Endurance Threshold

This is a concept I began thinking about a few years. Since that time it developed into a usable tool. This post was sparked by Aidan asking if I find the MAF test correlates well with race performance. It is all related to the way I train and what I use as a guide to progression.

To explain the endurance threshold, it is how far you can go at a certain pace until there is a significant increase in effort/intensity to be able to maintain that pace. The pace can usually be maintained beyond this point, but it is obviously much harder to do so. Joe Friel has referred to this as decoupling. His explanation is worth a read, plus the adaption for running on Ultrarunning. For me, I believe I use the concept slightly differently, and without all the extra in-depth analysis that he seems to take it.

Basically it comes back to developing enough stamina to maintain the appropriate pace for the distance required.

A personal example of establishing my endurance threshold was my marathon pb in 2009. In preparation I ran a 30km race at predicted marathon pace. For the 30km I hit the pacing pretty much spot on. Most of the way this gave me a heart rate of 156-159bpm. Then from 27km it felt harder and the heart rate jumped to 162-168. So for that pace my endurance threshold was 27km. For the marathon itself I managed to extend it out to about 32km, before things started getting harder to hold the same pace. Currently, on the few recent long runs, running at what might be 100km pace equivalent at this stage (I hope to get faster), the 3:30-3:45 time mark is where everything seems to get harder. I've used time here, because the of the quite varied terrain I am covering make using kilometers a bit too inaccurate. For a race that will likely take longer than 10 hours, an endurance threshold of 3:45, really needs to be extended.

How does the MAF test relate?

Basically it just serving as a tool to measure pace versus relative stress (as measured by heart rate). If I keep the heart rate and course constant (weather I can't do much about), then hopefully I am getting a guide at how my sub-maximal speed is progressing. The MAF pace will most likely be faster than 100km race pace, but I won't rely on it to guide my race. Pacing, effort and heart rate profiles will have more meaning from my longer runs.


  1. No matter the goal race I reckon it's always a good sign if the MAF test is improving. Still, for a 100k race TOF (time on feet) seems like a good guide. How much do you need though? 5, 6, 7, 8 hours for a 10 hour race?

    I like to record heart/beats per km over particular courses (rather than rely on a MAF test on a particular day which might happen to be windy or hot). If I'm around 700 for a medium effort over 10k I know I'm in good shape. Would love to improve that down to 680 which I think would indicate certain M50 PBs.

    1. Very true Ewen, improvement in MAF pace generally is good thing across the board. Faster MAF should usually mean faster race times. Of course there are other aspects to race fitness to take into account. Your heart beats per kilometer test makes sense and I remember reading your posts on the topic quite a while ago. I think it comes back to finding some tests we can do reasonably often to help guide the effectiveness of our training. The tests themselves can be different for each person.

      How long for the endurance threshold? I don't really know, but am aiming for 6 hours. That will be the length of my longest training runs. Hopefully it extends beyond this, but I don't plan on testing if it is before race day. Of course when going longer and longer I expect a few more ups and downs in effort versus pace even though the average may still be linear.

    2. Thanks Jason. Makes sense. The mental side would be big in an ultra of that length - being able to push through the low points.


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