Free Lactate Threshold Calculator
LT1, LT2 & OBLA from blood lactate step tests — instant training zones
Lactate threshold test
Enter your step test — LT1, LT2 and your zones are read from the curve.
Protocol & pre/post values (optional)
Protocol tips — how to enter your test
- Base La= at rest, before test
- Row 1= first workload step
- Lactate column= measured value at sampling time
- Power / HR= intensity of that step
Fill in your lactate test above — the curve and thresholds appear here.
Or load the demo data to see an example.
How the lactate threshold calculator works
A lactate step test raises the intensity in stages — 3 to 5 minutes each, a blood sample at the end of every stage — and plots lactate against power or pace. At easy intensities lactate sits close to its resting value; as the effort climbs it starts to rise, then rises steeply. The two bends in that curve are the thresholds.
LT1, the aerobic threshold, is where lactate first leaves its baseline — the top of what you can sustain for hours. LT2, the anaerobic threshold, is where production outruns clearance and the curve turns upward; it is the intensity you can hold for roughly an hour. The calculator reads both off a fitted curve and shows the fixed-point methods beside them: OBLA at 4.0 mmol/L, the individual anaerobic threshold at baseline + 1.5 mmol/L, D-max and log-log.
Enter four or more stages with power or pace and lactate — heart rate makes the zones better — and the curve, LT1 and LT2 are drawn immediately. A free account adds the remaining methods, the confidence score and training zones built from the thresholds.
Questions
- How many stages does a lactate test need?
- At least four; six to eight give the curve enough shape to place both thresholds. Start well below your expected LT1 and keep the steps even — 20–30 W on the bike, 15–20 s/km running — so the bend is not hidden in a single big jump.
- What lactate value is LT2?
- There is no single number. OBLA fixes it at 4.0 mmol/L, which suits many trained athletes, but individuals turn anywhere from 2.5 to 5.5 mmol/L. That is why the calculator reads the shape of the curve rather than a line across it, and shows the fixed-point methods for comparison.
- Does it work for running and swimming?
- Yes. For pace sports the intensity axis is pace (or speed), slower on the left and faster on the right, and the thresholds come out as min/km or min/100 m with the heart rate at each.
Ready to track your full training load?
LaChart combines lactate testing, training analytics, Strava and Garmin sync and coach collaboration in one place.
