Understanding the effectiveness of different exercise training programme designs on V̇O2peak in COPD: a component network meta-analysis.

Pulmonary rehabilitation programmes including aerobic training improve cardiorespiratory fitness in patients with COPD, but the optimal programme design is unclear. We used random effects additive component network meta-analysis to investigate the relative effectiveness of different programme components on fitness measured by V̇O2peak in COPD. The included 59 studies involving 2191 participants demonstrated that V̇O2peak increased after aerobic training of at least moderate intensity with the greatest improvement seen following high intensity training. Lower limb aerobic training (SMD 0.56 95% CI 0.32;0.81, intervention arms=86) and the addition of non-invasive ventilation (SMD 0.55 95% CI 0.04;1.06, intervention arms=4) appeared to offer additional benefit but there was limited evidence for effectiveness of other exercise and non-exercise components.

Neuromuscular electrostimulation for adults with chronic obstructive pulmonary disease.

BACKGROUND: In people with chronic obstructive pulmonary disease (COPD), the use of neuromuscular electrostimulation (NMES) either alone, or together with conventional exercise training, might improve the condition of the peripheral muscles, increase exercise capacity and functional performance, reduce symptoms and improve health-related quality of life (HRQoL). OBJECTIVES: To determine the effects of NMES, applied in isolation or concurrently with conventional exercise training to one or more peripheral muscles, on peripheral muscle force and endurance, muscle size, exercise capacity, functional performance, symptoms, HRQoL and adverse events in people with COPD. SEARCH METHODS: We searched the Cochrane Airways Group Specialised Register, the Physiotherapy Evidence Database, clinical trial registries and conference abstracts on 14 March 2018. SELECTION CRITERIA: Randomised controlled trials that recruited adults with COPD if they had compared outcomes between a group that received NMES and a group that received usual care or compared outcomes between a group that received NMES plus conventional exercise training and a group that participated in conventional exercise training alone. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed risk of bias using the Cochrane 'Risk of bias' tool. We expressed continuous data as either the standardised mean difference (SMD) or mean difference (MD) with the corresponding 95% confidence interval (CI). We assessed the quality of evidence using the GRADE approach. MAIN RESULTS: Nineteen studies met the inclusion criteria of which 16 contributed data on 267 participants with COPD (mean age 56 to 76 years and 67% were men). Of these 16 studies, seven explored the effect of NMES versus usual care and nine explored the effect of NMES plus conventional exercise training versus conventional exercise training alone. Six studies utilised sham stimulation in the control group. When applied in isolation, NMES produced an increase in peripheral muscle force (SMD 0.34, 95% CI 0.02 to 0.65; low-quality evidence) and quadriceps endurance (SMD 1.36, 95% CI 0.59 to 2.12; low-quality evidence) but the effect on thigh muscle size was unclear (MD 0.25, 95% CI -0.11 to 0.61; low-quality evidence). There were increases in six-minute walk distance (6MWD) (MD 39.26 m, 95% CI 16.31 to 62.22; low-quality evidence) and time to symptom limitation exercising at a submaximal intensity (MD 3.62 minutes, 95% CI 2.33 to 4.91). There was a reduction in the severity of leg fatigue on completion of an exercise test (MD -1.12 units, 95% CI -1.81 to -0.43). The increase in peak rate of oxygen uptake (VO2peak) was of borderline significance (MD 0.10 L/minute, 95% CI 0.00 to 0.19).For NMES with conventional exercise training, there was an uncertain effect on peripheral muscle force (SMD 0.47, 95% CI -0.10 to 1.04; very low-quality evidence) and there were insufficient studies to undertake a meta-analysis on the effect on quadriceps endurance or thigh muscle size. However, there was an increase in 6MWD in favour of NMES combined with conventional exercise training (MD 25.87 m, 95% CI 1.06 to 50.69; very low-quality evidence). In people admitted to either in an intensive care unit or a respiratory high dependency centre, NMES combined with conventional exercise reduced the time taken for participants to first sit out of bed by 4.98 days (95% CI -8.55 to -1.41; very low-quality evidence), although the statistical heterogeneity for this analysis was high (I2 = 60%). For both types of studies (i.e. NMES versus usual care and NMES with conventional exercise training versus conventional exercise training alone), there was no risk difference for mortality or minor adverse events in participants who received NMES. AUTHORS' CONCLUSIONS: NMES, when applied in isolation, increased quadriceps force and endurance, 6MWD and time to symptom limitation exercising at a submaximal intensity, and reduced the severity of leg fatigue on completion of exercise testing. It may increase VO2peak, but the true effect on this outcome measure could be trivial. However, the quality of evidence was low or very low due to risk of bias within the studies, imprecision of the estimates, small number of studies and inconsistency between the studies. Although there were no additional gains in quadriceps force with NMES plus conventional exercise training, there was evidence of an increase in 6MWD. Further, in people who were the most debilitated, the addition of NMES may have accelerated the achievement of a functional milestone, that is, the first time someone sits out of bed.

The effects of exercise modality and intensity on energy expenditure and cardiorespiratory response in adults with obesity and treated obstructive sleep apnoea.

To inform recommendations for the exercise component of a healthy lifestyle intervention for adults with obesity and treated obstructive sleep apnoea (OSA), we investigated the total energy expenditure (EE) and cardiorespiratory response to weight-supported (cycling) and unsupported (walking) exercise. Individuals with treated OSA and a body mass index (BMI) > 30 kg/m2 performed an incremental cardiopulmonary exercise test on a cycle ergometer and a treadmill to determine the peak oxygen uptake [Formula: see text]. Participants subsequently completed two endurance tests on each modality, matched at 80% and 60% of the highest [Formula: see text] determined by the incremental tests, to intolerance. The cardiorespiratory response was measured and total EE was estimated from the [Formula: see text]. Sixteen participants completed all six tests: mean [SD] age 57 [13] years and median [IQ range] BMI 33.3 [30.8-35.3] kg/m2. Total EE during treadmill walking was greater than cycling at both high (158 [101] vs. 29 [15] kcal; p < 0.001) and moderate (178 [100] vs. 85 [59] kcal; p = 0.002) intensities, respectively, with similar cardiorespiratory responses and pattern of EE during rest, exercise and recovery. Contrary to current guidelines, walking might be the preferred training modality to achieve the combination of weight loss and increased cardiorespiratory fitness in adults with obesity and treated OSA.

Comparing peak and submaximal cardiorespiratory responses during field walking tests with incremental cycle ergometry in COPD.

BACKGROUND AND OBJECTIVE: Field and laboratory-based tests are used to measure exercise capacity in people with COPD. A comparison of the cardiorespiratory responses to field tests, referenced to a laboratory test, is needed to appreciate the relative physiological demands. We sought to compare peak and submaximal cardiorespiratory responses to the 6-min walk test, incremental shuttle walk test and endurance shuttle walk test with a ramp cycle ergometer test (CET) in patients with COPD. METHODS: Twenty-four participants (FEV(1) 50 ± 14%; 66.5 ± 7.7 years; 15 men) completed four sessions, separated by ≥24 h. During an individual session, participants completed either two 6-min walk tests, incremental shuttle walk tests, endurance shuttle walk tests using standardized protocols, or a single CET, wearing a portable gas analysis unit (Cosmed K4b(2)) which included measures of heart rate and arterial oxygen saturation (SpO(2)). RESULTS: Between tests, no difference was observed in the peak rate of oxygen uptake (F(3,69) = 1.2; P = 0.31), end-test heart rate (F(2,50) = 0.6; P = 0.58) or tidal volume (F(3,69) = 1.5; P = 0.21). Compared with all walking tests, the CET elicited a higher peak rate of carbon dioxide output (1173 ± 350 mL/min; F(3,62) = 4.8; P = 0.006), minute ventilation (48 ± 17 L/min; F(3,69) = 10.2; P < 0.001) and a higher end-test SpO(2) (95 ± 4%; F(3,63) = 24.9; P < 0.001). CONCLUSIONS: In patients with moderate COPD, field walking tests elicited a similar peak rate of oxygen uptake and heart rate as a CET, demonstrating that both self- and externally paced walking tests progress to high intensities.

Rollator use does not consistently change the metabolic cost of walking in people with chronic obstructive pulmonary disease.

OBJECTIVES: To (1) evaluate whether the use of a rollator changed metabolic cost during a controlled walking task, and (2) explore relationships between the difference in dyspnea and metabolic cost associated with rollator use. DESIGN: Single-group interventional study in which patients completed 2 corridor walks: 1 without and 1 with a rollator, at the same individualized constant speed. SETTING: Rehabilitation hospital. PARTICIPANTS: Patients with chronic obstructive pulmonary disease (N=15; 10 men; median age [interquartile range; IQR]=69 [12]y; forced expiratory volume in 1 second=42 [20]% predicted). INTERVENTION: Rollator use. MAIN OUTCOME MEASURES: Oxygen uptake, converted to metabolic equivalent units (METs), and minute ventilation were measured throughout both tasks using a portable gas analysis system; dyspnea and arterial oxygen saturation (SpO(2)) were collected on completion. RESULTS: Median [IQR] walk speed [IQR] was 48 (10)m/min. Walking with a rollator, compared with walking without, reduced dyspnea (median [IQR]=1.0 [1.5] vs 2.0 [2.0]; P=.01) without changing energy expenditure (median [IQR]=2.8 [1.2] vs 3.2 [0.9] METs; P=.65), minute ventilation (median [IQR]=30.3 [9.6] vs 27.7 [9.9]L/min; P=.50), or SpO(2) (median [IQR]=92 [8]% vs 94 [10]%; P=.41). The association between the reduction in dyspnea and any difference in energy expenditure related to rollator use was of borderline significance (r(s)=.50; P=.06). Six of the 8 participants who experienced a reduction in dyspnea also demonstrated a reduction in the metabolic cost of walking. CONCLUSIONS: The mechanism responsible for the amelioration in dyspnea during rollator-assisted walking is multifactorial. A reduction in the metabolic cost of walking may play a part in some, but not all, patients.

Has my patient responded? Interpreting clinical measurements such as the 6-minute-walk test.

To correctly interpret clinical measurements it is necessary to understand the standard deviation and the standard error; the former reflects the range or variability of individuals within a sample and the latter reflects the precision for which the group parameters have been estimated. When evaluating an individual patient, test measurement properties such as repeatability will assist in concluding whether a repeated test, measured to monitor the response to an intervention, has changed beyond its natural variability. Using the "best" test has an inherent bias and ignores the natural test variation, whereas the average of repeated tests is more representative of the true value, making it more discriminative to change. Serial measurements to follow progress will increase a clinician's confidence in the observed effects of treatment.

Chronic obstructive pulmonary disease and socioeconomic status: a systematic review.

BACKGROUND: Along with age and sex, socioeconomic status is one of the most powerful determinants of health. We conducted a systematic review to examine the consistency and magnitude of the association between socioeconomic status and COPD health outcomes to determine the potential impact of SES disparity on the COPD population. METHODS: Electronic databases to October 2011 were searched for studies of adults who had or were at risk for COPD that quantified an association between a measure of socioeconomic status and at least one COPD health outcome. Two authors independently reviewed studies, assessed study quality, and for eligible studies, extracted data. RESULTS: Regardless of the population, socioeconomic status measure or COPD outcome examined, with few exceptions, consistent significant inverse associations between socioeconomic status and COPD outcomes were found. Most studies found that individuals of the lowest socioeconomic strata were at least twice as likely to have poor outcomes as those of the highest (range from no difference to 10-fold difference). CONCLUSIONS: Social and economic disadvantage appears to have a significant consistent impact on COPD mortality and morbidity. These findings point to the need for public health strategies and research to address socioeconomic status disparity in individuals with COPD.

Measurement properties of the SenseWear armband in adults with chronic obstructive pulmonary disease.

RATIONALE: The SenseWear armband (SAB) is designed to measure energy expenditure (EE). In people with chronic obstructive pulmonary disease (COPD), EE estimated using the SAB (EE(SAB)) is a popular outcome measure. However, a detailed analysis of the measurement properties of the SAB in COPD is lacking. OBJECTIVE: To examine the sensitivity of EE(SAB), agreement between EE(SAB) and EE measured via indirect calorimetry (EE(IC)), and its repeatability in COPD. METHODS: 26 people with COPD (forced expiratory volume in 1 s (FEV(1))=49+/-18% predicted; 15 males) spent 6 min in five standardised tasks that comprised supine, sitting, standing and two walking speeds. A subgroup (n=12) walked using a rollator. Throughout each task, measurements of EE(SAB) and EE(IC) were collected. The protocol was repeated on a second day. RESULTS: EE(SAB) increased between standing and slow walking (2.4, metabolic equivalents (METs) 95% CI 2.2 to 2.7) as well as slow and fast walking (0.5 METs, 95% CI 0.3 to 0.7). Considering all tasks together, the difference between EE(SAB) and EE(IC) was -0.2 METs (p=0.21) with a limit of agreement of 1.3 METs. The difference between days in EE(SAB) was 0.0 METs with a coefficient of repeatability of 0.4 METs. Rollator use increased the variability in EE(SAB), compromising its repeatability and agreement with EE(IC). CONCLUSIONS: EE(SAB) was sensitive to small but important changes. There was fair agreement between EE(SAB) and EE(IC), and measurements of EE(SAB) were repeatable. These observations suggest that the SAB is useful for the evaluation of EE in patients with COPD who walk without a rollator.

Interval versus continuous training in individuals with chronic obstructive pulmonary disease--a systematic review.

BACKGROUND: In patients with chronic obstructive pulmonary disease (COPD), interval exercise has gained recent attention as a possible means of achieving greater physiological training effects compared with continuous exercise. The primary aim of this systematic review was to compare the effects of interval versus continuous training on peak oxygen uptake, peak power, 6 minute walk test (6MWT) distance and health-related quality of life in individuals with COPD. METHODS: Randomised controlled trials comparing the effects of interval versus continuous training in patients with COPD were identified after searches of six databases and reference lists of appropriate studies in May 2009. Two reviewers independently assessed study quality. Weighted mean differences (WMD) with 95% CIs were calculated using a random effects model for measures of exercise capacity and health-related quality of life. RESULTS: Eight randomised controlled trials, with a total of 388 patients with COPD, met the inclusion criteria. No significant differences were found for peak power (WMD 1 W, 95% CI -1 to 3) or peak oxygen uptake (WMD -0.04 l/min, 95% CI -0.13 to 0.05) between interval and continuous training. The WMD for the Chronic Respiratory Questionnaire dyspnoea score was -0.2 units (95% CI -0.5 to 0.0). There was no difference in 6MWT distance between groups (WMD 4 m, 95% CI -15 to 23). CONCLUSIONS: Interval and continuous training modalities did not differ in their effect on measures of exercise capacity or health-related quality of life. Interval training may be considered as an alternative to continuous training in patients with varying degrees of COPD severity.

Change in V˙O2peak in Response to Aerobic Exercise Training and the Relationship With Exercise Prescription in People With COPD: A Systematic Review and Meta-analysis.

BACKGROUND: Despite the wide-ranging benefits of pulmonary rehabilitation, conflicting results remain regarding whether people with COPD can improve their peak oxygen uptake (V˙O2peak) with aerobic training. RESEARCH QUESTION: The goal of this study was to investigate the effect of aerobic training and exercise prescription on V˙O2peak in COPD. STUDY DESIGN AND METHODS: A systematic review was performed by using MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature, and Cochrane databases for all studies measuring V˙O2peak prior to and following supervised lower-limb aerobic training in COPD. A random effects meta-analysis limited to randomized controlled trials comparing aerobic training vs usual care was conducted. Other study designs were included in a secondary meta-analysis and meta-regression to investigate the influence of program and patient factors on outcome. RESULTS: A total of 112 studies were included (participants, N = 3,484): 21 controlled trials (n = 489), of which 13 were randomized (n = 288) and 91 were uncontrolled (n = 2,995) studies. Meta-analysis found a moderate positive change in V˙O2peak (standardized mean difference, 0.52; 95% CI, 0.34-0.69) with the intervention. The change in V˙O2peak was positively associated with target duration of exercise session (P = .01) and, when studies > 1 year duration were excluded, greater total volume of exercise training (P = .01). Similarly, the change in V˙O2peak was greater for programs > 12 weeks compared with those 6 to 12 weeks when adjusted for age and sex. However, reported prescribed exercise intensity (P = .77), training modality (P > .35), and mode (P = .29) did not affect V˙O2peak. Cohorts with more severe airflow obstruction exhibited smaller improvements in V˙O2peak (P < .001). INTERPRETATION: Overall, people with COPD achieved moderate improvements in V˙O2peak through supervised aerobic training. There is sufficient evidence to show that programs with greater total exercise volume, including duration of exercise session and program duration, are more effective. Reduced effects in severe disease suggest alternative aerobic training methods may be needed in this population. CLINICAL TRIAL REGISTRATION: PROSPERO; No.: CRD42018099300; URL: https://www.crd.york.ac.uk/prospero/.

Effects of one-legged exercise training of patients with COPD.

BACKGROUND: Most patients with severe COPD are limited by dyspnea and are obliged to exercise at low intensity. Even those undergoing training do not usually have increased peak oxygen uptake (Vo2). One-legged exercise, at half the load of two-legged exercise, places the same metabolic demands on the targeted muscles but reduces the ventilatory load, enabling patients to increase work capacity. The purpose of this study was to determine whether one-legged exercise training would improve aerobic capacity compared with two-legged training in stable patients with COPD. METHODS: Eighteen patients with COPD (mean FEV(1), 38 +/- 17% of predicted [+/- SD]) were randomized to two groups after completing an incremental exercise test. Both trained on a stationary cycle for 30 min, 3 d/wk, for 7 weeks. Two-legged trainers (n = 9) cycled continuously for 30 min, whereas one-legged trainers (n = 9) switched legs after 15 min. Intensity was set at the highest tolerated and increased with training. RESULTS: Both groups increased their training intensity (p < 0.001) and total work (p < 0.001). After training, the change in peak Vo2 of the one-legged group (0.189 L/min; confidence interval [CI], 0.089 to 0.290 L/min; p < 0.001) was greater than that of the two-legged group (0.006 L/min; CI, - 0.095 to 0.106 L/min; p = 0.91). This was accompanied by greater peak ventilation (4.4 L/min; CI, 1.8 to 7.1 L/min; p < 0.01) and lower submaximal heart rate (p < 0.05) and ventilation (p < 0.05) in the one-legged trained group. CONCLUSION: Reducing the total metabolic demand by using one-legged training improved aerobic capacity compared with conventional two-legged training in patients with stable COPD.

Modifying track layout from straight to circular has a modest effect on the 6-min walk distance.

BACKGROUND: The protocol used for the 6-min walk test (6MWT) influences its results. The only study to examine the effect of modifying track layout performed a retrospective analysis and concluded that institutions using continuous tracks yield greater distances than those using straight tracks. Agreement between the distances measured on different tracks could not be examined. We evaluated the effect of modifying track layout on walk distance and examined the agreement and repeatability of distances measured on different tracks. METHODS: In a prospective, randomized, cross-over study, 27 COPD subjects (FEV(1), 38 +/- 14% [mean +/- SD]; 15 men) attended three separate test sessions, completing six 6MWTs. To familiarize all subjects with both tracks, the first two sessions comprised two 6MWTs on either a circular or straight track. During the final session, each subject was tested once on the straight and once on the circular track. RESULTS: The distance walked on the circular track exceeded the straight track by 13 +/- 17 m (p < 0.001). The limit of agreement between tracks was 33 m. Coefficient of repeatability values when the test was completed on different days for the straight and circular tracks were 51 m and 65 m, respectively. CONCLUSIONS: When evaluating changes in 6-min walk distance in groups of patients, track layout should be standardized. However, the effect of modifying track layout on an individual's walking distance is small compared to their daily variability in walk distance. Therefore, standardizing track layout for any given individual may be inconsequential when evaluating the change in distances from tests performed on different days.

Gait Speed: Validity of Measurement in Patients With Severe Chronic Lung Disease, Including Prognostic and Practical Implications.

Gait speed is used increasingly to predict function and future well-being among healthy elderly people as well as for those with long-term medical conditions. When selecting outcome measures such as walking speed, it is important to include the circumstances under which the measurement is made to avoid bias and ensure accurate recommendations. We completed a retrospective chart review of walking test results from patients with chronic lung disease to demonstrate the practical implications of reporting gait speed from either a standing or walking start. In this cohort of 99 patients (55 with COPD), gait speed from a standing start underestimated usual gait speed (difference = 6.1 m/min [5.3-6.9 m/min]) with poor agreement (8 m/min [6.6-9.4 m/min]) between the two methods of reporting speed. The standing start speed incorrectly identified some patients as at higher risk for poor health. In a practical example, gait speed from a standing start produced 11 false-negative evaluations of the ability to complete a road crossing at usual speed. We present walking speeds using both methods, which illustrate the importance of construct validity and measurement protocol.

The Impact of Listening to Music During a High-Intensity Exercise Endurance Test in People With COPD.

BACKGROUND: In people with COPD, dyspnea is the primary symptom limiting exercise tolerance. One approach to reducing dyspnea during exercise is through music listening. A constant speed endurance test reflects a high-intensity aerobic exercise training session, but whether listening to music affects endurance time is unknown. This study aimed to determine the effects of listening to music during a constant speed endurance test in COPD. METHODS: Participants with COPD completed two endurance walk tests, one with and one without listening to self-selected music throughout the test. The primary outcome was the difference in endurance time between the two conditions. Heart rate, percutaneous oxygen saturation, dyspnea, and rate of perceived exertion were measured before and after each test. RESULTS: Nineteen participants (mean [SD]: age, 71 [8] years; FEV1, 47 [19] % predicted) completed the study. Endurance time was greater (1.10 [95% CI, 0.41-1.78] min) while listening to music (7.0 [3.1] min) than without (5.9 [2.6] min), and reduced end-test dyspnea (1.0 [95% CI, -2.80 to -1.80] units) (with music, 4.6 [1.7] units; vs without music, 5.6 [1.4] units, respectively). There was not a significant difference in heart rate, percutaneous oxygen saturation, or leg fatigue. There were no adverse events under either condition. CONCLUSIONS: In COPD, dyspnea was less while listening to music and was accompanied by an increased tolerance of high-intensity exercise demonstrated by greater endurance time. Practically, the effect was modest but may represent an aid for exercise training of these patients. TRIAL REGISTRY: Australian New Zealand Clinical Trials Registry; No. ACTRN12617001217392.

Response to one-legged cycling in patients with COPD.

BACKGROUND: In patients with COPD, exercise intensity is often limited by the ventilatory system. We hypothesized that by exercising with a smaller muscle mass, ventilatory-limited patients would perform more high-intensity, muscle-specific work. The study objectives were as follows: (1) to determine the limitations of exercising with a smaller muscle mass, compared with conventional two-legged exercise; and (2) to determine the endurance time, using the same muscle-specific intensity, during one-legged vs two-legged exercise. METHODS: Nine patients (mean +/- SD FEV1, 36 +/- 13% of predicted) completed incremental exercise, and nine other patients (mean FEV1, 42 +/- 16% of predicted) completed constant-power exercise. Nine healthy subjects (FEV1, 104 +/- 14% of predicted) completed both tests. All subjects completed tests using two-legged and one-legged pedaling. RESULTS: Peak oxygen uptake (VO2peak) was similar during one-legged and two-legged incremental exercise among patients (difference, 0.03 L/min; 95% confidence interval [CI], -0.10 to 0.16 L/min; p = 0.60), as were ventilation and dyspnea scores. VO2peak was lower during one-legged vs two-legged exercise (-0.57 mL/min; 95% CI, -0.81 to -0.32 mL/min; p < 0.001) among healthy subjects with substantial ventilatory and heart rate reserve. Patients endured one-legged pedaling at a constant power longer than two-legged pedaling (16.97 min; 95% CI, 9.98 to 23.96 min; p < 0.001), resulting in greater work (12.48 kilojoules [kJ]; 95% CI, 2.58 to 22.39 kJ; p = 0.02). Healthy subjects completed similar work (-4.02 kJ; 95% CI, -18.59 to 10.55 kJ; p = 0.54) with one-legged vs two-legged pedaling. CONCLUSION: These observations demonstrate the effectiveness of using one-legged exercise at the same muscle-specific intensity in extending the duration of exercise among patients with COPD. This has important implications for training approaches designed to enhance exercise function among ventilatory-limited patients.

Is quadriceps endurance reduced in COPD?: a systematic review.

BACKGROUND: Although the aerobic profile of the quadriceps muscle is reduced in COPD, there is conflicting evidence regarding whether this leads to reduced quadriceps muscle endurance. We, therefore, performed a systematic review of studies comparing quadriceps endurance in individuals with COPD with that in healthy control subjects. METHODS: Relevant studies were identified by searching six electronic databases (1946-2011). Full-text articles were obtained after two researchers independently reviewed the abstracts. The results were combined in a random effects meta-analysis, and metaregression models were fitted to assess the influence of the type of measurement. RESULTS: Data were extracted from 21 studies involving 728 individuals with COPD and 440 healthy control subjects. Quadriceps endurance was reduced in those with COPD compared with healthy control subjects (standardized mean difference, 1.16 [95% CI, 1.02-1.30]; P < .001) with a 44.5 s (4.5-84.5 s; P = .029) reduction in COPD (large effect size) when measured using a nonvolitional technique. The relationship between quadriceps endurance in those with COPD and control subjects did not differ when comparing nonvolitional and volitional techniques (P = .22) or when high- or low-intensity tasks (P = .44) were undertaken. CONCLUSIONS: Quadriceps endurance is reduced in individuals with COPD compared with healthy control subjects, independent of the type of task performed.