There is a lot of confusion around threshold training. The short definition is “comfortably hard”, but the long definition is much more complicated. There are technically two thresholds: the aerobic threshold and the anaerobic threshold. The aerobic threshold (LT1) is the lowest speed that produces a sustained increase in blood lactate levels above baseline (the body generally has some level of blood lactate in circulation, often ~0.7mmol/L). LT1 usually occurs at a blood lactate level around 1.5mmol/L. The anaerobic threshold (LT2) is the speed just before the blood lactate levels begin to rise exponentially, usually around 3.0mmol/L. However, there are individual difference in the concentration of blood lactate that indicates a threshold. For example, some people LT1 occurs at 1.5mmol/L, for others is occurs at 2.0mmol/L. Due to these individual differences, the best way to accurately determine where the thresholds occur is to do a full blood lactate threshold test.
This test consists of 3-4min intervals run at increasing speeds, with blood lactate measurements taken between each interval. After blood lactate reaches a level above 4.0mmol/L, the test is done. From the results, the athlete can see when LT1 and LT2 are reached, what those speeds are, and what the level of lactate is at those speeds. Of course, this type of testing is not always available, so heart rate or effort can also be used for threshold training, but it takes quite a bit of experience to do threshold training correctly without a test. I decided to do a lactate threshold test to make sure that I was in the correct pace ranges for my threshold training. Watch the video below to see the results.
