I've been having the same issue. I used the site http://www.runningforfitness.org/ to try and figure out my HR and monitor using a Polar Heart Monitor Thingy.
It offers various ways to calculate max HR and HR zones to train in. Even at that, i'm finding the slow run zone it suggests is too slow.
The Polar HR monitor you use should have a test setting in which it'll analyse your resting HR coupled with your vital stats to suggest a max HR, etc. If you have the manual, give it a read.
denotes Subscriber-only content | 
Paulb323
