Understanding lactate values: what the numbers in your report mean
A lactate report shows how your body responds to increasing load. Up to a certain point the blood lactate value stays low, after that it rises clearly. One or two thresholds are derived from this curve, and your training zones from them. A single lactate value says little on its own. What is meaningful is the curve, the threshold power and the heart rate at which you reach it.
What lactate actually is
Lactate is not a waste product and not the cause of muscle soreness. It is produced continuously in energy metabolism, even at rest, and is just as continuously used again: among other things as an energy source in other muscle fibres, in the heart muscle and in the liver1.
What is measured is the concentration in the blood. It depends, among other things, on how much lactate is produced, used and transported. A low single value does not directly mean that little lactate is being produced or that there is a balance.
What your report says
Most reports contain the same building blocks, even if they look different. This overview helps you place them.
A note on the abbreviation IAS: in the German-language literature, IAS usually stands for the individual anaerobic threshold3. Plenea uses IAS differently, for the lower, aerobic threshold. The table follows Plenea’s terminology.
| Item | What it means |
|---|---|
| Resting lactate | Baseline value before exercise. Serves as a reference point in some analysis methods. |
| Stage values | One lactate value per load stage. Only the series produces the curve. |
| Aerobic threshold (abbreviated IAS in Plenea reports) | Lower transition: up to this point you can sustain the load well over a long time. |
| Anaerobic threshold / IANS | Upper transition. An estimate that depends on the model. It is not automatically a directly determined maximal lactate steady state. |
| Heart rate at the threshold | The heart rate at which you reached this load. In training, it is the practical variable for managing intensity. |
| Training zones | Zones derived from the threshold, usually five, with values in heart rate, pace or watts. |
| Analysis model | The calculation method used to determine the thresholds. Important for later comparisons. |
Why there are two thresholds in the report
The transition from easy to hard does not happen all at once, but in two steps. Below the first threshold you can work for a very long time. Between the two thresholds it becomes more demanding, but remains stable for a certain time. Energy metabolism remains predominantly aerobic overall1. Above the second threshold, lactate keeps rising. There you can only sustain the load for a limited time.
The second threshold gets particular attention in the report because almost all training zones are based on it.
Some reports state only one threshold. This is often due to the method used: some models define only one transition point by design.
What you do with it in training
What is useful is not the number itself, but the zones derived from it. For endurance athletes, most of the training volume takes place below the first threshold, often easier than chosen by gut feeling4. Intensive training has its place, but in smaller proportions and set deliberately.
Use the variable that is most stable in your sport: watts for cycling, pace for running on flat ground, heart rate as an additional check. In heat, with lack of sleep or after an infection, your heart rate can be higher without your fitness having changed.
And: training zones from a running test do not apply unchanged to cycling. At the same metabolic state, heart rate on the bike is often lower than when running5. If you transfer the zones unchanged, you risk going too fast.
- Do most of your volume in the easy zone
- Plan intensive sessions deliberately instead of letting them happen in passing
- In heat, when tired or after infections, adjust the values downwards
- Have zones converted for another sport, do not just adopt them
- After a longer break, test again before you train by zones again
What the test does not tell you
A lactate test is performance diagnostics, not a medical examination. It says nothing about whether your heart is healthy, whether you can tolerate exercise or whether a complaint is harmless. Such questions belong in a separate sports medicine assessment.
Nor does it say anything about technique, strength or race tactics, or how well you will perform in a particular race. And it is a snapshot: sleep, nutrition, prior exercise and stress on the test day affect the result.
So do not compare your values with those of other people, nor with reports from other organisations. Different protocols and analysis methods produce differences that can be larger than any training progress.
The most useful question to ask of your report is not “Is the value good?” but “How has it changed since my last test under the same conditions?”
Frequently asked questions
Is a high lactate value bad?
No, on its own a single value says little. What matters is the load at which it occurs. A high value at very high power is unremarkable. The same value at an easy pace would be a sign worth noting. It is the curve that counts, not the single point.
Does lactate cause muscle soreness?
No. Muscle soreness is caused by tiny structural damage in the muscles, especially after unaccustomed or braking movements2. A few hours after training, lactate has long since been cleared.
Why is my threshold value not 4 mmol/l?
Because the 4 mmol/l mark is only one of several analysis methods. Individual methods determine the threshold from your own curve, which lies above or below it depending on the person and training status3.
Can I transfer my running zones to the bike?
Not unchanged. Heart rate can differ between sports5. Fixed deductions are only rules of thumb. Whoever supports you should check the zones separately for each sport.
How often should I get tested?
That depends on the question and on your history so far. After illness or injury, it must first be clarified whether you can tolerate exercise. A fixed schedule cannot be recommended in general.
Sources
- 1
Brooks GA. The Science and Translation of Lactate Shuttle Theory. Cell Metabolism. 2018;27(4):757–785.
- 2
Cheung K, Hume P, Maxwell L. Delayed onset muscle soreness: treatment strategies and performance factors. Sports Medicine. 2003;33(2):145–164.
- 3
Stegmann H, Kindermann W, Schnabel A. Lactate kinetics and individual anaerobic threshold. International Journal of Sports Medicine. 1981;2(3):160–165.
Original researchDOI 10.1055/s-2008-1034604PubMed 7333753
- 4
Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? International Journal of Sports Physiology and Performance. 2010;5(3):276–291.
- 5
Millet GP, Vleck VE, Bentley DJ. Physiological differences between cycling and running: lessons from triathletes. Sports Medicine. 2009;39(3):179–206.
General information for athletes. No medical advice and no diagnosis. The organisation that carried out the test is responsible for interpreting your report.
Further reading
Your report where your training is.
In the athlete portal you find your report, zones and plan together, not as a PDF attached to an email. They were approved by the person who supports you.