Cardiac Reserve and Pulmonary Gas Exchange Kinetics in Patients With Stroke

Effects of respiratory muscle training on post-stroke rehabilitation: A systematic review and meta-analysis

BACKGROUND

Stroke often results in significant respiratory dysfunction in patients. Respiratory muscle training (RMT) has been proposed as a rehabilitative intervention to address these challenges, but its effectiveness compared to routine training remains debated. This systematic review and meta-analysis aim to evaluate the effects of RMT on exercise tolerance, muscle strength, and pulmonary function in post-stroke patients.

AIM

To systematically assess the efficacy of RMT in improving exercise tolerance, respiratory muscle strength, and pulmonary function in patients recovering from a stroke, and to evaluate whether RMT offers a significant advantage over routine training modalities in enhancing these critical health outcomes in the post-stroke population.

METHODS

Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, a comprehensive search across PubMed, Embase, Web of Science, and the Cochrane Library was conducted on October 19, 2023, without temporal restrictions. Studies were selected based on the predefined inclusion and exclusion criteria focusing on various forms of RMT, control groups, and outcome measures [including forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), maximal voluntary ventilation (MVV), peak expiratory flow (PEF), maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), and 6-min walking test (6MWT)]. Only randomized controlled trials (RCTs) were included. Data extraction and quality assessment were conducted independently by two reviewers using the Cochrane Collaboration's risk of bias tool. Statistical analyses, including those using the fixed-effect and random-effects models, sensitivity analysis, and publication bias assessment, were performed using Review Manager software.

RESULTS

A total of 15 RCTs were included. Results indicated significant improvements in MIP (12.51 cmH2O increase), MEP (6.24 cmH2O increase), and various pulmonary function parameters (including FEV1, FVC, MVV, and PEF). A substantial increase in 6MWT distance (22.26 meters) was also noted. However, the heterogeneity among studies was variable, and no significant publication bias was detected.

CONCLUSION

RMT significantly enhances walking ability, respiratory muscle strength (MIP and MEP), and key pulmonary function parameters (FEV1, FVC, MVV, and PEF) in post-stroke patients. These findings support the incorporation of RMT into post-stroke rehabilitative protocols.

Effects of high-intensity interval robot-assisted gait training on cardiopulmonary function and walking ability in chronic stroke survivors: A multicenter single-blind randomized controlled trial

BACKGROUND

Chronic stroke can impair cardiopulmonary function, mobility, and daily activities. This study assessed the impact of robot-assisted gait training (RAGT) on such impairments.

OBJECTIVE

To investigate the effects of robot-assisted gait training on cardiopulmonary function, walking ability, lower extremity function and strength, activities of daily living (ADLs), and blood test results among individuals with chronic stroke.

METHODS

A multicenter, prospective, single-blinded, randomized controlled trial with 22 chronic stroke participants compared RAGT against a control exercise regimen. RAGT involved three days weekly sessions of high-intensity interval training for 8 weeks (24 sessions) with a Morning Walk® device. The control group also performed home exercises. (24 sessions) Measures included VO2max, Functional Ambulatory Category, 2-minute walk test, 10-meter walk test, Motricity Index-Lower, Korean version of the Fugl-Meyer Assessment Scale, Modified Barthel Index, Berg Balance Scale, muscle strength, InBody body composition, and blood tests (cholesterol, lipid, glucose).

RESULTS

RAGT significantly improved VO2max, gait, balance, and lower limb strength compared with controls, with significant improvements in 2-minute walk test, 10-meter walk test, Motricity Index-Lower, and Fugl-Meyer Assessment outcomes. No changes were seen in muscle mass or blood markers.

CONCLUSION

RAGT enhances cardiopulmonary function and ambulatory capacity in chronic stroke patients, underscoring its potential in stroke rehabilitation.

Stroke and breathing

Stroke remains a leading cause of neurologic disability with wide ranging effects, including a variety of respiratory abnormalities. Stroke may influence the central control of the respiratory drive and breathing pattern, airway protection and maintenance, and the respiratory mechanics of inspiration and expiration. In the acute phase of stroke, the central control of breathing is affected by changes in consciousness, cerebral edema, and direct damage to brainstem respiratory centers, resulting in abnormalities in respiratory pattern and loss of airway protection. Common acute complications related to respiratory dysfunction include dysphagia, aspiration, and pneumonia. Respiratory control centers are located in the brainstem, and brainstem stroke causes specific patterns of respiratory dysfunction. Depending on the exact location and extent of stroke, respiratory failure may occur. While major respiratory abnormalities often improve over time, sleep-disordered breathing remains common in the subacute and chronic phases and worsens outcomes. Respiratory mechanics are impaired in hemiplegic or hemiparetic stroke, contributing to worse cardiopulmonary health in stroke survivors. Interventions to address the respiratory complications are under researched, and further investigation in this area is critical to improving outcomes among stroke survivors.

The reliability of VO2 kinetics during a 6-minute walking test is influenced by walk speed

[Purpose] This study aimed to investigate the reliability of time constant measurements of oxygen intake at fast and comfortable speeds during a 6-min waling test. [Participants and Methods] The study included 10 healthy young males who walked at 4.5 km/h and 6.0 km/h twice for 6 min each in speed treadmill. Breath-by-breath gas exchange data were continuously measured and used to calculate the time constant of oxygen uptake. The reproducibility and variability of the variables were verified using the limit of agreement, inter-class correlation coefficient, coefficient of variation, and standard error of measurement. [Results] The limit of agreement was −8.5 to 2.3 s and −3.9 to 2.1 s for speeds 4.5 km/h and 6.0 km/h, respectively. The inter-class correlation coefficient, coefficient of variation, and standard error of measurement of the time constant for both speeds were 0.52 and 0.83, 11.2% and 6.4%, and 5.3 s and 1.8 s, respectively. [Conclusion] The results of this study suggested that the cardiopulmonary response, in terms of oxygen uptake, was more consistent during fast walking than during comfortable walking in a 6-min walking test with constant speed.

A Single Bout of Constant-Load Exercise Test for Estimating the Time Constant of Oxygen Uptake Kinetics in Individuals With Stroke

Objective

To examine the relationship between the time constant of oxygen uptake kinetics during the onset of exercise (τVO₂) estimated from a single exercise bout and that obtained from three averaged exercise bouts in individuals with stroke.

Methods

Twenty participants with stroke performed three bouts of a constant-load pedaling exercise at approximately 80% of the workload corresponding to the ventilatory threshold to estimate τVO₂. The VO₂ data from the first trial of three bouts were used to estimate τVO₂ for a single bout. Additionally, data collected from three bouts were ensemble-averaged to obtain τVO₂ for three averaged bouts as the criterion.

Results

There was a very high correlation between τVO₂ for a single bout (34.8±14.0 seconds) and τVO₂ for three averaged bouts (38.5±13.4 seconds) (r=0.926, p<0.001). However, τVO₂ for a single bout was smaller than that for three averaged bouts (p=0.006).

Conclusion

τVO₂ for a single bout could reflect the relative difference in τVO₂ for three averaged bouts among individuals with stroke. However, it should be noted that τVO₂ for a single bout may be underestimated compared to τVO₂ for three averaged bouts.

Cardiorespiratory responses to exercise related to post-stroke fatigue severity

Physical deconditioning after stroke may induce post-stroke fatigue. However, research on this association is limited. Our primary objective was to investigate the associations of post-stroke fatigue severity with oxygen uptake ([Formula: see text]O₂) at peak exercise and the time constant of [Formula: see text]O₂ kinetics (τ[Formula: see text]O₂) at exercise onset. The secondary objective was to examine the associations between fatigue and cardiorespiratory variables potentially affecting [Formula: see text]O₂ during exercise. Twenty-three inpatients from a subacute rehabilitation ward were enrolled in this study. The median (interquartile range) Fatigue Severity Scale (FSS) score, as a measure of fatigue, was 32 (range 27-42) points. The FSS score was not associated with [Formula: see text]O₂ at peak exercise during a symptom-limited graded exercise test (rho = - 0.264; p = 0.224), whereas it was significantly associated with τ[Formula: see text]O₂ during a submaximal constant-load exercise test (rho = 0.530; p = 0.009). A higher FSS score also significantly correlated with a longer time constant of cardiac output (CO) kinetics (rho = 0.476; p = 0.022). Our findings suggest that severe post-stroke fatigue is associated with delayed increases in [Formula: see text]O₂ and CO at the onset of exercise. Our findings can contribute to the development of an appropriate rehabilitation programme for individuals with post-stroke fatigue.

Cardiorespiratory mechanisms underlying the impaired oxygen uptake kinetics at exercise onset after stroke

BACKGROUND

Oxygen uptake (V˙O₂) kinetics at the onset of exercise is slower in patients with stroke than in healthy adults. However, little is known about the cardiorespiratory mechanisms underlying the impaired V˙O₂ kinetics.

OBJECTIVES

This study aimed to investigate the relative effect of impaired oxygen delivery and utilisation on V˙O₂ kinetics at the onset of submaximal exercise in patients with stroke by comparing the time constants of cardiac output (τCO) and V˙O₂ (τV˙O₂). In addition, we aimed to examine the association between the kinetics of cardiorespiratory variables and functional outcomes.

METHODS

We included 21 patients with stroke (15 males, mean [SD] age 58.7 [9.5] years, mean days post-stroke 67.9 [30.9]). A submaximal constant-load exercise test was performed to measure τV˙O₂, τCO, and the time constant of arterialvenous oxygen difference (τAVO₂diff). The ratio of τCO to τV˙O₂ was calculated to assess the matching of oxygen delivery and consumption. Fugl-Meyer lower-extremity motor scores, comfortable gait speeds, and Functional Independence Measure motor scores were used as functional variables.

RESULTS

Mean (SD) τAVO₂diff was markedly shorter than τV˙O₂ and τCO (26.1 [7.1] vs. 38.7 [10.2] and 46.6 [23.2 s], P<0.05), with no significant difference between τV˙O₂ and τCO (P=0.444). The greater ratio of τCO to τV˙O₂ was related to poorer motor function (rho=-0.484, P=0.026) and slower comfortable gait speed (r=-0.482, P=0.027).

CONCLUSIONS

An increase in CO was slower than that in AVO₂diff in patients with stroke. Therefore, V˙O₂ kinetics in patients with stroke appears to be affected by a delayed increase in CO rather than AVO₂diff. Furthermore, these patients with motor and gait impairments may have a poor matching of oxygen delivery and consumption during exercise onset.

Underlying mechanisms of oxygen uptake kinetics in chronic post-stroke individuals: A correlational, cross-sectional pilot study

Post-stroke individuals presented deleterious changes in skeletal muscle and in the cardiovascular system, which are related to reduced oxygen uptake ([Formula: see text]) and take longer to produce energy from oxygen-dependent sources at the onset of exercise (mean response time, MTRON) and during post-exercise recovery (MRTOFF). However, to the best of our knowledge, no previous study has investigated the potential mechanisms related to [Formula: see text] kinetics response (MRTON and MRTOFF) in post-stroke populations. The main objective of this study was to determine whether the MTRON and MRTOFF are related to: 1) body composition; 2) arterial compliance; 3) endothelial function; and 4) hematological and inflammatory profiles in chronic post-stroke individuals. Data on oxygen uptake ([Formula: see text]) were collected using a portable metabolic system (Oxycon Mobile®) during the six-minute walk test (6MWT). The time to achieve 63% of [Formula: see text] during a steady state (MTRON) and recovery (MRTOFF) were analyzed by the monoexponential model and corrected by a work rate (wMRTON and wMRTOFF) during 6MWT. Correlation analyses were made using Spearman's rank correlation coefficient (rs) and the bias-corrected and accelerated bootstrap method was used to estimate the 95% confidence intervals. Twenty-four post-stroke participants who were physically inactive took part in the study. The wMRTOFF was correlated with the following: skeletal muscle mass (rs = -0.46), skeletal muscle mass index (rs = -0.45), augmentation index (rs = 0.44), augmentation index normalized to a heart rate of 75 bpm (rs = 0.64), reflection magnitude (rs = 0.43), erythrocyte (rs = -0.61), hemoglobin (rs = -0.54), hematocrit (rs = -0.52) and high-sensitivity C-reactive protein (rs = 0.58), all p < 0.05. A greater amount of oxygen uptake during post-walking recovery is partially related to lower skeletal muscle mass, greater arterial stiffness, reduced number of erythrocytes and higher systemic inflammation in post-stroke individuals.

Effectiveness of Respiratory Muscle Training for Pulmonary Function and Walking Ability in Patients with Stroke: A Systematic Review with Meta-Analysis

Background: Neurological dysfunction due to stroke affects not only the extremities and trunk muscles but also the respiratory muscles. Aim: to synthesise the evidence available about the effectiveness of respiratory muscle training (RMT) to improve respiratory function parameters and functional capacity in poststroke patients. Methods: a systematic electronic search was performed in the MEDLINE, EMBASE, SPORTDiscus, PEDro and Web of Science databases, from inception to May 2020. Study selection and data extraction: randomised controlled trials (RCTs) that examined the effects of RMT versus non-RMT or sham RMT in poststroke patients. We extracted data about respiratory function, respiratory muscle strength and functional capacity (walking ability, dyspnea, balance, activities of daily life), characteristics of studies and features of RMT interventions (a type of RMT exercise, frequency, intensity and duration). Two reviewers performed study selection and data extraction independently. Results: nineteen RCTs met the study criteria. RMT improved the first second forced expiratory volume (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF), maximal expiratory pressure (MEP), maximal inspiratory pressure (MIP) and walking ability (6 min walking test), but not Barthel index, Berg balance scale, and dyspnea. Conclusions: RMT interventions are effective to improve respiratory function and walking ability in poststroke patients.

Addition of proprioceptive neuromuscular facilitation to cardiorespiratory training in patients poststroke: study protocol for a randomized controlled trial

BACKGROUND

Individuals affected by stroke present with changes in cardiovascular and respiratory functions. Cardiorespiratory training (CRT) is one of the classic intervention guidelines for cardiorespiratory fitness. CRT in association with the proprioceptive neuromuscular facilitation (PNF) technique for respiratory muscles could improve the quality of life, cardiorespiratory function and gait parameters of patients after stroke.

OBJECTIVE

To assess the effects of respiratory and trunk patterns of CRT associated with PNF on the quality of life, gait, oxygen consumption, respiratory muscle strength and thoracic volumes.

METHODS/DESIGN

A blind, randomized clinical trial with allocation confidentiality will be performed. Forty patients will be randomized into four groups: CRT-lower limb (LL) plus PNF; CRT-LL and respiration; CRT-upper limb (UL) plus PNF; or CRT-UL and respiration. Individuals will be evaluated at three different times (pretreatment, after 20 days of treatment and 1 month after the end of treatment). The treatment protocol consists of respiratory exercises, 30 min of CRT (cycle ergometer) and then repetition of the respiratory exercises, performed three times a week over a period of 20 days. Primary outcome measures are quality of life, gait, balance, peak oxygen uptake and rib cage compartment volumes. As secondary outcomes, respiratory function and maximal inspiratory and expiratory pressures will be measured.

DISCUSSION

The association of PNF with CRT may be a viable and accessible alternative to increase cardiorespiratory function in patients with stroke.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03171012. Registered on 6 June 2017.

Cardiorespiratory factors related to the increase in oxygen consumption during exercise in individuals with stroke

BACKGROUND

Understanding the cardiorespiratory factors related to the increase in oxygen consumption ([Formula: see text]) during exercise is essential for improving cardiorespiratory fitness in individuals with stroke. However, cardiorespiratory factors related to the increase in [Formula: see text] during exercise in these individuals have not been examined using multivariate analysis. This study aimed to identify cardiorespiratory factors related to the increase in [Formula: see text] during a graded exercise in terms of respiratory function, cardiac function, and the ability of skeletal muscles to extract oxygen.

METHODS

Eighteen individuals with stroke (aged 60.1 ± 9.4 years, 67.1 ± 30.8 days poststroke) underwent a graded exercise test for the assessment of cardiorespiratory response to exercise. The increases in [Formula: see text] from rest to first threshold and that from rest to peak exercise were measured as a dependent variable. The increases in respiratory rate, tidal volume, minute ventilation, heart rate, stroke volume, cardiac output, and arterial-venous oxygen difference from rest to first threshold and those from rest to peak exercise were measured as the independent variables.

RESULTS

From rest to first threshold, the increases in arterial-venous oxygen difference (β = 0.711) and cardiac output (β = 0.572) were significant independent variables for the increase in [Formula: see text] (adjusted R2 = 0.877 p < 0.001). Similarly, from rest to peak exercise, the increases in arterial-venous oxygen difference (β = 0.665) and cardiac output (β = 0.636) were significant factors related to the increase in [Formula: see text] (adjusted R2 = 0.923, p < 0.001).

CONCLUSION

Our results suggest that the ability of skeletal muscle to extract oxygen is a major cardiorespiratory factor related to the increase in [Formula: see text] during exercise testing in individuals with stroke. For improved cardiorespiratory fitness in individuals with stroke, the amount of functional muscle mass during exercise may need to be increased.

Proprioceptive Neuromuscular Facilitation for Accessory Respiratory Muscles Training in Patients After Ischemic Stroke

This study focused on how pulmonary function is affected by proprioceptive neuromuscular facilitation (PNF) of accessory respiratory muscles in the chronic post-stroke phase. The study involved patients who had had ischemic stroke 6 months or more before the PNF treatment investigated. The objective was to define the effect of PNF on bioelectrical resting and maximum activity of the accessory muscles. Patients were randomly assigned to PNF treatment and just positioning treatment as a reference for comparison; 30 patients each. Electromyography of accessory muscles was investigated before and after physiotherapeutic treatments. We found that there was a greater reduction in EMG activity in all muscles investigated after PNF compared to positioning treatment alone. A reduction of muscle activity due to PNF concerned both affected and unaffected body side, but it was greater on the affected side. We conclude that a reduction of the accessory respiratory muscle activity due to PNF treatment could be of benefit in chronic stoke patients in that it would help normalize breathing pattern and thereby prevent the development of hypoxia.

Near-Infrared Spectroscopy Is Promising to Detect Iliac Artery Flow Limitations in Athletes: A Pilot Study

Endurance cyclists have a substantial risk to develop flow limitations in the iliac arteries during their career. These flow limitations are due to extreme hemodynamic stress which may result in functional arterial kinking and/or intravascular lesions. Early diagnosis may improve outcome and could prevent the necessity for surgical vascular repair. However, current diagnostic techniques have unsatisfactory sensitivity and cannot be applied during exercise. Near-infrared spectroscopy (NIRS) has shown great diagnostic potential in peripheral vascular disease and might bring a solution since it measures tissue oxygenation in real time during and after exercise. This report describes the first experiences of the application of NIRS in the vastus lateralis muscle during and after maximal graded cycling exercise in ten healthy participants and in three patients with flow limitations due to (1) subtle functional kinking, (2) an intravascular lesion, and (3) severe functional kinking. The results are put into perspective based on an empirically fitted model. Delayed recovery, showing clearly different types of patterns of tissue reoxygenation after exercise, was found in the affected athletes compared with the healthy participants. In the patients that had kinking of the arteries, tissue reoxygenation was clearly more delayed if NIRS was measured in provocative position with flexed hip. In this pilot experiment, clearly distinctive reoxygenation patterns are observed during recovery consistent with severity of flow limitation, indicating that NIRS is a promising diagnostic tool to detect and grade arterial flow limitations in athletes. Our findings may guide research and optimization of NIRS for future clinical application.

Pathophysiology of exercise intolerance in chronic diseases: the role of diminished cardiac performance in mitochondrial and heart failure patients

OBJECTIVE

Exercise intolerance is a clinical hallmark of chronic conditions. The present study determined pathophysiological mechanisms of exercise intolerance in cardiovascular, neuromuscular, and metabolic disorders.

METHODS

In a prospective cross-sectional observational study 152 patients (heart failure reduced ejection fraction, n=32; stroke, n=34; mitochondrial disease, n=28; type two diabetes, n=28; and healthy controls, n=30) performed cardiopulmonary exercise testing with metabolic and haemodynamic measurements. Peak exercise O2 consumption and cardiac power output were measures of exercise tolerance and cardiac performance.

RESULTS

Exercise tolerance was significantly diminished in patients compared with controls (ie, by 45% stroke, 39% mitochondria disease, and 33% diabetes and heart failure, p<0.05). Cardiac performance was only significantly reduced in heart failure (due to reduced heart rate, stroke volume, and blood pressure) and mitochondrial patients (due reduced stroke volume) compared with controls (ie, by 53% and 26%, p<0.05). Ability of skeletal muscles to extract oxygen (ie, arterial-venous O2 difference) was diminished in mitochondrial, stroke, and diabetes patients (by 24%, 22%, and 18%, p<0.05), but increased by 21% in heart failure (p<0.05) compared with controls. Cardiac output explained 65% and 51% of the variance in peak O2 consumption (p<0.01) in heart failure and mitochondrial patients, whereas arterial-venous O2 difference explained 69% (p<0.01) of variance in peak O2 consumption in diabetes, and 65% and 48% in stroke and mitochondrial patients (p<0.01).

CONCLUSIONS

Different mechanisms explain exercise intolerance in patients with heart failure, mitochondrial dysfunction, stroke and diabetes. Their better understanding may improve management of patients, their stress tolerance and quality of life.

Arterial Stiffness in Subacute Stroke: Changing Pattern and Relationship with Functional Recovery

BACKGROUND

To examine changing patterns in arterial stiffness and functional outcome in patients with subacute stroke, and to determine which parameter shows a strong correlation with the reversal of arterial stiffness, during a 3-month period of comprehensive rehabilitation therapy.

METHODS

This descriptive, observational cohort study enrolled 60 patients (43 male and 17 female; average age, 62.7 years), and all received conventional rehabilitation therapy, during a 3-month period. Brachial-ankle pulse wave velocity (baPWV) was measured as an index of arterial stiffness. Functional assessments included the 6-minute walk test (6MWT), Fugl-Meyer Assessment of hemiparetic upper and lower limbs, the functional ambulatory category, the Berg balance scale, the Korean Mini-Mental Status Examination, and the Korean-Modified Barthel Index. All measurements were conducted at baseline and 1 and 3 months after stroke onset.

RESULTS

Rehabilitation therapy resulted in a statistically significant improvement in baPWV since 3 months post stroke. Another functional outcome measure showed statistically significant improvements since 1 month after rehabilitation. Multivariable linear regression analysis revealed that a change in baPWV was significantly correlated with changes in the 6MWT.

CONCLUSIONS

Three months of comprehensive rehabilitation therapy led to statistically significant improvements in arterial stiffness and functional outcomes during the subacute phase of stroke. Thus, the comprehensive rehabilitation focused on improving gait endurance would be warranted in subacute stroke patients.

Independently ambulant, community-dwelling stroke survivors have reduced cardiorespiratory fitness, mobility and knee strength compared to an age- and gender-matched cohort

BACKGROUND

Most exercise interventions for stroke survivors are designed for those who have substantial motor and functional disabilities. There remains a group of well-recovered stroke survivors who have yet to be investigated in terms of their physical capacity and fitness levels.

OBJECTIVE

To assess and compare the physical capacities of independently ambulant, community-dwelling stroke survivors to age- and gender-matched comparison participants.

METHODS

Data were obtained from 17 stroke survivors participating in the How FITSS? Trial, all with functional ambulatory category of ≥4 and a self-selected walking speed ≥0.8 m s^-1. An additional 17 healthy control participants were recruited. Cardiorespiratory fitness (CRF) was measured using oxygen consumption (VO_2peak), and additional measures of walking speed (m s^-1), leg strength and body composition were also assessed. Differences between groups were assessed by matched pairs t-tests. Effect sizes were calculated using Cohen's d.

RESULTS

There were no significant differences in age, BMI, muscle mass or body fat between groups (p > 0.05). Peak VO₂ was lower in the stroke group for the shuttle walk test (p = 0.037) and progressive cycle test (p = 0.019), as were all CRF test performance measures (p < 0.05). Stroke survivors walked significantly (p < 0.001) slower at both self-selected and fast speeds. Effect sizes of group differences for all leg strength variables were medium to large, with peak torque lower in the stroke group for all trials.

CONCLUSIONS

Despite being independently ambulant and community dwelling, the CRF, walking speed and leg strength of this group were reduced compared to non-stroke comparison participants. These patients may benefit from undertaking targeted exercise programmes.

Ventilatory threshold may be a more specific measure of aerobic capacity than peak oxygen consumption rate in persons with stroke

BACKGROUND

After stroke, aerobic deconditioning can have a profound impact on daily activities. This is usually measured by the peak oxygen consumption rate achieved during exercise testing (VO2-peak). However, VO2-peak may be distorted by motor function. The oxygen uptake efficiency slope (OUES) and VO2 at the ventilatory threshold (VO2-VT) could more specifically assess aerobic capacity after stroke, but this has not been tested.

OBJECTIVES

To assess the differential influence of motor function on three measures of aerobic capacity (VO2-peak, OUES, and VO2-VT) and to evaluate the inter-rater reliability of VO2-VT determination post-stroke.

METHODS

Among 59 persons with chronic stroke, cross-sectional correlations with motor function (comfortable gait speed [CGS] and lower extremity Fugl-Meyer [LEFM]) were compared between the different aerobic capacity measures, after adjustment for covariates, in order to isolate any distorting effect of motor function. Reliability of VO2-VT determination between three raters was assessed with intra-class correlation (ICC).

RESULTS

CGS was moderately correlated with VO2-peak (r = 0.52, p < 0.0001) and weakly correlated with OUES (r = 0.41, p = 0.002) and VO2-VT (r = 0.37, p = 0.01). LEFM was weakly correlated with VO2-peak (r = 0.26, p = 0.055) and very weakly correlated with OUES (r = 0.19, p = 0.17) and VO2-VT (r = 0.14, p = 0.31). Compared to VO2-peak, VO2-VT was significantly less correlated with CGS (r difference = -0.16, p = 0.02). Inter-rater reliability of VO2-VT determination was high (ICC: 0.93, 95% CI: 0.89-0.96).

CONCLUSIONS

Motor dysfunction appears to artificially lower measured aerobic capacity. VO2-VT seemed to be less distorted than VO2-peak and had good inter-rater reliability, so it may provide more specific assessment of aerobic capacity post-stroke.

Decreased tidal volume may limit cardiopulmonary performance during exercise in subacute stroke

PURPOSE

The aim of this retrospective study was to determine whether pulmonary function was reduced at submaximal and peak exercise in subacute stroke (SG) when compared with sedentary adults (CON).

METHODS

Ten individuals with subacute stroke and 10 sedentary, age- and gender-matched adults performed cardiopulmonary exercise testing (CPET), using a recumbent stepper. We used independent t tests to determine between-group differences at peak effort. We used repeated-measures analysis of variance with Test Minute (minutes 1-6) as the within-subject factor and Group (SG, CON) as the between-subject factor to assess cardiopulmonary submaximal performance.

RESULTS

The SG had significantly lower values (P < .05) for oxygen uptake, minute ventilation ((Equation is included in full-text article.)E), and tidal volume (VT) than CON at peak effort of the CPET. During CPET submaximal effort, we report a significant main effect for Test Minute and Group for VT and respiratory rate but no main effect of Group for (Equation is included in full-text article.)E. To maintain adequate (Equation is included in full-text article.)E during submaximal effort and decreased VT, higher respiratory rate was observed.

CONCLUSIONS

These results suggest that diminished VT in subacute stroke patients may limit performance during submaximal and peak effort of CPET. Rehabilitation professionals should consider methods for improving pulmonary function during stroke rehabilitation.

Effects of Respiratory Muscle Training on Respiratory Function, Respiratory Muscle Strength, and Exercise Tolerance in Patients Poststroke: A Systematic Review With Meta-Analysis

OBJECTIVE

To examine the effects of respiratory muscle training on respiratory function, respiratory muscle strength, and exercise tolerance in patients poststroke.

DATA SOURCES

We searched MEDLINE, Cochrane Library, Embase, SciELO, Physiotherapy Evidence Database (PEDro), and CINAHL (from the earliest date available to November 2015) for trials.

STUDY SELECTION

Randomized controlled trials (RCTs) that examined the effects of respiratory muscle training versus nonrespiratory muscle training in patients poststroke. Two reviewers selected studies independently.

DATA EXTRACTION

Extracted data from the published RCTs. Study quality was evaluated using the PEDro Scale. Weighted mean differences (WMDs), standard mean differences (SMDs), and 95% confidence intervals (CIs) were calculated.

DATA SYNTHESIS

Eight studies met the study criteria. Respiratory muscle training improved maximal inspiratory pressure WMDs (7.5; 95% CI, 2.7-12.4), forced vital capacity SMDs (2.0; 95% CI, 0.6-3.4), forced expiratory volume at 1 second SMDs (1.2; 95% CI, 0.6-1.9), and exercise tolerance SMDs (0.7; 95% CI, 0.2-1.2). No serious adverse events were reported.

CONCLUSIONS

Respiratory muscle training should be considered an effective method of improving respiratory function, inspiratory muscle strength, and exercise tolerance in patients poststroke. Further research is needed to determine optimum dosages and duration of effect.

Exercise Induces Peripheral Muscle But Not Cardiac Adaptations After Stroke: A Randomized Controlled Pilot Trial

Objective

To explore the physiological factors affecting exercise-induced changes in peak oxygen consumption and function poststroke.

Design

Single-center, single-blind, randomized controlled pilot trial.

Setting

Community stroke services.

Participants

Adults (N=40; age>50y; independent with/without stick) with stroke (diagnosed >6mo previously) were recruited from 117 eligible participants. Twenty participants were randomized to the intervention group and 20 to the control group. No dropouts or adverse events were reported.

Interventions

Intervention group: 19-week (3times/wk) progressive mixed (aerobic/strength/balance/flexibility) community group exercise program. Control group: Matched duration home stretching program.

Main Outcome Measures

(1) Pre- and postintervention: maximal cardiopulmonary exercise testing with noninvasive (bioreactance) cardiac output measurements; and (2) functional outcome measures: 6-minute walk test; timed Up and Go test, and Berg Balance Scale.

Results

Exercise improved peak oxygen consumption (18±5 to 21±5mL/(kg⋅min); P<.01) and peak arterial-venous oxygen difference (9.2±2.7 to 11.4±2.9mL of O₂/100mL of blood; P<.01), but did not alter cardiac output (17.2±4 to 17.7±4.2L/min; P=.44) or cardiac power output (4.8±1.3 to 5.0±1.35W; P=.45). A significant relation existed between change in peak oxygen consumption and change in peak arterial-venous oxygen difference (r=.507; P<.05), but not with cardiac output. Change in peak oxygen consumption did not strongly correlate with change in function.

Conclusions

Exercise induced peripheral muscle, but not cardiac output, adaptations after stroke. Implications for stroke clinical care should be explored further in a broader cohort.

Predicting Heart Rate at the Ventilatory Threshold for Aerobic Exercise Prescription in Persons With Chronic Stroke

BACKGROUND AND PURPOSE

Treadmill aerobic exercise improves gait, aerobic capacity, and cardiovascular health after stroke, but a lack of specificity in current guidelines could lead to underdosing or overdosing of aerobic intensity. The ventilatory threshold (VT) has been recommended as an optimal, specific starting point for continuous aerobic exercise. However, VT measurement is not available in clinical stroke settings. Therefore, the purpose of this study was to identify an accurate method to predict heart rate at the VT (HRVT) for use as a surrogate for VT.

METHODS

A cross-sectional design was employed. Using symptom-limited graded exercise test (GXT) data from 17 subjects more than 6 months poststroke, prediction methods for HRVT were derived by traditional target HR calculations (percentage of HRpeak achieved during GXT, percentage of peak HR reserve [HRRpeak], percentage of age-predicted maximal HR, and percentage of age-predicted maximal HR reserve) and by regression analysis. The validity of the prediction methods was then tested among 8 additional subjects.

RESULTS

All prediction methods were validated by the second sample, so data were pooled to calculate refined prediction equations. HRVT was accurately predicted by 80% HRpeak (R, 0.62; standard deviation of error [SDerror], 7 bpm), 62% HRRpeak (R, 0.66; SDerror, 7 bpm), and regression models that included HRpeak (R, 0.62-0.75; SDerror, 5-6 bpm).

DISCUSSION AND CONCLUSIONS

Derived regression equations, 80% HRpeak and 62% HRRpeak, provide a specific target intensity for initial aerobic exercise prescription that should minimize underdosing and overdosing for persons with chronic stroke. The specificity of these methods may lead to more efficient and effective treatment for poststroke deconditioning.Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, http://links.lww.com/JNPT/A114).

Feasibility of cardiopulmonary exercise testing and training using a robotics-assisted tilt table in dependent-ambulatory stroke patients

Background

We evaluated the feasibility of an augmented robotics-assisted tilt table (RATT) for incremental cardiopulmonary exercise testing (CPET) and exercise training in dependent-ambulatory stroke patients.

Methods

Stroke patients (Functional Ambulation Category ≤ 3) underwent familiarization, an incremental exercise test (IET) and a constant load test (CLT) on separate days. A RATT equipped with force sensors in the thigh cuffs, a work rate estimation algorithm and real-time visual feedback to guide the exercise work rate was used. Feasibility assessment considered technical feasibility, patient tolerability, and cardiopulmonary responsiveness.

Results

Eight patients (4 female) aged 58.3 ± 9.2 years (mean ± SD) were recruited and all completed the study. For IETs, peak oxygen uptake (V'O_2peak), peak heart rate (HR_peak) and peak work rate (WR_peak) were 11.9 ± 4.0 ml/kg/min (45 % of predicted V'O_2max), 117 ± 32 beats/min (72 % of predicted HR_max) and 22.5 ± 13.0 W, respectively. Peak ratings of perceived exertion (RPE) were on the range "hard" to "very hard". All 8 patients reached their limit of functional capacity in terms of either their cardiopulmonary or neuromuscular performance.

A ventilatory threshold (VT) was identified in 7 patients and a respiratory compensation point (RCP) in 6 patients: mean V'O₂ at VT and RCP was 8.9 and 10.7 ml/kg/min, respectively, which represent 75 % (VT) and 85 % (RCP) of mean V'O_2peak. Incremental CPET provided sufficient information to satisfy the responsiveness criteria and identification of key outcomes in all 8 patients.

For CLTs, mean steady-state V'O₂ was 6.9 ml/kg/min (49 % of V'O₂ reserve), mean HR was 90 beats/min (56 % of HR_max), RPEs were > 2, and all patients maintained the active work rate for 10 min: these values meet recommended intensity levels for bouts of training.

Conclusions

The augmented RATT is deemed feasible for incremental cardiopulmonary exercise testing and exercise training in dependent-ambulatory stroke patients: the approach was found to be technically implementable, acceptable to the patients, and it showed substantial cardiopulmonary responsiveness. This work has clinical implications for patients with severe disability who otherwise are not able to be tested.

Cardiovascular Stress Induced by Whole-Body Vibration Exercise in Individuals With Chronic Stroke

BACKGROUND

Although whole-body vibration (WBV) has sparked tremendous research interest in neurorehabilitation, the cardiovascular responses to WBV in people with stroke remain unknown.

OBJECTIVE

The aim of this study was to determine the acute effects of different WBV protocols on oxygen consumption (V̇o2), heart rate (HR), rate of perceived exertion (RPE), blood pressure (BP), and rate-pressure product (RPP) during the performance of 6 different exercises among people with chronic stroke (time since onset ≥6 months).

DESIGN

A repeated-measures design was used.

METHODS

Each of the 48 participants experienced all 3 WBV protocols in separate sessions: (1) no WBV, (2) low-intensity WBV (peak acceleration=0.96 unit of gravity of Earth [g]), and (3) high-intensity WBV (1.61g). The order in which they encountered the WBV protocols was randomized, as was the order of exercises performed during each session. Oxygen consumption, HR, and RPE were measured throughout the study. Blood pressure and RPP were measured before and after each session.

RESULTS

Low-intensity and high-intensity WBV induced significantly higher V̇o2 by an average of 0.69 and 0.79 mL/kg/min, respectively, compared with the control condition. These protocols also increased HR by an average of 4 bpm. The 2 WBV protocols induced higher RPE than the control condition during static standing exercise only. Although the diastolic and systolic BP and RPP were increased at the end of each exercise session, the addition of WBV had no significant effect on these variables.

LIMITATIONS

The results are generalizable only to ambulatory and community-dwelling people with chronic stroke.

CONCLUSIONS

Addition of high- and low-intensity WBV significantly increased the V̇o2 and HR, but the increase was modest. Thus, WBV should not pose any substantial cardiovascular hazard in people with chronic stroke.

Cardiorespiratory Fitness after Stroke: A Systematic Review

Cardiorespiratory fitness programs are increasingly used in stroke rehabilitation. Maximal oxygen uptake is the gold standard measurement of cardiorespiratory fitness; however, no recent publications have collated evidence about maximal oxygen uptake levels following stroke. We therefore performed a systematic review of maximal oxygen uptake in stroke survivors, aiming to observe changes in levels over time, and associations with severity of stroke. We searched Medline and Embase until April 2011, and included cross-sectional studies, longitudinal studies, and baseline data from intervention trials. Studies had to recruit at least 10 stroke survivors, and report direct measurement of maximal/peak oxygen uptake. We then compared maximal oxygen uptake with published data from age and gender-matched controls. The search identified 3357 articles. Seventy-two full texts were retrieved, of which 41 met the inclusion criteria. Time since stroke ranged from 10 days to over seven-years. Peak oxygen uptake ranged from 8 to 22 ml/kg/min, which was 26–87% of that of healthy age- and gender-matched individuals. Stroke severity was mild in most studies. Three studies reported longitudinal changes; there was no clear evidence of change in peak oxygen uptake over time. Most studies recruited participants with mild stroke, and it is possible that cardiorespiratory fitness is even more impaired after severe stroke. Maximal oxygen uptake might have been overestimated, as less healthy and older stroke survivors may not tolerate maximal exercise testing. More studies are needed describing mechanisms of impaired cardiorespiratory fitness and longitudinal changes over time to inform the optimal ‘prescription’ of cardiorespiratory fitness programs for stroke survivors.

Cardiopulmonary response to exercise testing in people with chronic stroke: a retrospective study

Background and Purpose. This study investigated the cardiopulmonary response and safety of exercise testing at peak effort in people during the chronic stage of stroke recovery. Methods. This retrospective study examined data from 62 individuals with chronic stroke (males: 32; mean (SD); age: (12.0) yr) participating in an exercise test. Results. Both males and females had low cardiorespiratory fitness levels. No significant differences were found between gender for peak HR (P = 0.27), or VO(2) peak (P = 0.29). Males demonstrated higher values for minute ventilation, tidal volume, and respiratory exchange ratio. No major adverse events were observed in the exercise tests conducted. Discussion and Conclusion. There are differences between gender that may play a role in exercise testing performance and should be considered when developing exercise programs. The low VO(2) peak of this cohort of chronic stroke survivors suggests the need for participation in exercise interventions.

Reduced cardiorespiratory fitness after stroke: biological consequences and exercise-induced adaptations

Evidence from several studies consistently shows decline in cardiorespiratory (CR) fitness and physical function after disabling stroke. The broader implications of such a decline to general health may be partially understood through negative poststroke physiologic adaptations such as unilateral muscle fiber type shifts, impaired hemodynamic function, and decrements in systemic metabolic status. These physiologic changes also interrelate with reductions in activities of daily living (ADLs), community ambulation, and exercise tolerance, causing a perpetual cycle of worsening disability and deteriorating health. Fortunately, initial evidence suggests that stroke participants retain the capacity to adapt physiologically to an exercise training stimulus. However, despite this evidence, exercise as a therapeutic intervention continues to be clinically underutilized in the general stroke population. Far more research is needed to fully comprehend the consequences of and remedies for CR fitness impairments after stroke. The purpose of this brief review is to describe some of what is currently known about the physiological consequences of CR fitness decline after stroke. Additionally, there is an overview of the evidence supporting exercise interventions for improving CR fitness, and associated aspects of general health in this population.