Does Lactate Threshold Even Exist?

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In the mid-90s, I began doing extensive lactate testing with the athletes I coached. For about ten years, I collected data before eventually abandoning the practice. Why? Because the results raised more questions than answers. Lactate values varied greatly from day to day, and the readings from a ramp protocol looked nothing like what we saw during sustained training efforts.

Across physiology and coaching circles, opinions on lactate testing range widely. Unfortunately, many discussions use misleading or inconsistent terminology. Often, the training prescriptions are reasonable, but the definitions and explanations create confusion.

The Elusive “Threshold”

Take the commonly referenced lactate/anaerobic threshold. There are 15–20 different ways to define it. None identify a true metabolic threshold; they are simply points along a curve—like trying to find a corner in a circle.

• Some say it’s the highest sustainable effort for an hour.
• Others describe it as the point where lactate accumulates faster than it can be cleared.
• Still others fix it to a percentage of max HR (85–90%), a 4 mmol point, or 1 mmol above baseline.

These are all arbitrary markers, not metabolic breakpoints. While threshold concepts correlate with performance, that correlation doesn’t prove that “threshold training” itself is uniquely effective. In fact, there is little consensus that training at threshold meaningfully shifts threshold upward. Research more strongly supports that higher intensity training increases fractional utilization of VO₂max.

An Example

The following graphic was shared by a prominent coach in Boulder Colorado. This is a typical lactate profile of an elite athlete. What we see is probably a good diagnostic tool for improved aerobic efficiency. In this case very high-power outputs with very low lactate. We can also see a clear point of increase in baseline lactate above the initial levels. Otherwise, it is not possible to identify any other thresholds. Read that, any lactate above 1.5 mm is increase in a linear fashion and it is not possible to identify another threshold unless one uses an arbitrary measure like 1 mm above the first increase in lactate at 3.1mm, ~415watts and 160 heart rate, or the 4 mm point, at 440 watts, and a heart rate of ~168.

What Ramp Tests Really Show

Ramp protocols often produce neat curvilinear graphs with clear “LT1” and “LT2.” But real-world tests rarely look so clean. Lactate begins to rise from LT1 onward and increases progressively. Defining LT2 as the point where production exceeds clearance is flawed, since lactate is always being produced, even at very aerobic intensities.

The reality: there is no single metabolic breakpoint separating the moderate and severe domains. Lactate curves from ramp tests are exponential. What we often want to see in them is not a threshold but the Maximal Lactate Steady State (MLSS) the highest intensity at which lactate remains stable for a set time (typically 30–60 minutes). Research shows MLSS can occur anywhere from 2.5 to 8 mmol, depending on the athlete.

Misinterpreting Threshold Proxies

• FTP (1-hour power): A valuable performance marker, but not a metabolic transition.
• % of Max HR: Sometimes aligns with “threshold,” sometimes not. For well-trained athletes, 90% of max HR may equate to ~95% of VO₂max, so is that threshold training or VO₂max training?

The stronger evidence suggests that in the high-intensity domain, the greater the fractional utilization of VO₂max, the greater the training effect. Training at 90–95% VO₂max may be more impactful than hovering at 80–90%.

Context Matters: Double Threshold and Elite Practices

The much-discussed Norwegian double-threshold model is worth contextualizing. These athletes already have years of high-level training. Double-threshold sessions are an additive base-phase tool, not a replacement for hard work. Once in competition periods, they still perform 2–3 sessions weekly at race intensity. Extrapolating this model to all athletes, especially younger ones, is misguided.

Using Lactate Testing Wisely

I don’t believe lactate testing is useless. When understood properly, it can:

• Track aerobic fitness adaptations (e.g., a flatter early curve, downward/rightward shifts).
• Help set ceilings on training intensity.
• Diagnose whether an athlete needs more low-intensity development.

But context is critical. Day-to-day variability is high, and training/racing demands differ. For events under an hour, athletes can sustain efforts well above any supposed threshold. Lactate or ventilation “breakpoints” don’t define these performances.

The Takeaway

• There is no single, universal lactate threshold.
• Metrics like FTP, % of max HR, or 4 mmol points are useful heuristics but not metabolic anchors.
• MLSS is closer to what we seek, but even that depends on time frames and event demands.
• Adaptations should be judged by performance needs, not by chasing arbitrary points on a curve.

In short: lactate testing can provide insight, but it is not a map to a mythical threshold. The real work lies in matching training to the adaptations needed for performance.