I know I've visited this topic in the past, but this blog is about things I think about while running, and lately I've been thinking about heart rates.
There is an aura around heart rates. People tend to assume that a low heart rate means you are in good physical condition. It is true, but not if you use the number as an absolute number. Having a rest hr of 65 means nothing. For me, it might mean trouble and for you it might mean you are in the best shape of your life. Running a tempo run with a hr of 145 means nothing if you don't also take into consideration the person's maximum heart rate and possibly the rest heart rate. The difference between the two is the heart rate reserve.
I see a lot of focus put on heart rate monitoring lately. A fact I find disturbing is that to calculate the all important maxHr (maximum heart rate) most books simply refer to the infamous formula used to calculate the maxHr from the age. I will not show the formula because it is USELESS. Sure, as an average for the whole population, it might be very precise, but as a running tool for you as a runner, it is no good. There is a very good chance that your maxHR is way off the number calculated using that average.
Case in point: me. My maxHr, according to the formula, should be around 178. My real maxHr, as observed in a number of races is around 195. For me to train using the training zones calculated using a maxHr of 178 makes my training stupidly easy and ineffective.
When I started running, I used those zones and found that I almost had to walk on my long runs, because I was supposed to maintain an hr of under 133 (75% of max). I quite simply could not do it. ANY kind of running brings my hr above 140. All my other types of runs were uncomfortable. Any kind of effort would blow the hr under which I was supposed to train. I thought I was physically challenged.
I tried the advice I saw in a book, and tried to find my ACTUAL maxhr by running hill repetitions. My hr did go up to 184 so I knew something was amiss. I decided to use 185 and my training felt better.
Finally, I ran a few races with my hr monitor and later when I analyzed the numbers I saw sustained periods with a hr of above 190. The highest I've seen was at then end of a 5k, with a value of 196. I never look at my hr while I race, but I still wear my Garmin and record the data.
So if you just bought yourself a heart rate monitor and you have a minimum of training, do yourself a favor and sign-up for the next 5k race in your area. Run it as hard as you can. Try for a good kick at the end. That should take you close to your maximum. That should make your training more effective and enjoyable, especially if the number you used was way off.