Regardless of what training plan you follow, chances are you’ll hear about paces expressed as a percentage of MAS or as a percentage of maximum heart rate (HRMax). I often see runners confuse these two percentages, which can result in completely different pace values. Once you have read this article and determined 3 personal parameters, you will no longer make these mistakes.
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How do you determine your maximum aerobic speed (MAS)?
The maximum aerobic speed is the speed at which the runner consumes the maximum amount of oxygen available to him, limited by his maximum oxygen volume (VO2Max). The aim of training is to increase the VO2Max and thus the MAS, especially through split sessions.
In practice, a runner is able to maintain their MAS for between 5 and 7 minutes. It is therefore possible to perform a MAS test on a track or road by running as fast as possible for 6 minutes and then multiplying the distance covered (in km) by 10 to obtain your MAS (in km/h).
So if you run 1.5 km in 6 minutes, your MAS is 15 km/h. There are also other tests, such as the famous beep tests that are often carried out in clubs. It is also possible to estimate your MAS based on your running results.
You will need a stopwatch to measure 6 minutes and possibly a GPS if you are not running on a track.
How do you determine your maximum heart rate (HRMax) and resting heart rate (RHR)?
I recommend that you read our article on determining your maximum and resting heart rate.
Link between heart rate and running speed using the Karvonen formula
At rest, your speed is zero. That’s obvious, you might say! At maximum effort you will reach your MAS, or even a little faster (it is possible to run at 110 or 120% MAS over short distances).
Between these two extremes, heart rate evolves almost linearly with speed, as the following graph shows, which I created during a maximum effort test on the treadmill.
A correlation can therefore be established between the speed and the reserve heart rate. The reserve heart rate is defined according to Karnoven’s formula: Reserve HR = maximum HR – resting HR.
This results in the following linear relationship: % MAS = % reserve heart rate
Example for the calculation %MAS = % Reserve HR
In my case, my resting HR is 45bpm and my HRMax is 195bpm: my reserve HR is therefore 150bpm.
If I want to run at 80% of my MAS (23 km/h) for marathon training (i.e. 18.5 km/h), the calculation of the reserve HR is as follows:
HR (80% of MAS) = resting HR + (reserve HR * % MAS) = 45 + (150* 80/100) = 165bpm.
If, like many runners, I had calculated % MAS = % HRMax, I would have had: 195 * 80% = 156bpm, i.e. a difference of 9 beats per minute and about 15 seconds per kilometer, 2 very different efforts…
When you start, the 3 parameters are: MAS, HRMax and RHR improve quickly, so don’t hesitate to re-determine them every 6 months.
Don’t forget that the heart rate increases during training with a heart rate monitor even at the same pace within a training session – this is the phenomenon of heart drift.
Why is there a difference between % MAS and % HR?
In the RunMotion Coach app, we give both figures as soon as the user enters a past race time (in My Profile) and their resting and maximum heart rate. We then use the same percentage of MAS and HR to calculate the equivalence.
However, there may be a difference between the two figures. This is often due to a slightly incorrect maximum heart rate of the MAS.
If you find that you are progressing slower than indicated at the given heart rate, then the MAS is certainly overestimated. It could also be due to a slightly overestimated HRMax.
If, on the other hand, you are running faster than indicated at a certain heart rate, it is probably because your MAS has been underestimated. Or a slightly underestimated HRMax.
A difference of 1 km/h in MAS can mean a difference of about 10 seconds per km in speed. In this article you will learn how to estimate your MAS based on race results.
Conclusion: If your training gives you a percentage of MAS, you can use the same percentage of reserve heart rate with your heart rate monitor. The RunMotion Coach app makes your training easier by showing you the pace and heart rate equivalents directly without you having to do these calculations manually 😉