Supervised lower limb endurance training programmes for people with COPD involve stationary cycling or treadmill or ground walking. The intensity of training is considered a key component to improve exercise capacity. As we wanted to explore whether more or less intense training is better for improving exercise capacity, symptoms and quality of life, we examined trials with higher or lower levels of training intensity in people with COPD.
Exercise training can be prescribed as interval or continuous. Interval training is brief periods (one to three minutes) of exercise at high intensity alternated with short periods of recovery whereas continuous training is completing the endurance training without a break. We compared interval training with continuous training to determine whether one type of training was superior to the other in gaining improvements in exercise capacity, symptoms and quality of life.
We found three studies comparing higher with lower-intensity training. Due to a small number of studies and participants, data are limited in evaluating the effects of different levels of training intensity on exercise capacity, breathlessness and quality of life. We also found eight studies that compared continuous with interval training. There was no significant difference between continuous and interval training in improvements in exercise capacity, breathlessness and quality of life.
Comparisons between the higher and lower training intensity were limited due to the small number of included studies and participants. Consequently, there are insufficient data to draw any conclusions on exercise capacity, symptoms and HRQoL for this comparison. For comparisons between continuous and interval training, both appear to be equally effective in improving exercise capacity, symptoms and HRQoL.
Intensity of exercise is considered a key determinant of training response, however, no systematic review has investigated the effects of different levels of training intensity on exercise capacity, functional exercise capacity and health-related quality of life (HRQoL) in people with chronic obstructive pulmonary disease (COPD). As type of training (continuous or interval) may also affect training response, the effects of the type of training in COPD also require investigation.
To determine the effects of training intensity (higher versus lower) or type (continuous versus interval training) on primary outcomes in exercise capacity and secondary outcomes in symptoms and HRQoL for people with COPD.
We searched for studies in any language from the Cochrane Airways Group Specialised Register, CENTRAL, MEDLINE, EMBASE, CINAHL, AMED, PsycINFO and PubMed. Searches were current as of June 2011.
We included randomised controlled trials comparing higher training intensity to lower training intensity or comparing continuous training to interval training in people with COPD. We excluded studies that compared exercise training with no exercise training.
We pooled results of comparable groups of studies and calculated the treatment effect and 95% confidence intervals (CI) using a random-effects model. We made two separate comparisons of effects between: 1) higher and lower training intensity; 2) continuous and interval training. We contacted authors of missing data.
We analysed three included studies (231 participants) for comparisons between higher and lower-intensity training and eight included studies (367 participants) for comparisons between continuous and interval training. Primary outcomes were outcomes at peak exercise (peak work rate, peak oxygen consumption, peak minute ventilation and lactate threshold), at isowork or isotime, endurance time on a constant work rate test and functional exercise capacity (six-minute walk distance). When comparing higher versus lower-intensity training, the pooled primary outcomes were endurance time and six-minute walk distance. There were no significant differences in endurance time improvement (mean difference (MD) 1.07 minutes; 95% CI -1.53 to 3.67) and six-minute walk distance improvement (MD 2.8 metres; 95% CI -10.1 to 15.6) following higher or lower-intensity training. However, heterogeneity of the endurance time results between studies was significant. When comparing continuous and interval training, there were no significant differences in any of the primary outcomes, except for oxygen consumption at isotime (MD 0.08; 95% CI 0.01 to 0.16) but the treatment effect was not considered clinically important. According to the GRADE system, studies were of low to moderate quality.