What is lactate threshold? The science behind triathlon’s favourite training buzz phrase
Lactate threshold is a phrase we seen thrown around a lot in the world of triathlon training. From behind the scenes videos of the PROs having blood samples taken from their ear lobes in the midst of a hard session. To workout titles and training zone explainers.
But what does lactate threshold actually mean? And how can improving yours benefit your fitness in the context of endurance sport? With expert insights from the physiologists at Loughborough University Performance Lab, after we spent the day there being put through our paces. We dive into what lactate threshold means, and how to raise yours.
What is lactate?
Before we start talking about lactate thresholds, first we need to understand what lactate itself actually is.
Lactate is best known as one of the main ‘waste’ products that occurs when the body breaks down carbohydrate to provide fuel to generate energy. Rhona Pearce, lead physiologist at Loughborough University explains: “When you exercise, you use a mixture of fats and carbohydrates as a fuel. When you break down carbohydrates, you produce lactate.”
However, while lactate might be a by-product of breaking down carbohydrate. Research has found that it’s not simply waste – our bodies can actually use lactate as another source of fuel. “You’re always producing a bit of lactate because you’re always using a bit of carbohydrate as a fuel,” Rhona says. “But then you’ll use that lactate as a fuel, and that’s what will clear it.”
Lactate might have a bit of a bad rep, but it’s not actually “just” a waste product. And producing it at a level where your body can clear it by turning it into fuel is useful for endurance athletes.
What does lactate threshold mean in endurance sport training?
In endurance sports like triathlon, when we talk about lactate threshold we usually mean the point at which we start to produce more lactate than our body can clear so it begins to accumulate in the blood. The accumulation of lactate in the blood during exercise is associated with fatigue – i.e. the point at which you have to slow down or stop. And so we test for lactate thresholds, because these give us indicators of the intensity we can exercise at for sustained periods of time.
“Lactate thresholds are when there’s a change in the lactate during an incremental exercise test,” explains Rhona. “So you do an incremental exercise test, where you start at a nice easy intensity and it gradually increases every few minutes. We do 4 or 6-minute stages, and we take a blood lactate sample at the end of every stage. As exercise intensity increases, we have to start using more carbohydrate so the rate at which you have to break down lactate increases, and it starts to accumulate in the blood.”
“We look at two break points which are the thresholds: we call them lactate threshold 1 (LT1) and lactate threshold 2 (LT2). LT1 is when the lactate values first start to rise above the baseline, so that is kind of the edge of your ‘easy’ training. The 2nd threshold is when your lactate values really start to accumulate. So above that intensity, you are using predominantly carbohydrates as a fuel and you’re not going to be able to carry on indefinitely because you’re not going to be able to replace them at the rate at which they’re being used.”
The two lactate thresholds essentially give us a guideline as to how fast/hard we can go when we’re training or racing. If we know we’ve got to sustain the effort for several hours, we need to stick to an intensity which keeps us below or at LT1. Meanwhile if it’s a shorter session or race, we can push up to LT2. “Depending on your endurance, LT2 can be sustained for around 30-60 minutes,” says Rhona. “If you look at running for example, the first threshold tends to correlate with marathon pace. And the 2nd threshold typically correlates with 10km pace.”
Lactate threshold testing
The accurate way to find out your lactate thresholds (LT1 and LT2) is by participating in an incremental exercise test in a lab. A small blood sample is taken (usually from the ear lobe) before the test to get a base line. Further samples are taken throughout the test, each time the intensity of exercise increases to get a precise measure of when blood lactate levels first increase – indicating you’ve reached your first lactate threshold. And then when they significantly increase again, indicating you’ve reached your second lactate threshold. Watch the video below from our day at Loughborough Performance Lab to see what the incremental exercise test involves, and read the article to see what the results showed us!
Some running and fitness watches also estimate your lactate threshold using pace/power and heart rate. This won’t be anywhere near as accurate as the lab testing, but it does give you an indication of the training zone to work in if you want to raise your thresholds and the pace you can hold depending on the length of your race or event.
Is it good to improve lactate threshold?
Improving your lactate threshold will enable you to push harder, for longer before fatigue sets in. The fitter we get, through training, the more efficient the body gets at clearing lactate by utilising it as a fuel source.
“LT2 is the exercise intensity above which there is a sustained increase in blood lactate concentration. This accumulation of lactate is associated with the onset of fatigue, therefore the higher the intensity this occurs at – the better for performance.”
– Lucija Petrovic, physiologist to Olympic gold medallist Cassandre Beaugrand.
In the context of long distance triathlon for example, raising your lactate threshold will essentially make your steady endurance pace quicker – so you can cover the swim, bike and run race distances faster without blowing up.
How to improve lactate threshold
To raise your lactate thresholds, you need to dial in your training and get specific with the intensity you’re working at.
Working on improving your LT1 will help you to improve your endurance pace. To raise your first lactate threshold, you should focus on incorporate more easy, aerobic cycling and running into your schedule. These Zone 2 sessions will help your body to build a strong aerobic base, which in turn will help it to become more efficient at clearing lactate by using it as a fuel source.
Improving your LT2 will help you to perform over shorter distances, for example sprint triathlons, 10km running races and <60 minute time trial cycling events. And it will help to boost your overall aerobic fitness (or functional threshold power in the context of cycling) so you can go faster, for longer. LT2 training will involve doing some interval work at Zone 4 and Zone 5 intensities. For example 5 x 4 minutes at Z4 heart rate/power output. Or shorter intervals at Zone 5 (for example 10 x 40s Zone 5 with 20s easy recovery). The aim is to accumulate time at your second lactate threshold, rather than going for a full gas effort.
Check out some of our favourite indoor cycling workouts to improve your FTP to help raise your threshold on the bike. And for runners, our pick of the best treadmill workouts for marathon training will help you to boost your first lactate threshold so your endurance pace gets quicker.
Are lactate and lactic acid the same thing?
Part of the reason lactate has a bit of a negative connotation is because we commonly get it mixed up with “lactic acid”. But as Rhona Pearce explains, “lactic acid and lactate are different things.”
It’s not actually the lactate that causes the horrible burning sensation in your muscles when you start to hit the wall. “The acid part is hydrogen ions, that’s what can cause that burning feeling. But when you produce lactate, you also then clear it.”
“When you’re below your 2nd threshold and particularly when you’re below your 1st threshold, you’re always producing a bit of lactate because you’re always using a bit of carbohydrate as a fuel. But then you’ll use that lactate as a fuel, and that’s what will clear it. Once you go above the second threshold, you can’t clear it as quickly as it’s being produced. So yes, lactate and hydrogen ions do accumulate – but it’s not necessarily a bad thing, particularly for an endurance athlete because at low intensities it is actually used as a fuel.”
The next time you’re pushing the big watts on the bike and you feel like your quads are on fire, you’ll know it’s not lactate that’s the culprit – but actually those pesky hydrogen ions!
