Exercise in chronic airflow limitation (CAL) is often limited by symptoms before the physiologic boundaries of maximal ventilatory or cardiovascular capacities are attained. Symptom amelioration should translate directly into improved exercise performance. We studied the impact of a 6-wk supervised multimodality endurance exercise program (EXT) on perceived breathlessness (B) and leg effort (LE) and sought a physiologic rationale for symptom improvement. Thirty patients with CAL (FEV1/FVC = 42 +/- 2%, mean +/- SEM) were tested before and after EXT. Their responses were compared with those of a matched control group (n = 30; FEV1/FVC = 44 +/- 2%) after a nonintervention period. Testing included pulmonary function tests, chronic dyspnea evaluation (Baseline/Transition Dyspnea Index [BDI/TDI]), and graded cycle exercise with cardioventilatory monitoring and Borg scaling of B and LE. Spirometry did not change (delta) post-EXT. EXT significantly (p < 0.001) reduced chronic breathlessness (TDI = +2.8 +/- 0.3) compared with control (TDI = 0.0 +/- 0.3). Exertional symptoms of B and LE also fell (p < 0.01) after EXT (slopes of B and LE relative to VO2 fell by 14 and 23%, respectively; delta B/VO2 was associated with delta LE/VO2, r = 0.52, p < 0.01). Post-EXT slopes of B over ventilation (VE) also decreased by 10% (p < 0.025). Total cycle work increased 142 +/- 70% (p < 0.001) post-EXT and correlated primarily with delta B/VO2 (r = -0.64, p < 0.001). The best correlate of delta B/VO2 was delta VE/VO2 (r = 0.47, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)