Lactate Threshold

Formula

Example

Cyclist with FTP 250W and HRmax 190. LT1 ≈ 175W / 140 bpm (top of Zone 2, fully aerobic). LT2 ≈ 250W / 170 bpm (the FTP definition, sustainable for ~60 min). Above 250W, lactate accumulates rapidly and the clock to exhaustion starts.

How Afitpilot Uses This

We do not currently capture lactate or measured threshold values, these require lab testing or field protocols (30-min TT, ramp test) we don't yet support. Threshold-zone work is prescribed indirectly via target RPE: RPE 6-7 sits around LT1 (top of Zone 2), RPE 8-9 sits around LT2 (tempo/threshold work). The 3-zone polarized model used in our endurance prescriptions maps directly to LT1/LT2, below LT1, between LT1-LT2 (the 'grey zone' to minimize), and above LT2 (high-intensity intervals).

Lactate threshold across athlete profiles

Known Limitations

• •Threshold values drift over a season, a well-trained cyclist's LT2 can rise 20-40W over 3-6 months of focused training. A threshold measured in January is not the threshold in May.
• •Lab lactate testing and field tests (FTP, Cooper, 30-min TT) produce different numbers, typically within 5-10% of each other but not identical. Pick one method and stick with it for trend tracking.
• •Threshold is highly sensitive to glycogen status, sleep, and heat. A 'good' threshold day and a 'bad' threshold day can differ by 5-10% at the same fitness level.
• •The notion of a sharp 'threshold' is a useful simplification, in reality, lactate accumulation curves are smooth. The threshold is a model-fit inflection, not a physiological cliff.

Science Context

The dual-threshold model (LT1, LT2) traces to Kindermann (1979) and Skinner-McLellan (1980), with refinements by Mader (1976, the 4 mmol/L OBLA concept) and Coyle (1984, the lactate-steady-state framework). The threshold concept underpins virtually every modern endurance training model: Coggan's power zones, Seiler's 3-zone polarized model, and Joe Friel's heart-rate zones all reference LT1 and LT2 as anchors. Research consistently identifies LT2 (or its proxies, FTP, marathon pace, MLSS) as one of the strongest predictors of endurance performance, often better than VO2max itself.

Related Terms

• AMRAPA conditioning format where you complete as many full rounds (or reps) of a prescribed set of movements as possible within a fixed time cap. AMRAP flips the usual work-then-rest structure: instead of a target number of rounds at an unknown pace, you fix the time and let the round count be the outcome, the score is the honest measure of how much work you produced.
• EMOMA conditioning format where you perform a prescribed set of reps at the start of every minute, then rest for whatever time remains before the next minute begins. EMOM trades AMRAP's pacing freedom for a forced rhythm, the clock, not your own judgement, decides when the next round starts.
• TabataA high-intensity interval format of 20 seconds of maximal effort followed by 10 seconds of rest, repeated for 8 rounds (4 minutes total per exercise). Tabata is one of the few interval structures with a specific named research study behind its exact timing, the 20/10 split isn't an arbitrary convention, it's what the original protocol tested.
• ChipperA long list of movements performed once through, front to back, in order, you 'chip away' at the list rather than repeating rounds. Chippers are the opposite structural choice from AMRAP or EMOM: instead of a short list repeated many times, it's a long list done once, usually against the clock for time.
• RPE (Rate of Perceived Exertion)A 1-10 self-reported scale measuring how hard a set felt. In strength training, RPE is anchored to "reps in reserve" (RIR): RPE 10 means you couldn't do another rep, RPE 8 means you had roughly 2 reps left, RPE 6 means about 4 reps in reserve.