Dyspnea, the perception of breathing discomfort, is the most troublesome symptom reported by patients with chronic obstructive pulmonary disease (COPD). Chronic dyspnea is clearly linked to poor perceived health status and activity restriction [1–3], and is an independent risk factor for mortality in this population [4]. In “the Confronting COPD Survey” almost 70% of the large sample of patients with moderate-to-severe COPD experienced dyspnea on climbing one flight of stairs [5]. Since dyspnea is precipitated or aggravated by physical activity in the majority of patients, the study of the mechanisms of activity-related dyspnea is particularly pertinent.