Influence of work rate incremental rate on the exercise responses in patients with COPD

Purpose: The peak work rate (Wpeak) measured during a progressive stepwise exercise test is commonly used to select the target training intensity for an exercise training program. In healthy subjects, a greater Wpeak is achieved when a faster rate of increase in work rate is used, whereas (V) over dot (O2) peak is independent of the rate of increase in work rate. This effect might be even more pronounced in chronic obstructive pulmonary disease (COPD) patients, in whom the (V) over dot (O2) kinetics during exercise are slower compared with healthy subjects. Methods: To investigate this, we studied 10 COPD patients (9 M/1 F, age: 65 +/- 5 yr [mean +/- SD], FEV1: 33 +/- 8%). They underwent, on separate days, three stepwise exercise tests on an ergocycle. For each test, increments of 5, 10, or 20 W.min(-1) were used in random order; the investigator was blinded as to which increment was used.(V) over dot (O2), (V) over dot (CO2), heart rate (HR), minute ventilation ((V) over dot E), breathlessness and leg fatigue at rest, at each work rate, and at maximal capacity were obtained. Results: Wpeak averaged 40 +/- 13, 53 +/- 14, and 66 +/- 19 W for the 5-, 10-, and 20-W protocol, respectively (P < 0.001), whereas (V) over dot (O2) peak was comparable at 0.96 +/- 0.16, 1.02 +/- 0.18, and 1.03 +/- 0.20 L.min(-1). As the rate of increase in work rate became faster, the (V) over dot (O2)/work rate relationship shifted to the right. This is exemplified by the (V) over dot (O2) at 40 W, which averaged 0.98 +/- 0.06, 0.90 +/- 0.09, and 0.83 +/- 0.10 L.min(-1) for the 5-, 10-, and 20-W protocol, respectively (P < 0.05). Similar observations were made for the relationship between HR, (V) over dot E, and symptom scores, and work rate. There was no significant differences in peak values for HR and (V) over dot E, and symptoms scores. Conclusions: We conclude that the work rate incremental rate influences the Wpeak achieved, whereas the peak values for (V) over dot (O2), HR, (V) over dot E, and symptom scores remain comparable. These findings have practical implications for the exercise evaluation of patients with CORD.