I have a Garmin Edge 500 with hear rate monitor, which I use while riding. Now I have all this hear rate data which I don't know how to apply. Can anyone point out how I should use this data for training, with the intention of racing?
I would also recommend Friel's book.
Basically, to train with a HRM, you need to set up your zones. There are three ways of doing this:
1) Based on an estimated maximum heart rate. This is better than nothing, but not by a lot, as it is an average. If you have a big heart, this may result in zones that are too high, while if you have a small heart, it may result in zones that are too low.
2) Based on a measured maximum. This is better than an estimated maximum, but isn't great because zones are better set using your anaerobic threshold, which changes based on your fitness level. As you get better trained, you want your zones to move up.
3) Based on a test, generally a field test that you perform on your bike. IIRC, Carmichael uses two 3-mile time trial efforts, while Friel uses one 20-minute effort. Both give decent numbers.
I would recommend the field test approach since you are just getting started. If you get serious, you may want to switch to using a power meter, which is better than using a HRM.
In addition to Google/books ("Total Heart Rate Training" by Joel Friel is a worthwhile read, IMO) have an Active Metabolic Rate test, VO2Max test, or something similar performed at a sports lab to measure exactly where your zones are. Don't waste time with "214-(age*0.8)" or other faith-based calculations.
As others have pointed, heart-rate alone is not enough to organize a comprehensive training program, and some preliminary steps (fitness tests, mostly) are necessary so that you can properly train guided by heart rate zones.
The main idea is the following: heart rate is one of the best measures of your physical effort. Each person have an individual maximum heart rate, depending on a lot of factors, mostly age. When you know your maximum rate, then it is possible to calculate the HEART RATE ZONES, as percent ranges of that maximum, which are directly related to training levels. Below a given zone there is no training, inside a given zone you keep the conditioning you already have, above a given zone you are improving your aerobic level, and so on. This can also be used to actively rest during an interval training, when you apply the next effort cycle only after some time below some threshold.
Of course, this talk applies specifically for TRAINING. If you ride only for fun, then you can use the heart rate just to compare efforts, more "informally" speaking. For example, if you ride the same route at the same speed many times, you can look for the higher heart rates and know during which rides you were more tired. Also, there are some ways to measure POWER with GPS devices (STRAVA does so if you provide your weight and the bike's weight). When you relate power and heart rate, you can obtain a measure of your fitness and/or efficiency at a given stretch.
With this flood of data nowadays, the possibilities are almost endless!
Hope this helps!