You know, after having a power meter now, I don't think I could go back to HR.

I've found it wildly unreliable, although I've started to spot some of the factors.

I'm mentioning this as the original poster, she asked about heart rates and all.

Good example....didn't get a good night of sleep? your HR will be higher than normal even if you keep the workload the same. riding high at altitude? your HR will be lower and so will the stroke volume, lowering your VO2 max - thus your performance. not drinking enough water or are dehydrated? yeap, HR gets affected. Worrying? uh-huh, more HR fluctuation.

In each of these cases, if you went strictly by HR, you'd end up altering your riding without needing to.

If I couldn't use a PM, I would honestly use RPE as I find that's much more consistent. Also it keeps you from having your rides being governed by a number on a watch which isn't always indicative of your condition.

A good compromise is to use both your HRM and RPE....if you are riding at a given pace and your HRM reads high, think about how you feel - does it agree with what the HRM says?

If you are interested, you can read more about RPE here:

http://www.sportfit.com/sportfitglossary/RPE.html

I think cadence was clearly explained above. Just an additional word about that....riding at a higher cadence, say 100 vs. 80, will result in a higher heart rate for the same amount of work. The caveat is, if you ride at the lower cadence you may end up fatiguing yourself faster. You'll find what range works for you - you'll naturally tend to pedal in it consistently.