COPD Consequences of Physical Inactivity

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735www.expert-reviews.com ISSN 1747-6348 2010 Expert Reviews Ltd

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10.1586/ERS.10.76

Chronic obstructive pulmonary disease (COPD)is a disease characterized by a usually progressiveairow limitation that is not ully reversible, andhas potential signifcant extrapulmonary eects[1]. The symptoms o this debilitating disease

may have huge impact on a patients daily lie.Physical activity is defned as any bodily

movement produced by skeletal muscles thatresults in energy expenditure. Exercise, on theother hand, is physical activity done on purpose,and carried out in a more structured mannerwith the aim o improving cardiorespiratoryor muscular ftness [101]. It is important to dis-tinguish physical activity rom physical ftness,unctional or exercise capacity. The latter threeindicate what a person is capable o doing whilephysical activity reects what someone actually

does. The measurement o physical activity isthereore dierent rom the measurement ophysical ftness, unctional or exercise capac-ity. Physical activity can be measured by directobservation, assessment o energy expenditure(e.g., doubly labeled water technique), diaries,questionnaires and perormance-based motionsensors (e.g., pedometers and accelerometers)[2]. The irst two are time consuming andexpensive and are thereore used less requently.Perormance-based motion sensors objectivelyquantiy the amount o daily physical activ-

ity perormed and is thereore more accurate

as compared with questionnaires and diaries,which depend on a per sons memory andinterpretation.

Regular physical activity improves bodycomposition, autonomic tone, coronary blood

ow, psychological wellbeing, glucose homeo-stasis and insulin sensitivity, enhances lipidlipoprotein profles and endothelial unction,reduces blood pressure and systemic inam-mation, decreases blood coagulation and aug-ments cardiac unction [3]. Physical inactivityis thereore a modifable risk actor or cardio-vascular disease and a variety o other diseasessuch as diabetes mellitus, cancer, hypertensionand dementia [3,4]. The recommended mini-mum amount o physical activity or adultsto promote and maintain physical health is

30 min o moderately intense aerobic physicalactivity at least 5 days a week or 20 min ovigorously intense aerobic physical activity atleast 3 days a week, or an equiva lent combina-tion. Every adult should also perorm muscularstrength and endurance exercises at least 2 dayseach week [5]. For elderly adults (age 65, or50 years with clinically signifcant chronicconditions and/or unctional limitations) it isnecessary to adjust the recommended intensityo aerobic activity to the elderly adults aerobicftness. Moreover, activities that maintain or

increase exibility are recommended next to

Jorine E Hartman1,H Marike Boezen2,Mathieu HG de Greef3,Linda Bossenbroek1

and Nick HTten Hacken1

1Department of Pulmonary Medicine,

University Medical Centre Groningen,

University of Groningen,

The Netherlands2Department of Epidemiology,

University Medical Centre Groningen,

University of Groningen,

The Netherlands3Department of Human Movement

Sciences, University Medical Centre

Groningen, University of Groningen,

The NetherlandsAuthor for correspondence:

University Medical Centre Groningen,Department of Pulmonary Medicine,

Internal mail address: AA11,

PO Box 30.001, 9700 RB Groningen,

The Netherlands

Tel.: +31 503 614 914

Fax: +31 503 619 320

[email protected]

The many health benets o regular physical activity underline the importance o this topic,especially in this period o time when the prevalence o a sedentary liestyle in the populationis increasing. Physical activity levels are especially low in patients with chronic obstructivepulmonary disease (COPD). Regular physical activity and an active liestyle has shown to bepositively associated with outcomes such as exercise capacity and health-related quality o lie,and thereore could be benecial or the individual COPD patient. An adequate level o physicalactivity needs to be integrated into daily lie, and stimulation o physical activity when absentis important. This article aims to discuss in more detail the possible role o regular physical activityor a number o well-known outcome parameters in COPD.

Keywords: COPD health benefts physical activity physical activity stimulation

Consequences of physical

inactivity in chronic obstructivepulmonary diseaseExpert Rev. Resp. Med, 4(6), 735745 (2010)


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balance exercises or elderly adults at risk to al l [6]. The latterwould be adequate or the major ity o COPD patients. To ourknowledge, there are no COPD-specifc recommendations oran adequate physical activity level. Most guidelines on themanagement o COPD mention the importance o increas-

ing the level o physical activity, however, this is oten relatedto treatment with pulmonary rehabilitation. The AmericanThoracic Society/European Respiratory Society statement onpulmonary rehabilitation provides practice guidelines or exer-cise training during pulmonary rehabilitation and emphasizesthe need or the transerence o exercise adherence to the homesetting[7]. Unortunately, the recommended amount o physicalactivity in daily lie is not specifed in these guidelines.

Several studies have shown that the level o physical activity inCOPD patients is low, especially compared with that o healthycontrols. A selection o these studies is shown in Table 1. Moreover,a recent study rom Sweden [8] has reported that the number o

COPD patients who do not reach the recommended amount ophysical activity according to the earlier stated guidelines [6] wassignifcantly higher than in patients with rheumatoid arthritis,diabetes mellitus and healthy subjects (COPD 84%, rheumatoidarthritis 74%, diabetes mellitus 72% and healthy 60%, respec-tively). This indicates that the level o physical activity in COPDpatients is also lower than in other diseases.

From the literature we can conclude that being physicallyactive has many health benefts in general, and that many COPDpatients lack an adequate level o physical activity. Consequently,a reduced level o physical activity may contribute to a lowerphysical ftness and wellbeing. The aim o this article is to discuss

in more detail the possible role o regular physical activity in anumber o well-known outcome parameters in COPD.

The role o physical activity in specifc COPD

characteristics

Lung function

Several cross-sectional studies have shown a signifcant relation-ship between physical activity and the orced expiratory volumein 1 s (FEV

1; correlation coefcients [r] ranges between 0.20

and 0.63) [919], while others did not [2023]. Dierent studiescategorized the liestyle o COPD patients as active or inactive,based on their level o physical activity. Higher FEV

1values

were ound in pat ients who reached the recommended amounto physical activity[6] (a minimum o 30 min o walking everyday) compared with those who did not [24] and in patients whoreported moderate or high levels o physical activity comparedwith patients who reported low levels o physical activity, defnedas time spent walking during leisure time [25]. By contrast, whenpatients were divided into groups based on their median physical

Table 1. Daily physical activity level in chronic obstructive pulmonary disease.

Study (year) Population n Mean FEV1

%of predicted

Outcomes Ref.

Accelerometer (DynaPort activity monitor) 12-h day Walking time

(min per day)

Sitting time

(min per day)Pitta et al. (2005) Controls

COPD patients

25

50

111

43

81

44

306

374

[15]

Pitta et al. (2009) COPD patients (Brazil)COPD patients (Austria)

40

40

46

48

56

40

296

388

[76]

Camillo et al. (2008) COPD patients 31 46 57 [44]

Pitta et al. (2006) COPD patients 23 39 57 338 [24]

Accelerometer (SenseWear) 24-h day Steps per day PAL

Troosters et al. (2010) ControlsCOPD patients

30

70

114

54

9372

5584

[13]

Watz et al. (2008) COPD patients 170 56 5882 1, 5 [41]

Watz et al. (2009) Chronic bronchitis 29 99 9000 1, 70 [35]

Accelerometer (SenseWear) 12-h day Daytime steps

Pitta et al. (2008) COPD patients 40 41 4178 [21]

Camillo et al. (2008) COPD patients 31 46 4603 [44]

Pedometer (type) Steps per day

Schonhoer et al. (1997)(Fitty 3)

Controls

COPD patients

25

25

NA

47

8590

3781

[10]

McGlone et al. (2006)(Omron HJ003)

COPD patients 124 46 3716 [9]

Duration measurement included 12 consecutive hours starting at waking up time.FEV

1: Forced expiratory volume in 1 s; n: Number o patients or controls; NA: Not available; PAL: Physical activity level score (total energy expenditure/basal metabolic

rate 24 h).

Hartman, Boezen, de Greef, Bossenbroek & ten Hacken


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activity level [26] or based on the level o energy expenditure inphysical activity[27], no dierence in FEV

1between groups

was

observed. However, these contradictory results may be explainedby the dierences in categorization used in these studies.

Surprisingly, one longitudinal study in the general population

demonstrated that lower physical activity (among other vari-ables) increased the 10-year decline in FEV

1in active smokers.

However, physical activity was not associated with lung unc-tion decline in young adults (


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exercise capacity measured by the 6MWT (r ranges: 0.420.76)[11,14,15,18,20,22,37] . Signifcant correlations between physical activ-ity and maximum reached workload (W

max) and peak oxygen

uptake (peak VO2) were also ound (r ranges: 0.330.63) [15,1820].

Only two studies did not fnd a signifcant correlation [23,26].

Apparently, there seems to be a strong association between physi-cal activity and exercise capacity. However, one study showed thatthe 6MWD was predictive o walking time in daily lie only inpatients with a 6-minute walk distance (6MWD) below 400 m[15]. This indicates that in COPD patients with a higher exercisecapacity the physical activity level is more variable. Two studiescategorized patients into groups based on their level o physicalactivity. A study that compared COPD patients who reachedthe recommended amount o physical activity with patients whodid not reach this level, showed that the relatively inactive grouphad a signifcantly worse distance on the 6MWT (76 vs 66%predicted), a lower peak VO

2(71 vs 49% predicted) and lower

Wmax (69 vs 40% predicted)[24]

. By contrast, when patients weredivided by the median number o pedometer counts, the groupsdid not dier in exercise capacity measured by the 6MWT [26].

Muscle function

Maintaining adequate muscle unction (orce and endurance)in the larger musculoskeletal groups such as the quadricep mus-cles is important in perorming daily activities like walking andremaining independent. Quadriceps weakness is ound to be asignifcant predictor o mortality in COPD patients [38]. Twostudies have shown a moderate correlation between physicalactivity and quadriceps unction (r: 0.45 and 0.60) [15,19], whiletwo others did not [39,40]. In both pairs, one study measured

muscle endurance and one maximal muscle orce. A group opatients who reached the recommended amount o physicalactivity also did not show signifcant dierence in quadricepspeak torque compared with inactive patients [24]. Little is knownabout the relationship between physical activity and handgriporce in COPD patients and the results published so ar areinconsistent [15,41].

Comorbidity

The prevalence o comorbidity in COPD is high and COPDpatients have been shown to be at increased risk o various dis-eases compared with an age matched non-COPD cohort (healthy

or patients with other diseases than COPD) [42]. In 200 COPDpatients, ater reviewing their medical chart, an average o 3.7chronic medical conditions (including COPD) were reported, andonly 6% o these patients did not have another chronic medi-cal condition apart rom COPD [43]. Comorbidities in COPDthat occur requently include osteoporosis, myocardial inarction,angina, ractures and glaucoma[42]. Interestingly, COPD patientswho reported lower levels o physical activity had comorbiditiesmore oten than those with moderate or high levels o physicalactivity [25]. Furthermore, in COPD patients, a reduced level ophysical activity correlated with let cardiac dysunction [41], hearthrate variability reduction [44], sel-reported diabetes, cataracts [27],

comorbid joint problems and a history o joint problems [22].

Highly prevalent in COPD patients is the metabolic syndrome,a cluster o metabolic risk actors such as hypertension, obesity andimpaired glucose tolerance [45,46]. Metabolic syndrome is associatedwith an increased risk o both Type 2 diabetes and cardiovasculardisease [47]. Moreover, COPD and chronic bronchitis patients with

metabolic syndrome showed signifcantly reduced levels o physicalactivity in comparison with those without metabolic syndrome [45].One review showed that exercise training has mildly or moderatelyavorable eects on many metabolic and cardiovascular risk ac-tors that constitute or are related to the metabolic syndrome andthus can play a role in its prevention and treatment, althoughmore research has to be conducted with metabolic syndrome asthe main outcome [48].

Chronic obstructive pulmonary disease is associated withincreased levels o systemic inammatory markers [49]. Higherlevels o systemic inammation (high-sensitivity C-reactiveprotein [hs-CRP], IL-6 and fbrinogen) have been shown to be

associated with reduced physical activity in patients with COPD[45]. Moreover, physical activity was an independent predictor ohs-CRP, IL-6 and fbrinogen level [45]. The authors o a reviewon the anti-inammatory eect o exercise in general, suggestthat myokines may be involved in mediating the health-benefcialeects o exercise and thereore may play an important role in theprotection against diseases associated with a low-grade systemicinammation [50]. Unortunately, there are only a ew studies thathave ocused on the eect o exercise training on inammatorymarkers in COPD, and these studies did not show changes ininammatory markers (e.g., TNF-a and IL-6) due to exercisetraining[51]. These data suggested that although exercise trainingdid not result in anti-inammatory eects in COPD patients, it

also did not have a proinammatory eect [51].Obesity, assessed by a BMI o 30 or higher, is highly prevalent in

patients with COPD, especially in those with Global Initiative orChronic Obstructive Lung Disease (GOLD) stages I and II [52]. Astudy in a general population, aimed at examining determinants osedentary liestyles in the EU, showed that obese people signifcantlymore oten had a sedentary liestyle compared with people withnormal weight (BMI: 2025 kg/m2) [53]. However, this relation wasnot ound in COPD patients. A ew studies ound no associationbetween BMI and physical activity [9,15,22,26]. In line with theseresults, dierent studies that classifed patients into groups based ontheir level o physical activity, ound that BMI was not signifcantly

dierent between active and inactive COPD patients [24,25,27].

Mortality

A ollow-up study with a mean duration o 12 years among 2386COPD patients showed that ater adjusting or all relevant con-ounders, subjects who reported low, moderate or high physicalactivity had a lower risk o all-cause mortality, and death romrespiratory causes or cardiovascular causes, than the group withvery low physical activity, defned as mainly sitting during work,no activity during work and no jogging or cycling[32]. The samewas also ound in the general population; minimal adherence toearlier stated guidelines o physical activity was associated with a

signifcant 2030% reduction in risk o all-cause mortality[54].



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Health-related quality of life

Health-related quality o lie (HRQL) is increasingly recognizedas an important patient-centered outcome, which may be aectedby a chronic disease like COPD. A signifcant positive correlationbetween physical activity and (one domain o) HRQL was re-

quently reported (r ranges: 0.200.42) [9,16,18,20,22,55], althoughone study ound dierent results or the dierent domainso HRQL [14], and one study did not fnd an association [56].Studies that classifed patients into groups based on physicalactivity showed conicting results. A study which divided thepatients into low, moderate and high energy expenditure inphysical activity showed that lower levels o HRQL (physicaland mental components) were independently associated witha low energy expenditure (OR physical component: 0.93; ORmental component: 0.96) [27]. By contrast, there were no sig-nifcant dierences in HRQL between patients who reachedthe recommended amount o physical activity and patients who

did not[24]

, nor between those with above compared with belowmedian physical activity[26]. However, outcomes o these stud-ies are incomparable since dierent questionnaires were usedto measure HRQL. Frequently used HRQL questionnaires areSt. Georges Respiratory Questionnaire, Short Form 36 HealthSurvey and Chronic Respiratory Questionnaire. A recent studywith a 5-year ollow-up showed that the COPD patients whomaintained a low physical activity level or decreased their physi-cal activity level during ollow-up, showed a signifcant decline inHRQL, while those maintaining a high level o physical activityor increasing their physical activity level showed an improvementin HRQL [25].

Psychological parameters

Psychological characteristics such as depressive symptoms andanxiety are highly prevalent in COPD patients. One reviewshowed that the prevalence o depression ranges between 7 and79%, and the prevalence o anxiety between 10 and 100% [57].The large variations can be explained by the dierences in sampleso COPD patients or the measures used or assessing psychiatricmorbidity (e.g., dierent questionnaires and clinical interviews)[57]. Furthermore, patients with severe airway obstruction (GOLDstages 3 and 4) were 2.5-times more likely to have depression thancontrols, while patients with mild or moderate COPD (GOLDstage 2) showed no increased risk or depression [58]. Moreover,

depressive symptoms in COPD patients is strongly associatedwith worse HRQL [59]. Two studies ound no association betweenphysical activity and the presence o depression [22,41]. To ourknowledge, no studies investigated the association between physi-cal activity and anxiety in COPD patients. Sel-efcacy in physi-cal activity, the belie that you are capable o perorming a physi-cal activity, has been shown to correlate positively with physicalactivity (r: 0.27 and 0.43) [11,14].

Can we improve physical activity in COPD?

Because regular physical activity has many health benefts in gen-eral but especially in COPD patients, it is important to improve

the level o physical activity in COPD patients. Most evidence

on eects o increasing physical activity in COPD is based onstructured exercise programs embedded in pulmonary rehabilita-tion settings, which are most oten oered to patients with moresevere COPD. Pulmonary rehabilitation usually consists o mul-tiple disciplines, o which exercise is an important component.

Pulmonary rehabilitation programs with a short duration (until12 weeks) have shown dierent results regarding its eects onphysical activity. A 3-week pulmonary rehabilitation programshowed that the increased level o physical activity was related tothe increasing intensity o the training sessions and the authorssuggested that there was no change in personal liestyle towardlonger periods o walking[56]. Two studies with a slightly longerrehabilitation program (612 weeks) also ound that there was nota signifcant increase in level o physical activity ater rehabilita-tion [26,60]. By contrast, three studies ound a signifcant increasein physical activity ater pulmonary rehabilitation with aboutthe same duration [17,61,62]. A pulmonary rehabilitation program

with a duration o 6 months showed that the mean walking timedid not improve signifcantly ater 3 months, but actually didater 6 months [36]. Unortunately, to our knowledge, no studyexamined the level o physical activity some time ater fnishingthe pulmonary rehabilitation program. Consequently, an indica-tion whether the patients have incorporated a more active liestyleaterwards is lacking.

The eects o a structured exercise intervention on pulmonaryrehabilitation are signifcant [6367] and emphasize the importanceo exercise or regular physical activity in COPD. However, a struc-tured ater-care program is oten lacking and, urthermore, thedisadvantages o a structured exercise program are that they areoten time-consuming, expensive and require a lot o organiza-

tion and, thereore, patients oten drop out. It is also importantthat patients integrate physical activity in daily lie and adopta physical active liestyle. Thereore, another way to improvephysical activity is by enhancing daily physical activities suchas walking, cycling and gardening, and thereby promoting anactive liestyle. The primary ocus o such a liestyle strategy isnot to improve unctional capacity like in pulmonary rehabilita-tion, but to establish new physical activity routines in daily lie,which could give better maintenance o the results in the longterm. One study in an older general population compared thelong-term eects o a structured exercise group to a home-basedliestyle intervention. Ater 1 year ollowing the intervention, the

liestyle intervention group maintained their increase in physicalactivity while the structured exercise group no longer had higherlevels o physical activity compared with the control group (with-out intervention) [68]. Obviously, education and/or counseling isan important component o liestyle physical activity enhance-ment. A successul example in COPD patients is a counselingprogram that used pedometers to monitor and motivate COPDpatients to increase their physical activity in daily lie. A total o12 weeks ater this program, the outclinic COPD patients whoreceived exercise counseling showed a signifcant increase in thenumber o steps per day as compared with those who receivedusual care [69]. Furthermore, ater 12 weeks, the counseling group

showed a signifcant improvement in arm and leg strength, HRQL

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and changes in intrinsic motivation score to be physically active[69]. The same counseling strategy was added to COPD patientswho already ollowed a rehabilitation program. Both the experi-mental (pulmonary rehabilitation plus exercise counseling) andcontrol group (only pulmonary rehabilitation program) showed

an increase in the number o steps per day, with the experimen-tal group showing the largest increase [70]. Comparably, anotherstudy looked at the eects o a daily sel-monitored walking train-ing at home ater a 7-week supervised pulmonary rehabilitationprogram. The integration o the daily walking training at homealready started during rehabilitation. The improvements in exer-cise capacity ater rehabilitation were maintained at 6 months andalthough slightly declined, were still signifcantly better at 1-yearollow-up compared with baseline [71]. These results show that aliestyle physical activity strategy and pulmonary rehabilitation orstructured exercise programs can be complementary.

In the reconvalescence phase o a COPD exacerbation it may

also be worthwhile to enhance physical activity. For example,one interesting study looked at the positive eects o a specializedwalking program or COPD patients admitted to the hospital oran exacerbation [72]. During their hospital admission, patientswalked six times per day and during the 6 months aterwardspatients were stimulated to walk three times per day. All patientskept a diary with walking distances and time spent on walking athome. In these 6 months the patients recorded a mean daily walk-ing distance o 2308 m, on an average o 157 walking days. Thetraining group increased their exercise perormance and qualityo lie while the control group, which did not receive any struc-tured training, did not (directly ater the hospitalization, ater 6and 18 months) [73]. These results show that the stimulation o

walking, an important component o daily physical activity, hasbenefts even in COPD patients shortly ater a hospitalizationdue to an exacerbation.

Conclusion & discussion

While physical act ivity has many health benefts in general, thelevel o physical activity in COPD patients appears to be low,compared with a healthy population but also with other patientgroups, and is thereore an important modifable risk actor inCOPD patients. Although there are general guidelines or therecommended minimum amount o physical activity or adults topromote and maintain health, it seems worthwhile to investigate

whether these guidelines are also suitable or COPD patients.Signifcant correlations were ound between physical activ-

ity and important disease outcomes o COPD like FEV1, dysp-

nea, exercise capacity, muscle unction, comorbidities, systemicinammation and HRQL. However, it should be recognized thatthe literature is limited and inconsistent, and that most correla-tions are only moderate. Furthermore, a ew other cross-sectionalstudies separated active COPD patients rom inactive COPDpatients, which could give interesting insight into the determi-nants and consequences o an inactive liestyle. Although notconsistent, an inactive liestyle was associated with lower FEV

1,

higher levels o dyspnea, higher number o COPD admissions,

worse exercise capacity and worse domains o HRQL. These

results are obtained rom cross-sectional data and thereore def-nite conclusions regarding a possible causeeect relationshipare difcult to draw.

To our surprise, no signifcant associations were ound betweenphysical activity and BMI in contrast with fndings in the general

population. This could be explained by the lower prevalence oobesity that has been ound in GOLD stage IV patients [74] andin patients with emphysema[75]. Apparently, the disease severityand phenotype o COPD are ar more important than BMI inthis perspective. An association between physical activity andpsychological actors, such as depression was also not ound. Weanticipate that other actors like motivation to be physically active,play an important role or the physical activity level o COPDpatients, however, studies on this relationship are lacking.

The prevalence o comorbidites in COPD is high and comor-bidities might play a determining role in the reduced level ophysical activity. For example, common conditions like arthrosis

and osteoporotic ractures reduce the COPD patients ability tobe physically active. Physical activity also has avorable eectson many metabolic and cardiovascular risk actors, which mighthave important implications or the prevention as well as manage-ment o many common comorbidities in COPD. Thereore, theexistence o comorbidities needs to be taken into account wheninvestigating physical activity in COPD, but also when develop-ing physical activity enhancement programs or COPD patients.

The dierent methods used to classiy COPD patients intoactive versus inactive makes it difcult to compare the results. Themethods used to measure (accelerometer, pedometer, question-naire and interview) and to express the variations in physicalactivity (e.g., minimal recommended physical activity level,

energy expenditure and time spent walking during leisure time)are extremely dierent. Furthermore, the question arises whichlevel o physical activity can be considered as an active liestylethat could lead to health benefts.

Clearly, more research is necessary to investigate the determi-nants and consequences o an inactive liestyle in COPD patients,as well as more insight into the best way to stimulate the physicalactivity level in this group o patients. Figure 1 shows a theoreticalramework o the role and consequences o physical inactivity inCOPD, embedded into background actors.

The eects o an increase in physical activity are oten obtainedrom research on structured exercise or pulmonary rehabilitation

programs. These programs have shown signifcant improvementsor important patient-centered outcome parameters, and the eectso stimulating physical activity during the hospitalization and pul-monary rehabilitation ater an acute exacerbation are promising.However, owing to the multidisciplinary structure o pulmonaryrehabilitation programs, it is difcult to identiy the isolated role oexercise, and it is well-known that the long-term eects o pulmo-nary rehabilitation in general are modest. Programs that ocusedparticularly on the enhancement o physical activity in daily lie,to change a patients liestyle, also show good results.

Both pulmonary rehabilitation and liestyle physical activ-ity enhancement seem to increase physical activity at least

immediately ater the program ends. Unortunately, there are



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no long-term data regarding physical activity ater pulmonaryrehabilitation or liestyle physical activity enhancement. In theauthors opinion, it is important that especial ly sedentary COPDpatients incorporate the desired increase in physical activity intodaily lie and maintain this behavior. Because most physical

activity and pulmonary rehabilitation programs do not have astructured atercare program, much attention should be paid tothis aspect already during the program. Education, counseling,preparing the patients towards the end o the program, transer tofrst-line healthcare providers and involving amily members andcolleagues at work might all contribute to a successul maintenanceo physical activity ater discharge.

We conclude that regular physical activity is positively associ-ated with important health outcome parameters o COPD andthat it may successul ly be improved by structured exercise andliestyle physical activity enhancement programs. Exacerbationsand dyspnea are probably important threats against maintain-

ing an adequate physical activity level in more severe COPDpatients. We believe that stimulation o embedding low- ormoderate-intensity physical activity in daily lie is important orthe long-term eects o specialized physical activity programs.Finally, the stimulation o physical activity should already startin the early stages o COPD, i appropriate also using high-intensity physical activity to prevent a sedentary liestyle laterin lie.

Expert commentary

In the past decade, physical activity has increasingly beennoticed as an important outcome variable in COPD and the

literature on the role o physical activity in COPD patients is

growing. The development o perormance-based motion sensors(e.g., pedometers and accelerometers) which are able to objec-tively measure the actual perormed level o physical activityhas given an important boost. Accelerometers are more techno-logically advanced devices, which detect body acceleration and

are able to determine the quantity and intensity o movements.An extensive review on physical act ivity monitoring in COPDcan be ound in [2]. The results o this new research area arepromising and indeed suggest that a higher physical activitylevel is healthy or most COPD patients. However, results arestill inconsistent, which may be caused by small study samples orcross-sectional study designs. Moreover, a lot o dierent instru-ments are being used to measure physical activity, which com-plicates the comparison o results. Furthermore, the literatureon the relationship between physical activity and psychologicalparameters is still limited.

The available literature shows that the physical activity level

in COPD is generally low. Structured exercise programs showgood results, but it is important that COPD patients integratephysical activity in their daily lie and adopt an active liestyle.More insight is necessary on the determinants o this physicalactivity level in order to develop more efcient programs tostimulate physical activity structurally in COPD patients. Inour opinion, studies are needed that explore the strategies toenhance physical act ivity. Furthermore, the optimal embedmentor these programs in the healthcare system needs to be estab-lished. Until now, much research has ocused on the more severeCOPD patients, however, it is also useul to already stimulate, inecessary, the level o physical activity o patients with mild and

moderate COPD. This inormation can lead to the development

Lung function

ComorbidityDyspnea

Exacerbations/hospitalizations

Health-relatedquality of life

Psychologicalparameters

Exercisecapacity

Musclefunction

Physical inactivity

Background factors

Age Body composition

Smoking status and history Genes Medication

Long-term oxygen therapy Nutrition

COPD

Figure 1. Theoretical ramework o the role o physical inactivity in chronic obstructive pulmonary disease.The possiblerole and consequences o physical inactivity or important COPD outcomes is shown. These relationships are embedded in COPD-relatedbackground actors. Next to COPD-related actors, the presence o disease other than COPD (called comorbidity) may infuencephysical activity.COPD: Chronic obstructive pulmonary disease.

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o more structured physical activity enhancement programsthat are suitable or COPD patients in all severity stages otheir disease.

Five-year view

We are convinced that the interest in physical activity in COPDwill persist and the knowledge about the role o physical activity inCOPD will grow. We expect that the developments in ICT mighthave a huge inuence on this feld. The development and refne-ment o the perormance-based motion sensors will continue.For example, accelerometers at this moment are mostly used inresearch settings but are becoming increasingly easier to use, andthus more applicable at home. Thereore, those instruments couldbe useul tools in the individually tailored stimulation o physicalactivity in COPD patients next to their measuring ability. This

could also be useul in the ast developing feld o home telemoni-toring. The combination o these devices and computers/internetwill provide the ability to give patients eedback on their physicalactivity level at their homes in a less time consuming and expen-sive manner. In 5 years, we expect that even more patients will be

amiliar with computer and internet use and thereore that thesemethods will become more easily applicable.

Financial & competing interests disclosure

Jorine E Hartman is sponsored by the Dutch Asthma Foundation (grant

number: 3.4.07.036). The authors have no other relevant aliations or

nancial involvement with any organization or entity with a nancial

interest in or nancial confict with the subject matter or materials discussed

in the manuscript apart rom those disclosed.

No writing assistance was utilized in the production o this manuscript.

Key issues Regular physical activity has important health benets in general.

The level o physical activity in chronic obstructive pulmonary disease (COPD) is low compared with matched controls but also with

other patient groups.

Physical activity is positively associated with orced expiratory volume in 1 s, dyspnea, exercise capacity, muscle unction, comorbidities,

systemic infammation, health-related quality o lie and hospital admissions in COPD patients.

Because o the many health benets o physical activity in general and especially or COPD patients, it is important to improve the level

o physical activity in COPD patients.

More research is necessary on the modiable predictors o a sedentary liestyle in COPD patients.

Structured exercise programs and pulmonary rehabilitation have shown important results or important outcome parameters in COPD,

but the literature on the eect o the level o physical activity is limited and not convincing.

Liestyle physical activity enhancement should ocus more on behavioral change in physical activity routines in daily lie, and could

result in better long-term outcomes. Such a strategy can exist next to, but also complementary to structured exercise programs or

pulmonary rehabilitation.


ReerencesPapers o special note have been highlighted as:

of interest

of considerable interest

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forolderadults.

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Largecross-sectionalstudyonthelevelof

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pulmonarydisease(COPD)patients

comparedwithdiabetesmellitusand

rheumatoidarthritispatientsanda

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of12yearsontheeffectofphysical

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101 World Health Organizationwww.who.int

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COPD Consequences of Physical Inactivity