By Mara Abbott, Special to The Denver Post Editor’s note: Mara Abbott was a professional cyclist for a decade and competed at the 2016 Olympic Games. The bass was pumping and the lights were flashing. The people around me shouted with joy and excitement, and a few had tears welling up in their eyes. A row of thighs pumped in perfect time to the music. I was in the middle of an indoor cycling class on my ’round-the-city exploration of Denver’s latest fitness trend.