Lactate Testing

Lactate testing measures the concentration of lactate (lactic acid's conjugate base) in your blood at progressively increasing exercise intensities. The test identifies two critical thresholds: LT1 (aerobic threshold, where lactate first rises above resting levels) and LT2 (anaerobic/lactate threshold, where lactate accumulates faster than your body can clear it). These thresholds define your training zones with far greater precision than heart rate or perceived effort alone.

The test protocol is straightforward: you run on a treadmill or ride a bike ergometer, increasing pace or power every 3–5 minutes. At the end of each stage, a small blood sample is taken from your fingertip or earlobe and analyzed with a portable lactate meter. The resulting graph — exercise intensity on the x-axis, blood lactate on the y-axis — reveals your exact threshold paces or powers.

Why does this matter? Because training at the right intensity is the single most important factor in endurance improvement. Most recreational athletes train too hard on easy days and too easy on hard days — the "moderate-intensity rut." Lactate testing removes guesswork: your easy runs should be below LT1, your tempo runs near LT2, and your intervals above LT2. Athletes who train by lactate-informed zones consistently improve faster than those training by feel or generic heart-rate formulas.

Test in conditions similar to your racing: same time of day, fueled vs. fasted, and on your target terrain if possible

Retest every 8–12 weeks during a training block to track threshold shifts and update training zones

Don't fixate on absolute lactate numbers — what matters is the pace/power at each threshold

Combine lactate testing with heart rate data: the pace where LT2 occurs AND the HR at that pace are both valuable