Threshold Running

So what is threshold pace running? When we speak about the threshold pace, we are referring to the pace of the anaerobic threshold (AT), which is defined as the maximum running speed at which your body is able to eliminate as much lactic acid as it accumulates over a longer period of time. It is basically the borderline between aerobic and anaerobic running. At this intensity, your body is burning mostly carbohydrates, and it is possible to run at threshold pace for about an hour before your glycogen stores are depleted and you have to slow down to avoid the accumulation of lactic acid, however, very fit marathoners or long distance runners can run at AT pace for up to two hours.

The lactic acid values in the blood is normally around 3.5-4.0 mmol/L when running at threshold pace, and the heart rate may be from around 86% to 92% of maximum.

How to find your AT

lactateFinding your AT is simple if you got a lactate measuring device and access to a treadmill. Simply do progressive intervals and measure the amount of lactate in your blood:

  1. Warmup 10-15 minutes at jogging speed.
  2. Run 5 minutes at pace X. In the beginning this should be a pace you know you can run aerobically.
  3. Jump off the mill and measure lactate.
  4. Increase pace X by 1km/h
  5. Repeat step 2-4 until you find that your lactate values exceed 3.5-4.0. That is when you exceed your AT.

After a test like that you should have a pretty good idea about what your AT is. If you want you can graph your results, putting speed on the X-axis and lactate on the Y-axis. An example of a guy with an AT at around 17km/t:

threshold pace running test

However, if you don’t have access to a lactate measuring device, it is possible to “feel” your way into knowing what your AT is by remembering these two words: comfortably hard. It should feel comfortable in the sense that you are not accumulating lactic acid in your legs, but still a little hard because it is the hardest aerobic running you can do and therefore requires some effort.


Now why would you want to increase your AT?

The AT is a supreme indicator of aerobic fitness, both for middle distance runners and especially for long distance runners. When it comes to the longer distances, like the 5k or the 10k, a runner’s performance is very largely, but not entirely, determined by his or hers anaerobic threshold.

Below is a chart describing in percent the distribution of aerobic/anaerobic energy during certain races. If you want to read more about that you can click here.


The more aerobic a race is, the higher is the importance of having a well developed AT in order to perform well. At 400m and 800m you may get away without, but at the 1500m and above it is an absolute necessity.

… and how?

The answer is simple: by running at a speed/intensity at or slightly below your anaerobic threshold. Experience, backed up by science, shows that the easiest way to increase the AT is by running at it or “pushing it up” from below it. Workouts may be done both as runs and as interval training. Some examples:

  • 1 hour run at “marathon-pace”, which is about 1km/t below AT speed
  • 30min run at AT speed
  • 8x1000m at AT speed with 1 minute rest
  • 9x(1min + 2min) with 30 seconds rest inside the series, and 45 seconds rest between series.

Have fun thresholding!

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