di. okt 12th, 2021

Dear readers,

How are you?

Today, during a nice long run, with plenty of time to let my thoughts divert, I was wondering:

What is your ideal heart rate during a marathon?

Of course, you can’t go all the way during a marathon because then you can’t sustain the effort, so you need to find out what is the maximum heart rate (and pace) that you can keep up, no?

Anyone who has ever started a marathon with too much enthusiasm (i.e. at a pace that proved to be completely unsustainable over the full 42.195 km, knows why this is an important question 🙂

1. Karvonen’s method

Karvonens method states that you can only run a marathon at 70% to 80% of your “heart rate reserve”.

Your heart rate reserve is the difference between your maximum heart rate and your heart rate at rest.

So if your heart rate at rest is roughly 60, and if your maximum heart rate is 180, then your heart rate reserve would fluctuate around 120, roughly.

If you use 70% of that “reserve”, you can add 84 heartbeats to the heart rate (60) at rest, so we would end up with 144.

That’s a little bit disappointing, frankly speaking.

With all due respect to Mr. Karvonen, at heart rate 144, I can hardly walk, and I would have to run marathons with a 15 minute break, every 5 kilometers.

2. An alternative method?

During a marathon I often run with an average heart rate of 170, minus a heart rate at rest of approx. 60 that is = 110, so I use more than 90% of my heart rate reserve.

So I would answer the question “What is your ideal heart rate during the marathon?” with this alternative method:

“The ideal heart rate during the marathon is the heart rate that corresponds to the highest possible pace that you can sustain for 42 kilometers and 195 meters”.

According to many experts on the subject it is best to run a marathon as “flat” as possible: if you start too fast, you will get yourself into trouble, and if you run too slow in the beginning, you will never make up for this during the second part of the marathon, because in the last quarter you always lose a minutes, unless your name happens to be “Eliud”.

If you run a flat pace, you can also try to keep your heart rate steady. 

However, 1) you need to experiment with this, what is the heart rate you can sustain for 42,195 km, and 2) even worse, this is subject to external circumstances. When the weather is hot, your heart rate will rise much faster, so it’s best to lower this “highest possible heart rate (and pace)” which you had in mind, or you could get into big trouble.

In my recent marathon, the temperature was much higher than I anticipated, that added more than 20 minutes to the second half of this marathon (link blog).

How to avoid guesswork?

3. Use a percentage based on your anaerobic threshold?

A third method, then 🙂

At runinfo.nl ( link ) they recommend a method based on your anaerobic threshold.

If your anaerobic threshold is 175, then these are the percentages they recommend for competition:

They assume a fairly high percentage, i.e. 93% of your anaerobic treshold.

For example, if that is 175, then you could complete the marathon at heart rate 163

That’s much higher than what we got from Karvonen’s method, but still less than what I actually run in a marathon.

sigh.

So, what do we conclude?

I’m not sure. 🙂

So we consulted someone who knows a lot about it, Paul Van Den Bosch. He concluded about this dilemma:

“If you have a specific target time in mind, you have to run based on target pace. Simply too many factors have an impact on your heart rate during the race: heat, stress, … So your heart rate is not reliable, during such race. So many runners achieve a suboptimal result, just by checking their heart rate all the time!” (link)

Waw.

Issue solved 🙂

Of course, if readers have a different opinion on this, I’d love to hear it!

Kind regards,

Peter

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