HR drift & long runs

I find that HR drift tends to cause my actual HR on long runs to drift upwards by about 10%points (WHR basis) whenever I do a long run.

Most guides incl Sean Fishpool's (in)famous article quote a range (eg 60-70%) for a long run. I find that in practice what I end up doing is starting towards the upper end of these ranges and holding my speed. This means that my HR drifts out of the range (and I can't bear to slow down).

For my last long run (2 hrs) my HR averaged (WHR basis) 79% with probbaly the first 20 mins <70%.

Am I doing this wrong? Should I be slowing and holding the HR.

What should this mean for my HR strategy for RACING a 1/2M or 10 miler?

For 10k's I seem to have evolved to start easy (first 4-5mins) then settling at 80-85% over the next 10 mins and then holding speed and letting HR rise to 90% before the "sprint" finish, averaging about 88% overall.

my guess would be to run the longer races at 5% points lower. ie not much harder than my "training runs". Views?


  • drewdrew ✭✭✭
    SFH, I've never noticed any heart rate drift for any runs less than about 18 miles. I personally think that's it's important to realise that this will happen and to possibly ignore your HR when it does start to drift and try and maintain your goal pace.

    But if you don't want to do this you could try experimenting during your long runs with different rates.
  • No drift for 18 miles?!!

    now we need the explanations
    1) one of us is a biological oddity
    2) you're fit, I've a way to go!

    I'd like to put money on explanation 2)

    anyway thanks, you're confirming my inclination to stick to the pace rather than HR when racing. However on my next Long run I'll try slowing down, maybe walking, maybe crawling...

  • Sfh

    I think you're right, your heart rate will drift during a run as you become more tired and have to work comparatively harder in order to maintain the same pace. As I learn more about HR training I'm tending to think the best use of an HRM is to get you in the right zone at the beginning of a run and then either:

    a) Ignore; or
    b) Slow down!
  • drewdrew ✭✭✭
    I've also noticed a very marked HR drift when I'm cycling at home on my turbo trainer. This starts almost immediately, although, in this instance, I believe it has a lot to do with overheating rather than being unfit.
  • If you are still running within your comfort zone for this run I cannot see the point of slowing down.
    After all if you wasn't wearing the HRM and your effort appeared the same you wouldn't reduce your pace.
    I use my HRM most of the time during training but prefer to use the average heart rate to gauge my overall effort.
    Drift can be caused by a number of factors e.g change of terrain,hot weather etc.

  • Do you think we would all walk back home if our HRM ever conks out during our long run?
  • I thought part of the aim of the long run was to encourage the body's metabolism to learn how to use fat reserves more whilst exercising rather than glycogen only.

    I understood that % fat use correlated with HR. Therefore you negate the metabolic purpose.
  • HR drift or 'Cardiac Drift' is a natural occurance. As you exercise your body becomes dehydrated, drinking slows this process but it will eventually happen. As you dehydrate your blood loses plasma volume and so your heart has to work harder do keep up, tiredness and lack of efficiency are also factors. What is important is to accept this is natural and work with it. If you are training to zones then it is important to stick to them. This is the most productive way of using your time and will give the most benefit. You are right about the fat burning point although the body always uses both fuels but in different ratios. A long run should be comfortable and you should finish feeling like you could do 'lots' more. If not, slow down. Try to correlate your percieved exertion with different heart rates, after a while you will be able to judge your HR from how you feel. This will help you pace yourself in longer runs. Good luck.
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