Threshold Series Part 4: Estimating Threshold Using Heart Rates

While the T-30 is a very accurate measure of threshold for intermediate and advanced swimmers, it is possible to estimate threshold pace using your heart rate. The best thing about heart rates is, they don’t lie. Plus, everyone has one!

This method requires the athlete be familiar with their max heart rate:

  1. You can get your max heart rate by actually working hard enough to get it as high as possible.
  2. You can estimate your max heart rate by taking 220 BPM and subtracting your age.

When I was in college, I was given a team handbook with a chart called, “Classification of Northwestern University Swimming Energy Systems.” Looking at anaerobic threshold, or EN2 pace, there are some heart rate guidelines:

    1. EN2/ threshold Pace should be swum between 30 to 40 BPM below the athletes maximum heart rate.
    2. On a max 200 scale, EN2/ threshold pace would be around 160-170 BPM.
    3. On a max 180 scale, EN2/ threshold pace would be around 140-150 BPM.

Furthermore, the Swimming chart describes EN2/ threshold sets as something that should feel, “a little uncomfortable” but NOT “hard.” Using heart rates as a guide helps solve pacing problems for you. A swimmer swimming repeat 600s will be able to get their heart rate within that 30-40 BPM range at a slower pace than that same swimmer would be if they were doing 100 meter repeats, which means they’d have to swim their 100s faster to be at their EN2/ threshold pace.

Tips: You don’t have to take your heart rate after every component of the set. When you do take your heart rate, use it to adjust your pacing. If you’re too high, slow down a little. If you’re too low, try to push yourself harder.

Tips: I have a theory that sprinters can get their heart rates higher than distance athletes. It is just a theory. My point, is know your heart.

Up Next: Threshold via White, Pink, Red

Sources: “Classification of Northwestern University Swimming Energy Systems,” unpublished.

Categories: Threshold Pace

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1 reply


  1. A Taste Of My Own Medicine: My T-30 | The Water Blogged Triathlete

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