I've never used a heart rate monitor before, so I'm a bit confused about the numbers I'm getting and perceived exertion. I do cardio on an exercise bike and do intervals at about 1:1 ratio for 20 min. According to the Internet, my "average maximum heart rate" is 185. When my heart rate is at 80-85%, 150-157, I can breath normally and my legs feel fine. I thought I would be huffing and puffing, but to get to that level I have to be at least in the 90% range. I try to keep an even pace/RPM at the higher intensity and during the rest period. During the rest period my heart rate drops to around 140. But during the "intensity" period my heart rate increases but breathing stays about the same. The perceived exertion is quite low. Is this normal? I thought training at 85% would be harder. Is it because of the "average maximum heart rate"? Could it be that my maximum heart rate is higher than average and so 150-160 is more like 75-80%?