If you’re an avid follower of endurance sports, you’ve probably seen lactate meters popping up on your favourite athletes' social media feeds over the last few years. Usually, these athletes will have their fingers pricked and lactate sampled between reps during a workout, before reporting the number displayed on the lactate meter.
Why are they doing this? And could following their lead help you dial in your training zones? Let's take a look...
What is lactate?
Despite lactate being the current buzzword in endurance circles, it certainly isn’t new. In fact, lactate was discovered nearly 250 years ago - in sour milk, no less - by the Swedish chemist Carl Wilhelm Scheele.
In the context of exercise, it's a little over 200 years since lactate was found in high concentrations in the muscles of exhausted stags. Arguably, this was the basis for a couple of common misconceptions:
Myth #1: Lactate causes fatigue
Let’s quickly dispel that myth. During hard efforts on the turbo trainer or running track, lactic acid is produced by the muscles, but this molecule quickly separates into lactate and a hydrogen ion (H+).
Accumulation of these H+ ions increases the acidity of the muscles and this interferes with the ability of the muscles to contract efficiently and leads to fatigue. The acidity is also what leads to the burning sensation during intense workouts, which I’m sure you’re familiar with.
Myth #2: Leftover lactate is just a waste product and must be eliminated from the body
Actually, lactate is an incredibly valuable energy source. During exercise, some level of lactate production is inevitable because it occurs when carbohydrate is broken down in the muscle to create energy. Critically, when lactate is produced at a rate where your body can clear it and turn it into energy, then it becomes really useful for endurance athletes.
And the great news? Your body’s ability to clear and recycle lactate can be trained. The right combination of training and strategic recovery will significantly enhance lactate metabolism.
How lactate threshold testing works
Over 30 years ago, Dr Michael Joyner - a world-leading exercise physiologist - proposed a model which suggested that an athlete’s performance during endurance events was dependent on three key variables:
- VO₂ max (the maximum amount of oxygen the body can utilise)
- Exercise economy (the amount of oxygen required to exercise at a specific speed)
- Lactate threshold (the highest sustainable intensity before lactate accumulates excessively)
This model turned out to be pretty accurate! It’s still used to predict endurance performance today. In fact, testing of these variables was a key feature of the athlete selection process for Nike’s 2017 Breaking2 project. And an intimate understanding of these variables for each athlete was used to meticulously plan training sessions and pacing strategies for the sub-two hour marathon attempt.
The methodology for systematic lactate testing was first developed in the 1970's by a group of researchers in Cologne. Unfortunately, this work is under-appreciated in the world of exercise physiology as it was mainly published in German - the concept of lactate threshold testing certainly wasn’t covered in my German GCSE!
Lactate threshold testing typically involves an incremental test on a stationary bike or treadmill - but it can also be done on a rowing ergometer or even in the swimming pool for experienced athletes.
Before starting the test, a baseline lactate measurement is taken from a small spot of blood obtained from pricking a finger tip or ear lobe. The test then starts at a relatively low level of exercise, and further lactate measurements are taken each time the speed or power is increased, which is usually every four to five minutes.
There's some variability in determining completion of the test as a result of differences in protocols and athletes, but the endpoint usually arrives when blood lactate levels are measured at over four millimoles per litre (mmol/L).
By plotting the lactate values obtained during the test against speed or power, you can create a lactate curve. And from this, you can identify two different lactate thresholds:
- Lactate threshold 1 (LT1 - the “O.G.” lactate threshold, or aerobic threshold)
This is the point at which blood lactate values begin to rise above baseline levels. This marks the transition from purely aerobic metabolism to a gradual shift in anaerobic energy generation. This is the highest intensity you can sustain for long periods with minimal lactate accumulation.
- Lactate threshold 2 (LT2 - also known as the lactate turn-point, or anaerobic threshold)
This is the intensity at which lactate begins to rise exponentially, because lactate production outpaces lactate clearance. Above this threshold, carbohydrates become the primary fuel source. As a result, sustaining exercise at this intensity is impossible because you'll either run out of fuel, or experience fatigue due to the accumulation of H+ ions.
More than 25 different models for threshold identification have been published in the literature, and deciding which model to use isn't an exact science. Most exercise physiologists tend to rely on their experience to visually inspect the speed/power versus lactate relationship in order to determine an athlete’s LT1 and LT2.
At this point, it’s important to note that LT2 isn't the same as functional threshold power (FTP) or critical speed. While these tests both offer a relatively simple solution for setting power or pace-based training zones, they only provide a proxy measure of LT2.
And because FTP or critical speed testing are reliant on your pacing ability and endurance, they can often be quite different from LT2. Even if executed well, an FTP or critical speed test certainly doesn’t tell you much about your aerobic and anaerobic capabilities.
How to use lactate testing to dial in your training zones
Wearing a heart rate monitor during a lactate threshold test is essential as it helps identify the heart rates which correspond to LT1 and LT2. And this means you can use heart rate to precisely guide your workouts to ensure you train within the correct zones.
Most endurance athletes will work to a three-zone or five-zone training model. So, it’s worth explaining how your lactate thresholds fit into each of these models.
The five-zone training model
The model that most of you will be familiar with allows training to be prescribed across the entire aerobic and anaerobic intensity range.
In this model, LT1 marks the boundary between zone 2 (endurance) and zone 3 (tempo), while LT2 defines the upper limit of zone 4 (threshold). Since these training zones are often linked to percentages of maximum heart rate, understanding the corresponding heart rate for LT1 and LT2 will help to accurately prescribe training intensities.
The three-zone training model
The simplest model that’s been made famous over the years by numerous Norwegian athletes - starting with the runner Marius Bakken in the late 90’s, through to the present day with the Ingebrigtsens, and triathletes Kristian Blummenfelt and Gustav Iden.
In this pyramidal model, most training is done in zone 1 (below LT1), some training in zone 2 (between LT1 and LT2), and a very small amount of training is completed in zone 3 (above LT2).
Using these thresholds to carefully guide training intensity means that you can tolerate high training volumes, with the overall goal being to maximise endurance adaptations while minimising fatigue.
A perfect example of this strategy being employed was published in a research paper co-authored by Blummenfelt’s coach, Olav Aleksander Bu. They reported that Kristian averaged 26.5 hours of training each week over a three-year period in which he won Olympic Gold, the IRONMAN® World Championship, and IRONMAN 70.3® World Championship!
Lactate testing vs. lactate monitoring
What the aforementioned Norwegians do repeatedly - and to some expense (lactate strips aren’t cheap!) - is monitor the intensity of their training sessions using blood lactate. Instead of relying solely on external metrics such as power or pace, lactate responses during threshold-type sessions offer information on the internal training load - and this is a powerful tool to regulate intensity during the session.
The result is a more ‘controlled’ threshold session. Therefore, recovery is more rapid, meaning that a greater weekly volume of higher-intensity sessions can be achieved.
If you’re a high-volume athlete, there may be some value in using lactate measures in training to monitor workload. But for the majority of athletes, this is likely to be unnecessary (despite it looking great on social media!).
Lactate testing, on the other hand, should be repeated regularly to understand the response to a specific training block or monitor training progression over time. It's certainly a much more sensitive marker of adaptation and progression than VO₂ max. Indeed, many endurance athletes don’t have a particularly remarkable VO₂ max. But what they are able to do is work at a high proportion of their VO₂ max for long periods, and this means exercising at a high speed or power without accumulating significant levels of lactate.
Should you get a lactate test?
As an exercise physiologist, I’ll admit to being biased. But the bottom line is that while lactate threshold testing may seem advanced, understanding your thresholds can reveal specific weaknesses and therefore help dial in your training zones.
Depending on the demands of your sport or event, the results of a lactate threshold test can determine the specific training you need to do to improve. If you’re planning to compete in ultramarathons, improving your LT1 will enhance your endurance capacity. If a sprint triathlon or 10km road race is your target, improving your LT2 will benefit your performance.
Whether you’re training for your first marathon, or aiming for a personal best, regular lactate threshold testing is a great way to help fine-tune your strategy, monitor improvements and maximise your performance.
Frequently asked questions
Does it matter if I complete a lactate test while cycling, running or rowing? Are my zones comparable across sports?
Yes, it matters. Your lactate thresholds are sport-specific, mainly because different muscle groups are engaged in different ways across disciplines. For example, running typically produces a higher lactate threshold than cycling because the total muscle mass engaged in running is greater, and consequently this results in a higher rate of oxygen consumption at LT1 and LT2.
It's been argued that lactate threshold heart rate might be somewhat comparable between disciplines, but power and pace zones will not translate directly between sports.
From my own experience, my heart rate at LT1 on the bike is always around 135-140bpm, but it's closer to 150bpm when I do a profiling test on the treadmill. That probably reflects my years of running from a very young age, but relatively fewer years spent cycling (I only started riding a bike in anger in my mid-20’s).
How do I improve my lactate threshold?
If you're aiming to improve your LT1, this will require a different training approach than when your focus is on improving LT2.
A higher LT1 allows you to sustain a faster pace or higher power output while remaining in a predominantly aerobic state - and is key for events like marathons or IRONMAN® races.
To improve LT1, you should incorporate more low-to-moderate intensity training (below or at LT1) because this will improve mitochondrial efficiency (the part of every cell responsible for generating energy) and capillary density (the number of blood vessels supplying muscles) and translate into greater levels of fat oxidation. This is essentially building your aerobic base and ‘pushing up’ your LT1.
Combining this with some ‘tempo’ sessions where you're working above LT1 (but well below LT2) for 20-30 minutes at a time is also beneficial, and is more akin to ‘pulling up’ your LT1.
Improving your LT2 will mean that you can sustain higher intensities for longer periods, which is critical for events like a half marathon or a cycling time trial.
Focus on incorporating sessions into your plan that involve working just below LT2 (the classic example is what we might call ‘sweetspot’ intervals), as well as VO₂ max sessions which require you to work above LT2 for 3 to 5 minutes at a time. Or even a combination of these two things in an ‘over-under’ workout is a good strategy to improve the ability to clear lactate more efficiently.
How often should I get a lactate test?
This really depends on your goals and training structure, but a good general recommendation is to get a lactate test at least once per year to help establish training zones and benchmark fitness. A better approach is to use lactate testing to track improvements and adjust training accordingly.
As an example, if your aim was to improve LT1 and you spent 2-3 months doing a block of lower-intensity aerobic work to achieve this, having another lactate test would be useful to a) check your level of improvement (i.e. whether you’ve responded to the training), and b) adjust your training zones to reflect your new level of fitness.
One thing we’d advise against is having a test just before a key race to ‘test where your fitness is’. Under these circumstances, the information isn’t particularly usable for setting training zones (which is the main purpose of lactate testing). You might be fatigued leading into the test or the test itself might compromise your taper and create fatigue before race day. If the improvement isn’t of the magnitude you’d hoped, it could put a dampener on your expectations leading into the race, knock your confidence, and you might overthink your pacing and strategy.
Where can I get a lactate threshold test?
We offer lactate threshold testing at the Precision Performance Lab in the UK. And if you'd like to know more about the services at the lab, you can book a free one-to-one video call with one of our Sports Science team.
