The aims of this review were to determine the level of evidence for exercise training in the management of patients with chronic obstructive pulmonary disease (COPD) and provide evidence-based recommendations on exercise training. This review was performed in PubMed and Cochrane Library. Included studies investigated patients with COPD who had been randomised to exercise training or no training. Six systematic reviews were included. The methodological quality was scored using a grading system (GRADE). The analysis showed that aerobic and resistance training in patients in a stable state of COPD results in improved health-related quality of life and decreased dyspnoea, anxiety and depression (moderately strong scientific evidence, grade +++), and increased physical capacity and decreased dyspnoea in daily activities (limited scientific evidence, grade ++). In patients with an acute exacerbation, aerobic and resistance training, performed directly after the exacerbation, results in improved health-related quality of life (moderately strong scientific evidence, grade +++), improved exercise capacity and decreased mortality and hospitalisation (limited scientific evidence, grade ++). Thus, patients with COPD should be recommended to take part in exercise training.
- Exercise training
- Physical activity
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Chronic obstructive pulmonary disease (COPD) is a progressive inflammatory disease characterised by chronic airway obstruction despite optimal bronchodilator treatment. Symptoms such as dyspnoea, cough and increased mucus production are typical.1
The prevalence of COPD in subjects >40 years old is 7–12%,2 but the undiagnosed population is large.3 According to the WHO, COPD is projected to be the third leading cause of death in 2030. COPD is mainly a result of smoking, and ∼50% of smokers in Sweden develop COPD.4 There is a strong relationship between the number of years as smokers and the risk of developing COPD. However, up to 20% of patients with COPD have not been smokers. Other risk factors for developing COPD include increased age, heredity, low socioeconomic status, occupational exposure to industrial pollution, and the burning of biomass fuels used for cooking and heating in poorly vented dwellings.5
Patients with COPD have structural changes in peripheral airways and lung tissue, which is mainly due to epithelial damage because of inhalation of toxic particles.6 The structural changes are irreversible. Peripheral airways are constricted (increased airway resistance) and have an increased tendency to collapse, while emphysema (destruction of alveolar walls) decreases gas exchange. When the disease progresses, there is a thickening of the vascular walls in the cardiopulmonary circulation (fibrosis), which negatively influences gas exchange and leads to hypoxaemia (low O2 tension) and hypercapnia (high CO2 tension). This contributes to increased blood pressure in the cardiopulmonary circulation (ie, pulmonary hypertension), which can lead to right cardiac failure (cor pulmonale).
Patients with moderate or severe COPD display hyperinflation (ie, air trapping), which reflects an increase in functional residual capacity and later also in total lung capacity. Hyperinflation increases the work of breathing. As a consequence of hyperinflation, the respiratory muscles work ineffectively (due to an inability of the diaphragm to shorten), and there is increased use of accessory respiratory muscles.7 During activities with increased ventilatory demand (eg, exercise training), dynamic hyperinflation (increased air trapping) prevents the tidal volume from increasing (as in healthy individuals), which leads to a rapid increase in breathing frequency; the subject experiences dyspnoea and cannot therefore continue the activity.8
Aside from negative effects in the pulmonary and vascular systems, other organs and systems are also affected in patients with COPD.9 Peripheral skeletal muscle function and heart function are negatively affected, hormone status is changed (low levels of androgens), and energy expenditure is increased. The peripheral skeletal muscles display structural and biochemical changes, low muscle mass, low proportion of type I fibres (oxidative) and high proportion of type II fibres (glycolytic), low capillary density, and low oxidative enzyme activity.10 Reasons for the reduced muscle function include muscle hypotrophy, decreased neural activity because of physical inactivity, increased level of intramuscular tissue hypoxaemia and hypercapnia, local and systemic inflammation, increased oxidative stress, and malnutrition. Oral corticosteroids, as part of the pharmacological treatment, can lead to steroid myopathy.11
A clinical diagnosis of COPD should be considered in any person who is over 40 years, has dyspnoea, chronic cough or sputum production, and a history of exposure to risk factors for the disease. Spirometry (dynamic spirometry) is required to make a clinical diagnosis, and the presence of a post-bronchodilator FEV1 (forced expiratory volume in 1 s)/FVC (forced vital capacity) <0.7 confirms the presence of persistent airflow limitation, and thus of COPD. According to spirometry, disease severity can be staged as mild (FEV1 >80% of predicted value), moderate (FEV1=50–80% of predicted value), severe (FEV1=30–50% of predicted value) and very severe (FEV1 <30% of predicted value). As this staging is based only on spirometry and does not therefore give a correct picture of the disease, the judgement should also be based on symptoms and exacerbations.1
Comorbidities, such as cardiovascular disease (hypertension, coronary artery insufficiency, cardiac failure and arrhythmia), metabolic conditions (hyperlipidaemia, diabetes, osteoporosis and osteoarthritis), skeletal muscle dysfunction, anaemia, infections, sleep apnoea, kidney insufficiency, swallowing insufficiency, gastro-oesophageal reflux, lung cancer, anxiety, depression and cognitive dysfunction, are common in patients with COPD.12 Having one or more comorbidities results in more hospitalisations and increased mortality.
There is great individual variation in how rapidly different patients lose lung function. Some patients can almost stop their lung function decline when they stop smoking, while others lose lung function rapidly—known as rapid decliners.13 Patients with repeated exacerbations, hypoxaemia, poor lung function, pulmonary hypertension, malnutrition (body mass index (BMI) <22 kg/m2) and comorbidities and who are current smokers or have a low level of physical activity have a bad prognosis.14
Smoking cessation is the most effective treatment and results in fewer symptoms and lower mortality. Pulmonary rehabilitation, including aerobic and resistance training, patient education, and nutrition, improves physical capacity, quality of life and dyspnoea.15 Exercise training and recommendations on physical activity have mainly been given when patients are in a stable state of the disease, but have been found to be important also in connection with an exacerbation.16 Pharmacological treatment includes inhaled bronchodilators and corticosteroids, which decrease symptoms, increase physical capacity and decrease the number of exacerbations. Influenza and pneumococcal vaccines can reduce serious illness and death and are therefore recommended. Long-term oxygen therapy (>15 h per day) increases survival in patients with severe resting hypoxaemia. Surgery to reduce lung volume is an option, but must be performed on strict indications.
Importance of exercise training in COPD
Exercise training is one of the cornerstones in the treatment of COPD and is recommended in guidelines.15 As a consequence of regular exercise training, the mitochondrial density and oxidative enzymes in skeletal muscles increase.10 Blood lactate decreases for the same level of work load—that is, oxygen can be used more effectively and thereby improve aerobic capacity.17 Minute ventilation at submaximal workload decreases, and oxygen uptake (VO2) and walking distance increase.15 Resistance training leads to increased cross-sectional area of mitochondria-rich type I and type IIa fibres, which helps to further increase total oxidative capacity of skeletal muscles.17
Patients with COPD and low physical activity level14 or physical capacity (6 min walking distance)18 have a bad prognosis. Having a low physical capacity or being physically inactive contribute to increased mortality, hospitalisations, low health-related quality of life, dyspnoea and limitations of the activities of daily life.15 It has also been shown that the level of physical activity is the strongest predictor of mortality in subjects with COPD.14 Therefore, it is of greatest value to investigate the effects of exercise training, so we can give recommendations to healthcare professionals and patients on how to exercise.
The aims of this review were to determine the level of evidence for exercise training in the management of patients with COPD and give evidence-based recommendations on exercise training in patients with COPD.
The literature search was performed in PubMed and Cochrane Library; the last search was performed on 10 March 2015. Requirements for inclusion in patients with stable disease were a frequency of exercise training of at least two sessions per week with each session lasting a minimum of 20 min. Requirements for inclusion in patients with an acute exacerbation were exercise training consisting of at least two sessions per week. Requirements for inclusion in patients who desaturate during exercise were exercise training with supplemental oxygen. Included studies were evaluated in terms of outcomes such as quality of life, physical capacity, dyspnoea, hospitalisation and mortality. Six systematic reviews were included. Four reviews including 52 randomised controlled trials (RCTs) and 2731 subjects19–22 investigated the effect of exercise training in patients with stable disease. One review including nine RCTs and 432 subjects investigated the effect of exercise training in subjects with an acute exacerbation.16 One review including five RCTs and 105 subjects investigated, in subjects who desaturate during exercise, the effect of exercise training with supplemental oxygen.23 The methodological quality of each review was scored using a grading system (GRADE).24
Effects of exercise training
In patients whose disease is in a stable state, there is moderately strong scientific evidence (grade +++) that aerobic and resistance training results in improved health-related quality of life20 and decreased dyspnoea,20–22 anxiety and depression.19 There is limited scientific evidence (grade ++) that aerobic and resistance training results in increased physical capacity20 ,22 and decreased dyspnoea in daily life.20–22 The aerobic training had been performed on a cycle ergometer or treadmill, continuously or in intervals, and the resistance training as upper or lower limb training. It had been performed 2–7 times a week, for 4 weeks to 12 months, and at an intensity of ≥60% of maximal capacity.
In patients with an acute exacerbation, there is moderately strong scientific evidence (grade +++) that aerobic and resistance training, performed directly after the exacerbation, results in improved health-related quality of life.16 There is limited scientific evidence (grade ++) that exercise training results in increased exercise capacity and decreased mortality and hospitalisation.16 The training had been supervised and included walking, resistance training and breathing exercises. It had been performed from five times a day to twice a week for 10 days to 6 months.
In patients who desaturate during exercise, there is limited scientific evidence (grade ++) that aerobic exercise with supplemental oxygen increases physical capacity and decreases dyspnoea.23 The aerobic training had been performed on a cycle ergometer or treadmill for 30–60 min, 3–5 times a week for 4–10 weeks. The intervention group used 3–5 L oxygen per minute or 35% oxygen.
Effect in relation to type of physical activity
The combination of aerobic and resistance training for upper and lower extremities results in increased aerobic capacity and muscle strength in subjects with COPD (limited scientific evidence, grade ++).20 There is moderately strong scientific evidence (grade +++) that aerobic exercise training in intervals (from 30 s to 3 min intervals) has the same positive effects as continuous training.22
Recommended exercise training for patients with COPD
Patients with stable COPD, FEV1 <80% of predicted value, and decreased physical capacity should be recommended aerobic and resistance exercise training to
improve health-related quality of life and decrease dyspnoea, anxiety and depression (moderately strong scientific evidence, grade +++)
increase physical capacity and decrease dyspnoea in daily activities (limited scientific evidence, grade ++) (table 1).
Patients with COPD, FEV1 <80% of predicted value, and acute exacerbation should be recommended supervised aerobic and resistance exercise in direct connection with the exacerbation to
improve health-related quality of life (moderately strong scientific evidence, grade +++)
increase physical capacity and lower the risk of hospitalisation and mortality (limited scientific evidence, grade ++)
Patients with COPD, FEV1 <50% of predicted value, who desaturate during exercise should be recommended aerobic exercise with supplemental oxygen to:
increase physical capacity and decrease dyspnoea (limited scientific evidence, grade ++).
Important aspects with regard to exercise training in COPD
Patients with COPD benefit from exercise training independent of age, gender, level of dyspnoea or disease severity. Exercise at higher intensities increases the physiological effects more,25 but adherence to programmes with very high intensity is often low.15 All exercise must be individualised. Patients with COPD who have been prescribed inhaled bronchodilators should take these before exercise training to minimise bronchoconstriction and to lower hyperinflation, and patients with comorbidities should take recommended medications to optimise the possibility of performing the training to achieve optimal effects from the training.
In subjects with a BMI <22 kg/m2 and those with a rapid decline in weight during the previous 6 months, contact with a dietician should be established to ensure positive energy balance before the start of training. Some might benefit from nutrients that could be used in connection with exercise training. Height and weight need to be measured on a regular basis to detect weight loss and decrease in BMI.
If resting oxygen saturation is <90%, contact with a physician should be established, since the patient may have respiratory insufficiency. If subjects desaturate <88% during exercise training, intensity can be decreased, interval training can be used or supplemental oxygen given (consultation with a physician is necessary, as oxygen is a drug). If oxygen saturation falls below 80% during a functional test (eg, 6 min walk test), the test should be stopped.26
Using walking aids during exercise training results in lower loads on respiratory muscles, which helps the patient to perform more work and thereby improve exercise capacity further.27 Pursed lip breathing during training is recommended to lower breathing frequency and increase oxygen saturation. If resting blood pressure is >180/110 mm Hg or uncontrolled, a referral to a physician should be made before exercise training is started.
Before each training session, oxygen saturation and heart rate should be assessed at rest and during and after exercise. Blood pressure should be assessed before the start of training, and the subjective rating of dyspnoea and leg fatigue should be assessed according to the Borg CR10 scale before, during and after exercise.28
In patients whose disease state is stable, aerobic exercise training can be performed continuously or in intervals, on land or in water and should be of moderate to high intensity (>60% of maximal capacity)—that is, 4–6 on the Borg CR10 scale or 12–14 on the Borg rate of perceived exertion (RPE) scale, two to three times a week.15 ,29 Exercise in water has been shown to be equally as effective as training on land.30 Resistance training for both arms and legs is recommended two to three times a week.31 Muscle endurance training can also be recommended and should be performed with low loads (55% of 1 RM (repetition maximum)) and 25 repetitions for two sets.32 Balance training in addition to aerobic and resistance training is recommended to patients with decreased balance. Flexibility exercises for upper and lower extremities are recommended to be carried out two to three times a week.15 Subjects who are severely ventilatory limited can start with resistance training, flexibility training, and aerobic exercise in intervals (30 s to 3 min intervals). The training period should preferably last for 6 months to achieve optimal effects on physical capacity and health-related quality of life. The training could be performed at the hospital, in primary care, in preventive care, or at home depending on each person's needs, health status and preferences.
Subjects with an acute exacerbation should be offered exercise training in connection with the exacerbation. Activities such as walking, stair climbing, cycling, standing-up from a chair, and resistance training can be performed. If the subject is in hospital, the training should start there. The training can be performed on a daily basis or two to three times a week. When the subject is discharged from hospital, the exercise training should continue at home, in primary care, in the community, or in home care. The best effect is achieved if the exercise training is supervised.
Subjects who desaturate during exercise training can, after consultation with a physician, be offered supplemental oxygen to keep oxygen saturation ≥90%. Aside from supplemental oxygen, the training can be performed in accordance with the recommendations for people in a stable state.
What are the findings?
Subjects with COPD improve health-related quality of life, decrease dyspnoea and improve physical capacity as a result of exercise training. This is evident both in patients in a stable state of the disease and patients with an acute exacerbation.
How might it impact on clinical practice in the future?
All subjects with COPD and decreased physical capacity or physical activity level should be recommended and offered exercise training.
This article is a shortened and revised text based on a chapter in the Swedish book Physical activity in the prevention and treatment of disease (FYSS 2015), Professional Associations for Physical Activity, Sweden.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.