With the 2026 Seville Marathon looming and my sights set on sub-3:10, I was looking for fresh insights to help plan my training block.
This led me to The Altitude Centre, a high-performance gym tucked away down a quiet side road behind Liverpool Street station in London, where athletes look to replicate a Kenya training camp or prepare for epic mountain climbs and gruelling desert ultramarathons by running in altitude or heat chambers.
But I was there for a lactate threshold test – a key piece of data to help me train smarter.
The test pinpoints the intensity at which lactate rapidly builds in the blood. The results are used to set training zones, based on heart rate and pace, to ensure the training is done at the right intensity for endurance (aerobic) or speed (anaerobic) work.
The ideal time to take the test is at the start of a training block, as this will map out the boundaries of your five training zones – recovery, endurance, tempo, threshold, and VO2 max.
You don’t need to be a pro athlete to take the test; it’s suitable for all levels as it will give you quality data you can use to manage your training, whatever your goals are.
My goal is to knock two minutes off my marathon PB, so I wanted to learn how to make that jump. The value of the test to another runner might be understanding how to run more efficiently in zone two, for example.
You’ll find the test on offer at sports science clinics like The Altitude Centre in London and some universities with sports science programmes, such as Plymouth Marjon University. The cost ranges from about £60 to more than £200, depending on the provider.
Once you have your data, you can manually adjust your training zones on your smartwatch, and you're all set.
I was put through my paces by James Barber, Lead Performance Specialist and a 2:39 marathoner, who had me running on a treadmill and jumping off at regular intervals to take fingertip blood samples, with the speed increasing after each sample was taken.
“Lactate threshold is the most valuable testing somebody can do,” James says.
“What we’re determining is the speed at which you go from an intensity you can hold all day to one you could only hold for maybe an hour to 90 minutes at a time.
“And then a second threshold where exercise is really time-limited – so where does exercise go from being really easy to quite hard to very hard?”
Lactate threshold and recovery metrics such as heart rate variability, which gives you a good indication of training readiness, are the key bits of data runners should be paying attention to, James says.
“Equally, there’s something to be said for tuning in to how your body feels,” James adds. “I think an over-reliance on data and what your watch is telling you isn’t necessarily healthy; it should be used as one piece of the puzzle.”
James recommends re-testing up to every six weeks or when you make a change in your training, to keep training zones up to date and track progress.
After I’d had my height and weight measured, he ran a quick lung function test to analyse the total amount of air I could exhale forcibly (forced vital capacity) and the total amount I could exhale in one second (forced expiratory volume one).
An optimal ratio of these two results is anything above 75% of the total lung capacity.
“We always like to have a look at lung function,” James says.
“We need oxygen in our muscles and in our brain to release energy, if there’s any kind of issues around the lungs or potentially any obstructions in the airway then we are only limiting the amount of air that can get into our lungs in the first place.”
The lactate test itself involved running on a treadmill in three-minute blocks, ramping up from an easy speed (about 6:40/km pace) to a hard speed (3:30/km pace).
In total, nine blood samples were taken to determine my lactate threshold one (LT1) and lactate threshold two (LT2).
“Everybody will have the small first rise [in blood lactate] and then a really marked second rise – the important thing to understand is the speeds and heart rates at which that happens as that is how the training zones are set,” James explains.
I ran the Frankfurt Marathon in October 2025 and since then have kept up my slow long runs while easing back on the speed work. The lactate test showed that my LT1 was in a good spot but followed very shortly by my LT2.
Having this data was invaluable as it showed I needed to increase both thresholds and gave me the zones to train in to achieve this.
To move the dials, I needed to vary my training and ensure I was boosting my LT2 by targeting higher-intensity workouts in zones three (tempo), four (threshold), and five (VO2 max).
I went into this block believing I needed to up my weekly distance from my last marathon (where I topped out at about 100K) if I were to bag a PB.
But James explained I could get faster without needing to ramp up what was already a decent amount of weekly mileage – now that I had my training zones, which enabled me to prioritise the quality and intensity of my runs.
“The way we see people getting the most value from the test is knowing how easy they should go on their easy days,” he says.
“It’s a pretty classic trap that runners fall into of trying to run everywhere quite hard and then never getting the quality of workout or the real high intensity because they are never fresh enough to do that.”
If you’ve got big running goals for 2026, a lactate threshold test will help you train smarter.
