Lactate Scientist: Why MOST Runners Get Lactate Threshold WRONG | Dr Peter Tran

Main ideas, concepts, and lessons

1) What lactate actually represents (and why blood lactate ≠ muscle lactate)

• Lactate is produced by cells when carbohydrate/glucose (or glycogen-derived glucose) is metabolized incompletely to meet energy demand.
• It’s a partially burned carbohydrate—it still contains energy but is not fully oxidized to end-products like water.
• Key clarification: A blood lactate reading reflects lactate in the blood, not necessarily lactate production levels inside the muscle at that moment.
• Lactate production happens both at rest and during exercise, but increases when energy demand rises, and the body uses fermentation alongside oxidative pathways.

2) Why “lactate threshold” labels can mislead

Many runners make an incorrect inference:

• “If my blood lactate is the same at the new, faster pace, I must be better.”

The video argues this isn’t necessarily true because:

• Performance changes can come from changes in lactate production and clearance (since blood lactate depends on both).
• Training may also change muscle characteristics (e.g., strength, buffering, and clearance dynamics), shifting the lactate curve for reasons other than “better lactate tolerance.”

3) Two lactate thresholds exist in testing theory (LT1 and LT2)

LT1 and LT2 come from lab-style ramp tests where lactate is measured as speed/power increases.

The lactate vs. intensity curve is described as:

• Flat/low baseline early,
• then a first noticeable rise,
• then a later steep/exponential rise.

Detailed bullet explanation of the LT1/LT2 curve (as described)

Typical lab protocol:

• Run on a treadmill with speed ramping in steps (e.g., “1600 m equivalent,” “2000 m equivalent,” etc.).
• Measure lactate at each step.

Plot interpretation:

• Y-axis: blood lactate concentration (mmol/L)
• X-axis: treadmill speed

Curve phases:

• Baseline: early jogging shows little lactate rise, fluctuating around a lower value (example given ~1 mmol/L).
• LT1: where lactate shifts from baseline to a more consistent increase
  • Example: ~1.5 mmol/L
• LT2: where lactate enters a steeper/exponential increase
  • Example inflection around values like ~2.5 → ~4.5 mmol/L
• LT2 is sometimes simplified as being around ~4 mmol/L, but the speaker emphasizes variability in real situations.

4) Why different researchers report different “numbers” for LT1 (e.g., 1.5 vs 2.0 mmol/L)

Discrepancies come from:

• Different definitions (what exact point counts as LT1)
• Different testing/zone model frameworks (point vs interval approaches)
• Different disciplinary backgrounds (e.g., biochemistry framing vs coaching/zone framing)

Bottom line: Exact naming/number placement matters less than:

• Tracking trends over time
• Understanding the goal of training sessions

5) MLSS vs LT2 (why lactate can exceed “LT2” and still be sustainable)

The video explains that some athletes can hold very high lactate levels without the runaway pattern suggested by LT2.

Key concept:

• MLSS = Maximal Lactate Steady State
  • Meaning: the highest intensity where lactate can be held without continual exponential accumulation.
  • It may occur at much higher lactate values than the simplified “~4 mmol/L LT2.”

Example scenario:

• Marathon goal pace/test: lactate around ~6 mmol/L
• Yet marathon performance was still possible → suggesting MLSS can be above LT2.

Mechanisms discussed:

• Lactate production can be high, while clearance (liver/kidney processes) keeps blood lactate stable.
• Training and genetics may contribute.
• Race context/mental readiness may enable sustaining higher intensities.

Relationship among lactate production, clearance, and steady blood levels

• Lactate is produced from incomplete carbohydrate metabolism.
• The body clears lactate (notably via liver processes such as gluconeogenesis; also kidneys).
• Therefore, blood lactate at a given intensity depends on:
  • how much lactate is produced in muscles and
  • how quickly it is cleared

6) Lactate readings are “snapshot in time” and can be distorted by many factors

A lactate test reflects:

• Current fitness/form
• Food intake
• Temperature
• Device/test conditions
• Sampling technique

Distortion examples mentioned:

• Bad sampling (contamination from strip/finger wipe issues)
• Caffeine
• Hydration
• Stress
• Sleep/cortisol patterns
• Time of day (morning lactate higher than afternoon)
• Carbohydrate intake (can raise baseline lactate even outside exercise)

7) How to use lactate practically (and what not to do)

The video warns against treating lactate like an exact trigger:

• “My LT2 is X, so if I don’t match it exactly, I’m done / if I match it exactly, I’m safe.”

Instead:

• Use lactate to guide training through trends, not single readings.

Practical methodology for using lactate (as taught)

• Treat lactate testing as support for training, not a rigid instruction set for the next workout.
• Use lactate in a longitudinal way:
  • collect multiple samples over time
  • look for trends between lactate and pace/power/effort
• Verify with real-world performance:
  • races are the real test of whether changes matter
  • one test months apart isn’t enough to steer training
• Apply safety/strategy:
  • there’s a risk of overreaching by chasing the edge of a number
  • if it feels too hard, it likely is too hard—avoid training at the risky boundary

8) “Shifting the lactate curve right” is not guaranteed to mean better performance

The classic idea:

• shifting the curve right means you can run faster before reaching the “hockey stick”

The video argues this doesn’t always translate to being better because:

• blood lactate can drop due to clearance changes, not necessarily improved muscle capability
• threshold changes might come with trade-offs (e.g., reduced muscle strength)

Practical example:

• Someone could decrease threshold pace but become slower in fast efforts (e.g., 400 m time worsens), hurting event performance.

Opposing forces (high-level concept)

The lactate curve shape reflects interactions of:

• aerobic capacity
• anaerobic capacity

Focusing only on one lactate-threshold metric can miss the bigger picture.

9) Fueling strategies and their relationship to lactate

The video links lactate to carbohydrate metabolism (glycolysis exceeding mitochondrial oxidation).

High-level message:

• High-carb fueling tends to produce higher lactate readings, but can support better training intensity and performance.
• High-fat/low-carb can keep lactate readings lower in some cases, but performance may suffer because intensity feels worse and energy pathways shift.

Important nuance:

• Low lactate doesn’t automatically mean “better adaptation.”
• You still need enough carbohydrate availability to support key pathways/enzymes and enable high-intensity training.

Caution about extremes:

• “Moderation” and goal alignment are emphasized.
• Overfueling can harm metabolic health (prediabetic indicators were referenced).

Energy drink note:

• Possibly useful during racing or hard sessions.
• Less advised at rest unless used strategically.

10) Continuous lactate sensing: the argument for better decision-making

The video discusses:

• CGMs (continuous glucose monitors) and parallels
• emerging continuous lactate meters

Brands/products like Athlix/Flux/Obla are presented as attempts to make lactate feedback more actionable than one-time lab snapshots.

Why continuous monitoring is proposed to help

• Lactate thresholds are individualized and context-dependent.
• Continuous or frequent lactate estimates can help:
  • identify readiness for training intensity
  • reduce reliance on stale/single-point values
  • create a buffer/range rather than a single “exact number”
• The video also compares lactate to “heart rate 2.0”:
  • heart rate is a lagging marker
  • lactate is closer to cellular stress/energy demand

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Methodologies / instructions explicitly implied or directly stated

A) Lactate testing interpretation workflow (conceptual)

• Do not treat a single lactate test as a prescription for exact next-session pace.
• Do interpret lactate as:
  • a “snapshot” of current status under a specific protocol
• Do collect enough data points across days/sessions.
• Do couple lactate trends with:
  • perceived exertion
  • pace/power
  • and (where available) heart rate
• Do use races/performance outcomes as final verification.

B) Handling uncertainty / avoiding overreaching

• If lactate-guided pacing feels like it’s on the edge, back off.
• Don’t “dance around the edge” of an unsafe threshold for marginal gains.
• Prefer securing most benefit with less risk (the video uses the “asymmetrical risk / alpha” concept).

C) Fueling strategy positioning (goal-dependent)

• For best performance:
  • prioritize carbohydrate availability
• For weight/fat loss goals:
  • high-fat/low-carb can be used periodically (not as a universal performance strategy)
• Avoid overly extreme dieting approaches; aim for moderation and metabolic health awareness.

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Speakers / sources featured (identified)

• Dr. Peter Tran (main speaker; referenced as “Peter” in dialogue)
• Humm Health (episode sponsor; referenced for discount/eligibility)
• Steve Magnus (mentioned in passing; discussed as having talked about increasing MLSS)
• Jan Olbrecht (book author referenced; “Science of Winning” / lactate testing in swimmers)
• Athlix (company; co-founder interviewed)
• Hex / Flux / Obla 1 (products/projects discussed by the Athlix co-founder)
• Continuous glucose monitors (CGMs) and wearable ecosystems (general references; no specific inventor/source named)