Lactate Threshold HR Calculator

The lactate threshold (LT) is the exercise intensity at which blood lactate begins to accumulate faster than it can be cleared. The corresponding heart rate is the lactate threshold heart rate (LTHR). Training at or near this intensity is highly effective for improving aerobic performance in runners, cyclists, and triathletes.

The standard field test (Friel method) involves a 30-minute maximal effort time trial on your main sport discipline. After a warm-up, go as hard as you can sustain for the full 30 minutes. Start recording average heart rate at the 10-minute mark. The average heart rate for the final 20 minutes is approximately 103 percent of LTHR; dividing by 1.03 gives LTHR, which is approximately equal to 95 percent of average HR over the full 30 minutes.

VO2 max is the maximum rate at which your body can consume oxygen during maximal exercise. Lactate threshold occurs at a lower intensity, typically 65 to 90 percent of VO2 max. LT is often a better predictor of endurance performance than VO2 max because it determines the pace you can sustain for long durations.

LTHR is the anchor for heart rate based training zones. Zone 1 (recovery) is below 85 percent of LTHR, Zone 2 (aerobic base) is 85 to 89 percent, Zone 3 (tempo) is 90 to 94 percent, Zone 4 (threshold) is 95 to 99 percent, and Zone 5 (above threshold) is at or above 100 percent of LTHR. Exact zone definitions vary by coach and methodology.

Yes. LTHR is typically 5 to 10 beats per minute lower for cycling than for running in the same athlete. This is because cycling uses less total muscle mass and there is no impact, so the cardiovascular system is not as stressed. Always derive LTHR separately for each sport.