In reply to robdan: Interesting topic, but there's a spectacular amount of bollox spouted about resting heart rate and how "mine's lower than yours so therefore I'm fitter than you" - it's a reasonable measure of how
your fitness is changing (ie if it was 55 and it's now 45 you've
probably got fitter) - but comparing RHR with other people as a way of measuring relative fitness levels is guff.
And as Enty says to take your RHR it's not just a case of taking when you're not rushing about - first thing in the morning lying in bed is probably about as accurate as you can get it. I just happen to have had a new strap for my HRM delivered this morning, so I know that when sat at my desk having just opened a new HRM strap my HR is 50 - but it's nearer 40 first thing in the morning. However my max HR is pretty low - maybe as low as 175, so my working heart range may be smaller than someone whose max is 200 but their RHR is 50.
I'm doing a bit of my running training keeping an eye on HR (as opposed to actually training to a HR "zone") as I'd like to know what my marathon HR should be, as one of the key things about running your best time in a marathon is holding yourself back early in the race, and HR is one way of monitoring that.