Low Max Heart Rate

by James Thomas
(Vancouver, BC, Canada)

Hi, I'm a 48 year old guy that started exercising 6 years ago. I had no athletic background. I've now completed 5 Ironman races (fastest 12:01).

When I started, my Max HR was in the high 170s, maybe low 180s. And it didn't take much to get it there.

I now find that my Max HR has dropped SIGNIFICANTLY (good, right), but I am unable to drive it high. i.e. I am doing 6 x 800m track repeats and on the last repeat, my HR hits 143. Not a typo: 143. And I'm running at 5:40 mile pace.

Should I just be happy that it's this low, or can I try and train it to go higher if I want to race faster?

I'd be interested to know what your thoughts might be.

Intelligent Triathlon Training replies:

From the information you have provided there is no obvious reason that we can see why your peak heart rate should be so low. Having said that, being able to hit a high max heart rate does not give an advantage performance-wise.

If heart rate goes too high, the blood will not be spending long enough in the lungs and muscles for oxygen to be extracted and used properly.

There is no reason that training would cause a drop in max heart rate (resting heart rate is different, training will result in it being lower due to cardiovascular development making the heart and circulation more efficient). The general rule of thumb for the change in max heart rate with age is 1 beat per year – this is however a rough guide.

Your change is therefore quite a lot more than would be expected, and quite surprising. It is not unusual to see heart rate not rise as quickly as you get fitter., but that should not affect the highest value seen.

There is the possibility that you are not able to run fast enough to fully stress your heart, although the session example you give seems pretty respectable! Although if you are having long rest intervals this could mean your heart rate drops and then doesn’t have enough time to get up during the rep, so keep an eye on your heart rate during recovery and see how low it drops.

The other thing to consider is what your heart rate gets up to during a hard bike session – for example a continuous ride with some hard climbs. If you see a higher heart rate here then the lower max heart rate is due to the type of run session you are doing.

If none of this sheds any light then it would be worth consulting your doctor in case there is a medical cause of this change.

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