Pulmonary rehabilitation (PR), involving exercise training, is the common treatment prescribed to chronic obstructive pulmonary disorder (COPD) patients. Whilst exercise does not cure COPD, it does treat the symptoms associated with the disease. Exercise training usually consists of aerobic endurance training, however, it is now debated that combination training (CT) of endurance and resistance training is the optimal training modality for patients with COPD for reducing symptoms and improving health-related quality of life (HRQoL).

Impaired exercise tolerance limiting daily activities, dyspnoea (breathlessness) and reduced quality of life (QoL) are common complaints of COPD patients. Endurance training (ET) has been shown to improve exercise tolerance, as seen in the endurance training section, but has little effect on peripheral muscle atrophy and weakness, which is in part responsible for the extensive symptoms and reduced work capacity seen in patients with COPD. Resistance training (RT) promotes muscle growth and strengthening, as seen in the resistance training section, and may represent a useful addition to whole-body ET (O’shea et al. 2009; Paoli et al. 2017).

Effect of combined training on muscle strength

Mador et al. (2004) found that, following CT, there was a significant increase in the strength of quadriceps, hamstrings, pectoralis major, and latissimus dorsi. Only improvements in quadriceps and latissimus dorsi significantly differed when compared to ET alone. A further study by Bernard et al. (1999) saw a significant increase in bilateral muscle mean cross-sectional area (MCSA), and an increase in the strength of quadriceps, pectoralis major, and latissimus dorsi, that all significantly differed from ET only. Improvements in muscle mass and strength confirm that peripheral muscles retain the ability to undergo structural adaptation in patients with COPD, and may go a long way to improving the performance of tasks of daily living. Improvements in muscle strength during CT are due to both muscle hypertrophy and improved neural recruitment patterns.

The majority of papers agree that CT provides a significant improvement in muscle strength compared to ET alone, however, in many cases, this improvement did not translate into additional improvement in exercise performance or HRQoL compared to that achieved by ET alone (Bernard et al., 1998). Furthermore, peripheral muscle strength is often not fully corrected following training, suggesting that either the training period was insufficient, or increasingly more likely, that factors other than chronic inactivity are involved in muscle atrophy and weakness in COPD patients (Clark et al. 2000; Berry et al. 2018).

Muscle strength improvement is still beneficial however as it is associated with improvements in body composition, neurohumoral changes, and bone mineral density (BMD). The improvements in BMD may prove beneficial for patients with COPD in whom osteoporosis is highly prevalent (Heinonen et al. 1996; McEvoy et al. 1998).

Effect of combined training on exercise performance, dyspnoea and quality of life (QoL)

Daabis et al. (2017) found that dyspnoea score, HRQoL and 6-minute walk test (6MWT) significantly improved following exercise training but the magnitude of changes was comparable for CT and ET. HRQoL was measured by the St. George’s Respiratory Questionnaire (SGRQ) and functional exercise capacity was measured by the 6MWT. Ortega et al. (2002) also saw improvements in dyspnoea, and a significant increase in the dimension of emotion was observed in the CT group, but this was not seen in fatigue.

Table 1. Changes in dyspnoea and health-related quality of life before and after different training modalities

Source: Ortega et al. 2002. American Journal of Respiratory and Critical Care Medicine, 166(5), 672

Lacasse et al. (1996) saw pronounced changes in functional exercise capacity. They also saw a significant reduction in heart rate, VE, and blood lactate in both CT and ET, suggesting a physiological effect, but no significant difference between groups was observed.

Mador et al. (2004) also showed significant improvements in dyspnoea and fatigue for CT and ET, but there was no significant difference in the extent of improvement between groups. QoL, as measured by the Chronic Respiratory Questionnaire (CRQ), improved in both ET and CT with no significant difference between groups in the extent of improvements, despite differences between groups in improvements in muscle strength and submaximal exercise endurance. It can be concluded that almost any exercise modality resulted in improvements in QoL, in some areas, in patients with COPD. There may be a ceiling effect however, beyond which the unchanged pulmonary function limits any further improvements, which could explain why CT is not significantly more beneficial than ET for improving QoL (Pulhan et al. 2011; Spruit et al. 2003).

Elements of the CRQ or SGRQ, used to test QoL HRQoL, where improved regardless of the exercise modality, and no modality led to improvements in all areas. It is therefore possible to conclude that some activities of daily living might be improved by RT addition and, if not performed frequently, might not be of sufficient impact to significantly alter the CRQ score. Furthermore, it cannot be fully concluded that CT is not of greater benefit than ET for improving the QoL for COPD patients.

Is combined training a better option for the treatment of COPD?

Ortega et al. (2002) concluded that RT was superior to ET to improve muscle strength and ET was superior to RT to improve submaximal exercise tolerance. CT produced improvements in peripheral muscle strength and endurance comparable to those obtained by each modality alone. Bernard et al. (1999), having reached similar results, further concluded that due to the combined benefits of CT, it should be prescribed as the preferred training modality for patients with COPD.

Daabis et al. (2017) and Spruit et al. (2013) found that CT elicits a reduced cardiorespiratory response compared with ET alone as it demanded a lower level of oxygen consumption and minute ventilation, due to the resistant training elements. CT may therefore be a more attractive and feasible exercise option over ET for patients with COPD who may not be able to complete high-intensity ET, or for patients during times of disease exacerbations.

CT also provides variation in training program. Variation can improve engagement of participants and the continuation of exercise training which is needed to see improvements, regardless of the exercise program followed (Zeng et al. 2018; Emtner et al. 2016).

The use of CT, as part of a pulmonary rehabilitation program, has been shown to limit the impact of the disease on the overall health and wellbeing of its sufferers. Depsite lack of significant evidence to conclude whether CT is of greater benefit than other exercise modalities, it is widely agreed that the additional benefits to muscle strength and endurance, and the variation it provides, makes CT a good exercise modality for the management of patients with COPD.

Written by: Stacey Harrington (17801465)

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