Exercise training has been shown to be an effective element in several studies. An important study in this respect was by Ries et al., comparing a comprehensive rehabilitation programme, including exercise training, with an educational programme . After 2 months, the rehabilitation group showed improved exercise tolerance, exercise endurance, perceived breathlessness, and perceived muscle fatigue in comparison with the education group. Earlier, Toshima and colleagues came to similar conclusions . This is very important, as it appears that exercise training can improve not only exercise tolerance but also dyspnoea, which is a important complaint in COPD.
Another issue is how patients with COPD should be trained. For a long time, it was commonly thought that no real physiological training response was possible in patients with COPD. A study by Casaburi et al. was very important in this respect. Exercise training at a high level of intensity (70% maximal workload) improved the maximal and submaximal exercise capacity more than exercise training at a lower level (30% maximal workload) . The study also showed that a reduction in ventilation was significantly related to a decrease in lactate. The drawback of this study was that the pa tients only had moderate COPD (FEV1 54% of predicted). The study by Maltais et al. is thus even more relevant, as it included patients with a FEV1 of 1.0 L . The authors showed that a 12-week leg cycling test resulted in a significant decrease in ventilation and lactate at the same workload. In addition, they showed that after training, the oxidative enzymes of the quadriceps muscle were increased, suggesting a true physiological training benefit. From these studies, it is known that patients with COPD can be trained in a physiological way and that the effects are greater when the training intensity is higher. The question is whether training continuously at a high level is of most benefit to a patient with severe COPD, when in view of the fact that interval training resembles the daily activity pattern best. A recent study by Coppoolse et al., comparing continuous training with interval training, is interesting in this respect. Different physiological response patterns were shown, reflecting specific types of training in either oxidative or glycolytic pathways . It is of interest to determine which type of exercise programme is beneficial to the individual patient.
On the basis of the literature reports, the ATS adopted the following training strategy : a rehabilitation programme should contain exercise training for at least 4weeks, and patients should receive endurance training for 20-30min three to five times a week at a level of 60% of the maximal workload. However, not all patients can train at this high level. In these patients, interval training consisting of 2-3 min at high intensity (60-80% of the maximal workload), with equal periods of rest, might be an alternative approach.
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