I have asthma too. I recently tried Advair on my doctor's recommendation, and now I can spin (well, ride the trainer at home), hike, ride, and even run with no asthma issues whatsoever. Your lungs should not be holding you back if your asthma is properly controlled. Lack of fitness, yes, but not asthma. You might want to check back with your doctor to see if an adjustment or change in meds is warrented.

Good luck!
Emily