Six things you need to know about… blood lactate threshold testing
Most riders will be familiar with the idea of functional threshold power and, indeed, the FTP test. It’s something which sends a shiver down the spine of any rider – a gruelling, no-holds-barred test used to benchmark your fitness.
However, lactate threshold testing is becoming more popular with riders – and for good reason. Lactate threshold testing enables you to establish your training zones with a greater degree of accuracy than a typical FTP test.
In my last article on polarised training, I talked a lot about lactate thresholds and how you can plan your training around them to get the most out of your time on the bike. The basic idea of polarised training, remember, is to spend 80 per cent of your time training at a ‘moderate’ intensity and 20 per cent at a ‘severe’ intensity, as dictated by your lactate threshold.
We then ran through how you can use your FTP test score, and the subsequent training zones established, to estimate your lactate thresholds, so you can implement a polarised training plan.
However, if you are looking for the ultimate in precision you need to measure your lactate thresholds individually, so you can use that information when planning your training. This is where lactate testing comes in.
Why should you do a lactate threshold test? And what’s wrong with an FTP or VO2 Max test?
If you use a power meter and are serious about making your training as accurate as possible, then you should consider a blood lactate test.
Why not just do a ‘regular’ FTP test? Let me explain. An FTP test uses a fixed percentage (95 per cent) of your 20-minute power to estimate your functional threshold power. This is because some of the power you produce over the test will some from anaerobic sources, so is therefore not sustainable. However, the percentage of anaerobic power varies massively from one cyclist to another and can even change during a season for a single cyclist. Coaches use 95 per cent as about average, however there is no guarantee it will be correct in a given athlete. A lactate threshold test, on the other hand, takes away the guess work as during the test your body’s individual response to exercise at different intensities can be tested.
Another advantage of a lactate threshold test over a FTP test that it can determine both the first and second lactate thresholds. In order to accurately follow a polarised training plan, an athlete or their coach needs to know their power output at both the first and second lactate thresholds. We’ll come on to exactly what they are.
A VO2 Max test, on the other hand, requires a lot more equipment than a lactate threshold test and is therefore only really feasible in a laboratory. While a VO2 Max follows a similar ramp test protocol to a lactate threshold test, the amount of oxygen used and carbon dioxide expelled are measured, along with the breathing rate, rather than blood lactate concentrations.
As well as determining your thresholds, a VO2 Max test will give you some information over and above a blood lactate test, notably an athlete’s economy, so it’s worth doing if you ever get the chance. The benefit of a blood lactate test, however, is that it’s a relatively simple test which can also be conducted in the field, not just in the lab, so it is possible to do follow-up tests on the bike
Sometimes you may find that if you do a VO2 Max test the scientists will measure blood lactate at the same time and, as a coach, if I had to choose one method of testing an athlete it would be to take this combined approach. It’s the best way to get a complete picture of the underlying physiology. Ultimately, however, it’s not a practical approach, due to both the equipment required and the fact it has to be done in the lab, so I recommend most athletes to undergo an lactate threshold test due to the combination of accuracy, ease and repeatability.
What does the test consist of?
A lactate threshold test is what is known as an incremental exercise step test, so it’s broken down into segments that progressively get harder. During each segment you will be asked to ride at a certain power output, which will then increase for the subsequent segment.
At the end of each segment, a blood sample will be taken and tested for blood lactate levels, which are then plotted onto a graph. It’s from this graph that we are able to establish your lactate thresholds.
How hard is the test?
While we’ve covered the basic format of a lactate threshold test, there are a number of different protocols – but they all have certain things in common.
For most tests, the power will be controlled by a smart trainer or an exercise bike in a laboratory. This will ensure you are riding at the correct intensity in each segment – so all you need to do is to keep pedalling.
The test will start at a very low intensity, which will feel nice and easy, but with each increasing segments things will get progressively harder – until you’re riding very hard. All in all, the test should take between 20 and 40 minutes.
Some tests will continue until you are no longer able to continue (exhaustion), whereas others might stop you once you have gone past the second lactate threshold.
However, no matter the protocol used, you need to ensure you are fresh coming into the test. Treat the test as you would a race, ensuring you are motivated beforehand. The test will be hard at the end, no doubt about that, but no harder than a tough training session.
How is blood taken?
If the idea of having a blood sample taken numerous times while riding a bike doesn’t sound too appealing, then don’t worry.
Blood is typically taken from either your ear lobe or the tip of your finger, using a lancet to make a small prick. This itself isn’t painful and is akin to a very small injection.
The same point is then used for each blood sample. Normally to extract blood only a small squeeze is necessary after the first sample, therefore only one prick from the lancet is required.
There are a number of ways that the blood can then be tested but most coaches and physiologists will use a handheld device similar to those used to measure blood sugar levels in diabetics. Laboratories will most likely use a desktop machine which gives a slightly more accurate reading. The blood lactate level will then be recorded against the relevant power output.
What will the test tell me?
As we’ve already covered, you have two lactate thresholds and the test will determine these.
Lactate threshold one
This is the highest power output at which there is a rise in blood lactate above your baseline or starting value. When you start the test your blood lactate reading will probably be very low, with a baseline measurement likely to be less than 1 mmol per litre of blood.
At a certain power output – lactate threshold one – you will see a rise in blood lactate above your baseline measurement. After this point you will see a fixed increase in blood lactate for each jump in power output until your reach your second lactate threshold.
As a result, lactate threshold one is the point on the graph where your blood lactate line starts to increase. This power output is the top of the moderate exercise domain – head back to my article on polarised training for more on that – and represents the maximum power output at which you should be doing your base rides.
Lactate threshold two
Once you have passed lactate threshold one, you will see that each time the intensity of the test increases, your blood lactate level will also increase – something that will continue until you reach lactate threshold two.
Basically, lactate threshold two represents the maximum power output you can sustain with stable blood lactate levels. As soon as you pass lactate threshold two in the test, things are going to get quite hard! You will now find that for every increase in power your blood lactate levels jump massively. You are effectively working on borrowed time and it won’t be too long before you have to stop the test.
Your second lactate threshold is marked on the graph at the point where any increase in blood lactate levels goes from being linear (i.e. a fixed increase in blood lactate for each increase in power output) to exponential (i.e. a big jump in blood lactate levels for even a small increase in power). It’s the point at which the graph switches from being a straight line to a curve and the power output is equivalent to the threshold power you might aim for in a 25-mile time trial – the kind of effort which is just about sustainable.
Once you have completed the test you will know your power output at lactate threshold one and lactate threshold two. The coach or scientist performing the testing should then be able to provide you with personalised training zones based of your lactate profile.
What if I get fitter? Won’t the zones then be out of date?
Having accurate training zones allows you to train with increased efficiency, ultimately helping you to get stronger on the bike. In short, this does mean you will need to re-test as your fitness improves. Hopefully you will be a rightwards shift in the lactate curve, which shows the improvement you want, as your body doesn’t need to produce as much lactate as it did previously to sustain a certain power output.
To track these improvements I recommend having multiple tests across a season to ensure your zones stay accurate. Plenty of coaches and sports testing facilities offer a discount on multiple tests, including Cadence Performance in London.
It is also possible to combine field testing (i.e. an FTP test) with lab-based lactate threshold testing. In the same week you do your initial lactate threshold test, do an FTP test and make a note of your score. Use the training zones established from your lactate profile but continue to do an FTP test at regular intervals as you put your training plan into action. Once you see a significant improvement in your FTP score, it’s time to do another blood lactate test.
Why not just rely on your FTP score to adjust your training zones? You might not always get the same improvement in lactate threshold one as you do at lactate threshold two, and vice versa. Therefore, as an example, if you see an improvement of ten watts in FTP power, you can’t simply move both thresholds up by ten watts. It’s important to re-test via a lactate profile test to ensure both threshold values are correct.
And there you have it – everything you need to know about blood lactate testing. If you’re serious about your training, and want to do a scientific test to ensure you can put an effective training plan in action, then a blood lactate test will help you do that.
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