Figure 1

Description of the investigations (experimental protocol). Symptom-limited incremental exercise testing was conducted on an electronically braked cycle ergometer using the Vmax Cardiopulmonary Exercise Testing System (Sensor Medics, Yorba Linda, CA). After a 2 min warm-up period (inactive: 30 watts; trained subjects: 50 watts, corresponding to ~15% of $\dot{V}{{\mathrm{O}}_2}_{,\mathrm{peak}}$), the workload was increased by 15–30 Watts/minute using a ramp protocol until exhaustion. The single breath DL_CO/DL_NO measurements were obtained at rest and at two levels of exercise (a first warm-up period was performed before the ramp exercise test, and at 50% of the maximal work rate, immediately after peak exercise acquisition).