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.

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.

Physical Activity to Prevent and Treat Hypertension: A Systematic Review

PURPOSE

This systematic umbrella review examines and updates the evidence on the relationship between physical activity (PA) and blood pressure (BP) presented in the 2008 Physical Activity Guidelines Advisory Committee Scientific Report.

METHODS

We performed a systematic review to identify systematic reviews and meta-analyses involving adults with normal BP, prehypertension, and hypertension published from 2006 to February 2018.

RESULTS

In total, 17 meta-analyses and one systematic review with 594,129 adults ≥18 yr qualified. Strong evidence demonstrates: 1) an inverse dose-response relationship between PA and incident hypertension among adults with normal BP; 2) PA reduces the risk of cardiovascular disease (CVD) progression among adults with hypertension; 3) PA reduces BP among adults with normal BP, prehypertension, and hypertension; and 4) the magnitude of the BP response to PA varies by resting BP, with greater benefits among adults with prehypertension than normal BP. Moderate evidence indicates the relationship between resting BP and the magnitude of benefit does not vary by PA type among adults with normal BP, prehypertension, and hypertension. Limited evidence suggests the magnitude of the BP response to PA varies by resting BP among adults with hypertension. Insufficient evidence is available to determine if factors such as sex, age, race/ethnicity, socioeconomic status, and weight status or the frequency, intensity, time, and duration of PA influence the associations between PA and BP.

CONCLUSIONS

Future research is needed that adheres to standard BP measurement protocols and classification schemes to better understand the influence of PA on the risk of comorbid conditions, health-related quality of life, and CVD progression and mortality; the interactive effects between PA and antihypertensive medication use; and the immediate BP-lowering benefits of PA.

Brain-derived neurotrophic factor, epigenetics in stroke skeletal muscle, and exercise training

Objective

(1) To compare paretic (P) vs nonparetic (NP) skeletal muscle brain-derived neurotrophic factor (BDNF) and the effects of resistive training (RT) on systemic and skeletal muscle BDNF mRNA expression in stroke; and (2) to compare the DNA methylation profile for BDNF and BDNFAS (BDNF antisense RNA) between P and NP muscle and the effects of aerobic exercise training (AEX) on DNA methylation in stroke.

Methods

In this longitudinal investigation, participants (50-76 years) with chronic stroke underwent a fasting blood draw, a 12-week (3×/week) RT intervention (n = 16), and repeated bilateral vastus lateralis muscle tissue biopsies (n = 10) with BDNF expression determined by RT-PCR. Five stroke survivors completed 6 months of AEX (3×/week) and had bilateral muscle biopsies. DNA methylation status in gene BDNF and BDNFAS was assessed by Illumina 450k methylation array.

Results

P muscle had ∼45% lower BDNF mRNA expression than NP muscle (6.79 ± 1.30 vs 10.52 ± 2.06 arbitrary units [AU], p < 0.05), and P muscle exhibited differential methylation status in the DNA sequences of BDNF (3 CpG [5'-C-phosphate-G-3'] sites, p = 0.016-0.044) and BDNFAS (1 CpG site, p = 0.016) compared to NP. Plasma BDNF and muscle BDNF messenger RNA (mRNA) expression did not significantly change after RT. BDNFAS DNA methylation increased after AEX in P relative to NP muscle (p = 0.017).

Conclusions

This is the first evidence that stroke hemiparesis reduces BDNF skeletal muscle expression, with our findings identifying methylation alterations on the DNA sequence of BDNF and BDNFAS gene. Preliminary results further indicate that AEX increases methylation in BDNFAS gene, which presumably could regulate the expression of BDNF.

The Scientific Foundation for the Physical Activity Guidelines for Americans, 2nd Edition

BACKGROUND

The 2018 Physical Activity Guidelines Advisory Committee Scientific Report provides the evidence base for the Physical Activity Guidelines for Americans, 2nd Edition.

METHODS

The 2018 Physical Activity Guidelines Advisory Committee addressed 38 questions and 104 subquestions selected for their public health relevance, potential to inform public policies and programs, maturity of the relevant science, and applicability to the general US population. Rigorous systematic literature searches and literature reviews were performed using standardized methods.

RESULTS

Newly described benefits of physical activity include reduced risk of excessive weight gain in children and adults, incidence of 6 types of cancer, and fall-related injuries in older people. Physical activity is associated with enhanced cognitive function and mental health across the life span, plus improved mental health and physical function. There is no threshold that must be exceeded before benefits begin to accrue; the accrual is most rapid for the least active individuals. Sedentary time is directly associated with elevated risk of all-cause and cardiovascular mortality, incident cardiovascular disease and type 2 diabetes, and selected cancer sites. A wide range of intervention strategies have demonstrated success in increasing physical activity.

CONCLUSION

The 2018 Physical Activity Guidelines Advisory Committee Scientific Report provides compelling new evidence to inform physical activity recommendations, practice, and policy.

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.

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.

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.

Robotically assisted treadmill exercise training for improving peak fitness in chronic motor incomplete spinal cord injury: A randomized controlled trial

OBJECTIVE

To assess the effectiveness of robotically assisted body weight supported treadmill training (RABWSTT) for improving cardiovascular fitness in chronic motor incomplete spinal cord injury (CMISCI).

DESIGN

Pilot prospective randomized, controlled clinical trial.

SETTING

Outpatient rehabilitation specialty hospital.

PARTICIPANTS

Eighteen individuals with CMISCI with American Spinal Injury Association (ASIA) level between C4 and L2 and at least one-year post injury. Interventions CMISCI participants were randomized to RABWSTT or a home stretching program (HSP) three times per week for three months. Those in the home stretching group were crossed over to three months of RABWSTT following completion of the initial three month phase.

OUTCOME MEASURES

Peak oxygen consumption (peak VO(2)) was measured during both robotic treadmill walking and arm cycle ergometry: twice at baseline, once at six weeks (mid-training) and twice at three months (post-training). Peak VO(2) values were normalized for body mass.

RESULTS

The RABWSTT group improved peak VO(2) by 12.3% during robotic treadmill walking (20.2 ± 7.4 to 22.7 ± 7.5 ml/kg/min, P = 0.018), compared to a non-significant 3.9% within group change observed in HSP controls (P = 0.37). Neither group displayed a significant change in peak VO2 during arm cycle ergometry (RABWSTT, 8.5% (P = 0.25); HSP, 1.76% (P = 0.72)). A repeated measures analysis showed statistically significant differences between treatments for peak VO(2) during both robotic treadmill walking (P = 0.002) and arm cycle ergometry (P = 0.001).

CONCLUSION

RABWSTT is an effective intervention model for improving peak fitness levels assessed during robotic treadmill walking in persons with CMISCI.

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.

Increased reward in ankle robotics training enhances motor control and cortical efficiency in stroke

Robotics is rapidly emerging as a viable approach to enhance motor recovery after disabling stroke. Current principles of cognitive motor learning recognize a positive relationship between reward and motor learning. Yet no prior studies have established explicitly whether reward improves the rate or efficacy of robotics-assisted rehabilitation or produces neurophysiologic adaptations associated with motor learning. We conducted a 3 wk, 9-session clinical pilot with 10 people with chronic hemiparetic stroke, randomly assigned to train with an impedance-controlled ankle robot (anklebot) under either high reward (HR) or low reward conditions. The 1 h training sessions entailed playing a seated video game by moving the paretic ankle to hit moving onscreen targets with the anklebot only providing assistance as needed. Assessments included paretic ankle motor control, learning curves, electroencephalograpy (EEG) coherence and spectral power during unassisted trials, and gait function. While both groups exhibited changes in EEG, the HR group had faster learning curves (p = 0.05), smoother movements (p </= 0.05), reduced contralesional-frontoparietal coherence (p </= 0.05), and reduced left-temporal spectral power (p </= 0.05). Gait analyses revealed an increase in nonparetic step length (p = 0.05) in the HR group only. These results suggest that combining explicit rewards with novel anklebot training may accelerate motor learning for restoring mobility.

Cardiovascular Health and Fitness After Stroke

Stroke patients have profound cardiovascular and muscular deconditioning, with metabolic fitness levels that are about half those found in age-matched sedentary controls. Physical deconditioning, along with elevated energy demands of hemiparetic gait, define a detrimental combination termed diminished physiological fitness reserve that can greatly limit that can greatly limit performance of activities of daily living. The physiological features that underlie worsening metabolic fitness in the chronic phase of stroke include gross muscular atrophy, altered muscle molecular phenotype, increased intramuscular area fat, elevated tissue inflammatory markers, and diminished peripheral blood flow dynamics. Epidemiological evidence further suggests that the reduced cardiovascular fitness and secondary biological changes in muscle may propagate components of the metabolic syndrome, conferring added morbidity and mortality risk. This article reviews some of the consequences of poor fitness in chronic stroke and the potential biological underpinnings that support a rationale for more aggressive approaches to exercise therapy in this population.

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

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.

Ambulatory Activity Intensity Profiles, Fitness, and Fatigue in Chronic Stroke

PURPOSE

The purpose of this study was to describe household and community ambulatory activity profiles and their relationship to fatigue and cardiovascular fitness in a sample of men and women with chronic hemiparetic stroke.

METHOD

We quantified community-based ambulatory activity profiles in terms of step counts and intensity, along with cardiovascular fitness and fatigue severity, in a convenience sample of 79 men and women with chronic hemiparetic stroke.

RESULTS

As captured by daily step activity monitoring, participants demonstrated extremely low step counts (1389 +/- 797 steps/day), and almost no step activity at high intensity (78 +/- 168 steps/day at a rate of >or=30 steps/ minute). Mean high intensity activity constituted less than 3 minutes/day. The mean VO2 peak was 13.02 +/- 4.26 mL/kg/min, consistent with profound aerobic deconditioning. Total, low, and high intensity ambulatory activity were associated with VO2 peak. Mean fatigue severity was 3.28 +/- 1.36 on a scale of 7.00, with 42% of the sample reporting severe fatigue. There were no statistically significant correlations between fatigue severity and ambulatory activity or fitness measures.

CONCLUSION

Our results show that step activity intensity is strongly associated with cardiovascular fitness, lending credence to the hypothesis that rehabilitation interventions that build aerobic conditioning can influence daily activity. The challenge is to appreciate the features of ambulatory behavior after stroke and to use this information to integrate both exercise interventions and behavioral components into the successful translation of structured activities into home and community routines.

Clinical application of a modular ankle robot for stroke rehabilitation

BACKGROUND

Advances in our understanding of neuroplasticity and motor learning post-stroke are now being leveraged with the use of robotics technology to enhance physical rehabilitation strategies. Major advances have been made with upper extremity robotics, which have been tested for efficacy in multi-site trials across the subacute and chronic phases of stroke. In contrast, use of lower extremity robotics to promote locomotor re-learning has been more recent and presents unique challenges by virtue of the complex multi-segmental mechanics of gait.

OBJECTIVES

Here we review a programmatic effort to develop and apply the concept of joint-specific modular robotics to the paretic ankle as a means to improve underlying impairments in distal motor control that may have a significant impact on gait biomechanics and balance.

METHODS

An impedance controlled ankle robot module (anklebot) is described as a platform to test the idea that a modular approach can be used to modify training and measure the time profile of treatment response.

RESULTS

Pilot studies using seated visuomotor anklebot training with chronic patients are reviewed, along with results from initial efforts to evaluate the anklebot's utility as a clinical tool for assessing intrinsic ankle stiffness. The review includes a brief discussion of future directions for using the seated anklebot training in the earliest phases of sub-acute therapy, and to incorporate neurophysiological measures of cerebro-cortical activity as a means to reveal underlying mechanistic processes of motor learning and brain plasticity associated with robotic training.

CONCLUSIONS

Finally we conclude with an initial control systems strategy for utilizing the anklebot as a gait training tool that includes integrating an Internal Model-based adaptive controller to both accommodate individual deficit severities and adapt to changes in patient performance.

Modular ankle robotics training in early subacute stroke: a randomized controlled pilot study

BACKGROUND. Modular lower extremity robotics may offer a valuable avenue for restoring neuromotor control after hemiparetic stroke. Prior studies show that visually guided and visually evoked practice with an ankle robot (anklebot) improves paretic ankle motor control that translates into improved overground walking.

OBJECTIVE

To assess the feasibility and efficacy of daily anklebot training during early subacute hospitalization poststroke.

METHODS

Thirty-four inpatients from a stroke unit were randomly assigned to anklebot (n = 18) or passive manual stretching (n = 16) treatments. All suffered a first stroke with residual hemiparesis (ankle manual muscle test grade 1/5 to 4/5), and at least trace muscle activation in plantar- or dorsiflexion. Anklebot training employed an "assist-as-needed" approach during >200 volitional targeted paretic ankle movements, with difficulty adjusted to active range of motion and success rate. Stretching included >200 daily mobilizations in these same ranges. All sessions lasted 1 hour and assessments were not blinded.

RESULTS

Both groups walked faster at discharge; however, the robot group improved more in percentage change of temporal symmetry (P = .032) and also of step length symmetry (P = .038), with longer nonparetic step lengths in the robot (133%) versus stretching (31%) groups. Paretic ankle control improved in the robot group, with increased peak (P ≤ .001) and mean (P ≤ .01) angular speeds, and increased movement smoothness (P ≤ .01). There were no adverse events.

CONCLUSION

Though limited by small sample size and restricted entry criteria, our findings suggest that modular lower extremity robotics during early subacute hospitalization is well tolerated and improves ankle motor control and gait patterning.

Cardiovascular fitness after stroke: Role of muscle mass and gait deficit severity

Functional disability after hemiparetic stroke may be compounded by physical deconditioning and muscular wasting, factors related to disuse and advancing age. However, the role of body composition, severity, and chronicity of gait deficits as determinants of exercise fitness after stroke is unknown. The purpose of this study was to determine whether oxygen consumption during peak exercise (VO2 peak) is associated with body composition, the severity, or duration of gait deficits in chronic (>6 months) hemiparetic stroke patients. Twenty-six patients (22 men, 4 women), aged 66 ± 9 years (mean ± standard deviation [SD]), completed a progressive graded treadmill test until fatigue to measure VO2 peak (1.3 ± 0.4 L/minute). Timed 30-foot walks were used to determine self-selected floor walking velocity (0.63 ± 0.31 m/s), an index of gait deficit severity. Percent body fat (30.4% ± 10.6%), total lean mass (52.0 ± 9.3 kg), lean mass of the paretic and nonaffected legs (17.2 ± 3.7 kg), and lean mass of the paretic and nonaffected thighs (13.2 ± 2.7 kg) were determined by dual-energy x-ray absorptiometry. Total lean mass (r = 0.60), lean mass of both legs (r = 0.58), paretic leg lean mass (r = 0.55), lean mass of both thighs (r = 0.64), and self-selected floor walking velocity (r = 0.53, all P < .01) correlated with VO2 peak. In contrast, percent body fat and latency since index stroke were unrelated to VO2 peak. In a stepwise regression analysis, lean mass of both thighs (r = 0.64, P < .001) and self-selected walking velocity (cumulative r = 0.78, P < .001) were independent predictors of VO2 peak and explained 61% of the variance. These results suggest that hemiparetic stroke patients are profoundly deconditioned, regardless of the latency since stroke, and that lower lean thigh mass and greater gait deficit severity predict even poorer peak exercise capacity.

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 K4b(2) 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 K4b(2) 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.

The Unified Parkinson's Disease Rating Scale as a predictor of peak aerobic capacity and ambulatory function

The Unified Parkinson's Disease Rating Scale (UPDRS) is a widely applied index of disease severity. Our objective was to assess the utility of UPDRS for predicting peak aerobic capacity (VO2 peak) and ambulatory function. Participants (n = 70) underwent evaluation for UPDRS (Total and Motor ratings), VO2 peak, 6-minute walk distance (6MW), and 30-foot self-selected walking speed (SSWS). Using regression, we determined the extent to which the Total and Motor UPDRS scores predicted each functional capacity measure after adjusting for age and sex. We also tested whether adding the Hoehn and Yahr scale (H-Y) to the model changed predictive power of the UPDRS. Adjusted for age and sex, both the Total UPDRS and Motor UPDRS subscale failed to predict VO2 peak. The Total UPDRS did weakly predict 6MW and SSWS (both p < 0.05), but the Motor UPDRS subscale did not predict these ambulatory function tests. After adding H-Y to the model, Total UPDRS was no longer an independent predictor of 6MW but remained a predictor of SSWS. We conclude that Total and Motor UPDRS rating scales do not predict VO2 peak, but that a weak relationship exists between Total UPDRS and measures of ambulatory function.

Randomized clinical trial of 3 types of physical exercise for patients with Parkinson disease

OBJECTIVE

To compare the efficacy of treadmill exercises and stretching and resistance exercises in improving gait speed, strength, and fitness for patients with Parkinson disease.

DESIGN

A comparative, prospective, randomized, single-blinded clinical trial of 3 types of physical exercise.

SETTING

The Parkinson's Disease and Movement Disorders Center at the University of Maryland and the Baltimore Veterans Affairs Medical Center, Geriatric Research Education and Clinical Center.

PATIENTS

A total of 67 patients with Parkinson disease who had gait impairment were randomly assigned to 1 of 3 arms of the trial. INTERVENTIONS; (1) A higher-intensity treadmill exercise (30 minutes at 70%-80% of heart rate reserve), (2) a lower-intensity treadmill exercise (50 minutes at 40%-50% of heart rate reserve), and (3) stretching and resistance exercises (2 sets of 10 repetitions on each leg on 3 resistance machines [leg press, leg extension, and curl]). These exercises were performed 3 times a week for 3 months.

MAIN OUTCOME MEASURES

The primary outcome measures were gait speed (6-minute walk), cardiovascular fitness (peak oxygen consumption per unit time [$$ VO2], and muscle strength (1-repetition maximum strength).

RESULTS

All 3 types of physical exercise improved distance on the 6-minute walk: lower-intensity treadmill exercise (12% increase; P=.001), stretching and resistance exercises (9% increase; P<.02), and higher-intensity treadmill exercise (6% increase; P=.07), with no between-group differences. Both treadmill exercises improved peak $$ VO2 (7%-8% increase; P<.05) more than did the stretching and resistance exercises. Only stretching and resistance improved muscle strength (16% increase; P<.001).

CONCLUSIONS

The effects of exercise were seen across all 3 exercise groups. The lower-intensity treadmill exercise resulted in the greatest improvement in gait speed. Both the higher- and lower-intensity treadmill exercises improved cardiovascular fitness. Only the stretching and resistance exercises improved muscle strength. Therefore, exercise can improve gait speed, muscle strength, and fitness for patients with Parkinson disease. The combination of treadmill and resistance exercises may result in greater benefit and requires further investigation.

Repeatability of aerobic capacity measurements in Parkinson disease

PURPOSE

Maximal or peak aerobic capacity (VO(2peak)) during a maximal-effort graded exercise test is considered by many to be the "gold standard" outcome for assessing the effect of exercise training on cardiorespiratory fitness. The reliability of this measure in Parkinson disease (PD) has not been established, where the degree of motor impairment can vary greatly and is influenced by medications. This study examined the reliability of VO(2peak) during a maximal-effort graded exercise test in subjects with PD.

METHODS

Seventy healthy middle-aged and older subjects with PD Hoehn and Yahr stage 1.5-3 underwent a screening/acclimatization maximal-effort treadmill test followed by two additional maximal-effort treadmill tests with repeated measurements of VO(2peak). A third VO(2peak) test was performed in a subset of 21 subjects.

RESULTS

The mean VO(2peak) measurement was 2.4% higher in the second test compared with the first test (21.42 ± 4.3 vs 21.93 ± 4.50 mL·kg(-1)·min(-1), mean ± SD, P = 0.03). The intraclass correlation coefficients (ICC) for VO(2peak) expressed either as milliliters per kilogram per minute or as liters per minute were highly reliable, with ICC of 0.90 and 0.94, respectively. The maximum HR (ICC of 0.91) and final speed achieved during the tests (ICC of 0.94) were also highly reliable, with the respiratory quotient being the least reliable of the parameters measured (ICC of 0.65).

CONCLUSIONS

Our results demonstrate that measurement of VO(2peak) is reliable and repeatable in subjects with mild to moderate PD, thereby validating use of this parameter for assessing the effects of exercise interventions on cardiorespiratory fitness.

Short-term ankle motor performance with ankle robotics training in chronic hemiparetic stroke

Cerebrovascular accident (stroke) often results in impaired motor control and persistent weakness that may lead to chronic disability, including deficits in gait and balance function. Finding ways to restore motor control may help reduce these deficits; however, little is known regarding the capacity or temporal profile of short-term motor adaptations and learning at the hemiparetic ankle. Our objective was to determine the short-term effects of a single session of impedance-controlled ankle robot ("anklebot") training on paretic ankle motor control in chronic stroke. This was a double-arm pilot study on a convenience sample of participants with chronic stroke (n = 7) who had residual hemiparetic deficits and an equal number of age- and sex-matched nondisabled control subjects. Training consisted of participants in each group playing a target-based video game with the anklebot for an hour, for a total of 560 movement repetitions in dorsiflexion/plantar flexion ranges followed by retest 48 hours later. Task difficulty was adjusted to ankle range of motion, with robotic assistance decreased incrementally across training. Assessments included robotic measures of ankle motor control on unassisted trials before and after training and at 48 hours after training. Following exposure to the task, subjects with stroke improved paretic ankle motor control across a single training session as indexed by increased targeting accuracy (21.6 +/- 8.0 to 31.4 +/- 4.8, p = 0.05), higher angular speeds (mean: 4.7 +/- 1.5 degrees/s to 6.5 +/- 2.6 degrees/s, p < 0.01, peak: 42.8 +/- 9.0 degrees/s to 45.6 +/- 9.4 degrees/s, p = 0.03), and smoother movements (normalized jerk: 654.1 +/- 103.3 s(-2) to 537.6 +/- 86.7 s(-2), p < 0.005, number of speed peaks: 27.1 +/- 5.8 to 23.7 +/- 4.1, p < 0.01). In contrast, nondisabled subjects did not make statistically significant gains in any metric after training except in the number of successful passages (32.3 +/- 7.5 to 36.5 +/- 6.4, p = 0.006). Gains in all five motor control metrics were retained (p > 0.05) at 48 hours in both groups. Robust maintenance of motor adaptation in the robot-trained paretic ankle over 48 hours may be indicative of short-term motor learning. Our initial results suggest that the anklebot may be a flexible motor learning platform with the potential to detect rapid changes in ankle motor performance poststroke.

Impaired economy of gait and decreased six-minute walk distance in Parkinson's disease

Changes in the biomechanics of gait may alter the energy requirements of walking in Parkinson's Disease (PD). This study investigated economy of gait during submaximal treadmill walking in 79 subjects with mild to moderate PD and the relationship between gait economy and 6-minute walk distance (6 MW). Oxygen consumption (VO(2)) at the self-selected treadmill walking speed averaged 64% of peak oxygen consumption (VO(2) peak). Submaximal VO(2) levels exceeded 70% of VO(2) peak in 30% of the subjects. Overall the mean submaximal VO(2) was 51% higher than VO(2) levels expected for the speed and grade consistent with severe impairment in economy of gait. There was an inverse relationship between economy of gait and 6MW (r = -0.31, P < 0.01) and with the self-selected walking speed (r = -0.35, P < 0.01). Thus, the impairment in economy of gait and decreased physiologic reserve result in routine walking being performed at a high percentage of VO(2) peak.

Chronic Stroke Survivors Benefit From High-Intensity Aerobic Treadmill Exercise

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.

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% CO 2 ). 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 CO 2 (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 V o 2 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.

Ankle training with a robotic device improves hemiparetic gait after a stroke

BACKGROUND

Task-oriented therapies such as treadmill exercise can improve gait velocity after stroke, but slow velocities and abnormal gait patterns often persist, suggesting a need for additional strategies to improve walking.

OBJECTIVES

To determine the effects of a 6-week visually guided, impedance controlled, ankle robotics intervention on paretic ankle motor control and gait function in chronic stroke.

METHODS

This was a single-arm pilot study with a convenience sample of 8 stroke survivors with chronic hemiparetic gait, trained and tested in a laboratory. Subjects trained in dorsiflexion-plantarflexion by playing video games with the robot during three 1-hour training sessions weekly, totaling 560 repetitions per session. Assessments included paretic ankle ranges of motion, strength, motor control, and overground gait function.

RESULTS

Improved paretic ankle motor control was seen as increased target success, along with faster and smoother movements. Walking velocity also increased significantly, whereas durations of paretic single support increased and double support decreased.

CONCLUSIONS

Robotic feedback training improved paretic ankle motor control with improvements in floor walking. Increased walking speeds were comparable with reports from other task-oriented, locomotor training approaches used in stroke, suggesting that a focus on ankle motor control may provide a valuable adjunct to locomotor therapies.

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.

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.

Predictors of response to treadmill exercise in stroke survivors

BACKGROUND

Aerobic treadmill exercise (T-EX) therapy has been shown to benefit walking and cardiorespiratory fitness in stroke survivors with chronic gait impairment even long after their stroke. The response, however, varies between individuals.

OBJECTIVE

The purpose of this post hoc analysis of 2 randomized controlled T-EX trials was to identify predictors for therapy response.

METHODS

In all, 52 participants received T-EX for 3 (Germany) or 6 (United States) months. Improvements in overground walking velocity (10 m/6-min walk) and fitness (peak VO(2)) were indicators of therapy response. Lesion location and volume were measured on T1-weighted magnetic resonance scans.

RESULTS

T-EX significantly improved gait and fitness, with gains in 10-m walk tests ranging between +113% and -25% and peak VO(2) between -12% and 88%. Baseline walking impairments or fitness deficits were not predictive of therapy response; 10-m walk velocity improved more in those with subcortical rather than cortical lesions and in patients with smaller lesions. Improvements in 6-minute walk velocity were greater in those with more recent strokes and left-sided lesions. No variable other than training intensity, which was different between trials, predicted fitness gains.

CONCLUSIONS

Despite proving overall effectiveness, the response to T-EX varies markedly between individuals. Whereas intensity of aerobic training seems to be an important predictor of gains in cardiovascular fitness, lesion size and location as well as interval between stroke onset and therapy delivery likely affect therapy response. These findings may be used to guide the timing of training and identify subgroups of patients for whom training modalities could be optimized.

Hemiparetic stroke alters vastus lateralis myosin heavy chain profiles between the paretic and nonparetic muscles

Skeletal muscle phenotype alterations following hemiparetic stroke contribute to disabilities associated with stroke. The phenotypic response following stroke is undefined. This investigation examined the myosin heavy chain (MHC) composition of the vastus lateralis (VL) of stroke survivors in paretic (P) and nonparetic (NP) muscle. Protein obtained from VL of 10 stroke survivors was isolated and purified, and MHC gel electrophoresis was performed. The MHC bands were quantified, and a paired sample two-tailed T test with significance set at p < or = 0.05 was performed. MHC I expression was significantly less in P versus NP VL (.93 vs. 1.00 arbitrary units [AU]). Significantly more IIx MHC was found in the P versus NP VL (1.33 vs. 1.0). No significant differences in type IIa MHC (1.07 P vs. 1.00 NP) were found. These changes in MHC composition suggest an alteration in muscle function due to stroke or the altered activity patterns of muscle following stroke.

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.

A proteomics analysis of the effects of chronic hemiparetic stroke on troponin T expression in human vastus lateralis

Stroke disability is attributed to upper motor neuron deficits resulting from ischemic brain injury. We have developed proteome maps of the Vastus lateralis to examine the effects of ischemic brain injury on paretic skeletal muscle myofilament proteins. Proteomics analyses from seven hemiparetic stroke patients have detected a decrease of three troponin T isoforms in the paretic muscle suggesting that myosin-actin interactions may be attenuated. We propose that ischemic brain injury may prevent troponin T participation in complex formation thereby affecting the protein interactions associated with excitation-contraction coupling. We have also detected a novel skeletal troponin T isoform that has a C-terminal variation. Our data suggest that the decreased slow troponin T isoform pools in the paretic limb may contribute to the gait deficit after stroke. The complexity of the neurological deficit on Vastus lateralis is suggested by the multiple changes in proteins detected by our proteomics mapping.

Plasma adiponectin levels are associated with insulin sensitivity in stroke survivors

OBJECTIVE

Adiponectin is an anti-inflammatory and insulin-sensitizing adipokine produced by adipose tissue. The purpose of this study was to determine the relationships between adiponectin and glucose metabolism in stroke survivors and to compare adiponectin levels between patients with stroke and nonstroke control subjects similar in age, sex, and body mass index.

METHODS

In all, 52 stroke survivors (35 men, 17 women) and 33 nonstroke control subjects (22 men, 11 women) had plasma adiponectin levels measured by RIA, an oral glucose tolerance test, and a peak oxygen consumption-graded treadmill test. Insulin resistance (IR) and insulin sensitivity were assessed using the homeostasis model assessment for IR (HOMA-IR) and insulin sensitivity index (ISI(M)).

RESULTS

Adiponectin levels were positively associated with age (r = 0.32, P < .05) and negatively associated with glucose homeostasis (fasting glucose: r = -0.42; insulin: r = -0.36; Glucose at (120 min): r = -0.39; HOMA-IR: r = -0.45; and ISI(M): r = 0.44, all P < .01) in stroke survivors. Adiponectin levels were significantly different among normal glucose-tolerant, impaired glucose-tolerant, and diabetic patients with stroke (11.1 +/- 0.99 v 9.56 +/- 0.99 v 5.75 +/- 1.55 ng/mL, P < .05). Adiponectin levels were 62% higher in patients with stroke than control subjects (9.29 +/- 0.62 v 5.80 +/- 0.40 ng/mL, P < .001) despite greater fasting insulin levels (81%) and 120-minute insulin (70%) in stroke survivors than control subjects (P < .05). HOMA-IR was 78% higher and ISI(M) was 81% lower in stroke survivors than control subjects (P < .05).

CONCLUSIONS

Plasma adiponectin levels are associated with age and insulin sensitivity but not adiposity in stroke survivors. The paradoxical finding that the more IR stroke survivors had higher adiponectin levels than more insulin-sensitive control subjects suggests that perhaps anti-inflammatory cytokines increase to counter an inflamed and IR state in stroke survivors.

Aerobic exercise improves cognition and motor function poststroke

BACKGROUND

Cognitive deficits impede stroke recovery. Aerobic exercise (AEX) improves cognitive executive function (EF) processes in healthy individuals, although the learning benefits after stroke are unknown.

OBJECTIVE

To understand AEX-induced improvements in EF, motor learning, and mobility poststroke.

METHODS

Following cardiorespiratory testing, 38 chronic stroke survivors were randomized to 2 different groups that exercised 3 times a week (45-minute sessions) for 8 weeks. The AEX group (n = 19; 9 women; 10 men; 64.10 +/- 12.30 years) performed progressive resistive stationary bicycle training at 70% maximal heart rate, whereas the Stretching Exercise (SE) group (n = 19; 12 women; 7 men; 58.96 +/- 14.68 years) performed stretches at home. Between-group comparisons were performed on the change in performance at "Post" and "Retention" (8 weeks later) for neuropsychological and motor function measures.

RESULTS

VO(2)max significantly improved at Post with AEX (P = .04). AEX also improved motor learning in the less-affected hand, with large effect sizes (Cohen's d calculation). Specifically, AEX significantly improved information processing speed on the serial reaction time task (SRTT; ie, "procedural motor learning") compared with the SE group at Post (P = .024), but not at Retention. Also, at Post (P = .038), AEX significantly improved predictive force accuracy for a precision grip task requiring attention and conditional motor learning of visual cues. Ambulation and sit-to-stand transfers were significantly faster in the AEX group at Post (P = .038), with balance control significantly improved at Retention (P = .041). EF measurements were not significantly different for the AEX group.

CONCLUSION

AEX improved mobility and selected cognitive domains related to motor learning, which enhances sensorimotor control after stroke.

Adaptive physical activity improves mobility function and quality of life in chronic hemiparesis

This study investigated the effects of an adaptive physical activity (APA) program on mobility function and quality of life (QOL) in chronic stroke patients. Twenty subjects with chronic hemiparesis completed a 2-month, combined group, class-home exercise regimen that emphasized mobility training. APA improved Berg Balance Scale scores (35 +/- 2 vs 45 +/- 2, p = 0.001), 6-minute walk distances (114 +/- 15 vs 142 +/- 7 m, p < 0.001), and Short Physical Performance Battery scores (3.2 +/- 0.4 vs 5.2 +/- 0.6, p < 0.001). Barthel Index scores increased (75 +/- 4 vs 84 +/- 4, p < 0.001), but Lawton scores were unchanged. Geriatric Depression Scale (p < 0.01) and Stroke Impact Scale (SIS), Mobility, Participation, and Recovery improved with APA (p < 0.03). APA has the potential to improve gait, balance, and basic but not instrumental activities of daily living profiles in individuals with chronic stroke. Improved depression and SIS scores suggest APA improves stroke-specific outcomes related to QOL.

Task-oriented treadmill exercise training in chronic hemiparetic stroke

Patients with stroke have elevated hemiparetic gait costs secondary to low activity levels and are often severely deconditioned. Decrements in peak aerobic capacity affect functional ability and cardiovascular-metabolic health and may be partially mediated by molecular changes in hemiparetic skeletal muscle. Conventional rehabilitation is time delimited in the subacute stroke phase and does not provide adequate aerobic intensity to reverse the profound detriments to fitness and function that result from stroke. Hence, we have studied progressive full body weight-support treadmill (TM) training as an adjunct therapy in the chronic stroke phase. Task-oriented TM training has produced measurable changes in fitness, function, and indices of cardiovascular-metabolic health after stroke, but the precise mechanisms for these changes remain under investigation. Further, the optimal dose of this therapy has yet to be identified for individuals with stroke and may vary as a function of deficit severity and outcome goals. This article summarizes the functional and metabolic decline caused by inactivity after stroke and provides current evidence that supports the use of TM training during the chronic stroke phase, with protocols and inclusion/exclusion criteria described. Our research findings are discussed in relation to associated research.

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.

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.

Motivators for treadmill exercise after stroke

PURPOSE

The purpose of this qualitative study was to explore factors that motivated older adults with ischemic stroke to engage in a task-oriented treadmill aerobic exercise (T-AEX) intervention study.

METHOD

Participants included community-dwelling individuals post stroke with mild-to-moderate hemiparetic gait deficits who completed a 6-month T-AEX study. A total of 29 participants attended focus groups or individual telephone interviews.

RESULTS

Thirty-nine codes were identified and were reduced to 8 themes: personal goals supported by 7 codes, psychological benefits supported by 8 codes, physical benefits supported by 10 codes, research-associated supervised treadmill exercise benefits supported by 5 codes, objective and verbal encouragement received supported by 4 codes, social support related to exercise supported by 2 codes, improvement in instrumental activities of daily living supported by 2 codes, and self-determination supported by 1 code. All themes reflected factors that influenced subjects' willingness to participate in the study and adhere to the exercise intervention. Of the themes identified, personal goals, physical benefits, and psychological benefits occurred most frequently.

CONCLUSION

This qualitative study provides information that may be used to enhance motivation to exercise in individuals with stroke and promote carryover and integration of exercise behaviors into everyday life.

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.

Skeletal muscle changes after hemiparetic stroke and potential beneficial effects of exercise intervention strategies

Stroke is the leading cause of disability in the United States. New evidence reveals significant structural and metabolic changes in skeletal muscle after stroke. Muscle alterations include gross atrophy and shift to fast myosin heavy chain in the hemiparetic (contralateral) leg muscle; both are related to gait deficit severity. The underlying molecular mechanisms of this atrophy and muscle phenotype shift are not known. Inflammatory markers are also present in contralateral leg muscle after stroke. Individuals with stroke have a high prevalence of insulin resistance and diabetes. Skeletal muscle is a major site for insulin-glucose metabolism. Increasing evidence suggests that inflammatory pathway activation and oxidative injury could lead to wasting, altered function, and impaired insulin action in skeletal muscle. The health benefits of exercise in disabled populations have now been recognized. Aerobic exercise improves fitness, strength, and ambulatory performance in subjects with chronic stroke. Therapeutic exercise may modify or reverse skeletal muscle abnormalities.

Daily ambulatory activity levels in idiopathic Parkinson disease

Patients with Parkinson disease (PD) may have decreased physical activity due to motor deficits. We recently validated the reliability of step activity monitors (SAMs) to accurately count steps in PD, and we wished to use them to evaluate the impact of disease severity on home activity levels in PD. Twenty-six subjects with PD (Hoehn and Yahr disease stage 2-4) were recruited to participate in a study of activity levels over 48 hours. Ability to achieve 95% device accuracy was an entry requirement. A Unified Parkinson Disease Rating Scale (UPDRS) evaluation was performed on all subjects, subjects were monitored for 48 hours, and total number of steps per day and maximum steps taken per hour were calculated. Out of 26 subjects, 25 met entry requirements. We calculated the number of steps taken per day, as well as maximal activity levels, and correlated these with UPDRS total score, the activity of daily living subscale, and the UPDRS motor function subscale off and on medication (all p < 0.01). Transition from Hoehn and Yahr stage 2 to stage 3 was associated with a decline in functional mobility (p < 0.005). A microprocessor-linked SAM accurately counted steps in subjects with PD. The number of steps taken correlated highly with disease severity. SAMs may be useful outcome measures in PD.