In doing a little research on heart rate zones, I came across this website. Running For Fitness has a cool little tool where you plug in your resting and maximum heart rates and it will provide you with training paces based on heart rate zones.
In my case, I have a resting heart rate of 55 (should probably test this again soon, as it's been a while - but it's hard to remember to check your heart rate in the morning before you get out of bed, when your alarm hasn't just startled you)
...and a maximum heart rate of 198 (for my maximum, I did not use one of the many formulas I've seen that involve subtracting some percentage of your age from a number in the 200-220 range; I've heard they can be inaccurate -- My heart rate has gone up to and stayed at 198 while really pushing myself while running, though I don't like it to be at that level for long!).
This is what it gave me:
(click to enlarge if needed)
Based on this little chart, I ran an easy run this afternoon trying really hard to keep my heart rate under 165. My Garmin FR 405CX has a feature in the Training section that allows you to create a workout based on Heart rate. I set it to stay within Zone 3 (the 151-165 range). It beeps at you if your heart rate is too high or too low (see video in links below)
This was actually a little too narrow of a range -- it was annoying as I was just getting started with running and my HR was below 151...it kept beeping to tell me my HR was not within the zone. I stopped the workout and changed the HR-based workout to be a custom zone, with 100 at the low end so it wouldn't annoy me for the first couple minutes of my run.
There's my run. It was 25 min; 2.14 miles. It was 47F and sunny out. I mostly did a good job staying under 165. It's tough! Especially after the first half mile or so once I'm warmed up.
Here are some links on heart rate-based workouts and figuring out your maximum heart rate, etc:
Runners World: How to Use a Heart Rate Monitor
Marathon Guide: Heart Monitor Training
How To Be Fit: Training with 5 Exercise Heart Rate Zones
Garmin: More Heart Rate Options (video - helpful for HR stuff on a Garmin FR405CX)
FitSugar: High Heart Rate After Running?
Do you have experience with heart rate monitors or with training based on heart rate?? I'd love to hear about it!