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Looking to take your training to the next level? Then it might be time to get a lactate test, which can tell you all about your body’s capacity to work harder and faster. 

If I say the word ‘lactate’, your mind might immediately conjure up images of breastmilk, suckling babies and maternity bras. Indeed, when I announced that I was going for a lactate test to the rest of the Stylist team, I was met with some confusion. No, I wasn’t revealing some massive baby-related secret – I was going to get my blood tested to see what speed I should (and could) be running at.

The current obsession with biohacking has seen a massive boom in at-home finger prick tests. I’ve done everything from testing for my ‘fitness DNA’ (I’m not built for running, apparently) to food intolerances (gluten, dairy, alcohol…), and I know how dubious they can be. 

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To have a better idea of how your body responds to various stimuli, you want to be tested in a controlled environment – with an expert on-hand to both do the testing and the explaining. So, when I was invited to test my lactate threshold by running supremos Anthony Fletcher and Laura Naylor from One Track, I was intrigued.

What I didn’t realise, however, was that I’d actually have to run. I imagined sitting on a sofa and having a little blood taken before being walked through a spreadsheet of data on my VO2 max. How wrong I was. 

What is a lactate test, and what’s the point of doing one?

Fletcher tells Stylist: “Lactate profiling is a testing protocol where exercise intensity is increased in stages, and the concentration of lactate in the blood is measured at the end of each stage. Each stage normally lasts between two and five minutes and there are normally six to eight stages in a test.

The point of lactate testing, he explains, depends on what your goal is. I’m training for a marathon, so this test may help me to better plan my long runs – and to know what speeds I should be aiming for during interval training. More generally, it’s a measure of the aerobic system and its ability to work at certain intensities.  

Is it linked to lactic acid?

If you’re a runner, then you’ll know only too well the agony of lactic acid build-up. That’s the sensation of cramping on a long run. At least… that’s what experts used to think it was. “We used to think that lactic acid was the burning sensation you feel when exercising at high intensity, but we now know that this is not the case,” Fletcher explains.

“In fact, lactic acid may not actually be measurable in humans as it very quickly splits into hydrogen ions and lactate.”

When we test for lactate, we’re actually looking at energy. 

Running and energy sources

Imagine this scenario: 

You’re preparing to go on a run. As you get out of bed, you push yourself up and out of the covers. That act of going from lying to standing uses ATP (adenosine triphosphate), aka anaerobic alactic energy. It’s an energy source that only lasts a few seconds, but we use it multiple times every day. It’s the energy that’s stored in our muscles we use when dodging wandering dogs, getting up from a chair and stepping back as someone comes towards us through a swinging door.

Once you’re dressed and out of the door, you start to run – feeling a bit rusty. You’re now using lactic energy, or glycolysis, which can last up to three minutes. You’re using glucose in the absence of oxygen (anaerobic) here, and this is one of our main energy pathways for hard-intensity exercise. The interesting thing about lactate acid is that aerobic muscle tissue – the heart, brain and many other systems within the body – can reverse lactate back into glucose again and use it as a fuel.

Once your body realises you’re not just doing a 100m sprint, it’ll kick into using the aerobic energy system. That’s your endurance, low-intensity energy source.  

Why intensity and energy are so important for runners

As runners, it’s important to be aware of how intensely we’re running because how fast or far we can go is inexorably linked to the energy we have available. Our goals are dependent on us tapping into the correct fuel sources. Imagine you’re going for a marathon PB: as you keep pushing ahead, your lactate levels rise. You’re going to run out of glucose much quicker than if you were to slow down and run at an easier speed – so you need to refuel on the trot.

“When we produce high levels of lactate, it generally means that we’re using high levels of our muscle glycogen, which may be good for promoting adaptation to exercise, but does take some time to replenish,” says Fletcher. That means refueling and recovery are critical.  

What exactly happens during a lactate test?

The test

  1. Up to eight run blocks, each lasting three minutes
  2. Each block is faster than the last (by one level)
  3. Between each block, you have your blood tested via a little ear prick
  4. The test ends when you’ve gone past your lactate turning point – the point at which the body is almost exclusively relying on glycose as a fuel source

I start running at an easy and gentle pace (level 8 on the treadmill). Four stages later (level 12), I’m feeling distinctly less calm; by stage seven (level 14), I’m dripping with sweat and replying with monosyllabic answers to Fletcher’s questions – and that’s when he informs me that the test is finished: I’d passed my lactate turning point. 

Lactate threshold and lactate turning point

What this test really looks for is the point at which you pass your lactate threshold (when lactate levels start rising above resting level and your body starts to switch to the more dominant fuel source) and your lactate turning point.

The lactate turning point (which happened to me at level 12) signifies the moment that your body is almost exclusively relying on glucose as a fuel source. “The aerobic system cannot keep up with the speed at which you are running, and the deficit is being made up by glucose,” Fletcher says.

Anything below that turning point is what’s known as ‘steady state’ cardio. For example, if your lactate turning point is at 10km/h, you might be able to keep your lactate reading stable at 8km/h for 20 minutes. However, speed up to 12km/h, and your lactate reading may start to soar within minutes, and it’ll keep rising. 

Finding your easy run pace should mean being able to talk and smile… unlike the moment you pass your lactate threshold.

What impacts your lactate readings?

It’s worth noting that I turned up to the test having had a black coffee and no breakfast. I wondered whether that might have had an impact on my results. According to my heart rate and lactate readings, I’m looking at a 50-minute 10k – four minutes slower than my 10k PB. Is that because I’d normally be more prepared ahead of a race?

“This is the pinch of salt that comes with one test of the physiology,” Fletch admits. “Remember, psychology has a big part to play in racing, and we can’t measure that until the day. Adrenaline can play a very big role; it can improve performance but too much isn’t good.”

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He does say, however, that while lactate turning point may be closely attributed to 10k race pace, other factors may come in on the day that mean you perform better than predicted. Sleep, nutrition, focus, crowds: all of these factors play a large role in on-the-day performance, especially caffeine.

“Making sure you are well fed and your glycogen stores are replenished is a big part of the recovery process/tapering for a race. The environment that you are racing in also has a large impact on your body’s ability to perform.”

How to improve your lactate threshold

My results showed that I should be running easy runs at 6mins/km or slower. A threshold tempo run is anything between 5.15 and 4.45mins/km. A hard run – the kind I’d probably be looking to do during a short race – is anything faster than 4.45mins/km.

If I want to improve those numbers, Fletcher suggests three possible options:

  1. More easy runs: “This can make your body very efficient at using fats as a fuel source, which is the main fuel of the aerobic system.”
  2. Interval training: “This puts a lot of lactate into the bloodstream and so gives the body the opportunity to become better at dealing with it. There is a myth that high-intensity work does not use the aerobic system – it does, and it can be a very beneficial stressor for developing aerobic pathways.” 
  3. A mix of the two: “This is probably the most sustainable option. Following a pyramidal approach to training where the main bulk of your volume is easy, a little bit of work is moderate, and a small amount of work is hard allows for developing the full spectrum of all energy systems, muscle, fibre types, psychology, neurology. The only thing is, it’s harder to design a plan that allows for both recovery and progression.  

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The aim is to see all those numbers go down – and the best way to do that is to give the above suggestions a go and pop back for a follow-up test in three months. I’ll be better prepared next time. 

Book your lactate test with One Track, £80.

Images: Getty/One Track

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