeasuresThe primary outcome was occurrence of adverse events, which included standardized criteria for terminating exercise testing, blood oxygen saturation (SpO2) <80%, or acute mountain sickness score >2. The increased cardiovascular strain imposed by normobaric hypoxia exposure at rest and during exercise was evaluated by changes in SpO2, heart rate (HR), blood pressure, and rating of perceived exertion (RPE).ResultsOne participant reported mild symptoms of nausea during exercise in normobaric hypoxia and discontinued participation. No other adverse events were recorded. Intermittent normobaric hypoxia exposure was associated with reduced SpO2 (MD = −7.4%, CI: −9.8 to −5.0) and increased HR (MD = 8.2, CI: 4.6 to 11.7) compared to intervals while breathing typical room air throughout the 20-min constant-load exercise period. The increase in HR was associated with a 10% increase in relative effort. However, reducing FIO2 had little effect on blood pressure and RPE measurements.ConclusionModerate normobaric hypoxia appeared to be a safe and feasible method to increase the cardiovascular strain of submaximal exercise in chronic hemiparetic stroke survivors. Future studies evaluating the effects of pairing normobaric hypoxia exposure with existing therapies on secondary prevention and functional recovery are warranted.

Task-Oriented Circuit Training as an Alternative to Ergometer-Type Aerobic Exercise Training after Stroke.

Moderate-intensity aerobic exercise training is an important treatment strategy to enhance functional recovery and decrease cardiometabolic risk factors after stroke. However, stroke related impairments limit access to ergometer-type exercise. The aims of the current study were (1) to evaluate whether our task-oriented circuit training protocol (intermittent functional training; IFT) could be used to sustain moderate-intensity aerobic workloads over a 10-week intervention period, and (2) to investigate its preliminary effects on cardiorespiratory fitness and metabolic profiles compared to constant-load ergometer-type exercise (CET). Forty chronic hemiparetic stroke survivors were randomized to receive 30 sessions of IFT or CET over ten weeks. Similar proportions of participants were randomized to IFT (7/19) and CET (9/18) sustained workloads associated with moderate-intensity aerobic exercise over the study period (p = 0.515). However, CET was associated with more substantial changes in maximal oxygen uptake (MD = 2.79 mL min−1 kg−1 CI: 0.84 to 4.74) compared to IFT (MD = 0.62 mL min−1 kg−1 CI: −0.38 to 1.62). Pre to post changes in C-reactive protein (−0.9 mg/L; p =0.017), short-term glycemia (+14.7 µmol/L; p = 0.026), and resting whole-body carbohydrate oxidation (+24.2 mg min−1; p = 0.046) were observed when considering both groups together. Accordingly, IFT can replicate the aerobic intensities sustained during traditional ergometer-type exercise training. More work is needed to evaluate the dose–response effects of such task-oriented circuit training protocols on secondary prevention targets across the continuum of stroke recovery.

Non-immersive Virtual Reality Rehabilitation Applied to a Task-oriented Approach for Stroke Patients: A Randomized Controlled Trial.

Virtual reality (VR) training allows the creation of the most applicable practice environment incorporated into computer-generated multisensory imagery. The purpose of this study was to investigate the effects of a virtual training program based on a RAPAEL smart glove on the upper extremity function and quality of life of community-dwelling individuals with chronic hemiparetic stroke. Thirty-six outpatients diagnosed as having a first stroke were selected to receive a therapeutic rehabilitation program at local rehabilitation units. Participants were allocated randomly into two groups: the non-immersive VR training (intervention) group and the recreational activity (control) group. The intervention group received non-immersive VR training using a RAPAEL smart glove for 30 minutes per session, 3 days a week for 8 weeks. The control group performed recreational activities for the same period and also participated in a conventional rehabilitation program for 30 minutes per session, 3 days a week for 8 weeks as an additional therapy. To analyze the effects of the non-immersive VR intervention on upper extremity function, four clinical measures, namely the box and block test (BBT), the Wolf motor function test (WMFT), the Jebsen-Taylor hand function test (JTT), and a grip strength test, were used in this study. For the secondary clinical outcome, the trail-making test (TMT) was used to determine any improvement in cognitive function. At week 8, upon completion of the non-immersive VR-training the intervention group demonstrated significantly greater WMFT scores (73.0±12.9 to 81.6±7.5), BBT scores (27.3±8.9 to 34.2±7.1), and grip strength (19.2±8.2 to 23.8±8.5) compared with WMFT scores (70.4±12.1 to 73.2±13.1), BBT scores (27.1±10.5 to 28.8±12.9), and grip strength (18.4±4.2 to 18.3±4.9) in the control group. This study suggests that virtual upper extremity training using the RAPAEL smart glove has reasonable and beneficial effects on upper extremity and cognitive function for chronic hemiparetic stroke survivors.

Intensifying Functional Task Practice to Meet Aerobic Training Guidelines in Stroke Survivors.

Objective: To determine whether stroke survivors could maintain workloads during functional task practice that can reach moderate levels of cardiometabolic stress (i.e., ≥40% oxygen uptake reserve (O2R) for ≥20 min) without the use of ergometer-based exercise.Design: Cross-sectional study using convenience sampling.Setting: Research laboratory in a tertiary rehabilitation hospital.Participants: Chronic hemiparetic stroke survivors (>6-months) who could provide consent and walk with or without assistance.Intervention: A single bout of intermittent functional training (IFT). The IFT protocol lasted 30 min and involved performing impairment specific multi-joint task-oriented movements structured into circuits lasting ~3 min and allowing 30–45 s recovery between circuits. The aim was to achieve an average heart rate (HR) 30-50 beats above resting without using traditional ergometer-based aerobic exercise.Outcome measures: Attainment of indicators for moderate intensity aerobic exercise. Oxygen uptake (O2), carbon dioxide production (CO2), and HR were recorded throughout the 30 min IFT protocol. Values were reported as percentage of O2R, HR reserve (HRR) and HRR calculated from predicted maximum HR (HRRpred), which were determined from a prior maximal graded exercise test.Results: Ten (3-female) chronic (38 ± 33 months) stroke survivors (70% ischemic) with significant residual impairments (NIHSS: 3 ± 2) and a high prevalence of comorbid conditions (80% ≥ 1) participated. IFT significantly increased all measures of exercise intensity compared to resting levels: O2 (Δ 820 ± 290 ml min−1, p < 0.001), HR (Δ 42 ± 14 bpm, p < 0.001), and energy expenditure (EE; Δ 4.0 ± 1.4 kcal min−1, p < 0.001). Also, mean values for percentage of O2R (62 ± 19), HRR (55 ± 14), and HRRpred (52 ± 18) were significantly higher than the minimum threshold (40%) indicating achievement of moderate intensity aerobic exercise (p = 0.004, 0.016, and 0.043, respectively).Conclusion: Sufficient workloads to achieve moderate levels of cardiometabolic stress can be maintained in chronic stroke survivors using impairment-focused functional movements that are not dependent on ergometers or other specialized equipment.

Contralesional Brain-Computer Interface Control of a Powered Exoskeleton for Motor Recovery in Chronic Stroke Survivors.

There are few effective therapies to achieve functional recovery from motor-related disabilities affecting the upper limb after stroke. This feasibility study tested whether a powered exoskeleton driven by a brain-computer interface (BCI), using neural activity from the unaffected cortical hemisphere, could affect motor recovery in chronic hemiparetic stroke survivors. This novel system was designed and configured for a home-based setting to test the feasibility of BCI-driven neurorehabilitation in outpatient environments. Ten chronic hemiparetic stroke survivors with moderate-to-severe upper-limb motor impairment (mean Action Research Arm Test=13.4) used a powered exoskeleton that opened and closed the affected hand using spectral power from electroencephalographic signals from the unaffected hemisphere associated with imagined hand movements of the paretic limb. Patients used the system at home for 12 weeks. Motor function was evaluated before, during, and after the treatment. Across patients, our BCI-driven approach resulted in a statistically significant average increase of 6.2 points in the Action Research Arm Test. This behavioral improvement significantly correlated with improvements in BCI control. Secondary outcomes of grasp strength, Motricity Index, and the Canadian Occupational Performance Measure also significantly improved. The findings demonstrate the therapeutic potential of a BCI-driven neurorehabilitation approach using the unaffected hemisphere in this uncontrolled sample of chronic stroke survivors. They also demonstrate that BCI-driven neurorehabilitation can be effectively delivered in the home environment, thus increasing the probability of future clinical translation. URL: http://www.clinicaltrials.gov. Unique identifier: NCT02552368.

Modulation of reactive response to slip-like perturbations: effect of explicit cues on paretic versus non-paretic side stepping and fall-risk.

This study aimed to examine the effect of explicit cuing on reactive stepping with the paretic limb during slip-like perturbations in stroke survivors and to identify differences in postural stability and fall-risk while stepping with either limb. Eleven chronic hemiparetic stroke survivors received slip-like stance perturbations in no-cue (implicit, no instructions) and cued (explicit, instructions to step with paretic limb) conditions. Frequency of stepping with the paretic limb was recorded. Differences between non-paretic and paretic steps for falls, number of compensatory steps, relative center-of-mass position (X COM/BOS), and velocity (Ẋ(COM/BOS)), and vertical limb support (hip descent-Z hip) were analyzed. Stepping with the paretic limb increased from 6% in no-cue condition to 42% in cued condition with no significant difference in number of falls and steps regardless of stepping limb. At liftoff of the compensatory step, stability was greater (anterior X COM/BOS) with paretic than non-paretic limb stepping whereas, at touchdown (TD) of the step, stability with paretic limb reduced (posterior X COM/BOS and Ẋ(COM/BOS)) due to a smaller compensatory step taken with the paretic versus non-paretic limb. There was no significant difference in peak Z hip regardless of stepping limb; however, the timing of peak Z hip differed (occuring prior to TD during non-paretic stepping and post-TD during paretic stepping). Thus, fall onset was earlier with non-paretic versus paretic stepping. The results support that explicit cueing can facilitate initiation of reactive step from the paretic limb as compared with the no-cue condition. Stepping with the paretic limb in the cued condition however altered time of fall onset. Regardless of the stepping side, individuals demonstrated a fall risk suggesting the need for interventions focusing on reactive step training with both the limbs.

Test–Retest Reliability of Portable Metabolic Monitoring After Disabling Stroke

Purpose. Impaired economy of gait, prevalent in chronic stroke secondary to residual gait deficits, is associated with intolerance for performing activities of daily living. Gait economy/efficiency is traditionally assessed by determining the rate of oxygen consumption during submaximal treadmill walking. However, the mechanics and energetics of treadmill versus overground walking are very different in stroke survivors with ambulatory deficits. Clearly, overground cardiopulmonary measures are needed to accurately profile movement economy after stroke. An obstacle to obtaining such measures after stroke has been the absence of reliable portable metabolic monitoring equipment. The purpose of this study was to establish the test–retest reliability of a portable metabolic monitoring device during overground walking in hemiparetic stroke survivors. Methods. Twenty-three chronic hemiparetic stroke survivors underwent two 6-minute walk tests while wearing a COSMED K4b2 portable metabolic measurement system. Intraclass correlations coefficients (ICC) were calculated for both cardiopulmonary parameters and distance covered to determine test–retest reliability. An ICC of ≥0.85 was considered reliable. Results. ICCs for relative Vo2 (0.90), absolute Vo2 (0.93), Vco2 (0.93), and minute ventilation (0.95) demonstrated high reliability, but not for heart rate (0.76) or respiratory exchange ratio (0.64). There was no significant difference in the distance each participant walked between the first and second tests, eliminating distance as a potential confounder of our analyses (ICC = 0.99). Conclusions. Our results strongly support the reliability of the K4b2 for quantifying overground gait efficiency after stroke. Use of this device may enable researchers to study how varying poststroke rehabilitation interventions affect this central measure of health and function.

Abstract 17: Motor Relearning Effects of Functional Electrical Stimulation in Lower Limb Hemiparesis

Objective: The primary objective of this study was to assess the effect of peroneal nerve stimulation (PNS) on lower limb motor impairment among chronic stroke survivors. The secondary objective was to assess the effect of PNS on lower limb functional mobility (disability) and overall quality of life. Design: A single-blinded randomized controlled trial, which enrolled 110 chronic hemiparetic stroke survivors (&gt;90 days post-stroke), compared the effect of ambulation training with a PNS device to ambulation training with usual care (ankle foot orthosis or no device). Subjects were treated for 12-wks (Device Usage period) and followed for a total of 6-mos post-treatment. Outcome assessments were performed at baseline, end of the Device Usage period, and 3-mos and 6-mos post-treatment. The primary outcome measure was the Fugl-Meyer Motor Impairment scale. Secondary outcome measures were the Modified Emory Functional Ambulation Profile (mEFAP) and the Stroke Specific Quality of Life scale (SSQOL). Change scores were analyzed via repeated measure ANOVA with treatment and baseline dorsiflexion status (absence or presence of partial dorsiflexion) as independent factors and the baseline measure as a covariate. Results: Change in Fugl-Meyer scores was not significantly influenced by either treatment group (PNS or usual care) or by the presence (DP) or absence (DA) of volitional dorsiflexion at baseline. However, there was a significant treatment group by dorsiflexion status interaction (F=13.46, p=.00) on change in mEFAP scores. Post-hoc subset analysis of the DP and DA subjects using treatment group as an independent factor and baseline mEFAP score as covariate showed a significant treatment group effect (DP subjects: F=6.57, p=0.012 and DA subjects: F=4.24, p=.05) on mEFAP changes scores. A series of independent t-tests which compared the mean mEFAP change in the DP subjects relative to treatment group showed significant differences in favor of the usual care group. However, the same series of independent t-tests in the DA subjects showed the opposite effect with significant differences in favor of the PNS group. SSQOL change scores were not significantly influenced by treatment group or dorsiflexion status. Conclusions: Ambulation training for 12 weeks with either PNS or usual care had similar effects on lower limb motor impairment and overall quality of life in chronic stroke survivors. However, post-hoc analysis found that while PNS enhanced functional mobility in chronic stroke survivors with absent dorsiflexion, usual care was superior in chronic stroke survivors who demonstrated preservation of volitional ankle dorsiflexion.

Cortical overlap of joint representations contributes to the loss of independent joint control following stroke

The loss of independent joint control in the paretic upper limb is a cardinal sign of movement disorders following stroke. However, the underlying neural mechanisms for such a loss following stroke are still largely unknown. In order to investigate the possible contribution of altered sensorimotor cortical activity to the loss of independent joint control, we measured electroencephalographic (EEG) and torque signals during the generation of static shoulder/elbow torques. We found significant increases in the overlap of shoulder and elbow joint representations at the cortical level in stroke subjects as compared to control subjects. Linear regression results demonstrated significant associations between the cortical overlap of joint representations and the degree of the loss of independent joint control. Therefore, we conclude that an increased overlap of cortical representations for shoulder and elbow contributes to the expression of the loss of independent shoulder/elbow control of the paretic upper limb in chronic hemiparetic stroke survivors.

Reliability of TMS motor evoked potentials in quadriceps of subjects with chronic hemiparesis after stroke

Transcranial magnetic stimulation (TMS) non-invasively measures excitability of central motor pathways in humans and is used to characterize neuroplasticity after stroke. Using TMS to index lower extremity neuroplasticity after gait rehabilitation requires test–retest reliability. This study assesses the reliability of TMS-derived variables measured at bilateral quadriceps of chronic hemiparetic stroke survivors. Results support using measures of both paretic and nonparetic motor threshold, motor evoked potential (MEP) latencies; and nonparetic MEP amplitudes. Implications for longitudinal research are discussed.

Muscle and reflex changes with varying joint angle in hemiparetic stroke

BackgroundDespite intensive investigation, the origins of the neuromuscular abnormalities associated with spasticity are not well understood. In particular, the mechanical properties induced by stretch reflex activity have been especially difficult to study because of a lack of accurate tools separating reflex torque from torque generated by musculo-tendinous structures. The present study addresses this deficit by characterizing the contribution of neural and muscular components to the abnormally high stiffness of the spastic joint.MethodsUsing system identification techniques, we characterized the neuromuscular abnormalities associated with spasticity of ankle muscles in chronic hemiparetic stroke survivors. In particular, we systematically tracked changes in muscle mechanical properties and in stretch reflex activity during changes in ankle joint angle. Modulation of mechanical properties was assessed by applying perturbations at different initial angles, over the entire range of motion (ROM). Experiments were performed on both paretic and non-paretic sides of stroke survivors, and in healthy controls.ResultsBoth reflex and intrinsic muscle stiffnesses were significantly greater in the spastic/paretic ankle than on the non-paretic side, and these changes were strongly position dependent. The major reflex contributions were observed over the central portion of the angular range, while the intrinsic contributions were most pronounced with the ankle in the dorsiflexed position.ConclusionIn spastic ankle muscles, the abnormalities in intrinsic and reflex components of joint torque varied systematically with changing position over the full angular range of motion, indicating that clinical perceptions of increased tone may have quite different origins depending upon the angle where the tests are initiated.Furthermore, reflex stiffness was considerably larger in the non-paretic limb of stroke patients than in healthy control subjects, suggesting that the non-paretic limb may not be a suitable control for studying neuromuscular properties of the ankle joint.Our findings will help elucidate the origins of the neuromuscular abnormalities associated with stroke-induced spasticity.

Neuromuscular Abnormalities Associated With Spasticity of Upper Extremity Muscles in Hemiparetic Stroke

Our objective was to assess the mechanical changes associated with spasticity in elbow muscles of chronic hemiparetic stroke survivors and to compare these changes with those recorded in the ankle muscles of a similar cohort. We first characterized elbow dynamic stiffness by applying pseudorandom binary positional perturbations to the joints at different initial angles, over the entire range of motion, with subjects relaxed. We separated this stiffness into intrinsic and reflex components using a novel parallel cascade system identification technique. In addition, for controls, we studied the nonparetic limbs of stroke survivors and limbs of age-matched healthy subjects as primary and secondary controls. We found that both reflex and intrinsic stiffnesses were significantly larger in the stroke than in the nonparetic elbow muscles, and the differences increased as the elbow was extended. Reflex stiffness increased monotonically with the elbow angle in both paretic and nonparetic sides. In contrast, the modulation of intrinsic stiffness with elbow position was different in nonparetic limbs; intrinsic stiffness decreased sharply from full- to mid-flexion in both sides, then it increased continuously with the elbow extension in the paretic side. It remained invariant in the nonparetic side. Surprisingly, reflex stiffness was larger in the nonparetic than in the normal control arm, yet intrinsic stiffness was smaller in the nonparetic arm. Finally, we compare the angular dependence of paretic elbow and ankle muscles and show that the modulation of reflex stiffness with position was strikingly different.

Weakness Is the Primary Contributor to Finger Impairment in Chronic Stroke

Kamper DG, Fischer HC, Cruz EG, Rymer WZ. Weakness is the primary contributor to finger impairment in chronic stroke. Objective To assess the relative contributions of several neurologic and biomechanic impairment mechanisms to overall finger and hand impairment in chronic hemiparetic stroke survivors. Design Repeated-measures design. Setting Clinical research laboratory. Participants Thirty stroke survivors with chronic hemiparesis. Fifteen subjects had severe hand motor impairment and 15 had moderate impairment, as measured with the Chedoke-McMaster Stroke Assessment. Interventions Not applicable. Main Outcome Measures The biomechanic factors stiffness and resting flexion torque, together with the neurologic factors spasticity, strength, and coactivation, were quantified by using a custom hand manipulator, a dynamometer, and electromyographic recordings. Both passive and active rotations of the metacarpophalangeal joints of the fingers were examined. Results Although subjects in the severely impaired group exhibited statistically greater passive stiffness and resting flexion torque than their moderately impaired counterparts ( P<.05), the overall effect of these biomechanic changes appeared small in relation to the deficits attributable to neurologic changes such as spasticity and, especially, weakness. In fact, weakness in grip strength and isometric extension accounted for the greatest portion of the variance between the 2 groups (η 2=.40 and η 2=.23, respectively). Conclusions Thus, deficits in hand motor control after stroke seem to derive mainly from weakness, which may be attributable to the loss of descending corticospinal pathway activation of motoneurons.

Evaluation of robotic training forces that either enhance or reduce error in chronic hemiparetic stroke survivors

This investigation is one in a series of studies that address the possibility of stroke rehabilitation using robotic devices to facilitate "adaptive training." Healthy subjects, after training in the presence of systematically applied forces, typically exhibit a predictable "after-effect." A critical question is whether this adaptive characteristic is preserved following stroke so that it might be exploited for restoring function. Another important question is whether subjects benefit more from training forces that enhance their errors than from forces that reduce their errors. We exposed hemiparetic stroke survivors and healthy age-matched controls to a pattern of disturbing forces that have been found by previous studies to induce a dramatic adaptation in healthy individuals. Eighteen stroke survivors made 834 movements in the presence of a robot-generated force field that pushed their hands proportional to its speed and perpendicular to its direction of motion--either clockwise or counterclockwise. We found that subjects could adapt, as evidenced by significant after-effects. After-effects were not correlated with the clinical scores that we used for measuring motor impairment. Further examination revealed that significant improvements occurred only when the training forces magnified the original errors, and not when the training forces reduced the errors or were zero. Within this constrained experimental task we found that error-enhancing therapy (as opposed to guiding the limb closer to the correct path) to be more effective than therapy that assisted the subject.