Coleen, I was running every day last year, and with may many 5ks, and couple of 10ks, I had AN pressing on the brain stem, and it was removed the end of January. Somehow, thinking back, I realized that running with its constant small jerks, bumps and vibrations, might have made it grow more and become more cystic. This is all very subjective, but reading my 5 page surgical report gave me a picture of multitude of small and big blood vessels, connective tissue, pockets that constitute the tumor, very tightly connected to vital structures in the base of the skull. I made a conscious decision to stop running at least until after my MRI in May. I miss the runners high, but do my conditioning, yoga, kick-boxing and other classes. I feel that decision is right for me....Respiratory center is not affected by AN, though, your dyspnea is not directly related to your AN.