I have a coach, which helps a lot. She had me do a lactic threshold field test, and then actually had me do a max heart rate test later because I think my HR was higher than she expected it to be. I also have a high heart rate during exercise, and my actual max HR is almost 20 beats higher than what the 220-age formula would give. Basically, the field test is run easy for 15-20 minutes until you're fully warmed up. Then you hit Lap on your watch and run 30 minutes at the hardest effort you can hold for the full 30 minutes. After the first 10 minutes, hit Lap again. The average HR for the last 20 minutes is your lactic threshold. Then, there are a lot of HR zone calculators online that once you know your LT heart rate, you can plug it in and get your zones. It is a really hard test! For me, it's like running between 5K and 10K PR effort. Unfortunately, I don't really have a handy source for heart rate training info. I googled to see if there was something succinct and informative, and everything I found was either way too detailed and technical or way too general. This article from beginnertriathlete.com (
http://www.beginnertriathlete.com/cms/article-detail.asp?articleid=633) is pretty good, though to use their calculators, I think you need to have an account. But there are a lot of other calculators that you can google. Anyway, the short of it is that the 220-age is an average, and doesn't actually give accurate max HR for everyone. You can also do it by perceived exertion, and I can certainly sense a change in my breathing when I go up from zone 2 into 3 and again from zone 3 up into 4. But the nice thing about the HR monitor is it's kept me honest, especially going up hills where otherwise I would just let myself increase effort instead of pulling back on the pace (and even walking if needed). I don't know if any of that helped!