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What is Lactate Acid

Lactate threshold is a term that coaches and riders often use, however it’s often unclear it means. We’ll use this article to demystify lactate threshold.

Lactate threshold refers to the amount amount of power a rider can produce while keeping their lactate (lactic acid) levels under control. The more power we put out on the bike the more lactate is produced and lactate only becomes a problem when we cannot process it fast enough.

Lactate has a bad name as the substance that makes your legs burn during exercise and the reason your legs are sore afterwards – but this actually isn’t the case.

Lactate is produced when your body burns glucose, this is happening the entire time (even when not exercising). Once produced, lactate actually gets reprocessed back into glucose and used as a fuel. Lactate processing takes place first of all in your muscles and this happens very quickly. It is only when there is too much lactate for your muscles to process that it gets shipped off in your blood stream for processing elsewhere in the body, this raises your blood lactate.

Lactate threshold occurs at the point where the amount of lactate in the blood reaches it’s highest sustainable level. In simple terms, your lactate threshold is how hard you can ride for a prolonged period without blowing up.

Lactate is mainly produced by type II (fast twitch) muscle fibres, while it is mainly processed by type I (slow twitch) muscle fibres. One more interesting fact about lactate before we look at what lactate threshold is – your brain neurons also use it as a fuel source, so far from being a bad thing that only makes your legs hurt, it is an incredibly important substance in your body.

Now we’ve got a handle on exactly what lactate is, let’s get to grips with lactate threshold.

Lactate threshold

Lactate threshold is a measure of how well our body can process lactate acid. Therefore, a rider that can put out a lot of power for a long time – for example, Tony Martin or Bradley Wiggins – will have a very high lactate threshold.

For efforts of ten minutes or longer, lactate threshold is the physiological factor that will determine how much power a rider can put out. The higher a rider’s lactate threshold, the more power they can sustain.

As I’ve discussed already, when you are riding hard you are recruiting your type II (fast twitch) fibres and this produces lactate. At the same time, your type I (slow twitch) fibres are busy processing that lactate. Lactate threshold is the point where your slow twitch fibres reach capacity – more lactate is being produced than what your muscles can process – and the lactate acid gets sent off in your blood to be processed elsewhere in your body.

The amount of lactate acid being transferred away from your muscles and into your blood is what is measured when we talk about blood lactate concentration. This is what is being measured in the small prick of blood taken during a lab test for those of you lucky (or unlucky) enough to have done one.

There has been a lot of discussion among sports scientists about at what level lactate threshold should be set but for ease it can be described as the maximum amount of power your can push with a blood lactate level of approximately 4mmol/litre of blood.

This all sounds very ‘coachy’ and, to be honest, it is. 4mmol/liter is seen as the maximum level of lactate in your blood that you can sustain without blowing up. Ride any harder and your blood lactate will increase exponentially and the effort will become unsustainable.

What does that mean out on the road? Essentially, lactate threshold is how hard you can ride for a prolonged period of time. The more lactate your muscles can process, the less is being passed into your blood and you’ll be able to ride harder, for longer. Sounds good, right?

Lactate threshold varies from ride to rider but ultimately it’s a key figure in determining riding your riding intensity. The good news is that it can be improved, too, but how can you determine your lactate threshold and use it to inform your training and racing?


A lot of riders and coaches use the terms threshold, lactate threshold and functional threshold power interchangeably. They all describe the intensity you can sustain for a prolonged period without blowing up.

But how long is a prolonged period of time? One hour, twenty minutes, four hours? This is the problem – the length of time often isn’t specified. In fact, the amount of time that an athlete can sustain 4mmol/litre lactate concentration is different from athlete-to-athlete and depends on how fit they are.

In the real world, there are a very limited number of coaches and athletes who use blood lactate levels as a training tool. This would require standing at the side of someone while they do their training, taking regular blood samples and testing them… hardly practical!

This is where FTP comes in. This is the power you can sustain for one hour – regardless of lactate concentration in your blood – and it’s a very useful landmark in determining training zones, which in turn will allow you to control and measure how hard you are riding, thus giving you the ability to target specific improvements in your form. Refer back to my article on training zones to find out more.

Lots of riders train with a power meter (or heart rate monitor) and, therefore, it is relatively simple to measure the power you can hold for one hour – simply go out and ride hard for an hour!

In practice riding at your limit for one hour is very tiring, requires an element of pacing and doesn’t fit particularly well into a training plan. But we cheat somewhat by doing a 20-minute test, from which you can take 95 per cent of the figure as a best estimate on what would be sustainable for one hour. From this figure you can also work out your training zones

A good warm-up is important and then you need a section of road twenty minutes long. Set off at a pace you feel you can just sustain for the full 20 minutes (this is probably slightly easier than you think) and aim to hold this intensity for 17 or 18 minutes, at which point give it everything until the end. You need to record your average power and average heart rate for the 20 minutes. To calculate your FTP take the power and multiply it by 0.95. Do the same for your average heart rate to calculate your threshold heart rate.

Now you know what lactate acid is, and you know your FTP, what can you do to improve it? After all, the higher your FTP, the more power you can sustain.

Training to improve your lactate threshold

Since the harder we ride the more lactate we produce, and lactate threshold is the maximum amount of lactate acid that can be processed, then it makes sense that the more lactate we can clear then the harder we can ride.

As a result, in order to improve lactate threshold then you need to improve the amount of lactate that can be processed by your muscles. As mentioned earlier, it’s the type I (slow twitch) muscle fibres that do the vast majority of the lactate processing.

Therefore, it follows that these muscle fibres need to be trained to process more and more lactate acid.As discussed in my article on base training, it is the mitochondria (essentially the power stations of your muscles) within slow twitch muscle fibres that process the lactate.

Therefore, you need to look at the level of training that gives the maximum training benefit to your mitochondria.

Knowing your SweetSpot we can see that the sweetspot intensity (between the upper end of zone three and lower end of zone four) is a very useful training tool for this. Therefore, training at sweetspot will give you the maximum gains on your lactate threshold.

However, it’s not that simple. Riding at lactate threshold requires you to also use your type II (fast twitch) fibres to produce power. As discussed in the sweetspot article, it is possible for muscle fibres to change from one type to another, and if you train too much at sweetspot (remember, sweetspot in not a bad thing in itself but it shouldn’t dominate your training) then your type II (fast twitch) fibres will start to be converted into type I (slow twitch) fibres. This will mean you can process more lactate – but with less powerful type II (fast twitch) fibres, the amount of power you can produce will be adversely affected.

So how else can you improve your lactate threshold?

Polarized training

To improve your lactate threshold effectively then you need to do two things – firstly increase the amount of lactate your type I (slow twitch) muscle fibres can process, but also increase the amount of power your type II (fast twitch) fibers can produce.

The new trend is what us coaches call polarized training plans. What we mean by this is a training plan which sees you either riding easy with lots of time in base zones or very hard, up and above threshold, and with not much riding in between. Essentially, your easy and hard training sessions are polarized.

Approximately 80 per cent of your training should be at an ‘easy’ intensity and 20 per cent should be ‘hard’.

Base training is teaching your type I (slow twitch) muscle fibres to become more efficient, not only at utilising oxygen, but also at clearing lactate. The more power the type I (slow twitch) fibres can produce, the more ‘free’ power is being produced – that is power without increased lactate levels.

On the other hand, your hard training sessions are designed to train the type II (fast twitch) fibres to produce lots of power, working at or above lactate threshold before recovering.

This means that when the two elements (easy and hard sessions) are combined, they add up to improved efficiency, an ability to process lots of lactate and plenty of power from type II fibres. All this results in an athlete with a high lactate threshold.

Finally, let’s take a look at two sessions are typical of a polarized training plan.

Typical lactate threshold training sessions

Here are two sessions that are typical of the polarized approach to training.

Base session

Three hours in zone two with a consistent cadence of 95rpm+.

Remember: it’s important to consistently remain in zone two, rather than using average heart rate/power over the duration of a ride.

Threshold session

Warm up with 15 minutes in zone two

2 x 10 minutes in upper zone four with ten minutes in zone one recovery between effort

10 minutes zone one

2 x 5 minutes in zone five with five minutes in zone one recovery between efforts

10 minutes cool down

The first session is working on the aerobic system. This will increase the number of mitochondria in the type I (slow twitch) muscle fibres, thus improving efficiency without jeopardising your amount of type II (fast twitch) ‘power’ fibres.

The second session is designed to increase the amount of power that the fast twitch fibers can produce. Putting the benefits of these two sessions together should lead to an increase in power at lactate threshold.

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