A Male Cyclist Riding A Trainer For A Fitness Test To Measure His Lactate Threshold

Understanding Lactate Threshold Testing for Greater Athlete Performance

BY Tom Epton

Could lactate threshold testing be the holy grail of endurance training? Understanding test protocols can help get athletes to new performance levels.

Lactate threshold training has become rather fashionable in recent years due to, in part, the success of several Norwegians across running and triathlon. Athletes, including Jakob Ingebritsen and Gustav Iden, have achieved success from intensity control using lactate measurements in training. Lactate is a commonly misunderstood substance in the body. Conventional wisdom dictates that lactate is bad — something that ‘builds up’ when you go hard — so ‘fitter’ athletes produce less and, therefore, can go at some given intensity for longer. But this is an oversimplified interpretation of what’s happening. Lactate isn’t the waste product, as once believed.

What is Lactate?

For athletes, lactate is a metabolic byproduct that plays a vital role in providing energy for exercise and can be measured to track performance. When the human body breaks down carbohydrates, lactate is produced. It’s an essential metabolite, a substance our body uses for fuel. It plays no part in fatigue as once thought. Despite this, blood lactate does increase with exercise intensity, much like heart rate and RPE (rate of perceived exertion). Lactate is measured in mmol/l (millimoles per liter of blood). The amount of lactate in our blood at various intensities can help us build a picture of the metabolic efficiency of an athlete.

Lactate Testing

The question of whether or not your athlete should get a lactate test is one of resources more than anything else. Lactate tests are extremely useful for identifying weaknesses, such as an athlete with a small aerobic base relative to their ability. That said, the usefulness of a test only extends as far as the protocol used during it. Unfortunately, there’s not really any standardized or recognized procedure for carrying out these tests but a key pitfall to watch out for is short step lengths. Blood lactate is not instantaneous. For example, suppose an athlete’s blood lactate concentration measures 1.5mmol/l at 300W, and two minutes later, they present the same measurement. They could measure a higher lactate value at the same intensity in five minutes or longer. Ideally, testing protocols use steps of at least five-minutes. The flip side of longer step lengths is that the test takes longer.

Going to a Sports Science Lab

Where you or your athlete is based dictates how accessible a sports science lab is to you, the price varies on where you are too, but expect it to cost around half the cost of a blood lactate analyzer. When your athlete goes into the lab, make sure the protocol meets a few standards…

  • Ask for step lengths of five minutes or more
  • Make sure your athlete can do the test on their own bike
  • Record power and heart rate on your athlete’s own devices 

Your athlete trains on their bike with their power meter and their heart rate monitor. None of these devices measure exactly the same as others, but they all measure consistently. If your athlete gets tested on an exercise bike that reads 5% higher than their power meter and zones are set from this, it’s a recipe for disappointment and overtraining. The most important thing is that measurements are consistent, so lab tests should mimic the training environment as closely as possible. This means that training zones calculated in the lap apply to training in the real world.

Buying a Lactate Analyzer 

The other option is going all-in and buying a lactate analyzer. These can typically be picked up for a few hundred dollars and have become popular amongst pros and keen amateurs alike over recent years.

To carry out a home lactate test, the athlete must perform the same protocol as they would in a lab. On a turbo trainer with erg mode enabled, this is relatively easy. In the case of running, the athlete may require some assistance with taking the measurements, but the testing principles are the same.

How to do a DIY Lactate Test:

Having an experienced practitioner perform a test is always preferable in a controlled environment, but there are instances where access is not available to a testing lab. Here are some tips on performing a test using a lactate analyzer in the field.

  1. Use a knowledgeable partner — taking blood lactate samples is relatively easy, but when an athlete is active and sweaty, they will need someone to do the sampling for them.
  2. Control intensity — tight intensity control is key to a successful lactate ramp test. If running, this can be achieved most efficiently on a smart trainer or a treadmill.
  3. Start easy — the first step of the ramp should be ‘recovery pace,’ very easy jogging or easy spinning. From there, increase the intensity by 20-30W every 5-8 minutes taking a lactate measurement at the end of every step.
  4. Take notes — when you complete any lab experiment, it’s important to take notes. You may find certain things work better than others, and writing this down during the test will help for future tests.
  5. Measure what you can — you may not always have access to lactate during sessions. You will want to know-how lactate values stack up to heart rate, RPE and power.

Lactate Values in Context

After the invention of power meters, it took coaches a long time to understand what numbers meant in context. Lactate values are the same. In healthy individuals, blood lactate concentrations are between 0 and 2mmol/l. As exercise intensity increases, this value will increase relatively steadily up to around 4-4.5mmol/l, and a rapid increase will be seen. Peak lactate values can be over 20mmol/l, but this is highly dependent on the athlete. Athletes with a ‘fast twitch’ tendency will likely be able to produce higher peak lactate values. A middle-distance runner is more likely to have a greater peak lactate production than a marathon runner. Peak lactate values may be reduced in athletes experiencing symptoms of overtraining.

VLa Max, AeT and AnT

Measuring an athlete’s lactate production in a number of contexts can provide us with a wealth of information. These are three useful concepts to understand when looking at lactate data.

VLa Max — This is the maximum lactate production rate in the muscles. This is a marker of the glycolytic energy system’s performance. A high VLa Max is beneficial for some athletes and detrimental for others. A high VLa Max is good for a sprinter, but for an Ironman athlete, not so much. If large amounts of energy over short periods of time are needed, a high VLa max is good, but it comes at the cost of a lower AnT relative to VO2 max.

VLa Max can be trained with repeated ‘long’ sprints. All-out repetitions of 30-60s with full recovery will encourage a high rate of glycolysis.

AeT — The aerobic threshold, often referred to as LT1, is the first point at which lactate rises above resting levels. For example, if a marathon runner capable of running 2:20 goes out and does a 30-minute jog at 8:00 min/mile, you would expect their lactate value to be baseline upon completion of that run. If they ran for 30 minutes at marathon pace, their blood lactate value would likely settle at their AeT by the end of the run. Raising your aerobic threshold is good for all endurance athletes, unlike raising VLa Max, which is only good for some athletes.

The aerobic threshold can be trained with proper zone two training.

AnT — The ‘anaerobic’ threshold, often referred to as LT2, is the point at which the increase in lactate becomes rapid. This is also known as the ‘lactate turn point,’ and it’s essentially the bottom of the acceleration on the exponential curve. The point at which lactate accumulation becomes rapid. This is roughly where a cyclist’s FTP might be and is the intensity an athlete can sustain for between 30 and 60 minutes, depending on how well-trained they are.

Training the second threshold can be complicated, and the most efficient way to do this is hotly debated. Generally speaking, repetitions at 95-105% of LT2 with a work-rest ratio of 2:1 is a good starting point.

Profiling Athletes Based on Their Lactate Curve

Athletes with differing strengths and weaknesses will be identifiable from their lactate curves, and these curves will evolve over time. In the base phase, which for Northern Hemisphere athletes is ongoing now for triathlon and cycling, many coaches are trying to shift their athlete’s lactate curve to the right — an indication that aerobic endurance training has been adapted to. The opposite might be seen after an end-of-season break where the curve has shifted left.

Lactate Testing Graph of two different tests of an athlete

The blue line in this graph is that of an athlete who has just restarted training after a break, and the orange line is after a base training period. We can see the shift to the right of the lactate curve that comes from an increased aerobic base. The uptick in lactate values as intensity increases starts later, indicating increased aerobic fitness. The shape of the curves remains similar, telling us this athlete’s metabolic profile has not changed much.

Triathlon — All Sports are not Equal

Lactate values are not the same across all sports. We know that lactate is produced in the muscles and then transported around in the blood. Simply put, different muscles mean different lactate values. This is why it’s important to replicate training conditions when testing, so intensity zones can be carefully matched across disciplines and why lactate tests done on the bike mean comparatively little in the context of running. Evaluating lactate levels for the bike and run independently is certainly a best practice, and even different bikes depending on the athlete and goals.

Key takeaways for coaches

  1. Lactate is not a waste product but an essential metabolite, and an athlete may need to create more or less of it, depending on their discipline.
  2. Not all lactate testing protocols are made equal, avoid step lengths of less than three minutes, and ideally, five to eight minutes should be used.
  3. An athlete’s lactate curve will shift over time depending on their training focus and current physiological state — these shifts, in the context of other metrics and an athlete’s feeling, can be used to decide what energy systems to train and which races to focus on.
  4. Lactate is produced in the muscles, so make sure test equipment uses the same muscles used via the training equipment.

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About Tom Epton

Tom Epton is a writer and data scientist based in the South East of England. He is a founding member and principal data scientist at PyTri Ltd, a consultancy specializing in applying data science techniques to performance sports and healthcare. Tom has a first-class BSc in Physics and has worked at several well-known brands on big data and machine learning projects. Away from work, he is an elite triathlete racing a mixture of draft-legal short courses on the British Super Series to middle-distance non-drafting triathlons. Tom also offers coaching, physiological testing and endurance sport consultancy services. Email him for more information.

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