Evaluating Test-Retest Reliability of Fatigability in Chronic Stroke.

OBJECTIVES: The subjective nature of fatigue may contribute to inconsistencies in prevalence rates for post-stroke fatigue. More objective performance fatigue measures may offer a more reliable construct of fatigue. Our goal was to establish test-retest reliability of fatigability in stroke during 6-minute walk (6MW) testing. Relationships between post-stoke fatigability and other constructs were assessed. MATERIALS AND METHODS: Twenty-three hemiparetic stroke survivors underwent two 6MW tests with portable metabolic monitoring performed at least 48 hours apart. Fatigability was defined as ratio of change in walking speed to distance covered during the 6MW. 6MW oxygen consumption (VO2), peak aerobic capacity (VO2peak), walking speed over-ground, dynamic gait index, fatigue, falls efficacy, and BMI were measured. RESULTS: Fatigability was highly correlated between both 6MW trials (ICC = 0.99, p < 0.001) with no significant difference between trials (0.08, p = 0.48). The strongest correlation was between fatigability and 6MW VO2 trial 1 and 2 (r = 0.92, p < 0.001 and r = 0.95, p < 0.001, respectively). Moderate-to-strong relationships were observed between fatigability for 6MW and fastest-comfortable walking speed (r = -0.82 and -0.77), self-selected walking speed (r = -7.8 and -0.78), 6MW walking speed (r = -0.80 and 0.80, VO2peak (r = -0.47 and -0.48) (p < 0.001), and DGI (r = -0.70 and -0.68, p < 0.001). CONCLUSION: This study establishes test-retest reliability for an objective measure of fatigue in stroke-related disability. The strong correlations between fatigability and other functional measures also provides insight into the contributors underlying fatigability in this population. REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01322607.

Strength Training for Skeletal Muscle Endurance after Stroke.

BACKGROUND AND PURPOSE: Initial studies support the use of strength training (ST) as a safe and effective intervention after stroke. Our previous work shows that relatively aggressive, higher intensity ST translates into large effect sizes for paretic and non-paretic leg muscle volume, myostatin expression, and maximum strength post-stroke. An unanswered question pertains to how our unique ST model for stroke impacts skeletal muscle endurance (SME). Thus, we now report on ST-induced adaptation in the ability to sustain isotonic muscle contraction. METHODS: Following screening and baseline testing, hemiparetic stroke participants were randomized to either ST or an attention-matched stretch control group (SC). Those in the ST group trained each leg individually to muscle failure (20 repetition sets, 3× per week for 3 months) on each of three pneumatic resistance machines (leg press, leg extension, and leg curl). Our primary outcome measure was SME, quantified as the number of submaximal weight leg press repetitions possible at a specified cadence. The secondary measures included one-repetition maximum strength, 6-minute walk distance (6MWD), 10-meter walk speeds, and peak aerobic capacity (VO2 peak). RESULTS: ST participants (N = 14) had significantly greater SME gains compared with SC participants (N = 16) in both the paretic (178% versus 12%, P < .01) and non-paretic legs (161% versus 12%, P < .01). These gains were accompanied by group differences for 6MWD (P < .05) and VO2 peak (P < .05). CONCLUSION: Our ST regimen had a large impact on the capacity to sustain submaximal muscle contraction, a metric that may carry more practical significance for stroke than the often reported measures of maximum strength.

An Engineering Model of Human Balance Control-Part I: Biomechanical Model.

We developed a balance measurement tool (the balanced reach test (BRT)) to assess standing balance while reaching and pointing to a target moving in three-dimensional space according to a sum-of-sines function. We also developed a three-dimensional, 13-segment biomechanical model to analyze performance in this task. Using kinematic and ground reaction force (GRF) data from the BRT, we performed an inverse dynamics analysis to compute the forces and torques applied at each of the joints during the course of a 90 s test. We also performed spectral analyses of each joint's force activations. We found that the joints act in a different but highly coordinated manner to accomplish the tracking task-with individual joints responding congruently to different portions of the target disk's frequency spectrum. The test and the model also identified clear differences between a young healthy subject (YHS), an older high fall risk (HFR) subject before participating in a balance training intervention; and in the older subject's performance after training (which improved to the point that his performance approached that of the young subject). This is the first phase of an effort to model the balance control system with sufficient physiological detail and complexity to accurately simulate the multisegmental control of balance during functional reach across the spectra of aging, medical, and neurological conditions that affect performance. Such a model would provide insight into the function and interaction of the biomechanical and neurophysiological elements making up this system; and system adaptations to changes in these elements' performance and capabilities.

Dynamic Balanced Reach: A Temporal and Spectral Analysis Across Increasing Performance Demands.

Standing balanced reach is a fundamental task involved in many activities of daily living that has not been well analyzed quantitatively to assess and characterize the multisegmental nature of the body's movements. We developed a dynamic balanced reach test (BRT) to analyze performance in this activity; in which a standing subject is required to maintain balance while reaching and pointing to a target disk moving across a large projection screen according to a sum-of-sines function. This tracking and balance task is made progressively more difficult by increasing the disk's overall excursion amplitude. Using kinematic and ground reaction force data from 32 young healthy subjects, we investigated how the motions of the tracking finger and whole-body center of mass (CoM) varied in response to the motion of the disk across five overall disk excursion amplitudes. Group representative performance statistics for the cohort revealed a monotonically increasing root mean squared (RMS) tracking error (RMSE) and RMS deviation (RMSD) between whole-body CoM (projected onto the ground plane) and the center of the base of support (BoS) with increasing amplitude (p < 0.03). Tracking and CoM response delays remained constant, however, at 0.5 s and 1.0 s, respectively. We also performed detailed spectral analyses of group-representative response data for each of the five overall excursion amplitudes. We derived empirical and analytical transfer functions between the motion of the disk and that of the tracking finger and CoM, computed tracking and CoM responses to a step input, and RMSE and RMSD as functions of disk frequency. We found that for frequencies less than 1.0 Hz, RMSE generally decreased, while RMSE normalized to disk motion amplitude generally increased. RMSD, on the other hand, decreased monotonically. These findings quantitatively characterize the amplitude- and frequency-dependent nature of young healthy tracking and balance in this task. The BRT is not subject to floor or ceiling effects, overcoming an important deficiency associated with most research and clinical instruments used to assess balance. This makes a comprehensive quantification of young healthy balance performance possible. The results of such analyses could be used in work space design and in fall-prevention instructional materials, for both the home and work place. Young healthy performance represents "exemplar" performance and can also be used as a reference against which to compare the performance of aging and other clinical populations at risk for falling.

Task-specific ankle robotics gait training after stroke: a randomized pilot study.

BACKGROUND: An unsettled question in the use of robotics for post-stroke gait rehabilitation is whether task-specific locomotor training is more effective than targeting individual joint impairments to improve walking function. The paretic ankle is implicated in gait instability and fall risk, but is difficult to therapeutically isolate and refractory to recovery. We hypothesize that in chronic stroke, treadmill-integrated ankle robotics training is more effective to improve gait function than robotics focused on paretic ankle impairments. FINDINGS: Participants with chronic hemiparetic gait were randomized to either six weeks of treadmill-integrated ankle robotics (n = 14) or dose-matched seated ankle robotics (n = 12) videogame training. Selected gait measures were collected at baseline, post-training, and six-week retention. Friedman, and Wilcoxon Sign Rank and Fisher's exact tests evaluated within and between group differences across time, respectively. Six weeks post-training, treadmill robotics proved more effective than seated robotics to increase walking velocity, paretic single support, paretic push-off impulse, and active dorsiflexion range of motion. Treadmill robotics durably improved gait dorsiflexion swing angle leading 6/7 initially requiring ankle braces to self-discarded them, while their unassisted paretic heel-first contacts increased from 44 % to 99.6 %, versus no change in assistive device usage (0/9) following seated robotics. CONCLUSIONS: Treadmill-integrated, but not seated ankle robotics training, durably improves gait biomechanics, reversing foot drop, restoring walking propulsion, and establishing safer foot landing in chronic stroke that may reduce reliance on assistive devices. These findings support a task-specific approach integrating adaptive ankle robotics with locomotor training to optimize mobility recovery. CLINICAL TRIAL IDENTIFIER: NCT01337960. https://clinicaltrials.gov/ct2/show/NCT01337960?term=NCT01337960&rank=1.

Higher Treadmill Training Intensity to Address Functional Aerobic Impairment after Stroke.

BACKGROUND: Peak aerobic capacity (VO2 peak) is severely worsened after disabling stroke, having serious implications for function, metabolism, and ongoing cardiovascular risk. Work from our laboratory and others has previously shown that modest improvements in VO2 peak are possible in stroke participants with aerobic exercise training. The purpose of the current investigation was to test the extent to which greater enhancements in VO2 peak after stroke are possible using a treadmill protocol with far greater emphasis on intensity progression compared with a protocol without such emphasis. METHODS: Using a randomized design, we compared stroke survivors engaged in higher intensity treadmill training (HI-TM, 80% heart rate reserve [HRR]) with those undergoing lower intensity treadmill training (LO-TM, 50% HRR). Measured outcomes were change in VO2 peak, 6-minute walk distance (6MWD), 30-ft walk times (30WT), and 48-hour step counts (48SC). LO-TM participants trained for a longer period of time per session in an effort to approximately match workload/caloric expenditure. Participants were randomized with stratification according to age and baseline walking capacity. RESULTS: HI-TM participants (n = 18) had significantly greater gains in VO2 peak (+34%) than LO-TM participants (n = 16; +5%) across the 6-month intervention period (P = .001, group × time interaction). Conversely, there was no statistical difference between groups in the changes observed for 6MWD, 30WT, or 48SC. CONCLUSIONS: HI-TM is far more effective than LO-TM for improving VO2 peak after disabling stroke. The magnitude of relative improvement for HI-TM was double compared with previous reports from our laboratory with probable clinical significance for this population.

Physical activity and exercise recommendations for stroke survivors: a statement for healthcare professionals from the American Heart Association/American Stroke Association.

PURPOSE: This scientific statement provides an overview of the evidence on physical activity and exercise recommendations for stroke survivors. Evidence suggests that stroke survivors experience physical deconditioning and lead sedentary lifestyles. Therefore, this updated scientific statement serves as an overall guide for practitioners to gain a better understanding of the benefits of physical activity and recommendations for prescribing exercise for stroke survivors across all stages of recovery. METHODS: Members of the writing group were appointed by the American Heart Association Stroke Council's Scientific Statement Oversight Committee and the American Heart Association's Manuscript Oversight Committee. The writers used systematic literature reviews, references to published clinical and epidemiology studies, morbidity and mortality reports, clinical and public health guidelines, authoritative statements, personal files, and expert opinion to summarize existing evidence and indicate gaps in current knowledge. RESULTS: Physical inactivity after stroke is highly prevalent. The assessed body of evidence clearly supports the use of exercise training (both aerobic and strength training) for stroke survivors. Exercise training improves functional capacity, the ability to perform activities of daily living, and quality of life, and it reduces the risk for subsequent cardiovascular events. Physical activity goals and exercise prescription for stroke survivors need to be customized for the individual to maximize long-term adherence. CONCLUSIONS: The recommendation from this writing group is that physical activity and exercise prescription should be incorporated into the management of stroke survivors. The promotion of physical activity in stroke survivors should emphasize low- to moderate-intensity aerobic activity, muscle-strengthening activity, reduction of sedentary behavior, and risk management for secondary prevention of stroke.

Dorsiflexion Specific Ankle Robotics to Enhance Motor Learning After Stroke: A Preliminary Report.

Background: Robotics has emerged as a promising avenue for gait retraining of persons with chronic hemiparetic gait and footdrop, yet there is a gap regarding the biomechanical adaptations that occur with locomotor learning. We developed an ankle exoskeleton (AMBLE) enabling dorsiflexion assist-as-needed across gait cycle sub-events to train and study the biomechanics of motor learning stroke. This single-armed, non-controlled study investigates effects of nine hours (9 weeks × 2 sessions/week) locomotor task-specific ankle robotics training on gait biomechanics and functional mobility in persons with chronic hemiparetic gait and foot drop. Subjects include N = 16 participants (8 male, 8 female) age 53 ± 12 years with mean 11 ± 8 years since stroke. All baseline and post-training outcomes including optical motion capture for 3-D gait biomechanics are conducted during unassisted (no robot) over-ground walking conditions. Findings: Robotics training with AMBLE produced significant kinematic improvements in ankle peak dorsiflexion angular velocity (°/s, + 44 [49%], p < 0.05), heel-first foot strikes (%steps, + 14 [15%], p < 0.01) toe-off angle (°, + 83[162%], p < 0.05), and paretic knee flexion (°, + 20 [30%], p < 0.05). Improvements in gait temporal-spatial parameters include increased paretic step length (cm, + 12 [20%], p< 0.05), reduced paretic swing duration (%GC, -3[6%], p < 0.05), and trend toward improved step length symmetry (-16 [11%], p = 0.08). Functional improvements include 10-meter comfortable (m/s, + 13 [16%], p < 0.01) and fastest (m/s, + 13 [15%], p<0.01) walking velocities, 6-minute timed walk distance (m, + 16 [19%], p < 0.01) and Dynamic Gait Index scores (+15 [15%], p < 0.01). Subjects' perceived improvements surpassed the minimal clinically important difference on the Stroke Impact Scale (SIS) mobility subscale (+11 [19%], p < 0.05). Conclusions: AMBLE training improves paretic ankle neuromotor control, paretic knee flexion, and gait temporal-distance parameters during unassisted over-ground walking in persons with chronic stroke and foot drop. This locomotor learning indexed by an increase in volitional autonomous (non-robotic) control of paretic ankle across training translated to improvements in functional mobility outcomes. Larger randomized clinical trials are needed to investigate the effectiveness of task-specific ankle robotics, and precise training characteristics to durably improve gait, balance, and home and community-based functional mobility for persons with hemiparetic gait and foot drop. Clinical trial identifier: NCT04594837.

Improved cerebral vasomotor reactivity after exercise training in hemiparetic stroke survivors.

BACKGROUND AND PURPOSE: Animal studies provide strong evidence that aerobic exercise training positively influences cerebral blood flow, but no human studies support the use of exercise for improving cerebral hemodynamics. This randomized study in stroke survivors assessed the effects of treadmill aerobic exercise training (TM) on cerebral blood flow parameters compared to a control intervention of nonaerobic stretching. METHODS: Thirty-eight participants (19 in TM group and 19 in control group) with remote stroke (>6 months) and mild to moderate gait deficits completed middle cerebral artery blood flow velocity measurements by transcranial Doppler ultrasonography before and after a 6-month intervention period. Middle cerebral artery blood flow velocity was assessed bilaterally during normocapnia and hypercapnia (6% CO2). Cerebral vasomotor reactivity (cVMR) was calculated as percent change in middle cerebral artery blood flow velocity from normocapnia to hypercapnia (cVMR percent) and as an index correcting percent change for absolute increase in end tidal CO2 (cVMR index). RESULTS: The TM group had significantly larger improvements than did controls for both ipsilesional and contralesional cVMR index (P≤0.05) and contralesional cVMR percent (P≤0.01). Statin users in the TM group (n=10) had higher baseline cVMR and lower training-induced cVMR change, indicating that cVMR change among those not using statins (n=9) primarily accounted for the between-group effects. There was a 19% increase in Vo2 peak for the TM group compared to a 4% decrease in the control group (P<0.01), and peak fitness change correlated with cVMR change (r=0.55; P<0.05). CONCLUSIONS: Our data provide the first evidence to our knowledge of exercise-induced cVMR improvements in stroke survivors, implying a protective mechanism against recurrent stroke and other brain-related disorders. Statin use appears to regulate cVMR and the cVMR training response.

Measurement of passive ankle stiffness in subjects with chronic hemiparesis using a novel ankle robot.

Our objective in this study was to assess passive mechanical stiffness in the ankle of chronic hemiparetic stroke survivors and to compare it with those of healthy young and older (age-matched) individuals. Given the importance of the ankle during locomotion, an accurate estimate of passive ankle stiffness would be valuable for locomotor rehabilitation, potentially providing a measure of recovery and a quantitative basis to design treatment protocols. Using a novel ankle robot, we characterized passive ankle stiffness both in sagittal and in frontal planes by applying perturbations to the ankle joint over the entire range of motion with subjects in a relaxed state. We found that passive stiffness of the affected ankle joint was significantly higher in chronic stroke survivors than in healthy adults of a similar cohort, both in the sagittal as well as frontal plane of movement, in three out of four directions tested with indistinguishable stiffness values in plantarflexion direction. Our findings are comparable to the literature, thus indicating its plausibility, and, to our knowledge, report for the first time passive stiffness in the frontal plane for persons with chronic stroke and older healthy adults.

Exercise intervention research in stroke: optimizing outcomes through treatment fidelity.

BACKGROUND: Demonstrating the treatment fidelity of an intervention is a key methodological requirement of any trial testing the impact of the intervention. PURPOSE: The purpose of this report was to serve as a model for evaluating treatment fidelity in stroke exercise intervention studies and to provide evidence for treatment fidelity in the Exercise Training for Hemiparetic Stroke Intervention Development Study. METHODS: Treatment fidelity was evaluated based on study design, training of interventionists, and delivery and receipt of the intervention. RESULTS: There were some concerns about design fidelity as the control group and intervention group traveled to the study location together and received different exercise programs in the same facility. With regard to training of interventionists, observations were utilized to help maintain adherence to the protocol. There was strong support for the delivery and receipt of the intervention with participants exposed to the anticipated number of exercise sessions. As per study protocol, there was evidence that progress toward the proposed physical activity goal was made. Treatment fidelity findings are reported using cumulative data rather than at points throughout the study. Thus the findings may be conservative with regard adherence, for example, to time spent in exercise. CONCLUSION: In addition to assurance of true testing of the intervention in this study, treatment fidelity of this work provides a useful model for replication and critically important information to better understand the type, dose, and length of exposure to exercise interventions that is needed to optimize stroke recovery.

CD31+ Circulating Angiogenic Cell Number and Subtypes are Reduced in Individuals with Chronic Stroke.

BACKGROUND AND PURPOSE: Reduced number and function of CD31+ circulating angiogenic cells (CACs) may explain vascular complications associated with the chronic phase stroke. The purpose of this study was to quantify CD31+ CAC paracrine function, total number and number of various subtypes of CD31+ CACs in individuals with chronic stroke compared with controls. METHODS: Peripheral blood mononuclear cells were isolated from chronic stroke participants and controls. CD31+ cells were quantified by flow cytometry, as was co-expression of CD31 in combination with CD14, CD3, CD11b, or CD34. Immunomagnetically selected CD31+ cells were cultured, and conditioned medium was used in a capillary-like network assay. RESULTS: Significantly lower levels of CD31+ CACs were found in stroke participants compared with controls (-24%; P=0.04). Additionally, CD31+/CD14+, CD31+/CD11b+ and CD31+/CD3+ cells were significantly lower in the chronic stroke group compared with controls (-45%, P=0.02; -47%, P=0.02 and -32%, P=0.03, respectively). There was no group effect on CD31+ CAC conditioned media-mediated capillary-like network formation. CONCLUSION: CD31+ CACs and subtypes may serve as potential therapeutic targets in chronic stroke recovery.

Physical activity and sleep: An updated umbrella review of the 2018 Physical Activity Guidelines Advisory Committee report.

Physical activity (PA) is widely considered to improve sleep, but a comprehensive review of the research on this topic has not been performed. In this umbrella review, conducted initially for the 2018 Physical Activity Guidelines for Americans Advisory Committee and updated to reflect more recent research, we examined whether PA enhances sleep outcomes across the lifespan as well as among individuals with sleep disorders. Systematic reviews and meta-analyses were utilized to assess the evidence. We also examined dose-response considerations and whether the association between PA and sleep was moderated by various factors (e.g., timing, sociodemographic characteristics). We found strong evidence that both acute bouts of PA and regular PA improved sleep outcomes. Moderate evidence indicated that longer bouts of PA (both acute and regular) improved sleep, and that the effects of PA on sleep outcomes were generally preserved across adult age groups and sex. Finally, moderate evidence demonstrated that PA improved sleep in adults with insomnia symptoms or obstructive sleep apnea. Several important areas in need of future research were also identified. Overall, the review supported the claim that PA improves sleep, but highlighted gaps that need to be addressed to facilitate more widespread utilization of PA for improving sleep.

Impaired leg vasodilatory function after stroke: adaptations with treadmill exercise training.

BACKGROUND AND PURPOSE: Resting and reactive hyperemic leg blood flows are significantly reduced in the paretic compared with the nonparetic limb after disabling stroke. Our objective was to compare the effects of regular treadmill exercise (TM) with an active control regimen of supervised stretching (CONTROL) on peripheral hemodynamic function. METHODS: This intervention study used a randomized, controlled design, in which participants were randomized with stratification according to age and baseline walking capacity to ensure approximate balance between the 2 groups. Fifty-three chronic, ischemic stroke participants (29 TM and 24 CONTROL) with mild to moderate hemiparetic gait completed bilateral measurements of lower leg resting and reactive hyperemic blood flow using venous occlusion strain gauge plethysmography before and after the 6-month intervention period. Participants also underwent testing to track changes in peak aerobic fitness across time. RESULTS: Resting and reactive hyperemic blood flows were significantly reduced in the paretic compared with the nonparetic limb at baseline before any intervention (-28% and -34%, respectively, P<0.01). TM increased both resting and reactive hyperemic blood flow in the paretic limb by 25% compared with decreases in CONTROL (P<0.001, between groups). Similarly, nonparetic leg blood flow was significantly improved with TM compared with controls (P<0.001). Peak aerobic fitness improved by 18% in TM and decreased by 4% in CONTROL (P<0.01, between groups), and there was a significant relationship between blood flow change and peak fitness change for the group as a whole (r=.30, P<0.05). CONCLUSIONS: Peripheral hemodynamic function improves with regular aerobic exercise training after disabling stroke.

Effects of unilateral robotic limb loading on gait characteristics in subjects with chronic stroke.

BACKGROUND: Hemiparesis after stroke often leads to impaired ankle motor control that impacts gait function. In recent studies, robotic devices have been developed to address this impairment. While capable of imparting forces to assist during training and gait, these devices add mass to the paretic leg which might encumber patients' gait pattern. The purpose of this study was to assess the effects of the added mass of one of these robots, the MIT's Anklebot, while unpowered, on gait of chronic stroke survivors during overground and treadmill walking. METHODS: Nine chronic stroke survivors walked overground and on a treadmill with and without the anklebot mounted on the paretic leg. Gait parameters, interlimb symmetry, and joint kinematics were collected for the four conditions. Repeated-measures analysis of variance (ANOVA) tests were conducted to examine for possible differences across four conditions for the paretic and nonparetic leg. RESULTS: The added inertia and friction of the unpowered anklebot had no statistically significant effect on spatio-temporal parameters of gait, including paretic and nonparetic step time and stance percentage, in both overground and treadmill conditions. Noteworthy, interlimb symmetry as characterized by relative stance duration was greater on the treadmill than overground regardless of loading conditions. The presence of the unpowered robot loading reduced the nonparetic knee peak flexion on the treadmill and paretic peak dorsiflexion overground (p < 0.05). CONCLUSIONS: Our results suggest that for these subjects the added inertia and friction of this backdriveable robot did not significantly alter their gait pattern.

Aerobic Exercise Recommendations to Optimize Best Practices in Care After Stroke: AEROBICS 2019 Update.

Most stroke survivors have very low levels of cardiovascular fitness, which limits mobility and leads to further physical deconditioning, increased sedentary behavior, and heightened risk of recurrent stroke. Although clinical guidelines recommend that aerobic exercise be a part of routine stroke rehabilitation, clinical uptake has been suboptimal. In 2013, an international group of stroke rehabilitation experts developed a user-friendly set of recommendations to guide screening and prescription-the Aerobic Exercise Recommendations to Optimize Best Practices in Care after Stroke (AEROBICS 2013). The objective of this project was to update AEROBICS 2013 using the highest quality of evidence currently available. The first step was to conduct a comprehensive review of literature from 2012 to 2018 related to aerobic exercise poststroke. A working group of the original consensus panel members drafted revisions based on synthesis. An iterative process was used to achieve agreement among all panel members. Final revisions included: (1) addition of 115 new references to replace or augment those in the original AEROBICS document, (2) rewording of the original recommendations and supporting material, and (3) addition of 2 new recommendations regarding prescription. The quality of evidence from which these recommendations were derived ranged from low to high. The AEROBICS 2019 Update should make it easier for clinicians to screen for, and prescribe, aerobic exercise in stroke rehabilitation. Clinical implementation will not only help to narrow the gap between evidence and practice but also reduce current variability and uncertainty regarding the role of aerobic exercise in recovery after stroke.

Reduced skeletal muscle capillarization and glucose intolerance.

OBJECTIVE: Reduced capillarization in hemiparetic skeletal muscle of chronic stroke patients can limit insulin, glucose, and oxygen supply to muscle, thereby contributing to impaired glucose metabolism and cardiovascular deconditioning. We hypothesized that compared to sedentary controls, stroke subjects have reduced skeletal muscle capillarization that is associated with glucose intolerance and reduced peak oxygen consumption (Vo(2peak)). METHODS: Twelve chronic stroke subjects (ages, 62.1+/-2.8 years), and matched sedentary controls with impaired (n=12) or normal (n=12) glucose tolerance underwent oral glucose tolerance tests, exercise tests, and vastus lateralis biopsies. RESULTS: Stroke subjects had lower capillarization in hemiparetic muscle than in nonparetic muscle and normal glucose tolerant controls ( approximately 22 and approximately 28%, respectively; P<0.05) and had similar bilateral capillarization, compared to controls with impaired glucose tolerance. Capillary density in hemiparetic muscle inversely correlated with 120-minute glucose (r=-0.70, P<0.01) and glucose area under the curve (r=-0.78, P<0.01). Vo(2peak) was approximately 40% lower in stroke subjects, compared to controls (P<0.001), but did not correlate with capillarization (P=n.s.). CONCLUSIONS: Hemiparetic muscle capillarization is reduced after stroke, and reduced capillarization is associated with glucose intolerance in stroke and control subjects. Interventions to increase skeletal muscle capillarization may prove beneficial for improving glucose metabolism in chronic stroke patients.

Community-based adaptive physical activity program for chronic stroke: feasibility, safety, and efficacy of the Empoli model.

OBJECTIVE: To determine whether Adaptive Physical Activity (APA-stroke), a community-based exercise program for participants with hemiparetic stroke, improves function in the community. METHODS: Nonrandomized controlled study in Tuscany, Italy, of participants with mild to moderate hemiparesis at least 9 months after stroke. Forty-nine participants in a geographic health authority (Empoli) were offered APA-stroke (40 completed the study). Forty-four control participants in neighboring health authorities (Florence and Pisa) received usual care (38 completed the study). The APA intervention was a community-based progressive group exercise regimen that included walking, strength, and balance training for 1 hour, thrice a week, in local gyms, supervised by gym instructors. No serious adverse clinical events occurred during the exercise intervention. Outcome measures included the following: 6-month change in gait velocity (6-Minute Timed Walk), Short Physical Performance Battery (SPPB), Berg Balance Scale, Stroke Impact Scale (SIS), Barthel Index, Hamilton Rating Scale for Depression, and Index of Caregivers Strain. RESULTS: After 6 months, the intervention group improved whereas controls declined in gait velocity, balance, SPPB, and SIS social participation domains. These between-group comparisons were statistically significant at P<.00015. Individuals with depressive symptoms at baseline improved whereas controls were unchanged (P<.003). Oral glucose tolerance tests were performed on a subset of participants in the intervention group. For these individuals, insulin secretion declined 29% after 6 months (P=.01). CONCLUSION: APA-stroke appears to be safe, feasible, and efficacious in a community setting.

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.

Progressive adaptive physical activity in stroke improves balance, gait, and fitness: preliminary results.

PURPOSE: We conducted a non-controlled pilot intervention study in stroke survivors to examine the efficacy of low-intensity adaptive physical activity to increase balance, improve walking function, and increase cardiovascular fitness and to determine whether improvements were carried over into activity profiles in home and community. METHOD: Adaptive physical activity sessions were conducted 3 times/week for 6 months. The main outcomes were Berg Balance Scale, Dynamic Gait Index, 6-Minute Walk Test, cardiovascular fitness (VO2 peak), Falls Efficacy Scale, and 5-day Step Activity Monitoring. RESULTS: Seven men and women with chronic ischemic stroke completed the 6-month intervention. The mean Berg Balance baseline score increased from 33.9+/-8.5 to 46+/-6.7 at 6 months (mean+/-SD; p=.006). Dynamic Gait Index increased from 13.7+/-3.0 to 19.0+/-3.5 (p=.01). Six-minute walk distance increased from 840+/-110 feet to 935+/-101 feet (p=0.02). VO2 peak increased from 15.3+/-4.1 mL/kg/min to 17.5+/-4.7 mL/kg/min (p=.03). There were no significant changes in falls efficacy or free-living ambulatory activity. CONCLUSION: A structured adaptive physical activity produces improvements in balance, gait, fitness, and ambulatory performance but not in falls efficacy or free-living daily step activity. Randomized studies are needed to determine the cardiovascular health and functional benefits of structured group physical activity programs and to develop behavioral interventions that promote increased free-living physical activity patterns.