Physical training to improve exercise capacity in people with cystic fibrosis

Review question

We reviewed the evidence about whether physical exercise training improves low aerobic fitness, improves health-related quality of life and slows the decline in lung function in people with cystic fibrosis. This is an update of previously published reviews.

Background

Cystic fibrosis affects many systems in the body, but mainly the lungs. It causes shortness of breath and limits the amount of exercise people with the condition can tolerate. The progress of lung disease leads to a low ability to exercise and physical inactivity, which in turn affects health and health-related quality of life. We looked for studies where people with cystic fibrosis of any age did aerobic training (continuous activity at a low to moderate intensity, such as jogging, cycling, swimming or walking) or anaerobic training (weight or resistance training or sprinting at a high intensity for a short duration) or a combination of both compared to no training.

Search date

The evidence is current to: 10 March 2015.

Study characteristics

This review includes 13 studies with a total of 402 volunteers; the numbers in each study ranged from just nine volunteers up to 72 volunteers in the largest study. One study was in adults, six were in children and adolescents and six studies included all age ranges. Four studies lasted less than one month and took place while the volunteers were in hospital; nine studies were outpatient-based and lasted from two months up to three years. The studies included volunteers with a wide range of severity of cystic fibrosis lung disease. There were differing levels of supervision in the studies and a mixture of types of training.

The outcome most often reported in the studies was the change in lung function; other commonly reported outcomes included peak oxygen consumption, health-related quality of life, change in muscle strength and change in body composition (e.g. muscle and fat).

Key results

Due to different study designs (type of exercise training, duration etc), we could not combine results from different studies. The short-term studies did not show differences between treatments. The longer studies showed that physical exercise training mostly improved aerobic capacity, there were some improvements in lung function and health-related quality of life, but these were not consistent across all studies. Longer, high quality studies with large numbers of volunteers are needed to increase the evidence for effects on important health outcomes in people with cystic fibrosis.

Quality of the evidence

We included a number of small studies and thought the quality of these studies was moderate at best. In four of the studies the volunteers' characteristics at the start of the studies were different between groups despite being put into the different treatment groups at random. It is not possible for people not to know which treatment group they are in when comparing exercise training to no exercise. However, we do not think the fact that people knew which treatment they were receiving would affect the results for lung function as long as the tests were done properly. In contrast, there may be bias when the people assessing a volunteer's cardiopulmonary fitness are not blinded to which group the volunteer is in. In less than half of the included studies, the investigators tried to prevent the outcome assessors from knowing which groups the participants were in; and in only one study was the lead researcher blinded. The studies did not routinely measure health-related quality of life and where it was measured, different measurement tools were used. Selective reporting of results maybe an issue, especially as most of the included studies were not listed in trial registries, which give advance details of the outcomes being measured. Overall, the quality of evidence was only low to moderate, but further better quality studies might change these findings.

Authors' conclusions: 

Evidence about the efficacy of physical exercise training in cystic fibrosis from 13 small studies with low to moderate methodological quality is limited. Exercise training is already part of regular outpatient care offered to most people with cystic fibrosis, and since there is some evidence for beneficial effects on aerobic fitness and no negative side effects exist, there is no reason to actively discourage this. The benefits from including physical exercise training in an individual's regular care may be influenced by the type and duration of the training programme. High quality randomised controlled trials are needed to comprehensively assess the benefits of exercise programmes in people with cystic fibrosis and the relative benefits of the addition of aerobic versus anaerobic versus a combination of both types of physical exercise training to the care of people with cystic fibrosis.

Read the full abstract...
Background: 

Physical exercise training may form an important part of regular care for people with cystic fibrosis. This is an update of previously published reviews.

Objectives: 

To determine the effects of physical exercise training compared to no training on aerobic exercise capacity, forced expiratory volume in one second, health-related quality of life and other patient-relevant (secondary) outcomes in cystic fibrosis.

Search strategy: 

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which comprises references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.

Date of the most recent search: 10 March 2015.

Selection criteria: 

All randomised and quasi-randomised controlled clinical trials comparing exercise training of any type and duration with conventional care in people with cystic fibrosis.

Data collection and analysis: 

Two authors independently selected studies for inclusion, assessed methodological quality and extracted data.

Main results: 

Of the 48 studies identified, 13 studies which included 402 participants, met the inclusion criteria. The numbers in each study ranged from nine up to 72 participants; one study was in adults, six were in children and adolescents and six studies included all age ranges. Four studies of hospitalised participants lasted less than one month and nine studies were outpatient-based, lasting between two months and three years. The studies included participants with a wide range of disease severity and employed differing levels of supervision with a mixture of types of training. There was also wide variation in the quality of the included studies.

This systematic review shows limited evidence from both short- and long-term studies that in people with cystic fibrosis aerobic or anaerobic physical exercise training or a combination of both has a positive effect on aerobic exercise capacity, pulmonary function and health-related quality of life. Although improvements are not consistent between studies and ranged from no effects to clearly positive effects, the most consistent effects of the heterogeneous exercise training modalities and durations were found for maximal aerobic exercise capacity (in four out of six studies) with unclear effects on FEV1 (in two out of 10 studies) and health-related quality of life (in two out of five studies).

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