Larry W. Forrester

Treadmill Exercise Rehabilitation Improves Ambulatory Function and Cardiovascular Fitness in Patients With Chronic Stroke A Randomized, Controlled Trial

Background and Purpose— Physical inactivity propagates disability after stroke through physical deconditioning and learned nonuse. We investigated whether treadmill aerobic training (T-AEX) is more effective than conventional rehabilitation to improve ambulatory function and cardiovascular fitness in patients with chronic stroke. Methods— Sixty-one adults with chronic hemiparetic gait after ischemic stroke (>6 months) were randomized to 6 months (3×/week) progressive T-AEX or a reference rehabilitation program of stretching plus low-intensity walking (R-CONTROL). Peak exercise capacity (Vo2 peak), o2 consumption during submaximal effort walking (economy of gait), timed walks, Walking Impairment Questionnaire (WIQ), and Rivermead Mobility Index (RMI) were measured before and after 3 and 6 months of training. Results— Twenty-five patients completed T-AEX and 20 completed R-CONTROL. Only T-AEX increased cardiovascular fitness (17% versus 3%, &dgr;% T-AEX versus R-CONTROL, P<0.005). Group-by-time analyses revealed T-AEX improved ambulatory performance on 6-minute walks (30% versus 11%, P<0.02) and mobility function indexed by WIQ distance scores (56% versus 12%, P<0.05). In the T-AEX group, increasing training velocity predicted improved Vo2 peak (r=0.43, P<0.05), but not walking function. In contrast, increasing training session duration predicted improved 6-minute walk (r=0.41, P<0.05), but not fitness gains. Conclusions— T-AEX improves both functional mobility and cardiovascular fitness in patients with chronic stroke and is more effective than reference rehabilitation common to conventional care. Specific characteristics of training may determine the nature of exercise-mediated adaptations.

Robot-Aided Neurorehabilitation: A Novel Robot for Ankle Rehabilitation

In this paper, we present the design and characterization of a novel ankle robot developed at the Massachusetts institute of technology (MIT). This robotic module is being tested with stroke patients at Baltimore Veterans administration medical center. The purpose of the on-going study is to train stroke survivors to overcome common foot drop and balance problems in order to improve their ambulatory performance. Its design follows the same guidelines of our upper extremity designs, i.e., it is a low friction, backdriveable device with intrinsically low mechanical impedance. Here, we report on the design and mechanical characteristics of the robot. We also present data to demonstrate the potential of this device as an efficient clinical measurement tool to estimate intrinsic ankle properties. Given the importance of the ankle during locomotion, an accurate estimate of ankle stiffness would be a valuable asset for locomotor rehabilitation. Our initial ankle stiffness estimates compare favorably with previously published work, indicating that our method may serve as an accurate clinical measurement tool.

Treadmill Exercise Activates Subcortical Neural Networks and Improves Walking After Stroke A Randomized Controlled Trial

Background and Purpose— Stroke often impairs gait thereby reducing mobility and fitness and promoting chronic disability. Gait is a complex sensorimotor function controlled by integrated cortical, subcortical, and spinal networks. The mechanisms of gait recovery after stroke are not well understood. This study examines the hypothesis that progressive task-repetitive treadmill exercise (T-EX) improves fitness and gait function in subjects with chronic hemiparetic stroke by inducing adaptations in the brain (plasticity). Methods— A randomized controlled trial determined the effects of 6-month T-EX (n=37) versus comparable duration stretching (CON, n=34) on walking, aerobic fitness and in a subset (n=15/17) on brain activation measured by functional MRI. Results— T-EX significantly improved treadmill-walking velocity by 51% and cardiovascular fitness by 18% (11% and −3% for CON, respectively; P<0.05). T-EX but not CON affected brain activation during paretic, but not during nonparetic limb movement, showing 72% increased activation in posterior cerebellar lobe and 18% in midbrain (P<0.005). Exercise-mediated improvements in walking velocity correlated with increased activation in cerebellum and midbrain. Conclusions— T-EX improves walking, fitness and recruits cerebellum-midbrain circuits, likely reflecting neural network plasticity. This neural recruitment is associated with better walking. These findings demonstrate the effectiveness of T-EX rehabilitation in promoting gait recovery of stroke survivors with long-term mobility impairment and provide evidence of neuroplastic mechanisms that could lead to further refinements in these paradigms to improve functional outcomes.

Lesion location alters brain activation in chronically impaired stroke survivors.

Recovery of motor function after stroke is associated with reorganization in central motor networks. Functional imaging has demonstrated recovery-dependent alterations in brain activation patterns when compared to healthy controls. These alterations are variable across stroke subjects. Factors identified as contributing to this variability are the degree of functional impairment, the time interval since stroke, and rehabilitative therapies. Here, the hypothesis is tested that lesion location influences the activation patterns. Using functional magnetic resonance imaging, the objective was to characterize similarities or differences in movement-related activation patterns in patients chronically disabled by cortical plus subcortical or subcortical lesions only. Brain activation was mapped during paretic and non-paretic movement in 11 patients with subcortical stroke, in nine patients with stroke involving sensorimotor cortex, and in eight healthy volunteers. Patient groups had similar average motor deficit as measured by a battery of scores and strength measures. Substantial differences between patients groups were found in activation patterns associated with paretic limb movement: whereas contralateral motor cortex, ipsilateral cerebellum (relative to moving limb), bilateral mesial (cingulate, SMA), and perisylvian regions were active in subcortical stroke, cortical patients recruited only ipsilateral postcentral mesial hemisphere regions, and areas at the rim of the stroke cavity. For both groups, activation in ipsilateral postcentral cortex correlated with motor function; in subcortical stroke, the same was found for mesial and perisylvian regions. Overall, brain activation in cortical stroke was less, while in subcortical patients, more than in healthy controls. For non-paretic movement, activation patterns were similar to control in cortical patients. In subcortical patients, however, activation patterns differed: the activation of non-paretic movement was similar to that of paretic movement (corrected for side). The data demonstrate more differences than similarities in the central control of paretic and non-paretic limb movement in patients chronically disabled by subcortical versus cortical stroke. Whereas standard motor circuitry is utilized in subcortical stroke, alternative networks are recruited after cortical stroke. This finding proposes lesion-specific mechanisms of reorganization. Optimal activation of these distinct networks may require different rehabilitative strategies.

Comparing brain activation associated with isolated upper and lower limb movement across corresponding joints

It was shown recently that functional activation across brain motor areas during locomotion and foot movements are similar but differ substantially from activation related to upper extremity movement (Miyai [ 2001 ]: Neuroimage 14:1186–1192). The activation pattern may be a function of the behavioral context of the movement rather than of its mechanical properties. We compare motor system activation patterns associated with isolated single‐joint movement of corresponding joints in arm and leg carried out in equal frequency and range. Eleven healthy volunteers underwent BOLD‐weighted fMRI while performing repetitive elbow or knee extension/flexion. To relate elbow and knee activation to the well‐described patterns of finger movement, serial finger‐to‐thumb opposition was assessed in addition. After identifying task‐related voxels using statistical parametric mapping, activation was measured in five regions of interest (ROI; primary motor [M1] and somatosensory cortex [S1], premotor cortex, supplementary motor area [SMA] divided into preSMA and SMA‐proper, and cerebellum). Differences in the degree of activation across ROIs were found between elbow and knee movement. SMA‐proper activation was prominent for knee, but almost absent for elbow movement (P < 0.05); finger movement produced small but constant SMA‐proper activation. Ipsilateral M1 activation was detected during knee and finger movement, but was absent for the elbow task (P < 0.05). Knee movement showed less lateralization in M1 and S1 than other tasks (P < 0.05). The data demonstrate that central motor structures contribute differently to isolated elbow and knee movement. Activation during knee movement shows similarities to gait‐related activation patterns. Hum. Brain Mapping 17:131–140, 2002.

Neural decoding of treadmill walking from noninvasive electroencephalographic signals

Chronic recordings from ensembles of cortical neurons in primary motor and somatosensory areas in rhesus macaques provide accurate information about bipedal locomotion (Fitzsimmons NA, Lebedev MA, Peikon ID, Nicolelis MA. Front Integr Neurosci 3: 3, 2009). Here we show that the linear and angular kinematics of the ankle, knee, and hip joints during both normal and precision (attentive) human treadmill walking can be inferred from noninvasive scalp electroencephalography (EEG) with decoding accuracies comparable to those from neural decoders based on multiple single-unit activities (SUAs) recorded in nonhuman primates. Six healthy adults were recorded. Participants were asked to walk on a treadmill at their self-selected comfortable speed while receiving visual feedback of their lower limbs (i.e., precision walking), to repeatedly avoid stepping on a strip drawn on the treadmill belt. Angular and linear kinematics of the left and right hip, knee, and ankle joints and EEG were recorded, and neural decoders were designed and optimized with cross-validation procedures. Of note, the optimal set of electrodes of these decoders were also used to accurately infer gait trajectories in a normal walking task that did not require subjects to control and monitor their foot placement. Our results indicate a high involvement of a fronto-posterior cortical network in the control of both precision and normal walking and suggest that EEG signals can be used to study in real time the cortical dynamics of walking and to develop brain-machine interfaces aimed at restoring human gait function.

Hemiparetic Gait Parameters in Overground Versus Treadmill Walking

Objective: Hemiparetic gait is characterized by high stride-cycle variability, di minished stance time, single-limb stance time, and stance/swing ratio in the paretic limb. Recent studies suggest treadmill (TM) training may improve the motor control underlying these variables, but supporting evidence is sparse. Methods: This study compared gait patterns of untrained chronic hemiparetic stroke patients (n = 18; mean, 39.5 months poststroke) during overground (OG) and TM walking at matched velocities. Variables included relative stance time, relative single-limb stance time, stance/swing ratio, peak force, and impulse. Within-subject variability of these meas ures (CV) was used to assess gait pattern stability. Results: OG and TM cycle dura tions were similar, but CVs differed (TM < OG, p < 0.05). In the paretic limb, dif ferences were seen in relative stance time, relative single-limb stance time, and stance/swing ratio, respectively (TM > OG, p < 0.05). These variables decreased in the nonparetic limb during TM walking (p < 0.05 for all). Improved interlimb sym metry and coordination were evidenced by decreased between-limb differences and improved relative temporal phasing, respectively, in the TM condition (p < 0.05). Conclusions: Collectively, these results demonstrate that the TM induces an imme diate alteration toward a more consistent and symmetric gait pattern. Further inves tigation is needed to determine whether TM training leads to motor relearning and neuroplasticity in chronic hemiparetic subjects. Key Words: Stroke—Rehabilitation— Hemiparetic gait-Treadmill-Gait symmetry.

Bilateral and Unilateral Arm Training Improve Motor Function Through Differing Neuroplastic Mechanisms A Single-Blinded Randomized Controlled Trial

Background and Purpose. This randomized controlled trial tests the efficacy of bilateral arm training with rhythmic auditory cueing (BATRAC) versus dose-matched therapeutic exercises (DMTEs) on upper-extremity (UE) function in stroke survivors and uses functional magnetic resonance imaging (fMRI) to examine effects on cortical reorganization. Methods. A total of 111 adults with chronic UE paresis were randomized to 6 weeks (3×/week) of BATRAC or DMTE. Primary end points of UE assessments of Fugl-Meyer UE Test (FM) and modified Wolf Motor Function Test Time (WT) were performed 6 weeks prior to and at baseline, after training, and 4 months later. Pretraining and posttraining, fMRI for UE movement was evaluated in 17 BATRAC and 21 DMTE participants. Results. The improvements in UE function (BATRAC: FM Δ = 1.1 + 0.5, P = .03; WT Δ = −2.6 + 0.8, P < .00; DMTE: FM Δ = 1.9 + 0.4, P < .00; WT Δ = −1.6 + 0.7; P = .04) were comparable between groups and retained after 4 months. Satisfaction was higher after BATRAC than DMTE (P = .003). BATRAC led to significantly higher increase in activation in ipsilesional precentral, anterior cingulate and postcentral gyri, and supplementary motor area and contralesional superior frontal gyrus (P < .05). Activation change in the latter was correlated with improvement in the WMFT (P = .01). Conclusions. BATRAC is not superior to DMTE, but both rehabilitation programs durably improve motor function for individuals with chronic UE hemiparesis and with varied deficit severity. Adaptations in brain activation are greater after BATRAC than DMTE, suggesting that given similar benefits to motor function, these therapies operate through different mechanisms.

Chronic stroke survivors benefit from high-intensity aerobic treadmill exercise: a randomized control trial.

Background and objective. Ambulatory subjects after stroke may benefit from gait-oriented cardiovascular fitness training, but trials to date have not primarily assessed older persons. Methods. Thirty-eight subjects (age >60 years) with residual hemiparetic gait were enrolled >6 months after stroke. Participants were randomized to receive 3 months (3×/week) progressive graded, high-intensity aerobic treadmill exercise (TAEX) or conventional care physiotherapy. Primary outcome measures were peak exercise capacity (Vo2peak) and sustained walking capacity in 6-minute walks (6MW). Secondary measures were gait velocity in 10-m walks, Berg Balance Scale, functional leg strength (5 chair-rise), self-rated mobility (Rivermead Mobility Index), and quality of life (SF-12). Results. Thirty-six participants completed the study (18 TAEX, 18 controls). TAEX but not conventional care improved Vo2peak (difference 6.4 mL/kg/min, P < .001) and 6MW (53 m, P < .001). Likewise, maximum walking speed (0.13 m/s, P = .01), balance (P < .05), and the mental subscore of the SF-12 (P < .01) improved more after TAEX. Gains in Vo2peak correlated with the degree at which training intensity could be progressed in the individual participant (P < .01). Better walking was related to progression in treadmill velocity and training duration (P < .001). Vo2peak and 6MW performances were still higher 1 year after the end of training when compared with the baseline, although endurance walking (6MW) at 1 year was lower than immediately after training (P < .01). Conclusion. This trial demonstrates that TAEX effectively improves cardiovascular fitness and gait in persons with chronic stroke.

Task-Oriented Aerobic Exercise in Chronic Hemiparetic Stroke: Training Protocols and Treatment Effects

Abstract Stroke is the leading cause of disability in older Americans. Each year 750,000 Americans suffer a stroke, two thirds of whom are left with neurological deficits that persistently impair function. Principal among them is hemiparetic gait that limits mobility and increases fall risk, promoting a sedentary lifestyle. These events propagate disability by physical deconditioning and “learned non-use,” with further functional declines accelerated by the sarcopenia and fitness decrements of advancing age. Conventional rehabilitation care typically provides little or no structured therapeutic exercise beyond the subacute stroke recovery period, based on natural history studies showing little or no further functional motor recovery beyond 6 months after stroke. Emerging evidence suggests that new models of task-oriented exercise have the potential to improve motor function even years after stroke. This article presents treadmill as a task-oriented training paradigm to optimize locomotor relearning while eliciting cardiovascular conditioning in chronic stroke patients. Protocols for exercise testing and longitudinal aerobic training progression are presented that provide fundamental formulas that safely approach the complex task of customizing aerobic training to gait deficit severity in the high CVD risk stroke population. The beneficial effects of 6 months task-oriented treadmill exercise on cardiovascular-metabolic fitness, energy cost of hemiparetic gait, ADL mobility task performance, and leg strength are discussed with respect to the central and peripheral neuromuscular adaptations targeted by the training. Collectively, these findings constitute one initial experience in a much broader neuroscience and exercise rehabilitation development of task-oriented training paradigms that offer a multisystems approach to improving both neurological and cardiovascular health outcomes in the chronic stroke population.