Cardiopulmonary Responses During Clinical and Laboratory Gait Assessments in People With Chronic Stroke

Are age-predicted equations valid in predicting maximum heart rate in individuals after stroke?

PURPOSE

To investigate the validity of six age-predicted maximum heart rate (HRmax) equations after stroke.

MATERIAL AND METHODS

Sixty individuals (54 (12) years; 64 (69) months after stroke) were included. A Cardiopulmonary Exercise Test (CPET) performed on a treadmill obtained the HRmax. The most used age-predicted equations were investigated: (1) 220-age, proposed by Fox; (2) 206.9- (0.67 × age), proposed by Gellish; (3) 208- (0.7 × age), proposed by Tanaka; (4) 216.6- (0.84 × age), proposed by Astrand; (5) 164- (0.72 × age) and (6) 200- (0.92 × age) proposed by Brawner.

RESULTS

No statistically significant agreement was found between the HRmax obtained by the CPET and the one predicted by the equations 1-5 (-0.18 ≤ 95% confidence interval ≤0.79). A significant and moderate agreement was found between the HRmax obtained by the CPET and the one predicted by equation (6) (95% CI= 0.05-0.75; Intraclass Correlation Coefficient= 0.51). Bland-Altman plots showed that equations (1-4) and (6) overestimated the HRmax. Equation (6) presented the lower mean difference.

CONCLUSIONS

The equations developed for non-disabled individuals (1-4) are not adequate to be used in individuals after a stroke. Equation (6) (Brawner) showed the best results to be used in individuals after stroke; however, it should be used cautiously.

Acute Intermittent Hypoxia With High-Intensity Gait Training in Chronic Stroke: A Phase II Randomized Crossover Trial

BACKGROUND

Studies in individuals with chronic stroke indicate high-intensity training (HIT) focused on walking improves locomotor function, which may be due to repeated activation of locomotor circuits and serotonin-dependent modulation of motor output. Separate studies in animals and individuals with spinal cord injury suggest acute intermittent hypoxia (AIH) can augment the effects of locomotor interventions through similar serotonin-dependent mechanisms, although no studies have coupled AIH with HIT in individuals poststroke. The goal of this study was to evaluate the safety and efficacy of AIH+HIT versus HIT alone in individuals with chronic stroke.

METHODS

This phase II double-blind randomized, crossover trial recruited individuals between 18 and 85 years old, >6 months poststroke, and self-selected speeds <1.0 m/s. Participants received up to 15 sessions of AIH for 30 minutes using 15 cycles of hypoxia (60-90 seconds; 8%-9% O2) and normoxia (30-60 seconds; 21% O2), followed by 1 hour of HIT targeting >75% heart rate reserve. The control condition received normoxia for 30 minutes before HIT. Following the first training phase, participants performed the second phase >1 month later. The primary outcomes were self-selected speed and fastest speed, a 6-minute walk test, and peak treadmill speed. A 3-way mixed-model ANOVA assessed the effects of time, training, and order of interventions.

RESULTS

Of 55 individuals screened, 35 were randomized to AIH+HIT or normoxia+HIT first, and 28 individuals completed both interventions, revealing greater gains in self-selected speeds (0.14 [0.08-0.18] versus 0.05 [0.01-0.10] m/s), fastest speed (0.16 [0.10-0.21] versus 0.06 [0.02-0.10] m/s), and peak treadmill speed (0.21 [0.14-0.29] versus 0.11 [0.06-0.16] m/s) following AIH+HIT versus normoxia+HIT (P<0.01) with no order effects. Greater gains in spatiotemporal symmetry were observed with AIH+HIT, with worse outcomes for those prescribed serotonin-mediated antidepressant medications.

CONCLUSIONS

AIH+HIT resulted in greater gains in locomotor function than normoxia+HIT. Subsequent phase III trials should further evaluate the efficacy of this intervention.

REGISTRATION

URL: https://clinicaltrials.gov/; Unique identifier: NCT04472442.

Influence of lower limb muscle isometric strength and cardiovascular parameters on locomotor capacity in children and adolescents

BACKGROUND

Although measures of exercise performance and physical activity are known to be related to 6-minute walk test (6mWT), the role of the strength of each muscle group of the lower limb in the locomotor capacity during the development period is unknown.

OBJECTIVE

To identify the role of the isometric strength of lower limb muscles and cardiovascular parameters on the locomotor capacity in children and adolescents, controlling for participants sex, age, and height.

METHODS

Participants (7 to 15 years old; female, n= 113; male, n= 128) were assessed for isometric strength (seven lower limb muscles), cardiovascular parameters (diastolic pressure, oxygen saturation, resting heart rate, respiratory rate), and 6mWT. Participants were split into nine age groups and separated by 1-year intervals.

RESULTS

Hip flexors-controlled for sex, age, and height-explained a meaningful percentage of the variance (R=2 0.45; p< 0.001) for 6mWT distance, and the resting heart rate explained a change in R2 of only 2% (p= 0.008).

CONCLUSIONS

Isometric strength of hip flexors explained ∼ 50% of the 6mWT distance, suggesting the importance of strength from an early age. Other factors, such as cardiovascular parameters, while relevant, may exert a secondary role on youth's capacity.

Gains in Daily Stepping Activity in People With Chronic Stroke After High-Intensity Gait Training in Variable Contexts

OBJECTIVE

Many physical therapist interventions provided to individuals with chronic stroke can lead to gains in gait speed or endurance (eg, 6-Minute Walk Test [6MWT]), although changes in objective measures of participation are not often observed. The goal of this study was to determine the influence of different walking interventions on daily stepping (steps per day) and the contributions of demographic, training, and clinical measures to these changes.

METHODS

In this secondary analysis of a randomized clinical trial, steps per day at baseline and changes in steps per day following 1 of 3 locomotor interventions were evaluated in individuals who were ambulatory and >6 months after stroke. Data were collected on 58 individuals who received ≤30 sessions of high-intensity training (HIT) in variable contexts (eg, tasks and environments; n = 19), HIT focused on forward walking (n = 19), or low-intensity variable training (n = 20). Primary outcomes were steps per day at baseline, at post-training, and at a 3-month follow-up, and secondary outcomes were gait speed, 6MWT, balance, and balance confidence. Correlation and regression analyses identified demographic and clinical variables associated with steps per day.

RESULTS

Gains in steps per day were observed across all groups combined, with no between-group differences; post hoc within-group analyses revealed significant gains only following HIT in variable contexts. Both HIT groups showed gains in endurance (6MWT), with increases in balance confidence only following HIT in variable contexts. Changes in steps per day were associated primarily with gains in 6MWT, with additional associations with baseline 6MWT, lower-extremity Fugl-Meyer scores, and changes in balance confidence.

CONCLUSION

HIT in variable contexts elicited gains in daily stepping, with changes primarily associated with gains in gait endurance.

IMPACT

Providing HIT in variable contexts appears to improve measures of participation (eg, daily stepping) that may be associated with clinical measures of function. Gains in multiple measures of mobility and participation with HIT in variable contexts may improve the efficiency and value of physical therapy services.

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.

Guidelines for the Evaluation of Cardiorespiratory Physiotherapy in Stroke Patients

Evaluation of stroke patients is prioritized over therapeutic interventions to restore cardiorespiratory capacity. This study aimed to develop a clinically applicable guideline to evaluate cardiorespiratory physiotherapy in stroke patients based on a literature review and a modified Delphi survey. The literature search included 13,498 articles in PubMed, EMBASE, CINAHL, and Cochrane Library electronic databases. We surveyed previous articles between January 2010 and June 2019. After the option elimination process, a total of 27 documents were selected and analyzed (draft: 18, modified Delphi survey: 9). The results of this research are roughly divided into two categories. First, 31 draft items were extracted, and a modified Delphi survey questionnaire was created from a literature review. Second, an expert was asked to make two modified Delphi surveys and to modify, delete, and supplement the entries in the statistical analysis at each level to finalize the steps to 20 items. The guidelines developed in this study reflect the selective use of cardiorespiratory physiotherapy evaluation methods in the clinical setting, based on the health status of individual patients. Moreover, the guidelines may help physiotherapists make informed decisions based on expert knowledge, thereby playing a crucial role in the patient-centered treatment planning process.

Energy Cost During the 6-Minute Walk Test and Its Relationship to Real-World Walking After Stroke: A Correlational, Cross-Sectional Pilot Study

BACKGROUND

After experiencing stroke, individuals expend more energy walking than people who are healthy. However, among individuals who have experienced stroke, the correlation between the energy cost of walking, as measured by validated tests (such as the 6-minute walk test), and participation in walking, as measured by more sensitive tools (such as an ambulatory activity monitor), remains unknown.

OBJECTIVE

The main objective of this study was to determine whether the energy cost of walking is correlated with participation in walking.

DESIGN

This study was a correlational, cross-sectional pilot study.

METHODS

Data from 23 participants who had experienced chronic stroke were analyzed. On the first day, data on oxygen uptake were collected using a portable metabolic system while participants walked during the 6-minute walk test. Then, the ambulatory activity monitor was placed on the participants' nonparetic ankle and removed 9 days later. The energy cost of walking was calculated by dividing the mean oxygen uptake recorded during the steady state by the walking speed.

RESULTS

The energy cost of walking was correlated with the following: the number of steps (Spearman rank correlation coefficient [rs] = -0.59); the percentage of time spent in inactivity (rs = 0.48), low cadence (rs = 0.67), medium cadence (rs = -0.56), high cadence (rs = -0.65), and the percentages of steps taken at low cadence (rs = 0.65) and high cadence (rs = -0.64).

LIMITATIONS

Individuals who were physically inactive, convenience sampling, and a small sample size were used in this study.

CONCLUSIONS

Higher energy costs of walking were associated with fewer steps per day and lower cadence in real-world walking in individuals who had experienced stroke.

Contributions of Stepping Intensity and Variability to Mobility in Individuals Poststroke

Background and Purpose- The amount of task-specific stepping practice provided during rehabilitation poststroke can influence locomotor recovery and reflects one aspect of exercise dose that can affect the efficacy of specific interventions. Emerging data suggest that markedly increasing the intensity and variability of stepping practice may also be critical, although such strategies are discouraged during traditional rehabilitation. The goal of this study was to determine the individual and combined contributions of intensity and variability of stepping practice to improving walking speed and distance in individuals poststroke. Methods- This phase 2, randomized, blinded assessor clinical trial was performed between May 2015 and November 2018. Individuals between 18 and 85 years old with hemiparesis poststroke of >6 months duration were recruited. Of the 152 individuals screened, 97 were randomly assigned to 1 of 3 training groups, with 90 completing >10 sessions. Interventions consisted of either high-intensity stepping (70%-80% heart rate reserve) of variable, difficult stepping tasks (high variable), high-intensity stepping performing only forward walking (high forward), and low-intensity stepping in variable contexts at 30% to 40% heart rate reserve (low variable). Participants received up to 30 sessions over 2 months, with testing at baseline, post-training, and a 3-month follow-up. Primary outcomes included walking speeds and timed distance, with secondary measures of dynamic balance, transfers, spatiotemporal kinematics, and metabolic measures. Results- All walking gains were significantly greater following either high-intensity group versus low-variable training (all P<0.001) with significant correlations with stepping amount and rate (r=0.48-60; P<0.01). Additional gains in spatiotemporal symmetry were observed with high-intensity training, and balance confidence increased only following high-variable training in individuals with severe impairments. Conclusions- High-intensity stepping training resulted in greater improvements in walking ability and gait symmetry than low-intensity training in individuals with chronic stroke, with potential greater improvements in balance confidence. Clinical Trial Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT02507466.