Effects of Training on the Tolerance to High-Intensity Exercise in Patients with Severe COPD

Abstract

Background: There has been no systemic investigation of the effects of training on endurance at different high-intensity work rates in patients with COPD to date. Objectives: We wanted to determine the effects of intense endurance training on tolerance to several high-intensity work rates and to establish the relationship between power (WR) and its tolerable duration (t) (t = W’/(WR – CP), being W’, the curvature constant, thought to be reflective of anaerobic energy availability and/or tolerance to the uncomfortable sensations associated with the high-intensity exercise, and CP the critical power. Methods: We studied 27 patients: age 62 ± 5 years; FEV₁ 1.2 ± 0.2 liters. Before and after the intervention, the subjects randomly underwent 4 high-intensity constant WR exercise tests. The endurance times of the highest 3 tests were used. Results: Ventilation reached approximately the same level in each of the tests. In response to the training, the average peak increased by 9 ± 5% (p < 0.0001), CP by 14 ± 12% (p < 0.0001) and W’ 18 ± 22% (p = 0.002). In 67% of the patients, CP increased, accompanied by changes in other related physiological variables of aerobic capacity. In the remaining 33%, W’ increased but not CP. Smaller or no changes in the other variables of aerobic capacity were found in those subjects. This latter group was significantly older and had more hyperinflation (i.e. higher RV/TLC%). Conclusions: Our results suggest that neither an incremental nor a single endurance test at constant WR provides an adequate characterisation of exercise tolerance at other WRs. CP and W’ appear to be important parameters characterizing exercise tolerance over a range high-intensity work rates and identifying two distinct types of response to training.