Effects and mechanisms of supramaximal high-intensity interval training on extrapulmonary manifestations in people with and without chronic obstructive pulmonary disease (COPD-HIIT): study protocol for a multi-centre, randomized controlled trial

BACKGROUND

Beyond being a pulmonary disease, chronic obstructive pulmonary disease (COPD) presents with extrapulmonary manifestations including reduced cognitive, cardiovascular, and muscle function. While exercise training is the cornerstone in the non-pharmacological treatment of COPD, there is a need for new exercise training methods due to suboptimal adaptations when following traditional exercise guidelines, often applying moderate-intensity continuous training (MICT). In people with COPD, short-duration high-intensity interval training (HIIT) holds the potential to induce a more optimal stimulus for training adaptations while circumventing the ventilatory burden often associated with MICT in people with COPD. We aim to determine the effects of supramaximal HIIT and MICT on extrapulmonary manifestations in people with COPD compared to matched healthy controls.

METHODS

COPD-HIIT is a prospective, multi-centre, randomized, controlled trial with blinded assessors and data analysts, employing a parallel-group designed trial. In phase 1, we will investigate the effects and mechanisms of a 12-week intervention of supramaximal HIIT compared to MICT in people with COPD (n = 92) and matched healthy controls (n = 70). Participants will perform watt-based cycling two to three times weekly. In phase 2, we will determine how exercise training and inflammation impact the trajectories of neurodegeneration, in people with COPD, over 24 months. In addition to the 92 participants with COPD performing HIIT or MICT, a usual care group (n = 46) is included in phase 2. In both phases, the primary outcomes are a change from baseline in cognitive function, cardiorespiratory fitness, and muscle power. Key secondary outcomes include change from baseline exercise tolerance, brain structure, and function measured by MRI, neuroinflammation measured by PET/CT, systemic inflammation, and intramuscular adaptations. Feasibility of the interventions will be comprehensively investigated.

DISCUSSION

The COPD-HIIT trial will determine the effects of supramaximal HIIT compared to MICT in people with COPD and healthy controls. We will provide evidence for a novel exercise modality that might overcome the barriers associated with MICT in people with COPD. We will also shed light on the impact of exercise at different intensities to reduce neurodegeneration. The goal of the COPD-HIIT trial is to improve the treatment of extrapulmonary manifestations of the disease.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT06068322. Prospectively registered on 2023-09-28.

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.

Muscle Power in Patients with Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-analysis

This study aimed to review the impact of training on muscle power in patients with chronic obstructive pulmonary disease (COPD). Randomized controlled trials evaluating the effects of exercise-based interventions on limbs muscle power and rate of force development in COPD patients were investigated. Five international databases were searched until October 2022. Meta-analyses were performed calculating the mean difference or standardized mean difference. Risk of bias in studies was assessed using Cochrane Risk of Bias tool 2.0. A total of nine studies were included in the analysis. There were concerns about risk of bias in seven out of nine studies. Comparison of exercising and non-exercising groups showed a significant effect of exercise in improving muscle power (P=0.0004) and rate of force development (P<0.001), in five and three trials, respectively. Four studies comparing different trainings showed no significant results on muscle power (P=0.45). Eight to 16 weeks of exercise-based intervention versus no intervention might be beneficial to enhance upper and lower limbs muscle power and rate of force development in people with COPD. In contrast, muscle power did not improve when different training modalities were compared. Future studies performing power training in COPD patients are encouraged.

Associations of the distance-saturation product and low-attenuation area percentage in pulmonary computed tomography with acute exacerbation in patients with chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) has high global health concerns, and previous research proposed various indicators to predict mortality, such as the distance-saturation product (DSP), derived from the 6-min walk test (6MWT), and the low-attenuation area percentage (LAA%) in pulmonary computed tomographic images. However, the feasibility of using these indicators to evaluate the stability of COPD still remains to be investigated. Associations of the DSP and LAA% with other COPD-related clinical parameters are also unknown. This study, thus, aimed to explore these associations.

Methods

This retrospective study enrolled 111 patients with COPD from northern Taiwan. Individuals' data we collected included results of a pulmonary function test (PFT), 6MWT, life quality survey [i.e., the modified Medical Research Council (mMRC) scale and COPD assessment test (CAT)], history of acute exacerbation of COPD (AECOPD), and LAA%. Next, the DSP was derived by the distance walked and the lowest oxygen saturation recorded during the 6MWT. In addition, the DSP and clinical phenotype grouping based on clinically significant outcomes by previous study approaches were employed for further investigation (i.e., DSP of 290 m%, LAA% of 20%, and AECOPD frequency of ≥1). Mean comparisons and linear and logistic regression models were utilized to explore associations among the assessed variables.

Results

The low-DSP group (<290 m%) had significantly higher values for the mMRC, CAT, AECOPD frequency, and LAA% at different lung volume scales (total, right, and left), whereas it had lower values of the PFT and 6MWT parameters compared to the high-DSP group. Significant associations (with high odds ratios) were observed of the mMRC, CAT, AECOPD frequency, and PFT with low- and high-DSP groupings. Next, the risk of having AECOPD was associated with the mMRC, CAT, DSP, and LAA% (for the total, right, and left lungs).

Conclusion

A lower value of the DSP was related to a greater worsening of symptoms, more-frequent exacerbations, poorer pulmonary function, and more-severe emphysema (higher LAA%). These readily determined parameters, including the DSP and LAA%, can serve as indicators for assessing the COPD clinical course and may can serve as a guide to corresponding treatments.

Isolated Resistance Training Programs to Improve Peripheral Muscle Function in Outpatients with Chronic Obstructive Pulmonary Diseases: A Systematic Review

This systematic review aims to establish which isolated resistance training (RT) programs have been used in outpatients with chronic obstructive pulmonary disease (COPD) and their impact on all aspects of peripheral skeletal muscle function. Electronic databases were systematically searched up to June 2021. The eligibility criteria were: (1) randomized controlled trials investigating the effects of supervised and isolated RT programs in outpatients with COPD and (2) RT programs lasting 8-12 weeks, (3) including at least one outcome measure related to trainable muscle characteristics. Initially, 6576 studies were identified, whereas 15 trials met the inclusion criteria. All the included trials reported that isolated RT improved both upper and lower limbs' maximal strength. Muscle endurance and power also increased after RT but received less attention in the analysis. Furthermore, few studies assessed the effect of RT on muscle mass and cross-sectional area, reporting only limited improvement. Isolated RT programs carried out 2-3 days a week for 8-12 weeks improved skeletal muscle function in individuals with COPD. The RT program should be specifically focused to the trainable muscle characteristic to be improved. For this reason, we further encourage the introduction of a detailed assessment of muscle function and structure during the pulmonary rehabilitation practice.

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 (FEV_1pred), and distance walked on the 6-minute walk test. Eighty-one patients with COPD (mean ± SD: age 67 ± 8 years, FEV_1pred 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.

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.

The association of objectively measured physical activity and sedentary behavior with skeletal muscle strength and muscle power in older adults: A systematic review and meta-analysis

BACKGROUND

Engaging in physical activity (PA) and avoiding sedentary behavior (SB) are important for healthy ageing with benefits including the mitigation of disability and mortality. Whether benefits extend to key determinants of disability and mortality, namely muscle strength and muscle power, is unclear.

AIMS

This systematic review aimed to describe the association of objective measures of PA and SB with measures of skeletal muscle strength and muscle power in community-dwelling older adults.

METHODS

Six databases were searched from their inception to June 21^st, 2020 for articles reporting associations between objectively measured PA and SB and upper body or lower body muscle strength or muscle power in community dwelling adults aged 60 years and older. An overview of associations was visualized by effect direction heat maps, standardized effect sizes were estimated with albatross plots and summarized in box plots. Articles reporting adjusted standardized regression coefficients (β) were included in meta-analyses.

RESULTS

A total of 112 articles were included representing 43,796 individuals (range: 21 to 3726 per article) with a mean or median age from 61.0 to 88.0 years (mean 56.4 % female). Higher PA measures and lower SB were associated with better upper body muscle strength (hand grip strength), upper body muscle power (arm curl), lower body muscle strength, and lower body muscle power (chair stand test). Median standardized effect sizes were consistently larger for measures of PA and SB with lower compared to upper body muscle strength and muscle power. The meta-analyses of adjusted β coefficients confirmed the associations between total PA (TPA), moderate-to-vigorous PA (MVPA) and light PA (LPA) with hand grip strength (β = 0.041, β = 0.057, and β = 0.070, respectively, all p ≤ 0.001), and TPA and MVPA with chair stand test (β = 0.199 and β = 0.211, respectively, all p ≤ 0.001).

CONCLUSIONS

Higher PA and lower SB are associated with greater skeletal muscle strength and muscle power, particularly with the chair stand test.

[Which physical tests for which objectives in pulmonary rehabilitation?]

Chronic respiratory disease is a major cause of morbidity and mortality worldwide and an important cause of disability including a reduction of exercise, functional and muscle capacity contributing to a decreased quality of life. In the context of pulmonary rehabilitation, a thorough patient-centered outcome assessment, including not only measures of lung function, but also exercise functional and muscle capacity, is imperative for a comprehensive disease management. Assessment of these impairments and dysfunctions with appropriate and change-sensitive procedures is thus necessary for personalizing the physical interventions and assessing the short- and long-term effectiveness of the intervention. The clinician currently has a wide variety of tests and measurements available to assess the physical and functional capacity of people with chronic respiratory disease. The aim of this review is to provide a pragmatic synthesis of the physical, functional and muscle capacity tests most commonly used in pulmonary rehabilitation. Ultimately, it should help the clinician to identify the relevant evaluations according to the objectives of the patients but also according to the available resources, the setting of pulmonary rehabilitation and the specific qualities of each test.

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.

Evaluation of isokinetic muscle strength of upper limb and the relationship with pulmonary function and respiratory muscle strength in stable COPD patients

Background

Upper limb muscle strength plays an important role in respiratory and pulmonary function, and limited research focuses on the role of strength and endurance of the elbow extensor and flexor. This study was conducted to accurately assess upper limb muscle function and quantified associations with pulmonary function and respiratory muscle strength in patients with stable chronic obstructive pulmonary disease (COPD).

Methods

In this cross-sectional study, patients with stable COPD treated in Yue-Yang Integrative Medicine Hospital from March 2014 to March 2016 were recruited. All participants underwent a pulmonary function test (forced expiratory volume in first second/forced vital capacity, FEV1/FVC; percentage value of predicted FEV1, FEV1%pred), a respiratory muscle strength test (maximal inspiratory pressure, MIP; maximal expiratory pressure, MEP), and an isokinetic test of dominant upper limb after a 24-hr interval (peak torque, PT; PT/body weight, PT/BW; total work, TW; endurance ratio, ER).

Results

A total of 88 patients with stable COPD (age: 65.5±8.7 years) were recruited, of which 73% (64 patients) were male. In the multiple stepwise regression analysis, sex remained as significant impactors in the final model for FEV1%pred (adjusted R²=0.243, P<0.001). Elbow flexor PT/BW and ER, sex, and BMI remained as significant impactors in the final model for FEV1/FVC (adjusted R²=0.255, P<0.01). Elbow flexor TW remained as significant impactors for MIP (adjusted R²=0.112, P=0.001), while elbow extensor PT and PT/BW and sex remained as significant impactors for MEP (adjusted R =0.385, P<0.01).

Conclusion

In stable COPD, pulmonary function and respiratory muscle strength are associated with upper limb muscle strength. In particular, elbow flexor endurance is likely an important impactor for pulmonary function and inspiratory muscle strength, while elbow extensor strength is of importance for expiratory muscle strength.

Handgrip strength measurement in patients with chronic obstructive pulmonary disease: Possible predictor of exercise capacity

BACKGROUND

Impaired exercise capacity is one of the most important prognostic factors for patients with chronic obstructive pulmonary disease (COPD). The 6-min walk test (6MWT) is a widely used method for assessing exercise capacity in patients with COPD. However, the 6MWT requires considerable effort from patients. Therefore, a less physically demanding, but also noninvasive, method is warranted. The objective of this study was to determine the predictors of the 6MWT distance (6MWD) in patients with COPD.

METHODS

This retrospective observational study enrolled 133 Japanese patients with COPD. All patients underwent the 6MWT, COPD assessment test (CAT), spirometry, respiratory muscle strength evaluation, body composition assessment, and handgrip strength (HGS) measurement. We examined the associations between the 6MWD and evaluated parameters.

RESULTS

From single regression analysis, the 6MWD was significantly correlated with age, CAT score, several spirometric measurements (e.g., percentages of forced vital capacity, forced expiratory volume in 1 s, and carbon monoxide diffusing capacity of the lungs [%DLCO]), respiratory muscle strength parameters (e.g., percentages of maximal expiratory and inspiratory pressures), skeletal muscle mass index, and HGS. In multiple regression analysis, age, CAT score, %DLCO, and HGS were independent predictors of the 6MWD. The %DLCO and HGS were strongly correlated as predictors of the 6MWD (p < 0.001).

CONCLUSIONS

We found that HGS was significantly correlated with the 6MWD compared with spirometric measurements or respiratory muscle strength parameters in Japanese patients with COPD, suggesting that HGS could be a simple and noninvasive predictor of the 6MWD in patients with COPD.

Measuring and monitoring skeletal muscle function in COPD: current perspectives

Skeletal muscle dysfunction is an important systemic consequence of chronic obstructive pulmonary disease (COPD) that worsens the natural cause of the disease. Up to a third of all people with COPD express some form of impairment which encompasses reductions in strength and endurance, as well as an increased fatigability. Considering this complexity, no single test could be used to measure and monitor all aspects of the impaired skeletal muscle function within the COPD population, resulting in a wide range of available tests and measurement techniques. The aim of the current review is to highlight current and new perspectives relevant to skeletal muscle function measurements within the COPD population in order to provide guidance for researchers as well as for clinicians. First of all, standardized and clinically feasible measurement protocols, as well as normative values and predictive equations across the spectrum of impaired function in COPD, are needed before assessment of skeletal muscle function can become a reality in clinical praxis. This should minimally target the quadriceps muscle; however, depending on the objective of measurements, eg, to determine upper limb muscle function or walking capacity, other muscles could also be tested. Furthermore, even though muscle strength measurements are important, current evidence suggests that other aspects, such as the endurance and power capacity of the muscle, should also be considered. Moreover, although static (isometric) measurements have been favored, dynamic measurements of skeletal muscle function should not be neglected as they, in a larger extent than static measurements, are related to tasks of daily living. Lastly, the often modest relationships between functional tests and skeletal muscle function measurements indicate that they evaluate different constructs and thus cannot replace one another. Therefore, for accurate measurements of skeletal muscle function in people with COPD, specific and formal measurements should still be prioritized.

Effectiveness of water-based Liuzijue exercise on respiratory muscle strength and peripheral skeletal muscle function in patients with COPD

Objects

The purpose of this study was to quantitatively assess the effects of water-based Liuzijue exercise on patients with COPD and compare it with land-based Liuzijue exercise.

Materials and methods

Participants were randomly allocated to one of three groups: the water-based Liuzijue exercise group (WG), the land-based Liuzijue exercise group (LG), and the control group (CG). CG participants accepted no exercise intervention, while training groups performed Liuzijue exercise according to Health Qigong Liuzijue (People's Republic of China) in different environments for 60-min sessions twice a week for 3 months.

Results

Of the 50 patients enrolled, 45 (90%) completed the 3-month intervention. The CG showed decreased expiratory muscle strength, extensor and flexor endurance ratio (ER) of the elbow joints and flexor peak torque (PT), total work (TW), and ER of the knee joints (p<0.05). Both training groups showed improved respiratory muscle strength, which differed from the CG (p<0.001). In addition, extensor and flexor TW of the elbow joints in the training groups were increased (p<0.01), and the WG differed from the CG in extensor TW and ER and flexor TW (p<0.01), while the LG differed from the CG in flexor TW and extensor ER (p<0.05). PT, PT/body weight (BW), and TW in the knee joint extensor in the training groups were increased as well (PT and PT/BW: p<0.05, TW: p<0.01), and the WG differed from the CG in terms of knee joints outcomes, while the LG differed from the CG in flexor TW only (p<0.05).

Conclusion

Water-based Liuzijue exercise has beneficial effects on COPD patients' respiratory muscle strength and peripheral skeletal muscle function, and additional benefits may exist in endurance of upper limbs and strength and endurance of lower limbs when compared with land-based Liuzijue exercise.

Effects of simple long-term respiratory care strategies in older men with COPD

OBJECTIVE

To evaluate a 24-month supervised, community-based maintenance exercise program after 3 months of pulmonary rehabilitation (PR) in comparison with a 27-month physical activity counseling program, in terms of the effects on maximal muscle strength, muscle power output, and exercise capacity, in individuals with COPD.

METHODS

Sixty-three men with moderate-to-severe COPD were recruited from two previous studies. Of those 63 participants, 31 were offered 3 months of PR followed by a 24-month supervised maintenance exercise program (24MME group) and 32 were offered a 27-month physical activity counseling program (27MPAC group). Measurements at 3 months and at the end of the study period included maximal strength of the upper and lower limbs, power output of the lower limbs, six-minute walk distance (6MWD), and quality of life.

RESULTS

At 27 months, the improvements in maximal strength of the upper and lower limbs were greater in the 24MME group than in the 27MPAC group (37.6 ± 28.3% and 28.4 ± 13.3%, respectively, vs. 8.8 ± 16% and 13.6 ± 16.4%, respectively; p < 0.05), as was the improvement in power output of the lower limbs (24.6 ± 18.4% vs. -2.3 ± 28.5%; p < 0.01). The increase in the 6MWD after 3 months was also greater in the 24MME group than in the 27MPAC group (33.2 ± 36.6 m vs. 2.9 ± 34.7 m; p < 0.05), although there were no differences between the two groups in terms of the Δ6MWD at 27 months (vs. baseline).

CONCLUSIONS

A supervised, community-based maintenance program is a successful long-term strategy to preserve the benefits of PR on peripheral muscle function and exercise capacity in individuals with COPD. However, physical activity counseling can maintain maximal muscle strength and exercise capacity in such individuals.