I have only recently started running and have targeted a 10k run in September to motivate myself. As a guide I am currently running a 4.5 mile circuit in 45 minutes once a week with other sessions in the gym including swimming, cycling and rowing.

I am trying to monitor my fitness by using a heart rate training program, the problem I have with this is that when I do my weekly run, my heart rate averages 175bpm which is approx. 93% of my maximum. According to this site and loads of others with heart rate information, I am either extremely fit, being able to maintain this rate for 45 minutes OR I am close to dropping dead.

I am overweight (85kg), I am only 165cm tall (or short!), I enjoy running and don't feel as though I am about to die when I'm running. Training guides suggest that I should be doing easy jogs with a max heart rate of 65-80%, but even during the first mile with a slowish jog my heart rate increases to 165+ and remains constant for the duration of the run. I'm not sure I can run any slower to decrease it.

Does anyone have any other advice or information on this that could help me out ?