A symptom-limited incremental cycle exercise test is performed on the same day, at least 6 hours after the bronchodilator test and at least 4 hours after the meal. After a steady-state resting period, a 3-min warm-up is conducted at about 20% of individually estimated maximal work load (Wmax), and the load is increased every minute in such a way that the test duration is >8 and <12 min. The following data are obtained breath by breath and expressed as 30-s averages: V'O2 and carbon dioxide production (V'CO2); minute ventilation (V'E); tidal volume (VT); respiratory rate; and ventilatory equivalents for oxygen and carbon dioxide. Blood pressure is measured every minute by a sphygmomanometer. Blood samples are withdrawn from the arterialized earlobe at rest and at near-maximal exercise. Tests are terminated at the point of symptom limitation (peak exercise). Upon exercise cessation, subjects are asked to verbalize their main reason for stopping exercise (breathing discomfort, leg discomfort or both).