What Is a Lactate Test?
A lactate test measures the concentration of lactate (a salt of lactic acid) in the blood during exercise. As exercise intensity increases, the body transitions from aerobic to anaerobic energy production, and blood lactate levels begin to rise rapidly.
Lactate threshold (LT) is the intensity point at which lactate production exceeds its removal. This marker is one of the best predictors of endurance athlete capacity. There are two main thresholds: aerobic (LT1, ~2 mmol/L) and anaerobic (LT2/OBLA, ~4 mmol/L).
📏 Testing Protocol
Standard incremental lactate test:
- Warm-Up: 10 min of light exercise (running/cycling).
- Starting level: 3-5 min of work at light load (e.g., running at 8 km/h or 100W cycling).
- First blood sample: from the earlobe or finger after the first level.
- Load increase: every 3-5 min, speed/power is increased by a fixed step (e.g., +1 km/h or +30W).
- Blood samples: taken at the end of each level (last 30 sec).
- Test end: when lactate exceeds 8-10 mmol/L or the athlete can no longer continue.
📊 Lactate Threshold Interpretation (running)
| Level | LT1 Speed (km/h) | LT2 Speed (km/h) | VO₂max (ml/kg/min) |
|---|---|---|---|
| Elite (marathon) | >18.0 | >20.0 | >75 |
| Very Good | 16.0-18.0 | 18.0-20.0 | 65-75 |
| Good | 14.0-16.0 | 16.0-18.0 | 55-64 |
| Intermediate | 12.0-14.0 | 14.0-16.0 | 45-54 |
| Beginner | <12.0 | <14.0 | <45 |
How to Use a Lactate Test
A lactate test measures the concentration of lactic acid salt in the blood when load is increased in steps. The athlete runs on a treadmill or pedals a bicycle, and every few minutes a blood sample is taken from the finger or earlobe. The load is increased steadily until the athlete can no longer continue or lactate reaches a predetermined limit.
The most important rule is to perform the test after rest and under the same conditions as previous attempts; otherwise, the numbers will not be comparable. Before the test, it is worth avoiding heavy exertion and following usual nutrition, and repeating measurements at the same time of day. The test must be supervised by a specialist, as blood sampling and load management require experience.
What the Result Shows
While the load is low, blood lactate remains low and almost unchanged. Upon reaching a certain intensity, it begins to rise — first slowly, then sharply. Those two breakpoints are the aerobic and anaerobic thresholds. They determine at what speed or power one can work for a long time without fatigue accumulation, and at what speed or power only for a short time.
This is a much more accurate way to determine training zones than heart rate measurement alone, because lactate directly reflects changes in energy production in the body as load increases.
How to Interpret Thresholds
- Aerobic threshold — the pace at which one can work for hours on end; it is suitable for long training sessions and recovery.
- Anaerobic threshold — the pace one can sustain for approximately half an hour to an hour; it is a benchmark for race pace.
- The gap between them — the zone in which endurance develops; the majority of training volume should take place precisely here.
- Above the anaerobic threshold — short, intense efforts that quickly accumulate fatigue.
It is important to compare not individual numbers but their change over time: if the same lactate level is reached at a higher speed, endurance has improved. More about other tests — fitness tests and BIP test.
Where the Test's Limits Are
A lactate test shows physiological capacity, but not everything. It does not reflect technique, psychological resilience or race tactics. In addition, the result is influenced by sleep, nutrition and even caffeine, so a single inaccurately performed measurement can be misleading. The test also requires equipment and a specialist, so in practice it is performed less often than simpler field tests, for example fitness tests at home.
Finally, thresholds are not constant — they change with training, so one measurement is not enough for the whole season; the result should be updated periodically.
How Often to Test
It is sufficient to repeat a lactate test every few months or before important competitions. Testing too often is expensive and provides no additional benefit, because endurance changes occur slowly. It is more important to train consistently and use the test as a checkpoint that shows whether the chosen direction is correct.