Just this year I discovered that my spring breathing issues on inclines are not a lack of fitness. I did a really challenging indoor cycling training program this winter, so I knew I was VERY fit this spring - but on hills I started to feel like a scuba diver who's oxygen tank had been turned off. I even had to cut short a group ride and be escorted slowly back to the car (and really I should have had them go get a car, 'cause I had spots before my eyes sometimes on the way back.) I had already started an extensive allergy test regimen, and soon discovered that I am "moderately" allergic to mold & tree pollen. No sign of asthma, in fact the guy who ran the pulmonary function test said I hit a new high for their machine! So the savvy allergy lab guys and I figured out that the allergy + my extreme outdoor exercise = asthma-like attack. I started immunotherapy shots that will hopefully improve the sensitivities to mold & pollen next season, but I did a little research and found out how common this is with cyclists, and I pressed my doctor a little to let me try the inhaler. (she wanted me to wait for the long-term fix, but she doesn't exercise and I don't think she understands how hard we work to attain a fitness level, and how awful it is to feel it slipping away.) The inhaler works well, no side effects, but I can find the bottom third of my lungs again! By the way, I'm 47. As I understand it, I might have had this issue my whole life, but never stressed my system enough to discover it.