Just to help slick1 out. The maximum heart rate (MHR) determined by 220 - age might be accurate for some, but many will find that it will vary either higher or lower. I know that I've hit 202 before, I'm 16 turning 17 this year. I've not like ever went all out to hit my highest heart rate, so I'm not really sure if it is 202. The Polar Fitness Test gets me a 205.

The aerobic range varies for people. The maximum aerobic range will be around 82% to 94% of your MHR. For fitter people, it would be close to the latter. It's like there are so many varied answers on the internet. Some people say it is from 83% to 92%, but it should generally be around there.

As for running, the heart rate will definitely be higher than when you are cycling at about the same intensity. Running comes smoothly when you do some speedwork, which is in fact your running economy increasing. The same goes for cycling. I feel much better on the bike as well, but people say that I look like a long-distance runner. So? The verdict is still out there.