Female Triathlete Working Out On Indoor Trainer Bike Testing Her Lactate Threshold At Home

The Importance of Lactate Threshold and How to Find Yours

BY Dr. Dan Plews

Find out why it's called "lactate threshold," why it matters, what it feels like during training, and methods to finding your ideal pace.

As endurance athletes, we spend a lot of time talking about thresholds. “What’s your FTP?” is basically the endurance equivalent to “What’s your bench?” in strength sports. 

Functional threshold power (FTP) is a metric gaining traction when it comes to training and load monitoring in cycling and triathlon. Typically calculated as 95% of an athlete’s best-effort power over 20 min, FTP is used to estimate the second physiological threshold, which defines the transition from steady-state to non-steady-state physiological responses to exercise. Above this second threshold (commonly referred to as the anaerobic threshold), physiological variables such as oxygen consumption, circulating lactate concentrations, and muscle and blood acidity cannot stabilise, causing fatigue to progressively develop.Whilst knowledge of this second threshold is definitely of significance to endurance athletes, we argue that the first physiological threshold – often referred to as the “aerobic threshold” or “lactate threshold” – is of greater significance to long-distance triathletes. In this blog, we are going to briefly describe what this first threshold is, why it is useful, and how you can find your individual lactate threshold.

What Is the First Threshold?

The first threshold (aka lactate threshold) defines the boundary between moderate and heavy exercise intensities. Below this threshold, blood lactate concentrations are stable and almost equal to baseline. Above it, blood lactate concentration may stabilise, but at concentrations above baseline. This physiological phenomenon is why many refer to the first threshold as “lactate threshold.”

What Training at Lactate Threshold Feels Like

When exercising at or below your lactate threshold, rapid energy systems (the energy systems used for short bursts of energy) aren’t really used, meaning that there isn’t much acidity built up in the muscles and blood. Lactate threshold is sometimes referred to as “conversation pace,” meaning you should be going easy enough to hold a conversation without undue effort. 

The Value of Lactate Threshold in Training

Training above your lactate threshold requires considerably more recovery time. Thus, when you include ample training at or below your lactate threshold, you can achieve higher volume. That is why many elite endurance athletes adhere to a pyramidal or polarised training intensity distribution, with upwards of ~75-80% of total training time accumulated at intensities below their lactate threshold. 

This isn’t to say that all of your training should take place below the lactate threshold; just that you want to be very specific about when and how you go above it so that you can adequately recover.

How to Find Your Lactate Threshold 

The most accurate way to find your lactate threshold is by getting it tested in a lab. This involves exercising at progressively increasing workloads and measuring your heart rate and blood lactate concentration throughout the session. Pricking your finger or earlobe is often required.

When you test in a lab, you’ll receive a report that shows your speed and heart rate at your lactate threshold. Knowing what your heart rate is at lactate threshold can be very useful for ensuring your training intensity remains easy for more than two hours into a session. 

In reality, few people have access to laboratory testing. But there are some ways you can estimate your threshold on your own, though.

The MAF Method

Phil Maffetone has proposed the Maximum Aerobic Function (MAF) estimate of lactate threshold heart rate as 180 minus your age in years, with some adjustment for training status. The accuracy of this method has not been tested empirically, and the possibility of meaningful error at an individual level can’t be overlooked. 

The Karoven Formula

Legendary physiologist Martti Karvonen also tried to estimate heart rates that should be used for different training intensities as far back as 1957 with his Karvonen formula. This formula uses percentages of the heart rate reserve (your maximum minus resting heart rate). This theory proposes that ~40-60% of your heart rate reserve is moderate-intensity, though it doesn’t consider other physiological responses. So, for example, if you had a maximum heart rate of 185 bpm and a resting heart rate of 40 bpm, your calculated heart rate reserve (185-40) would be 145 bpm. The Karvonen formula suggests taking 40-60% of this number and then adding your resting heart rate. In this case, 60% of 145 bpm = 87 bpm; 87 bpm + 40 RHR = 127 bpm. This would be the suggested upper end of moderate-intensity exercise. In our experience having tested numerous athletes in the lab using metabolic and lactate data, this number appears much lower than an expected aerobic threshold in athletes.

The Talk Test

Another method that has seen some attention in the literature relates to exercise below the lactate threshold being conversational. The “Talk Test” is a method where your lactate threshold is identified as the workload at which you can no longer comfortably talk. 

The effectiveness of this test for identifying lactate threshold power and heart rate was examined in a cohort of 18 well-trained cyclists back in 2013. In this study, the cyclists performed an incremental test in the laboratory to estimate the lactate threshold on two occasions: once with physiological measures, and once with a talk test. In the latter test, participants were asked to read a paragraph (38 words) aloud at the end of each stage, with the lactate threshold identified when the participants could not talk comfortably. There were no significant, systematic differences between lactate threshold power or heart rate estimates using the physiological data or the talk test, with strong correlations observed between the two measures. Therefore, this test could easily be done at home, and it may provide a useful means of estimating the all-important lactate threshold. 

How to Perform Your Own Talk Test

The talk test doesn’t require any lab equipment but provides results very close to those found in the lab. This makes it one of the best and easiest ways to find your lactate threshold at home. Here is one way you could perform your own cycling-based talk test:

  • Choose a 30-40 word paragraph you are familiar with (like the words to your national anthem or your favourite poem)
  • Put on your heart rate monitor
  • After a 10-min warm-up, start the test at a very easy power output
  • Increase your power output by 20 W every four minutes (you could either program this using ergometer mode or just do it manually)
  • Read the passage aloud during the last 30 seconds of each stage
  • Stop the test when you can no longer comfortably read the passage aloud (when you have to breathe heavily after every few words)
  • Use the power output of the last stage that you could read comfortably in as your lactate threshold power estimate, and take the heart rate from 3:00-3:30 of that stage as your lactate threshold heart rate estimate (reading the passage may interfere with your heart rate, so don’t use the last 30-seconds while you were reading!)

Finding your lactate threshold is crucial when it comes to off-season training. At EndureIQ offers off-season training for athletes at every level within TrainingPeaks. You can check the plans out here.


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About Dr. Dan Plews

Dr. Dan Plews has over 20 years of experience as a coach, competitor, academic, and scientist at the highest level. He coaches the 2022 Ironman World Champion Chelsea Sodaro, Javier Gomez, and other high-level pros and age-group athletes. In addition, he holds the age-group course record for the Ironman World Championships in Kona. He has also worked as an Olympic physiologist and has published over 60 peer-reviewed publications in sport science and exercise physiology.

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