Lactate Thresholds — Why It Matters for Athletes

Lactate thresholds — LT1 and LT2 — are key metabolic points that define the boundaries of training zones.

LT1 — First Lactate Threshold

LT1 is the lowest exercise intensity at which a measurable increase in blood lactate concentration is observed compared to resting lactate concentration.

In the context of endurance training, LT1 is marked as the first elevation in lactate concentration above resting levels. This should not be confused with the second lactate threshold, LT2, which occurs at higher exercise intensities.

The first lactate threshold typically averages between 1.3 and 2.5 mmol/L. In most athletes specializing in long-distance races, in our 'TRS Endurance Studio' metabolic tests we observe FatMax at or slightly above LT1.

LT1 is only needed as an indirect marker of fat and carbohydrate expenditure, since nothing fundamentally changes when you run faster or slower than the first threshold. When you train slightly above LT1, lactate concentration will remain in a steady state.

LT2 — Second Lactate Threshold

LT2, on the other hand, is a true 'threshold' because it clearly distinguishes two intensities from each other:

Above LT2 — lactate concentration will rise over time; there is no longer a lactate steady state. The faster your pace above LT2, the quicker you will reach your peak lactate and will have to reduce your pace.

Below LT2 — lactate concentration will not increase over time. A lactate steady state exists. You can run at this intensity for a prolonged period until you become limited by energy availability or other factors, such as electrolyte balance.

With LT1, there is no such clearly visible difference below and above the threshold.

Maximum Lactate Steady State

LT2 is the highest intensity at which muscle and blood lactate can reach a constant concentration, which is why it is commonly referred to as the maximum lactate steady state (MLSS). In other words, it is the point at which the rate of lactate production exactly equals the rate of clearance, where any decrease in intensity will lead to a drop in lactate levels, and any increase in intensity will lead to non-linear lactate accumulation.

You may also see the term 'lactate threshold' used interchangeably with OBLA (onset of blood lactate accumulation), anaerobic threshold, or VT2 (ventilatory threshold). However, all these terms have slightly different meanings due to different measurement methods. In 'classic' terms, for example, the ventilatory threshold, when measured based on RER, should coincide with the lactate threshold, but in practice this rarely occurs, especially in athletes who specialize in various ultra-distances.

The second lactate threshold typically averages between 2.5 and 4.5 mmol/L. On average, you can sustain this intensity for approximately 60–90 minutes based on 'classic' data, but in practice it can be much longer — it all depends on the amount of available energy in the form of carbohydrates.

Training Zones

Looking at the classic 3-zone model, it can be roughly distributed as follows:

Training Zone 1: below LT1 (1–2 mmol/L)
Training Zone 2: between LT1 and LT2 (2–4.5 mmol/L)
Training Zone 3: above LT2 (above 4.5 mmol/L)

How to determine your lactate threshold

Thresholds are found with a step test. The logic is the same in a lab and on a track.

The athlete works in 3–5 minute steps, increasing pace or power at each one. At the end of every step a drop of blood is taken from a finger or earlobe and measured with an analyzer. The result is a curve: intensity on one axis, lactate on the other.

LT1 shows up as the first steady rise above resting level — usually 1.3–2.5 mmol/L. LT2 (also called the anaerobic threshold) is the point after which lactate stops stabilising and climbs from step to step.

Three conditions, without which the test is useless:

— **the same protocol when you repeat it.** Step length changes the result: on three-minute steps lactate has no time to plateau, and the threshold comes out higher than it is;
— **the same conditions.** Food the day before, time of day, temperature, warm-up — each shifts the curve;
— **fresh strips from one batch.** Batch-to-batch spread is most visible exactly where the answer is decided, around 4 mmol/L.

One bad step ruins the whole test, so it is worth measuring twice at the contested points.

How to raise your lactate threshold

The threshold moves not because you run fast more often, but because muscles clear lactate better. Hence three directions of work:

**Volume in zone one.** Below LT1 mitochondria and capillaries grow — that is, the ability to consume lactate as fuel. The dullest and the most effective part.

**Work at threshold.** Intervals of 8–20 minutes around LT2 with short rests. The point is not to get tired but to hold, for a long time, the intensity where production and clearance are roughly equal.

**Short work above threshold.** Intervals near maximal oxygen uptake raise the ceiling the threshold then follows.

Re-test no more often than every 6–8 weeks: adaptation will not show up faster, and measurement spread would eat the difference.