Assessing Functional Capacity in Directly and Remotely Monitored Home-Based Settings in Individuals With Chronic Respiratory Diseases: Protocol for a Multinational Validation Study.

BACKGROUND: Pulmonary rehabilitation is widely recommended to improve functional status and as secondary and tertiary prevention in individuals with chronic pulmonary diseases. Unfortunately, access to timely and appropriate rehabilitation remains limited. To help close this inaccessibility gap, telerehabilitation has been proposed. However, exercise testing is necessary for effective and safe exercise prescription. Current gold-standard tests, such as maximal cardiopulmonary exercise testing (CPET) and the 6-minute walk test (6MWT), are poorly adapted to home-based or telerehabilitation settings. This was an obstacle to the continuity of services during the COVID-19 pandemic. It is essential to validate tests adapted to these new realities, such as the 6-minute stepper test (6MST). This test, strongly inspired by 6MWT, consists of taking as many steps as possible on a "stepper" for 6 minutes. OBJECTIVE: This study aims to evaluate the metrological qualities of 6MST by (1) establishing concurrent validity and agreement between the 6MST and CPET, as well as with the 6MWT; (2) determining test-retest reliability in a home-based setting with direct and remote (videoconferencing) monitoring; and (3) documenting adverse events and participant perspectives when performing the 6MST in home-based settings. METHODS: Three centers (Centre de recherche de l'Institut universitaire de cardiologie et de pneumologie de Québec in Québec, Groupement des Hôpitaux de l'Institut Catholique de Lille in France, and FormAction Santé in France) will be involved in this multinational project, which is divided into 2 studies. For study 1 (objective 1), 30 participants (Québec, n=15; France, n=15) will be recruited. Two laboratory visits will be performed to assess anthropometric data, pulmonary function, and the 3 exercise tolerance tests (CPET, 6MWT, and 6MST). Concurrent validity (paired sample t tests and Pearson correlations) and agreement (Bland-Altman plots with 95% agreement limits) will be evaluated. For study 2 (objectives 2 and 3), 52 participants (Québec, n=26; France, n=26) will be recruited. Following a familiarization trial (trial 1), the 6MST will be conducted on 2 separate occasions (trials 2 and 3), once under direct supervision and once under remote supervision, in a randomized order. Paired sample t test, Bland-Altman plots, and intraclass correlations will be used to compare trials 2 and 3. A semistructured interview will be conducted after the third trial to collect participants' perspectives. RESULTS: Ethical approval was received for this project (October 12, 2023, in Québec and September 25, 2023, in France) and the first participant was recruited in February 2024. CONCLUSIONS: This study innovates by validating a new clinical test necessary for the development and implementation of new models of rehabilitation adapted to home and telerehabilitation contexts. This study also aligns with the United Nations Sustainable Development Goals by contributing to augmenting health care service delivery (goal 3) and reducing health care access inequalities (goal 11). TRIAL REGISTRATION: ClinicalTrials.gov NCT06447831; https://clinicaltrials.gov/study/NCT06447831. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/57404.

Reference equations for quadriceps strength, endurance and power: a multicentre study.

Introduction: The lack of reference values of lower-limb muscle function hinders the clinical recommendations of its measurement in patients with COPD. Therefore, this study aimed to develop reference equations to predict reference values for quadriceps strength, endurance and power and evaluate their construct validity in patients with COPD. Methods: Quadriceps strength, endurance and power were assessed in 158 healthy individuals and 87 patients with COPD. In addition, patients with COPD performed a 6-min walk test (6MWT) and a 1-min sit-to-stand test (1STS). Multiple linear regressions were performed to develop reference equations. The proportion of patients with COPD with reduced quadriceps function was determined, and correlations between quadriceps strength, endurance and power expressed in percentage of predicted values and 6MWT and 1STS performance were used to document the construct validity of the reference equation. Results: Except for quadriceps isometric endurance, the proposed reference equations explained 50-70% of the variance of the quadriceps properties in healthy individuals. All quadriceps properties were systematically reduced in a large proportion of patients with COPD compared to healthy individuals. Correlation coefficients between quadriceps properties expressed in percentage of predicted values and 6MWT and 1STS performance ranged between 0.28 and 0.49 (all p<0.05). Conclusion: In healthy individuals, age, sex, height and body mass index explained 50-70% of the variance of quadriceps strength, endurance and power. When expressed in percentage of predicted values, these quadriceps properties correlated with 6MWT and 1STS performance, suggesting construct validity of the reference values in patients with COPD.

Automated O2 Titration Alone or With High-Flow Nasal Cannula During Walking Exercise in Chronic Lung Diseases.

BACKGROUND: Exercise-induced O2 desaturation contributes to dyspnea and exercise intolerance in various respiratory diseases. This study assessed whether automated O2 titration was superior to fixed-flow O2 to improve exertional dyspnea and walking exercise endurance. We also aimed at evaluating possible additive effects of high-flow nasal cannula coupled with automated O2 titration on these outcomes. METHODS: Subjects with chronic respiratory diseases and exercise-induced desaturation performed a 3-min constant-speed shuttle test (CSST) and an endurance shuttle walking test (ESWT) with either (1) fixed-flow O2, (2) automated O2 titration targeting an SpO2 of 94% (± 2%), and (3) automated O2 titration + high-flow nasal cannula according to a randomized sequence. The main outcome was Borg dyspnea score at the end of the 3-min CSST. Secondary outcomes included endurance time and dyspnea during ESWT and oxygenation status during exercise. RESULTS: Ten subjects with COPD, 10 with interstitial lung disease, 5 with pulmonary hypertension, and 3 with cystic fibrosis completed the study. Compared to fixed-flow O2, automated O2 titration did not reduce dyspnea at the end of the 3-min CSST. Endurance time during the ESWT was prolonged with automated O2 titration (mean difference 298 [95% CI 205-391] s, P < .001), and dyspnea at isotime was reduced. No further improvement was noted when high-flow nasal cannula was added to automated O2 titration. Compared to fixed-flow O2, O2 flows were higher with automated O2 titration, resulting in better oxygenation. CONCLUSIONS: Automated O2 titration was superior to fixed-flow O2 to alleviate dyspnea and improve exercise endurance during the ESWT in subjects with a variety of chronic respiratory diseases. Adding high-flow nasal cannula to automated O2 titration provided no further benefits.

Functional clinical impairments and frailty in interstitial lung disease patients.

Background: Patients with interstitial lung disease (ILD) often present with persistent dyspnoea and reduced exercise capacity and quality of life (QoL), but their functional limitation in relation to their frailty status remains unclear. We thus aimed to compare exercise tolerance, functional mobility, and muscle function and composition between ILD participants and healthy subjects and according to their frailty status. Methods: A total of 36 ILD participants and 15 heathy subjects performed a 6-min walk test, a 1-min sit-to-stand test, a Short Physical Performance Battery test, a hand grip test and complete quadriceps function testing. Patient-related impacts were assessed via questionnaires. Muscle composition was obtained using noncontrast computed tomography scans. The frailty status of patients with ILD was determined using the Fried frailty phenotype assessment. Results: Compared with control subjects, ILD participants exhibited significantly lower performance in every exercise and functional capacity test, higher dyspnoea and depression scores, and worse QoL. In ILD participants, the same observations were noted for the frail subgroup compared with the robust subgroup. No differences in muscle function and composition were observed between the ILD and control group, but mid-thigh muscle cross-sectional area and skeletal muscle index were significantly reduced in frail ILD participants. Conclusions: ILD patients present reduced exercise tolerance and functional capacity, and have decreased health-related QoL, when compared with healthy subjects. Physical frailty seems to be associated with worse clinical status, exercise tolerance, muscle and functional impairment, and decreased QoL. The 1-min sit-to-stand test may be a good discriminatory test for frailty status in ILD patients.

Role of progression of training volume on intramuscular adaptations in patients with chronic obstructive pulmonary disease.

Introduction: Quadriceps dysfunction is a common systemic manifestation of chronic obstructive pulmonary disease (COPD), for which treatment using resistance training is highly recommended. Even though training volume is suggested to be a key explanatory factor for intramuscular adaptation to resistance training in healthy older adults, knowledge is scarce on the role of progression of training volume for intramuscular adaptations in COPD. Methods: This study was a sub-analysis of a parallel-group randomized controlled trial. Thirteen patients with severe to very severe COPD (median 66 yrs, forced expiratory volume in 1 s 44% predicted) performed 8 weeks of low-load resistance training. In a post hoc analysis, they were divided into two groups according to their training volume progression. Those in whom training volume continued to increase after the first 4 weeks of training outlined the continued progression group (n = 9), while those with limited increase (<5%) or even reduction in training volume after the initial 4 weeks composed the discontinued progression group (n = 4). Fiber-type distribution and oxidative muscle protein levels, i.e., citrate synthase (CS), hydroxyacyl-coenzyme A dehydrogenase (HADH), mitochondrial transcription factor A (TfAM) as well as quadriceps endurance measures (total work from elastic band and isokinetic knee extension tests), were assessed before and after the intervention period. Results: The continued progression group sustained their training volume progression during weeks 5-8 compared to weeks 1-4 (median +25%), while the discontinued progression group did not (median -2%) (p = 0.007 between groups). Compared with baseline values, significant between-group differences in fiber type distribution and TfAM muscle protein levels (range ± 17-62%, p < 0.05) and in individual responses to change in Type I and Type IIa fiber type proportion, CS, HADH, and TfAM muscle protein levels outcomes (median 89 vs. 50%, p = 0.001) were seen in favor of the continued progression group. Moreover, only the continued progression group had a significant increase in HADH muscle protein levels (+24%, p = 0.004), elastic band (+56%, p = 0.004) and isokinetic (+7%, p = 0.004) quadriceps endurance, but the between-group differences did not reach statistical significance (range 14-29%, p = 0.330-1.000). Discussion: The novel findings of the current study were that patients with COPD who had a continued progression of training volume across the 8-weeks intervention had an increased proportion of Type I fibers, and TfAM muscle protein levels and decreased proportion of Type II fibers compared to those that did not continue to progress their training volume after the initial weeks. Additionally, HADH muscle protein levels and quadriceps endurance measurements only improved in the continued progression group, although no significant between-group differences were seen. These findings highlight the importance of continued progression of training volume during resistive training to counteract quadriceps dysfunction within the COPD population. Still, considering the small sample size and the post hoc nature of our analyses, these results should be interpreted cautiously, and further research is necessary.

Quadriceps physiological response during the 1-min sit-to-stand test in people with severe COPD and healthy controls.

We compared quadriceps oxygenation and surface electromyography (sEMG) responses during the 1-min sit-to-stand (1STS) in 14 people with severe COPD and 12 controls, in whom cardiorespiratory response, near-infrared spectroscopy signals (oxy [Hb-Mb], deoxy [Hb-Mb], total [Hb-Mb], and SmO2) and sEMG signals of the quadriceps were recorded. Time duration of each sit-to-stand cycle and the total work performed during the 1STS were measured. The quadriceps oxygenation parameters were normalized by reporting their values according to the total work during 1STS. The rate of sit-to-stand maneuvers decelerated in people with COPD leading to smaller total work compared with controls. The pattern of quadriceps oxygenation response during 1STS was similar between groups. However, in COPD, the recovery after 1STS was characterized by larger overshoots in oxy [Hb-Mb], total [Hb-Mb], and SmO2. When corrected for the cumulative total work, the increase in muscle O2 extraction (deoxy [Hb-Mb]) during the first 30 s of recovery was greater in people with COPD compared to controls. Quadriceps sEMG changes suggestive of a fatiguing contraction pattern was observed only in people with COPD. All together, these results highlighted physiological misadaptation of people with severe COPD to the 1STS.

Physical and affective components of dyspnoea are improved by pulmonary rehabilitation in COPD.

BACKGROUND: Dyspnoea is a multidimensional experience of breathing discomfort, but its affective dimension is unfrequently assessed in people with chronic obstructive pulmonary disease (COPD). We evaluated the effectiveness of a home-based pulmonary rehabilitation (PR) programme on the physical and affective components of dyspnoea assessed by the Dyspnoea-12 (D-12) questionnaire. We also determined the baseline characteristics that contributed to the change in D-12 scores. METHODS: In this retrospective study, 225 people with COPD (age, 65±11 years; forced expiratory volume in 1 s (FEV1), 35±15% of predicted value) were enrolled into a person-centric home-based PR, consisting of a weekly supervised 90 min home session during 8 weeks. D-12 questionnaire, health status, anxiety and depressive symptoms, exercise tolerance and general fatigue were assessed at baseline (M0), at the end of PR programme (M2), and 8 (M8) and 14 months (M14) after M0. Multivariable analysis of covariance (ANCOVA) models were performed to identify the baseline characteristics that contributed to the change in D-12 scores. RESULTS: Both physical and affective components of dyspnoea and all the other outcome measures were improved at M2, M8 and M14 compared with baseline (p<0.05). Baseline body mass index was the only significant independent predictor of the changes in physical dyspnoea score, while the change in the affective dimension of dyspnoea after PR was associated with FEV1, anxiety symptoms and exercise tolerance (6 min stepper test). However, since these variables had only a small impact on the changes in D-12 questionnaire scores, results from the ANCOVA analysis should be taken cautiously. CONCLUSION: Both physical and affective components of dyspnoea were improved, at short term and long term, by 8 weeks of individualised home-based PR. The present results support the importance of assessing dyspnoea as a multidimensional experience during PR, warranting replication by robustly designed randomised and controlled studies.

Acute Cardiopulmonary and Muscle Oxygenation Responses to Normocapnic Hyperpnea Exercise in COPD.

PURPOSE: This study aimed to investigate cardiorespiratory responses and intercostal muscle oxygenation during normocapnic hyperpnea exercise in chronic obstructive pulmonary disease (COPD). METHODS: Twenty-two patients with COPD performed a cardiopulmonary cycling exercise test to assess peak oxygen consumption (V˙O2peak) and minute ventilation (V˙Epeak). They also performed a normocapnic hyperpnea exercise alone, at 50%-60% of V˙Epeak to exhaustion, using a respiratory device (Spirotiger) connected to a gas analyzer to monitor V˙O2, V˙E, and end-tidal CO2 partial pressure. Cardiac output, and intercostal and vastus lateralis muscle oxygenation were continuously measured during exercise using finger photoplethysmography and near-infrared spectroscopy, respectively. Arterial blood gases (arterial PCO2) and inspiratory capacity were obtained at rest and at the end of hyperpnea exercise. RESULTS: The hyperpnea exercise lasted 576 ± 277 s at a V˙E of 34.5 ± 12.1 L·min-1 (58% ± 6% of V˙Epeak), a respiratory rate of 22 ± 4 breaths per minute, and a tidal volume of 1.43 ± 0.43 L. From rest to the end of hyperpnea exercise, V˙O2 increased by 0.35 ± 0.16 L·min-1 (P < 0.001), whereas end-tidal CO2 partial pressure and arterial PCO2 decreased by ~2 mm Hg (P = 0.031) and ~5 mm Hg (P = 0.002, n = 13), respectively. Moreover, inspiratory capacity fell from 2.44 ± 0.84 L at rest to 1.96 ± 0.59 L (P = 0.002). During the same period, heart rate and cardiac output increased from 69 ± 12 bpm and 4.94 ± 1.15 L·min-1 at rest to 87 ± 17 bpm (P = 0.002) and 5.92 ± 1.58 L·min-1 (P = 0.007), respectively. During hyperpnea exercise, intercostal deoxyhemoglobin and total hemoglobin increased by 14.26% ± 13.72% (P = 0.001) and 8.69% ± 12.49% (P = 0.003) compared with their resting value. However, during the same period, vastus lateralis oxygenation remained stable (P > 0.05). CONCLUSIONS: In patients with COPD, normocapnic hyperpnea exercise provided a potent cardiorespiratory physiological stimulus, including dynamic hyperinflation, and increased intercostal deoxyhemoglobin consistent with enhanced requirement for muscle O2 extraction.

Home-based Pulmonary Rehabilitation is Effective in Frail COPD Patients with Chronic Respiratory Failure.

Daily life disability and vulnerability is often reported in patients with chronic obstructive pulmonary disease (COPD) and chronic respiratory failure. Although pulmonary rehabilitation is feasible in this population, its benefits on functional status and physical frailty is uncertain. This study aimed to evaluate the short- and medium-term effectiveness of a home-based pulmonary rehabilitation program in COPD patients with chronic respiratory failure. We also evaluate the impact of frailty status on the efficacy of the intervention. Forty-seven participants underwent an 8-week home-based program. Functional capacity, physical frailty (Fried criteria), exercise tolerance, health-related quality of life, general fatigue, and anxiety and depressive symptoms were assessed at baseline (M0), and at 8 weeks (M2) and 8 months (M8) following study inclusion. For the group as a whole, functional capacity, physical frailty, health-related quality of life, and fatigue scores were all improved at M2 and M8 (p<0.05), while exercise tolerance and depressive symptoms were only improved at M8 (p<0.01). However, when the group was divided according to frailty status, only the frail patients had improved health-related quality of life, general fatigue, and anxiety and depressive symptom scores after pulmonary rehabilitation (p<0.05). In COPD patients with chronic respiratory failure, home-based pulmonary rehabilitation may be effective for improving functional capacity, physical frailty, and health-related quality of life at short- and medium-term. Physical frailty was not a barrier for benefiting from the intervention, and almost 80% of the patients who were frail prior to the program improved their frailty status after pulmonary rehabilitation.

Impact of a Mobile Telerehabilitation Solution on Metabolic Health Outcomes and Rehabilitation Adherence in Patients With Obesity: Randomized Controlled Trial.

BACKGROUND: Obesity is a major public health issue. Combining exercise training, nutrition, and therapeutic education in metabolic rehabilitation (MR) is recommended for obesity management. However, evidence from randomized controlled studies is lacking. In addition, MR is associated with poor patient adherence. Mobile health devices improve access to MR components. OBJECTIVE: The aim of this study is to compare the changes in body composition, anthropometric parameters, exercise capacity, and quality of life (QOL) within 12 weeks of patients in the telerehabilitation (TR) program to those of usual care patients with obesity. METHODS: This was a parallel-design randomized controlled study. In total, 50 patients with obesity (BMI>30 kg/m²) were included in a TR group (TRG) or a usual care group (UCG) for 12 weeks. Patients underwent biometric impedance analyses, metabolic exercise tests, actimetry, and QOL and satisfaction questionnaires. The primary outcome was the change in fat mass at 12 weeks from baseline. Secondary outcomes were changes in body weight, metabolic parameters, exercise capacity, QOL, patients' adhesion, and satisfaction. RESULTS: A total of 49 patients completed the study. No significant group × time interaction was found for fat mass (TRG: mean 1.7 kg, SD 2.6 kg; UCG: mean 1.2 kg, SD 2.4 kg; P=.48). Compared with the UCG, TRG patients tended to significantly improve their waist to hip ratios (TRG: -0.01 kg, SD 0.04; UCG: +0.01 kg, SD 0.06; P=.07) and improved QOL physical impact (TRG: +21.8, SD 43.6; UCG: -1.2, SD 15.4; P=.005). Significant time effects were observed for body composition, 6-minute walk test distance, exercise metabolism, sedentary time, and QOL. Adherence (95%) and satisfaction in the TRG were good. CONCLUSIONS: In adults with obesity, the TR program was not superior to usual care for improving body composition. However, TR was able to deliver full multidisciplinary rehabilitation to patients with obesity and improve some health outcomes. Given the patients' adherence and satisfaction, pragmatic programs should consider mobile health devices to improve access to MR. Further studies are warranted to further establish the benefits that TR has over usual care. TRIAL REGISTRATION: ClinicalTrials.gov NCT03396666; http://clinicaltrials.gov/ct2/show/NCT03396666.

Isotonic quadriceps endurance is better associated with daily physical activity than quadriceps strength and power in COPD: an international multicentre cross-sectional trial.

Knowledge about modifiable determinants of daily physical activity (PA) in patients with chronic obstructive pulmonary disease (COPD) is crucial to design effective PA interventions. The present study aimed to determine the contribution of quadriceps strength, power and endurance to daily PA in COPD. Additionally, for quadriceps endurance, we also aimed to determine to what extent the association varies according to the mode of movement (isotonic, isometric, or isokinetic). Using a multicentre cross-sectional trial design we determined the contribution of quadriceps function to daily PA (steps, sedentary time and time spent doing moderate-to-very-vigorous physical activity [MVPA]) using bivariate and partial Pearson correlation analysis (r) and multiple linear regression models (ΔR2). Pre-determined controlling factors were sex, age, body mass index (BMI), COPD-assessment test, forced expiratory volume in one second in percent of the predicted value (FEV1pred), and distance walked on the 6-minute walk test. Eighty-one patients with COPD (mean ± SD: age 67 ± 8 years, FEV1pred 57 ± 19%, daily steps 4968 ± 3319, daily sedentary time 1016 ± 305 min, and MVPA time 83 ± 45 min) were included. Small to moderate bivariate correlations (r = .225 to .452, p < .05) were found between quadriceps function and measures of PA. The best multiple linear regression models explained 38-49% of the variance in the data. Isotonic endurance was the only muscle contributor that improved all PA models; daily steps (ΔR2 = .04 [relative improvement 13%] p = .026), daily sedentary time (ΔR2 = .07 [23%], p = .005) and MVPA-minutes (ΔR2 = .08 [20%], p = .001). Isotonic endurance was also independently associated with most PA variables, even when controlling for strength, power or isometric-isokinetic endurance properties of the muscle (r = .246 to .384, p < .05). In contrast, neither strength, power, isometric-or isokinetic endurance properties of the muscle was independently associated with PA measures when controlling for isotonic endurance (r = .037 to .219, p > .05). To conclude, strength, power, and endurance properties of the quadriceps were low to moderately associated with PA in patients with COPD. Isotonic quadriceps endurance was the only quadriceps property that was independently associated with the different measures of PA after controlling for a basic set of known determinants of PA, quadriceps strength or power, or isometric or isokinetic quadriceps endurance. Future longitudinal studies should investigate its potential as a modifiable determinant of PA.

Physical Frailty in COPD Patients with Chronic Respiratory Failure.

BACKGROUND: The prevalence of physical frailty and its clinical characteristics in advanced chronic obstructive pulmonary disease (COPD) is unknown, as well as the usefulness of functional capacity tests to screen for physical frailty. The aim of the study was to evaluate the proportion and clinical portrait of COPD patients with chronic respiratory failure exhibiting physical frailty at the time of referral to home-based pulmonary rehabilitation. We also evaluate the usefulness of the short physical performance battery (SPPB) and timed-up and go (TUG) as potential screening tools for physical frailty. Finally, we evaluated the specific contribution of gait speed to the frailty Fried total score. METHODS: This was a prospective observational study in which physical frailty was defined using Fried criteria (body mass loss, exhaustion, low physical activity, slower walking and weakness). Clinical portrait was documented from daily physical activity, exercise tolerance, functional capacity, anxiety and depressive symptoms, health-related quality of life, and fatigue scores. The ability of the SPPB and TUG to predict physical frailty was investigated using receiver operating characteristic curves. Contribution of each Fried criteria was evaluated with a principal component analysis (PCA). RESULTS: Amongst the 44 included participants (FEV1, 33 ± 13% of predicted), 19 were physically frail. Frail individuals had lower daily steps number, exercise tolerance and functional capacity, and higher fatigue, anxiety, and depressive symptom scores (p<0.05) compared to non-frail individuals. SPPB and TUG did not have an acceptable detection accuracy for screening physical frailty. PCA indicated that gait speed was the main contributor to the Fried total score of physical frailty. CONCLUSION: Physical frailty affects a large proportion of COPD patients with chronic respiratory failure starting a home-based intervention and was associated with worse clinical status. Although the present results need to be confirmed by adequately powered studies, gait speed seems to have the potential to become a simple screening tool for physical frailty in this population.

Specific Contribution of Quadriceps Muscle Strength, Endurance, and Power to Functional Exercise Capacity in People With Chronic Obstructive Pulmonary Disease: A Multicenter Study.

OBJECTIVE: Various functional muscle properties affect different aspects of functional exercise capacity in people with chronic obstructive pulmonary disease (COPD). The purpose of this study was to investigate the contribution of quadriceps muscle strength, endurance, and power to 6-Minute Walking Distance (6MWD) and 1-minute sit-to-stand test (1STS) performance in people with COPD. METHODS: The study was a prospective, multicenter, cross-sectional study. Anthropometrics, Medical Research Council dyspnea scale, lung function, 6MWD, and 1STS number of repetitions were assessed. Isometric quadriceps strength and endurance, isotonic quadriceps endurance, isokinetic quadriceps strength, and power were assessed on a computerized dynamometer while functional quadriceps power was determined during 5 sit-to-stand repetitions. Univariate and multivariate analyses were performed to determine the contribution of functional muscle properties to the 6MWD and the 1STS number of repetitions. RESULTS: The study included 70 people with COPD (mean % predicted forced expiratory volume in 1 second = 58.9 [SD = 18.2]). The 6MWD correlated with each functional muscle property except the isometric quadriceps endurance. The number of repetitions during the 1STS correlated with each functional muscle property except isometric measurements. Multivariate models explained 60% and 39% of the variance in the 6MWD and 1STS number of repetitions, respectively, with quadriceps power determined during 5 sit-to-stand repetitions being the muscle functional property with the strongest contribution to the models. CONCLUSION: Except for isometric endurance, quadriceps strength, endurance, and power were associated with functional exercise capacity in people with moderate COPD. Among these functional muscle properties, muscle power contributed the most to the 6MWD and 1STS number of repetitions, suggesting that muscle power is more relevant to functional exercise capacity than muscle strength or endurance in people with COPD. IMPACT: Understanding the individual contribution of muscle properties to functional status is important to designing interventions. This study provides the guidance that muscle power may be more important to functional exercise capacity than muscle strength or endurance in people with COPD.

Effects of Low-Load/High-Repetition Resistance Training on Exercise Capacity, Health Status, and Limb Muscle Adaptation in Patients With Severe COPD: A Randomized Controlled Trial.

BACKGROUND: Training volume is paramount in the magnitude of physiological adaptations following resistance training. However, patients with severe COPD are limited by dyspnea during traditional two-limb low-load/high-repetition resistance training (LLHR-RT), resulting in suboptimal training volumes. During a single exercise session, single-limb LLHR-RT decreases the ventilatory load and enables higher localized training volumes compared with two-limb LLHR-RT. RESEARCH QUESTION: Does single-limb LLHR-RT lead to more profound effects compared with two-limb LLHR-RT on exercise capacity (6-min walk distance [6MWD]), health status, muscle function, and limb adaptations in patients with severe COPD? STUDY DESIGN AND METHODS: Thirty-three patients (mean age 66 ± 7 years; FEV1 39 ± 10% predicted) were randomized to 8 weeks of single- or two-limb LLHR-RT. Exercise capacity (6MWD), health status, and muscle function were compared between groups. Quadriceps muscle biopsy specimens were collected to examine physiological responses. RESULTS: Single-limb LLHR-RT did not further enhance 6MWD compared with two-limb LLHR-RT (difference, 14 [-12 to 39 m]. However, 73% in the single-limb group exceeded the known minimal clinically important difference of 30 m compared with 25% in the two-limb group (P = .02). Health status and muscle function improved to a similar extent in both groups. During training, single-limb LLHR-RT resulted in a clinically relevant reduction in dyspnea during training compared with two-limb LLHR-RT (-1.75; P = .01), but training volume was not significantly increased (23%; P = .179). Quadriceps muscle citrate synthase activity (19%; P = .03), hydroxyacyl-coenzyme A dehydrogenase protein levels (32%; P < .01), and capillary-to-fiber ratio (41%; P < .01) were increased compared with baseline after pooling muscle biopsy data from all participants. INTERPRETATION: Single-limb LLHR-RT did not further increase mean 6MWD compared with two-limb LLHR-RT, but it reduced exertional dyspnea and enabled more people to reach clinically relevant improvements in 6MWD. Independent of execution strategy, LLHR-RT improved exercise capacity, health status, muscle endurance, and enabled several physiological muscle adaptations, reducing the negative consequences of limb muscle dysfunction in COPD. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT02283580; URL: www.clinicaltrials.gov.

Reliability of quadriceps muscle power and explosive force, and relationship to physical function in people with chronic obstructive pulmonary disease: an observational prospective multicenter study.

Background: Muscle power declines with age and is a stronger determinant of physical function than strength. Muscle power using computerized dynamometry has not been investigated in COPD.Objectives: To determine: 1) test-retest reliability of quadriceps power using a standardized protocol with computerized dynamometry; and 2) associations between quadriceps strength and power, and functional capacity.Design/Setting: Prospective observational study in four Canadian research labs.Participants: People with mild to very severe COPD.Methods: Tests were conducted on two days. Quadriceps muscle maximal strength was evaluated during a static maneuver using maximal voluntary isometric contractions (MVIC). Rate of torque development (RTD) during MVIC was used to assess explosive force. Muscle power was measured using a dynamic, isotonic protocol from which peak and average power and peak velocity were derived. Functional capacity was assessed with the Short Physical Performance Battery (SPPB). Reliability was assessed using intraclass correlation coefficients (ICC), standard error of measurements (SEM), and Bland Altman plots. Spearman and Pearson correlation coefficients were used for associations.Results: 65 patients (age 69 ± 8 years; FEV1 48 ± 21% of predicted) were included. ICC was 0.77 for RTD and 0.87-0.98 for isotonic power measures (95%CI 0.63-0.99, p < .001); SEM < 10% for average/peak power and peak velocity, and > 30% for RTD. SPPB had moderate correlation with average power, but not with MVIC or RTD.Conclusion: The standardized isotonic protocol with computerized dynamometry was reliable in assessing quadriceps power in COPD. Our data highlights that average power correlates best with functional capacity, indicating higher relevance than static measures when investigating determinants of function.

Long-Term Effectiveness of a Home-Based Pulmonary Rehabilitation in Older People with Chronic Obstructive Pulmonary Disease: A Retrospective Study.

Background: Long-term effectiveness of pulmonary rehabilitation (PR) is still uncertain in older people with severe chronic obstructive pulmonary disease (COPD). The objective was to compare the effects of home-based PR in people with COPD above and below the age of 70 years. Methods: In this retrospective study, 480 people with COPD were recruited and divided into those ≤70 (n=341) and those >70 years of age (n=139). All participants underwent an 8 weeks of home-based PR, consisting of a weekly supervised 90-minute home session. Six-minute stepper test (6MST), timed-up and go test (TUG), Hospital Anxiety and Depression Scale, and Visual Simplified Respiratory Questionnaire (VSRQ) were assessed at baseline (M0), at 2 (M2), 8 (M8), 14 (M14) months after baseline. Results: The older group was described by fewer current smokers (p <0.001), more long-term oxygen therapy use (p = 0.024), higher prevalence of comorbidities (p<0.001), lower 6MST score and higher TUG score (p<0.001), compared to the younger group. Both groups improved every outcome at M2 compared to baseline. At M2, 88% of people ≤70 years of age and 79% of those above 70 were considered as responders in at least one evaluated parameter (p = 0.013). Both groups maintained the benefits at M14, except for the VSRQ score and the number of responders to this outcome in the older group. Conclusion: Regardless of the age, personalized home-based PR was effective for people with COPD in the short term. Above 70 years, an ageing effect appeared on the long-term effectiveness of quality of life benefit.

Validation and Cardiorespiratory Response of the 1-Min Sit-to-Stand Test in Interstitial Lung Disease.

PURPOSE: To assess the 1-min sit-to-stand test (1STS) test-retest reliability and construct validity and its associated cardiorespiratory response in comparison to the 6-min walk test (6MWT) and symptom-limited cycling cardiopulmonary exercise test (CPET) in people with interstitial lung disease (ILD). METHODS: Fifteen participants with ILD performed two 1STS tests, a 6MWT and a CPET. The three tests were administered on three separate visits, and cardiorespiratory parameters were continuously recorded during the tests. RESULTS: The number of repetitions during both 1STS tests was 22 ± 4 and 22 ± 4 (mean difference of 0.53 ± 2.00 repetitions, P = 0.32) with an intraclass correlation of 0.937 (95% confidence interval, 0.811-0.979]) and a minimal detectable change of 2.9 repetitions. The number of 1STS repetitions was highly correlated with the 6MWT distance (r = 0.823, P < 0.001) and with the peak cycling power output expressed in % predicted values (r = 0.706, P < 0.003). Oxygen consumption (V˙O2) peak during the 1STS reached 83% and 78% of V˙O2 peak during 6MWT and CPET, respectively. Peak 1STS HR, minute ventilation (V˙E,), V˙O2 values, as well as nadir SpO2 were achieved during the recovery phase of the test, whereas peak 6MWT and CPET HR, V˙E, V˙O2 and nadir SpO2 always occurred at the end of the test. The three tests elicited a similar fall in SpO2 ranging between 8% and 12%. Symptom scores after the 1STS were similar to those seen at the end of the 6MWT but lower than those of CPET. CONCLUSIONS: The 1STS showed excellent test-retest reliability in patients with ILD in whom it elicited a substantial, but submaximal cardiorespiratory response. Our data also support the construct validity of the 1STS to assess functional exercise capacity in patients with ILD and to detect exercise-induced O2 desaturation.

Cardiorespiratory Response during the 1-min Sit-to-Stand Test in Chronic Obstructive Pulmonary Disease.

PURPOSE: This study aimed to assess the cardiorespiratory response during a 1-min sit-to-stand test (1STS) in comparison with cycling cardiopulmonary exercise test (CPET) in people with chronic obstructive pulmonary disease (COPD) and in healthy subjects and to evaluate whether 1STS may induce leg fatigue in these individuals. METHODS: Fourteen people with severe COPD and 12 healthy subjects performed a 1STS and a CPET during which cardiorespiratory response, perception of dyspnea, and leg fatigue were assessed. Quadriceps strength was assessed before and after 1STS, and contractile fatigue was defined as a postexercise fall in quadriceps twitch force greater than 15% of resting values. RESULTS: In COPD, peak V˙O2, V˙E, and HR achieved during 1STS reached 113%, 103%, and 93% of the corresponding values during CPET, respectively. Decrease in SpO2 from preexercise to peak exercise and the magnitude of dynamic hyperinflation were similar between 1STS and CPET. Borg dyspnea and leg fatigue scores were higher for CPET than 1STS. In healthy subjects, peak cardiorespiratory demand and symptom scores were higher during CPET compared with 1STS. A V˙O2 overshoot during recovery was observed only in people with COPD. After 1STS, the V˙O2 half-time recovery of COPD was 152 ± 25 s compared with 74 ± 18 in healthy subjects (P < 0.01). Ten people with COPD and five healthy subjects were considered as fatiguers. CONCLUSION: The 1STS induced a similar cardiorespiratory stress to that of CPET and was associated with contractile quadriceps fatigue in people with severe COPD. The V˙O2 overshoot and slower recovery time of cardiorespiratory variables seen in COPD demonstrate the clinical relevance of monitoring the recovery phase of exercise.

The Relevance of Limb Muscle Dysfunction in Chronic Obstructive Pulmonary Disease: A Review For Clinicians.

"Chronic obstructive pulmonary disease (COPD) is often accompanied by extrapulmonary manifestations such as limb muscle dysfunction. This term encompasses several features, including atrophy, weakness, and reduced oxidative capacity. Clinicians should become accustomed with this manifestation of COPD because of its relevance for important outcomes such as exercise tolerance and survival. Measuring muscle strength and mass can be performed with simple and valid tools that could be implemented in clinical practice. One identified, limb muscle dysfunction is amenable to therapy such as exercise training that has been repeatedly shown to improve muscle mass, strength, and oxidative capacity in COPD."

Fixed Handheld Dynamometry Provides Reliable and Valid Values for Quadriceps Isometric Strength in People With Chronic Obstructive Pulmonary Disease: A Multicenter Study.

BACKGROUND: Quadriceps weakness is associated with poor clinical outcomes in chronic obstructive pulmonary disease (COPD). However, quadriceps isometric strength assessment has not been routinely adopted in clinical practice because of the lack of homogeneity in the devices and protocols and the lack of reliability studies. OBJECTIVE: The objectives of this study were to determine the test-retest reliability and the criterion validity of a commercially available handheld dynamometer for evaluating the quadriceps isometric maximal voluntary contraction (iMVCquad) using a standardized protocol and to investigate the relationship between iMVCquad and functional capacity in people with COPD. DESIGN: This was a prospective, observational, multicenter trial. METHODS: Participants with mild to severe COPD from 4 Canadian sites were tested on 2 separate days. Five iMVCquad measurements were obtained following a standardized procedure with a fixed handheld dynamometer (iMVCquad-HHD), and then 5 iMVCquad measurements were obtained with a computerized dynamometer (iMVCquad-CD; the gold standard). Functional capacity was assessed with the Short Physical Performance Battery. Intraclass correlation coefficients, standard errors of measurement, Bland-Altman plots, and Spearman correlation coefficients were used for analyses. RESULTS: Sixty-five participants (mean age = 69 years [SD = 8]; forced expiratory volume in 1 second = 48% of predicted value [SD = 21]) completed the study. The mean iMVCquad-HHD values on visits 1 and 2 were 102.7 (SD = 51.6) and 105.6 (SD = 58.8) N·m, respectively; the standard error of measurement was 11.4 N·m. The between-visits intraclass correlation coefficient for iMVCquad-HHD was 0.95 (95% confidence interval  = 0.92-0.97), with a mean bias of 2.0 (Bland-Altman plot). There was a strong correlation between iMVCquad-HHD and iMVCquad-CD (Spearman correlation coefficient = 0.86). There was no correlation between iMVCquad-HHD and Short Physical Performance Battery total score. LIMITATIONS: Participants had stable COPD with few comorbidities and were more physically active than the general population of people with COPD; results might not be applicable to patients with acute exacerbations of the disease or more comorbidities. Assessment order between handheld and computerized dynamometers has not been randomized, but analyses did not highlight any systematic bias or learning effect. CONCLUSIONS: Quadriceps strength assessment can be implemented in a reliable and valid way in people with COPD using a fixed handheld dynamometer and standardized procedure. This protocol should be established in clinical practice to facilitate the assessment of muscle strength in people with COPD.