Rest heart-rate as a measure of aerobic capabilities

I think that in general fitter people have a lower rest heart rate, but on its own rest heart rate is not much of an indication. Usually people measure the time it takes for their heart rate to return to its rest state. The fitter a person is the quicker it should be to go from a high heart rate to the rest state.

According to my gym guide it is very reliable. in fact, polar watches are the best. I also have one for my spinning lessons........I found it fantastic.

As for the calories listed (polar watch) , I doubt it is reliable.

Elinoar

I have the Polar F11 Heart Rate Monitor

In general, it's true that as one becomes more fit ones resting heart rate tends to decline.  Super-fit endurance athletes may have resting heart rates of 45 or 50, whereas the average is 70-75.  But people start from different places -- some people have a tendency to higher heart rate or lower heart rate regardless of fitness level.  And what MackTheKnife said is important, it's probably a better indicator of fitness how fast your heartbeat returns to its rest state.

Another thing to watch for with resting heart rate is that you have to be really resting, like just waking up or having been laying down for 20 minutes or so.  As you're going about your day-to-day activities, even if not exercising, your heart rate will probably be above its resting rate.  And just before exercising your heart may speed up in anticipation of the exercise to come.

The heart monitor is a great tool, but I'd be very wary of a fixed "fitness index".

Fitter people have a lower resting eheart rate

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