I received the following comment on my 2012 in Summary post and thought it and it's response warranted a post of its own as it's a common topic with MAF...

Hello Colin

Revisiting this post as posted here before but not sure if it would be better in the MAF post. I digress.
When you started using the MAF principle; did you experience your heart rate monitor pinging off before you even felt you where actually getting into your stride?

I have tried this for a month now (and even though you suggest trying for 3 months at least) I am finding it utterly soul destroying. I feel like it want to rip the HRM off and smash it to smithereens because it must be lying to me, constantly pinging saying heart rate too high, I am barely moving.
I have read Dr Mafftones Big book of endurance and this situation is often referenced, people can seemingly run happily a lot faster than they can slower. Driving me nuts.
Just wondering if you had to go through this phase or your aerobic capacity was already sufficient to operate at a low HR?

The only thing that stops me throwing the HRM in the next brook is, it works fine when out on the bike. Can keep the HR nicely at may max level of 135bpm.
I can only conclude. Running is far more taxing than cycling, my aerobic capacity or running economy is shockingly poor or both.

Any words of wisdom would be much appreciated. Failing that, the simple cold truth, is my own conclusion about right.

Jason the dis heartend

Don't feel dis-heartened, you're not alone. This is actually a very common issue and I did indeed experience the same frustration as you are experiencing. My body used to be primed for fast training and I could and would whiz through training sessions at significantly higher heart rates. This however isn't very good for MAF and I had to be patient.

One suggestion you might like to try is adding 5 or 10 BPM to your MAF limit and try that for a few weeks to a month, then slowly start decreasing back down to your calculated MAF value. A colleague experienced the same issue as you and found this worked really well for him. He didn't drop back to his calculated MAF HR in the end though, but he is an older athlete (the MAF calc starts to become a bit sketchy in older trained athletes) and his new calculated HR was significantly lower than he'd been training at before.

Come to think of it, I effectively did this myself without even realising it as I spent a few months before completely switching to MAF following some of the ideas of "Hadd's Approach to Distance Training" as mentioned and referenced in my Does Maximum Aerobic Function (MAF) Training Work? post.

Once your body gets used to running at such a low HR, you'll find you will still get days like this when you feel like you're not moving and your HRM just won't stop beeping. Generally these indicate you're going a lot quicker than you really think you are (everyone loves to feel on top of the world), you're running in tougher climatic conditions (wind, heat and cold do crazy things with the HR), you're tired, or your body may not be 100% and could be giving you an early indication of either over-training or a pending cold.

On these days I try to slow my pace and lower my HR whilst taking into account all of these factors. If I still can't get my HR down and can't explain the elevation, I cut my run short and head for the showers. My body is probably telling me something and ignoring it will just annoy me and possibly lead to injury or illness.

So in summary, don't feel disheartened and don't give in just yet. It's perfectly normal. Try running at a slightly higher HR for a few weeks and see how you get on.