American Journal of Respiratory and Critical Care Medicine

Physical inactivity is common in patients with chronic obstructive pulmonary disease (COPD) compared with age-matched healthy individuals or patients with other chronic diseases. Physical inactivity independently predicts poor outcomes across several aspects of this disease, but it is (at least in principle) treatable in patients with COPD. Pulmonary rehabilitation has arguably the greatest positive effect of any current therapy on exercise capacity in COPD; as such, gains in this area should facilitate increases in physical activity. Furthermore, because pulmonary rehabilitation also emphasizes behavior change through collaborative self-management, it may aid in the translation of increased exercise capacity to greater participation in activities involving physical activity. Both increased exercise capacity and adaptive behavior change are necessary to achieve significant and lasting increases in physical activity in patients with COPD. Unfortunately, it is readily assumed that this translation occurs naturally. This concise clinical review will focus on the effects of a comprehensive pulmonary rehabilitation program on physical activity in patients with COPD. Changing physical activity behavior in patients with COPD needs an interdisciplinary approach, bringing together respiratory medicine, rehabilitation sciences, social sciences, and behavioral sciences.

“Lack of activity destroys the good condition of every human being, while movement and methodical physical exercise save it and preserve it.” This frequently quoted phrase (13), attributed to Plato, tells us that the association between physical inactivity and poor outcome, including the beneficial effects of its treatment, has been known since antiquity. More recently, the World Health Organization noted that physical inactivity, which is unfortunately present in 1 of 3 adults (4), is among the 10 leading risk factors for death worldwide (5). The importance of a focus on the problem of physical inactivity in chronic obstructive pulmonary disease (COPD) is based on several factors: (1) COPD is a major public health problem that is highly prevalent (6), and is currently the third leading cause of death worldwide (7); (2) physical inactivity appears to be more common in patients with COPD compared with age-matched healthy individuals (8) or even patients with other chronic diseases (e.g., coronary artery disease or rheumatoid arthritis) (9); (3) physical inactivity independently predicts poor outcomes across several aspects of this disease (10, 11); (4) physical inactivity (at least in principle) is treatable in patients with COPD (12), although a causal link between increases in physical activity and improvements in health outcome has not been established (13); (5) physical activity substantially decreases over time in patients with COPD and to a greater extent than in non-COPD subjects (11); (6) a sustained low level of physical activity over time is associated with an accelerated progression of exercise intolerance and muscle depletion (14); and (7) clinicians may underappreciate the importance of physical inactivity in their respiratory patients.

This concise clinical review will first cover the definition of physical activity (which is a different construct than exercise capacity), its prevalence and significance in COPD, its objective measurement, risk factors for physical inactivity, and potential ways to improve or maintain one or more components of physical fitness. Pulmonary rehabilitation has arguably the greatest positive effect of any current therapy on exercise capacity in COPD (15). As such, gains in this area should facilitate increases in physical activity. Furthermore, because pulmonary rehabilitation also emphasizes behavior change through collaborative self-management, it may aid in the translation of increased exercise capacity to greater participation in activities involving physical activity. Accordingly, the second part of this review will focus on the effects of this comprehensive intervention on this important outcome.

The 2013 Statement on Pulmonary Rehabilitation from the American Thoracic Society (ATS) and European Respiratory Society (ERS) defines pulmonary rehabilitation as “a comprehensive intervention based on a thorough patient assessment followed by patient-tailored therapies, which include, but are not limited to, exercise training, education, and behavior change, designed to improve the physical and psychological condition of people with chronic respiratory disease and to promote the long-term adherence of health-enhancing behaviors” (16). This definition clearly states that optimization of functional status and increased participation are prominent goals for this intervention. Physical activity is a prominent component of functional status. Participation, which is an important aspect of quality of life, indicates the abandonment of a sedentary, home-bound lifestyle for a more active involvement in activities of daily living. Exercise training and collaborative self-management education, which are integral components of comprehensive pulmonary rehabilitation (17), both directly and indirectly promote physical activity and participation. Exercise training increases physical exercise tolerance (18), allowing patients to have the capacity to do more things, whereas self-efficacy teaching encourages patients to go out and do more (19).

Although pulmonary rehabilitation has no direct effect on the physiologic derangements in lung function, it provides the greatest improvements in dyspnea, exercise tolerance, and health-related quality of life of any intervention available for patients with chronic respiratory disease (16). It also decreases subsequent healthcare use, especially when provided following an exacerbation of COPD (20). The benefits from pulmonary rehabilitation result from a decrease in the negative effects of comorbidities (e.g., physical deconditioning resulting from sedentary behavior and reductions in anxiety and depression) and from enhanced self-efficacy (e.g., the early recognition and appropriate treatment of exacerbation of COPD) (21).

Physical activity can be defined as “any bodily movement produced by skeletal muscles that results in energy expenditure” (22, 23). Therefore, physical activity in daily life can be considered as “the totality of voluntary movement produced by skeletal muscles during every day functioning” (24, 25) and is assessed by the quantification of this totality of movements during daily life. In distinction, exercise is “a subset of physical activity that is planned, structured, repetitive and purposeful” (22) and has its own assessment methods (e.g., maximal and submaximal exercise tests) (26, 27). Physical activity is a complex behavior influenced by a combination of individual, sociocultural, and environmental factors (23). It can be characterized by type, intensity, duration, patterns, routines, and activity-related symptoms (28). Types of physical activity include, but are not limited to, leisure time, domestic, and occupational activities (29). Activities of daily living refers to a subset of physical activity that encompasses basic, everyday tasks required for personal self-care and independent living (29, 30). Performance of activities of daily living has its own assessment methods, such as specific activities of daily living questionnaires and functional tests (3135).

Questionnaires and motion sensors are the more commonly used assessment methods to quantify physical activity in patients with COPD (36). Despite their widely recognized usefulness, questionnaires are prone to inaccuracy when used on an individual level (23). Motion sensors, which are small devices worn on the body to detect movement, and therefore, are used to quantify physical activity over a period of time, are becoming increasingly available. These devices include pedometers (step counters) and accelerometers (detection of body acceleration). Pedometers quantify steps in a given period (despite a considerable misdetection in slow-walking subjects) (3740), provide a rough estimate of energy expenditure, and can also be successfully used as a motivational tool to increase physical activity (4143). Accelerometers have the advantage of being more sensitive to detection of physical activity differences in inactive and slowly moving individuals, and are more accurate and sensitive to light activities (25). Different devices provide a variety of outcomes, such as time spent above a certain intensity threshold (e.g., moderate or vigorous physical activity), time spent in sedentary behavior, average metabolic equivalent of task, physical activity level index, vector magnitude units, and/or energy expenditure estimation. Output from the various types of accelerometers varies considerably, making it difficult to compare devices (44).

Patients with COPD have significantly lower levels of daily physical activity compared with healthy control subjects; they spend significantly less time walking, walk at a lower intensity than their healthy counterparts, and most do not meet current recommendations for levels of physical activity (8, 4552). Physical inactivity is not only a feature of advanced COPD; it is already reduced in subjects with a new spirometry-based diagnosis of mild or moderate COPD (53), even preceding the onset of breathlessness (54).

Physical activity in patients with COPD is dependent on many factors, including physiologic, behavioral, social, environmental, and cultural factors. See Watz and colleagues for all details about factors associated with physical activity in patients with COPD (23). In brief, daily physical activity is only weakly associated with post-bronchodilator FEV1 (23). However, there is a strong inverse association between daily physical activity and dynamic hyperinflation (55), which correlates strongly with exertional dyspnea in COPD (56). In contrast to resting lung function testing, performance on lower limb muscle function tests and (field) exercise tests correlates better with physical activity in COPD (27, 50, 57, 58). Daily symptoms (i.e., dyspnea and fatigue) are associated with lower physical activity levels in patients with COPD (45, 50, 59). Impaired health status is weakly-to-moderately related to physical activity in patients with COPD (50, 6063). Interestingly, this association was confirmed in a 5-year longitudinal observational study that showed that a decline in physical activity was associated with a decline in health status in patients with COPD (64). Self-efficacy (i.e., individuals’ belief in their capacity to execute behaviors necessary to produce specific outcomes [65]) is only weakly associated with daily physical activity in patients with COPD (60, 66, 67). In addition, sociodemographic and environmental factors all have the potential to influence daily physical activity among patients with COPD (6875). Physical activity levels may also be influenced by the day of the week, with activity lower on weekends compared with weekdays (28, 45, 76). Exacerbations clearly reduce physical activity levels in patients with COPD (77, 78), in particular, in very severe exacerbations that necessitate hospitalization (79, 80). Medical comorbidities may also independently or synergistically affect physical activity levels (50, 51, 59, 61, 8188).

Physical activity levels predict important outcomes in COPD. Lower physical activity levels are associated with a higher risk of an exacerbation-related hospitalization (79, 8994). In addition to baseline levels of physical activity predicting COPD-related hospitalization, a decline in physical activity over time also predicts this outcome, also after adjustment for age, FEV1, and previous hospitalizations (95). Lower physical activity levels also increase the risk of all-cause mortality in patients with COPD after controlling for relevant confounding factors (10, 93, 94). A decline in physical activity over time also predicts mortality (11). Reflecting these strong associations, physical activity has been included as a factor in multidimensional prognostic scores for all-cause and respiratory mortality (96) or exacerbations and COPD-related hospitalization in patients with stable COPD (97). These outcome studies underscore the importance of promoting physical activity in the earliest stages of COPD, with a goal of more than 2 hours per week.

The cornerstones of pulmonary rehabilitation are exercise training and education, which are aimed at behavior change through promoting self-efficacy (21). For pulmonary rehabilitation to have its greatest long-term impact, the increases in exercise capacity demonstrated in the rehabilitation center would ideally translate into increases in physical activity in the home and community settings (16). Both exercise capacity increase and adaptive behavior change are necessary to achieve significant and lasting increases in daily physical activity in patients with COPD (Figure 1). Unfortunately, it is readily assumed that this translation occurs naturally. Twelve studies have evaluated the effects of pulmonary rehabilitation on physical activity and have had inconsistent results.

Positive Studies

In a randomized controlled trial, Sewell and colleagues (98) compared the effects of two approaches to exercise training on physical activity in 180 patients with COPD. Physical activity was measured over 2 consecutive days using an activity monitor (Z80-32k V1 Int; Gaewiler Electronics; Hombrechtikon, Switzerland). The pulmonary rehabilitation (7 wk, 2 sessions/wk) consisted of a weekly 1-hour session of supervised aerobic training and a weekly 1 hour of supervised circuit training exercises, and twice weekly educational sessions. The circuit training differed between groups; there was either a conventional program of general strengthening exercises or a program of goal-directed exercise based on problematic daily activities. Exercise performance, performance of problematic daily activities, and health status all improved significantly compared with baseline. Physical activity expressed as total activity counts increased significantly after both interventions, without any difference between groups. This study was the first to demonstrate that directly measured physical activity improved after pulmonary rehabilitation. However, in a secondary analysis, the authors reported that the response in physical activity might be susceptible to seasonal variation, with the best results in the winter (75).

Mercken and colleagues (99) evaluated the effects of an 8-week inpatient pulmonary rehabilitation program on physical activity in 11 patients with moderate-to-very severe COPD. Physical activity was measured over 9 consecutive days using an uniaxial accelerometer (Physical Activity Monitor AM 100; Pam BV, Oosterbeek, the Netherlands). The pulmonary rehabilitation (8 wk, 5 sessions/wk) consisted of exercise training of the upper and lower extremities (aerobic and strength exercise training, education, and when appropriate, psychosocial and behavioral interventions. Exercise performance and exercise-induced oxidative stress improved significantly compared with baseline. Physical activity (measurement unit was not reported) increased significantly compared with baseline.

Walker and colleagues (51) evaluated the effects of an 8-week outpatient pulmonary rehabilitation program on physical activity in 24 patients with moderate-to-very severe COPD. Physical activity was measured over 7 consecutive days using an accelerometer (Dynaport Activity Monitor; McRoberts BV, The Hague, the Netherlands). The pulmonary rehabilitation (8 wk, 2 supervised sessions/wk, 1 unsupervised session/wk) consisted of exercise training of the upper and lower extremities (aerobic and strength exercise training), and educational sessions. Lower limb muscle function, exercise performance, performance of problematic daily activities, symptoms of anxiety and depression, and health status all improved significantly compared with baseline. Physical activity expressed as a percentage of time spent mobile, mean activity score (×103 counts/h), or as mean intensity of activity score (×103 counts/h) also increased significantly compared with baseline. Improvement in leg activity counts was positively correlated with baseline lung function; those with better pulmonary function had greater increases in activity after rehabilitation. Interestingly, changes in physical activity were not significantly related to changes in muscle strength or walking distance, although these variables improved with pulmonary rehabilitation. This discord in outcomes points to the influence of other components of pulmonary rehabilitation, such as promoting self-efficacy, in achieving positive outcome in physical activity.

Negative Studies

Steele and colleagues (100) assessed the effects of an 8-week, hospital-based, outpatient pulmonary rehabilitation program in 41 patients with mild-to-very-severe COPD. Physical activity was measured 5 days before entry into the pulmonary rehabilitation program and during the final week of the program using a triaxial accelerometer (RT3; Stay Healthy Inc., Monrovia, CA). The pulmonary rehabilitation (8 wk, 2 sessions/wk) was not described in detail. Changes in exercise performance have not been reported. Physical activity expressed as vector magnitude units per minute differed between a preprogram non-exercise day and a supervised exercise day in the last week of the pulmonary rehabilitation program. Nevertheless, physical activity did not change significantly when pre- and post-program nonexercising days were compared or for the full 5 days of activity assessment.

Coronado and colleagues (52) assessed the effects of 3-week inpatient pulmonary rehabilitation program in 15 patients with mild-to-very-severe COPD. Physical activity was measured on the first and last day of the pulmonary rehabilitation program using an uniaxial accelerometer (The Self-Contained Activity Monitor, ADXL05; Analog Devices, Norwood, MA). The pulmonary rehabilitation (3 wk, 6–7 sessions/wk) consisted of exercise training (aerobic and strengthening exercises) and outdoor walking. Lower limb muscle function, exercise performance, mood status, and health status increased significantly. The percentage of total time spent in medium-intensity activity increased significantly compared with baseline, but did not remain after exclusion of training periods.

Dallas and colleagues (39) evaluated the effects of a 6- to 12-week, hospital-based outpatient pulmonary rehabilitation program on physical activity in 54 patients with severe COPD. Physical activity was measured over 7 consecutive days using a pedometer (NL-2000 Activity Monitor; New Lifestyles Inc., Lees Summit, MO) during the first and last week of the pulmonary rehabilitation program. The pulmonary rehabilitation (6–12 wk, 2–3 sessions/wk) consisted of exercise training of the upper and lower extremities (aerobic and strengthening exercises), educational sessions, and psychosocial support. Symptoms, exercise performance, and health status all improved significantly compared with baseline. Physical activity level expressed in pedometer counts per hour did not change.

Saunders and colleagues (101) assessed the effects of seven pulmonary rehabilitation programs (community-based or hospital-based) on physical activity in 294 patients with moderate-to-severe COPD. Physical activity was measured over 7 consecutive days using a step counter (Yamax Digiwalker, Warminster, PA). The pulmonary rehabilitation (6–12 wk, 2–3 sessions/wk) consisted of exercise training (aerobic and strengthening exercises) and educational sessions. Changes in exercise performance were not reported. Physical activity level expressed in steps per day did not change.

Mador and colleagues (102) evaluated the effects of an 8-week pulmonary rehabilitation program on physical activity in 24 patients with moderate-to-severe COPD. Physical activity was measured over 7 consecutive days using a triaxial accelerometer (RT3; Stay Healthy Inc.). The pulmonary rehabilitation (8 wk, 3 sessions/wk) consisted of calisthenics (with and without weights), ergometry cycling, treadmill walking, and multidisciplinary educational sessions. Lower limb muscle function, exercise performance, and health status all improved significantly compared with baseline. Physical activity level expressed in vector magnitude units per minute did not change.

Mixed-Result Studies

Pitta and colleagues (103) studied the impact of a 12- to 24-week, hospital-based outpatient pulmonary rehabilitation program on physical activity in 41 patients with severe COPD. Physical activity was measured over 5 consecutive weekdays using an accelerometer (Dynaport Activity Monitor; McRoberts BV). The pulmonary rehabilitation (12 wk, 3 sessions/wk, followed by 12 wk, 2 sessions/wk) consisted of supervised exercise training (endurance/strengthening exercises), educational sessions, and visits for support and/or counseling with a pulmonary physician, a nutritionist, a psychologist, an occupational therapist, a respiratory nurse, and a social assistant. Symptoms, lower limb muscle function, exercise performance, performance of problematic daily activities, and health status were significantly better at 12 and 24 weeks compared with baseline. Mean walking time was only significantly better after 24 weeks, not at 12 weeks. Mean movement intensity during walking was significantly better at 12 and 24 weeks after compared with baseline. The time spent standing, sitting, and lying down, and the number of blocks of continuous walking done per day did not change.

Demeyer and colleagues (104) evaluated the effects of a similar pulmonary rehabilitation program as Pitta and colleagues (103) on physical activity in 57 patients with moderate-to-severe COPD. Physical activity was measured over 7 consecutive days using a biaxial accelerometer (Sensewear Pro Armbands; BodyMedia, Inc., Pittsburgh, PA). The possible change in exercise performance was not described. The number of steps per day increased significantly 12 weeks after baseline (with 4–7 d of measurement), whereas time spent in at least moderate physical activity or the mean metabolic equivalents of task level did not change.

Egan and colleagues (105) studied the short-term improvements in physical activity in 47 patients with severe COPD after a 7-week, hospital-based outpatient pulmonary rehabilitation program. Physical activity was measured over 5 consecutive days using a biaxial accelerometer (Sensewear Pro Armbands; BodyMedia, Inc.). The pulmonary rehabilitation (7 wk, 2 sessions/wk, with a recommended 3 further days of 30 min of moderate intensity exercise) consisted of a progressive exercise circuit (strength/flexibility/endurance), multidisciplinary interactive educational sessions, and home inspiratory muscle training program. Symptoms, exercise performance, and health status all improved significantly compared with baseline. Total energy expenditure decreased significantly compared with baseline, whereas there was no change in the average number of daily steps, time spent sedentary, or time spent in active exercise.

In summary, a randomized controlled trial comparing the effects of a pulmonary rehabilitation program on daily physical activity with “usual care” in patients with COPD is lacking. Most studies were noncontrolled, small-sized, and observational. All pulmonary rehabilitation programs consisted of a supervised exercise training program and educational (multidisciplinary) sessions. Only a few also contained psychological counseling, occupational therapy, and dietary counseling. Interestingly, exercise performance improved significantly after pulmonary rehabilitation in all studies (if reported), whereas physical activity did not. This suggests a differing trajectory in exercise and activity outcomes. An editorial writer, who commented on the differing trajectories, quipped insightfully, “one needs 3 months to train the muscle, but 6 months to train the brain” (106).

Although pulmonary rehabilitation improves exercise performance in patients with COPD (107), this is not always accompanied by an increase in physical activity in daily life (108). The reasons for this are not clear, because a comprehensive pulmonary rehabilitation program arguably contains the necessary ingredients to improve physical activity in patients with COPD (Figure 1).

Because self-reported physical activity is unreliable (109), attention has focused on using physical activity monitors in patients with COPD (76, 110112). Pedometers, which are insensitive to detecting activity in slowly moving individuals with COPD, have had negative results (39); more sensitive motion detectors, such as triaxial accelerometers, are more likely to detect changes in activity (103).

The choice of physical activity outcome assessment may determine the success or failure of the pulmonary rehabilitation program’s demonstrable effect on the physical activity. Most COPD trials have focused on the impact of pulmonary rehabilitation on the total number of steps per day, walking time, and/or the time spent in moderate to vigorous intensity (108). Demeyer and colleagues reported a significant increase in steps per day following a 3-month outpatient pulmonary rehabilitation program, which was not accompanied by increases in metabolic equivalents or time spent in moderate- or high-intensity physical activity (104).

In some of the observational studies, physical activity was measured while patients were already/still participating in the pulmonary rehabilitation program (39, 52, 100). Preferably, physical activity should be measured in free-living conditions before and after a pulmonary rehabilitation program (not during). This will increase the validity of the findings.

Patients with COPD do not appear to increase the amount of time in moderate-to-vigorous intense activities after pulmonary rehabilitation (104), but they can still adopt a more active lifestyle, through engaging in leisure activities or doing more domestic household activities (98). Therefore, we may need to transition our thinking from “physical activity” to “active living.” This concept includes leisure, occupational, and household activities, as well as active transportation (walking and bicycling) (113), most of which many may not be detected by the currently available physical activity measurements. In addition, it is important to better understand physical activity patterns. Which is more important: more time spent in higher intensity physical activity or less time spent in a sedentary state? This latter approach is in line with the philosophy of Sparling and colleagues, who argue that a reduction in sedentary time and an increase in light activities may prove more realistic and pave the way to more intense exercise in older adults than just focusing on moderate to vigorous intense physical activities (114). Even a slight increase in physical activity in the most sedentary subjects may have significant health benefits (Figure 1) (115).

The duration and content of pulmonary rehabilitation services, which vary widely among pulmonary rehabilitation trials, may explain some of the variance in change in physical activity (17). This is brought out in the results of the previously described study by Pitta and colleagues (103). Moreover, the differences in behavior change strategies among centers may also explain some of this variance (116). For example, a pulmonary rehabilitation program, with a lifestyle physical activity counseling program incorporating feedback from a pedometer, increased the number of patients’ steps per day to a greater extent than did pulmonary rehabilitation without this counseling (42). Also, specificity of the exercise training modality seems to play an important role. Twelve weeks of Nordic walking increased walking time and walking intensity in patients with COPD and was still present 6 months after the intervention (117).

Changing a complex health behavior such as physical activity is very difficult, so interventions should be guided by sound theoretical models. This seems lacking in the current pulmonary rehabilitation construct. One of the most commonly applied theories is social cognitive theory (SCT) (118). The “active agent” in SCT is self-efficacy, which is theorized to have both direct and indirect effects on behavior. Although there is evidence of pulmonary rehabilitation programs increasing self-efficacy (19), this is not always the case. It has been empirically demonstrated that the time point at which self-efficacy is measured influences the extent to which it increases or decreases across the intervention period (119). Efficacy expectations assessed at baseline are likely overestimations that are recalibrated in the early stages of the exercise program. Thus, generally weak, but consistent relationships with physical activity may be a function of poor temporal measurement or self-efficacy measures that do not accurately reflect the actual behavior. Because interventions do not appear to be able to change moderate-to-vigorous physical activities in patients with COPD, measures reflecting moderate-to-vigorous physical activities are likely to be weakly related to behavior. A recent self-efficacy enhancing intervention improved light physical activity by approximately 21 minutes per day, as measured by accelerometry. This was substantially greater than two exercise interventions without the efficacy enhancement component (120, 121). Targeting the primary sources of efficacy as integral parts of pulmonary rehabilitation for COPD might bring about important changes in light physical activity that, if maintained, could lead to more intense active living. Other self-regulatory approaches to increasing adherence behavior in older adults hold promise for COPD. For example, higher levels of executive function and use of self-regulatory strategies were associated with greater self-efficacy, which led to greater exercise adherence (122). However, reliance on individual-level approaches to behavior change is unlikely to have potent effects on physical activity. Consideration of how individual factors interact within the social and environmental milieu in which individuals exist is warranted (123). Socioecological variables may also modulate the effect of pulmonary rehabilitation on physical activity (124). These include intrapersonal, interpersonal/cultural, organizational, physical environment, and policy variables (125, 126). For example, walking is related to pedestrian infrastructure and concerns for safety in older adults (127). Moreover, neighbors’ social support and positive neighborhood satisfaction will increase the likelihood of walking (128), whereas a lower socioeconomic status will lower walking activity in older adults (129). Outdoor air quality also needs to be taken into consideration, because physical activity in clean air has larger health benefits compared with physical activity in traffic-related polluted areas (130, 131). To date, neighborhood walkability, and the influence of interpersonal relationships, formal community engagement, and outdoor air quality on physical activity have not been studied in patients with COPD. Several studies do report that COPD patients’ surroundings and transport/finance have been identified as barriers to participation in physical activity (132134). In contrast, health benefits (65%), enjoyment (44%), continuation of an active lifestyle in the past (28%), and functional reasons (i.e., daily activities, transportation, and so on) (26%) have been identified as reasons for patients with COPD to stay/become physically active (133).

Changing physical activity behavior in patients with COPD needs an interdisciplinary approach, bringing together respiratory medicine, rehabilitation sciences, social sciences, and behavioral sciences. This concise clinical review has presented data that patients with COPD are generally very inactive, and that this physical inactivity is detrimental to both quality and quantity of life. Therefore, increased efforts to better understand the determinants of physical activity, as well as effective strategies to improve this variable, must be a prominent goal in pulmonary rehabilitation. Physical activity is now listed as one of the main outcome measures of pulmonary rehabilitation programs by the ATS/ERS Official Statement on Pulmonary Rehabilitation (107). Despite this, only a minority of healthcare professionals have identified physical activity as one of the main outcomes of pulmonary rehabilitation (33.5% in Europe; and 21.9% in North America) (17).

Future research in this area should include both advancing the science and optimizing patients’ treatment. The following are suggested areas to focus on:

The science:

1.

The potential disease-modifying effects of increased physical activity (light/moderate/vigorous intensity) in patients with COPD;

2.

The determinants of physical activity (light/moderate/vigorous intensity) in patients with COPD;

3.

Self-management strategies that best promote physical activity (light/moderate/vigorous intensity), including long-term increases in activity;

4.

The interaction of pharmacological and non-pharmacological interventions on physical activity (light/moderate/vigorous intensity);

5.

The relationship between changes in the traditional outcomes of pulmonary rehabilitation (exercise capacity, dyspnea, and functional and health status) and changes in physical activity (light/moderate/vigorous intensity);

6.

The best instruments to measure physical activity in clinical practice (light/moderate/vigorous intensity);

7.

The minimal important difference for physical activity measures, as they relate to health status, healthcare use, and mortality (light/moderate/vigorous intensity); and

8.

Randomized, adequately powered, controlled trials that evaluate whether increases in physical activity resulting from the therapeutic intervention lead to improvements in health outcome, including healthcare use and mortality. This would establish the needed causality link.

The patient:

1.

Introduce physical activity early on in the pulmonary rehabilitation curriculum and incorporate it as a standard outcome measure;

2.

Tailor physical activity to the individual patient, taking into account exercise capacity, morbidities and/or disabilities, home and community environment, and behavioral and cultural factors;

3.

Focus on resumption of exercise and physical activity after an exacerbation of COPD, including establishing realistic goals and maintaining support by the professional team; and

4.

Maintain and foster ongoing lines of communication among the patient and the healthcare team to detect changes in the patient’s condition that interfere with ongoing exercise and activity, thereby allowing for an early intervention.

The authors thank the anonymous reviewers for their excellent suggestions.

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Correspondence and requests for reprints should be addressed to Martijn A. Spruit, Ph.D., P.T., Department of Research and Education, CIRO, Hornerheide 1, 6085 NM Horn, the Netherlands. E-mail:

Author Contributions: M.A.S., F.P., E.M., R.L.Z., and L.N. all contributed to the conception and design of this work; they all participated in writing, revising, and approving the manuscript; and they are in agreement as to the integrity of the work and the contributions of all the authors.

CME will be available for this article at www.atsjournals.org

Originally Published in Press as DOI: 10.1164/rccm.201505-0929CI on July 10, 2015

Author disclosures are available with the text of this article at www.atsjournals.org.

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