The authors concluded that the long-term effects of strength training in patients with chronic obstructive pulmonary disease remained unknown and further research was required. There were limitations in the reporting of the review methods, but the authors’ conclusions reflected the lack of evidence and are likely to be reliable.

To determine if the positive effects of strength training in patients with chronic obstructive pulmonary disease (COPD) are sustained after the initial training period.

MEDLINE (from 1966), CENTRAL (from 1948), and PEDro (from 1929) were searched to May 2008 for studies published in English; search terms were reported. Reference lists of included studies, reviews, and guidelines were screened.

Randomised controlled trials, controlled trials, clinical trials, cross-over studies, and case reports that evaluated any type, duration or intensity of strength training either alone or in combination with other types of training or education in patients with a diagnosis of COPD were eligible for inclusion. Studies had to report a measure of muscle strength pre- and post-intervention, and after at least 12 weeks of follow-up.

The included studies used training programmes based on multi-gym equipment or elastic resistance bands; training sessions occurred three days per week. Duration of follow-up was 12 weeks after an initial 12-week training period in two studies and 12 months after an initial six-month training period in one study. In the longer study, training equipment was left with the patients, but the participation rate in maintenance training was low. Control interventions were usual care or continued baseline activity in two studies and endurance and combined endurance with strength training in one study. Participants were predominantly male, aged 60 to 70 years with moderate-to-severe airflow obstruction. Outcome measures were isometric quadriceps peak torque at 60 degrees knee flexion, one repetition maximum lift for several muscle groups, and hand-held dynamometry for various movements.

Two reviewers independently selected studies.

Validity was assessed using the Physiotherapy Evidence Database (PEDro) scale; criteria included randomisation, allocation concealment, baseline comparability, blinding, loss to follow-up less than 15%, intention-to-treat analysis, between-group comparison, and power estimates and variability. The maximum possible score was 10 points.

The authors did not state how many reviewers assessed validity.

The authors did not state how the data were extracted for the review, nor how many reviewers performed the data extraction.

The studies were combined in a narrative synthesis.

Three studies were included (n=198 patients).

PEDro scores ranged from five to seven out of 10. Limitations included lack of blinded outcome assessment (two studies), lack of intention-to-treat analysis (two studies) and follow-up data for less than 85% of patients (two studies).

Two of the three studies showed that post-intervention benefits were maintained at follow-up.

One study, with a six-month initial training programme, reported that the significant post-intervention increase in quadriceps strength, in the strength training group compared with usual care, was maintained at 12-month follow-up. One study with a 12-week initial training programme reported that the significant benefits in strength post-intervention, compared with baseline, were maintained at 12-week follow-up (p<0.05) in all intervention groups (strength training, endurance, and both).

One study with a 12-week initial training programme reported that none of the post-intervention benefits, in the strength training group compared with usual baseline activity, were maintained at 12-week follow-up.

The long-term effects of strength training in patients with COPD remained unknown and further research was required.

This review addressed a clear research question with detailed inclusion criteria. Several relevant sources were searched, but no attempts were made to minimise publication or language bias. Methods were used to minimise reviewer errors and bias in the selection of studies, but it was not clear whether similar steps were taken in the assessment of validity or data extraction. Validity was assessed and the results were reported in full. In view of the diversity among studies, a narrative synthesis was appropriate. There were limitations in the reporting of the review methods, but the authors’ conclusions reflected the lack of evidence and are likely to be reliable.

Practice: The authors did not state any implications for practice.

Research: The authors stated that further trials were required to evaluate the sustainability of strength training in homogeneous populations, training programmes, and methods of outcome assessment. They also suggested examining the effect of strength training on other outcomes, such as quality of life and measures of activity.

Not stated.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.