Threshold running – What’s the rush?

Feb 3, 2021

Threshold running is pretty simple and not as complex as it’s made out to be. It involves running at a pace where lactate does not accumulate significantly in the blood during the workout, but rather stays at a constant level. The pace feels faster/harder than your easy run pace but is slower than your 5K or 10K race pace.

Threshold running

What is lactic acid and when does it increase?

Lactic acid itself isn’t responsible for the muscle fatigue that causes you to do the skeleton dance at the end of a fast run or race. In fact, it is actually an energy source. The cause of your muscle fatigue is actually the result of a build-up of hydrogen ions. Hydrogen ions lower the blood pH and make the muscles acidic. This acidity irritates muscle nerve endings and causes that pain, heaviness, and burning. For each lactate molecule produced by the body, one hydrogen ion is also formed.

As you probably already know, your body breaks down glucose for energy, and a by-product of this process is lactate. During easy running, your body reconverts and recycles this lactic acid back into energy and carries away hydrogen ions with it.

Therefore, the production of lactate, and the clearance of hydrogen, will remain relatively constant while running at an easy aerobic pace, which doesn’t require a huge demand for energy.

But, as you continue to run faster which demands more energy, the production of lactic acid will increase.

Why is threshold running important?

If you want to run faster for longer without crashing or if you want to avoid slowing down dramatically the longer you run, include threshold training in your running programme.

Running beyond your lactic acid threshold with workouts like the ones below, will train your body to process it more efficiently into a fuel, and at the same time, improve your capacity to buffer those hydrogen ions, to prevent that burning discomfort we know all too well!


A session per week of threshold training is enough to start seeing improvements if you do these regularly. The pace should feel relatively easy, especially if you’ve been used to doing quick, shorter intervals. Start by adding 2 x 5 minute threshold intervals to a 45 minute run, with a 2 minute break in between.

You can gradually increase the length of the intervals. If you’re training for a half-marathon or marathon, adding 10 or 20 minute intervals at threshold pace to a long run is a brilliant way to improve fitness and build endurance (remember, speed follows endurance).

Good luck!

Christine Prokopiak

Christine is a running coach and nutrition specialist based with Sole Buddies #LiveLife in Cape Town. She is also the co-anchor for the GerhardandChristineLiveLife podcast, and co-founder of For The Long Run, a social upliftment project and registered NPO in Fisantekraal. Read more about Sole Buddies here. 

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