When we crank up the intensity, we need more ATP than ETC can produce at its maximal output. The only way to make up the difference is to rev up Glycolysis. In doing so, our cells make lots of lactate that spills into the blood. When the concentration of lactate in the blood starts to climb, our brain senses this and we start to feel nauseous. Within a few minutes we are forced to drop the intensity, ATP demand reduces, Glycolysis is slowed, lactate is cleared from the blood, and all is back to normal.
The advantage of having a high LT is that you can work at a higher intensity for a longer time before lactate levels become intolerable. Lactate threshold is measured by having someone either run on a treadmill or ride a stationary bike while increasing the intensity of exercise every three to five minutes until exhaustion. During this test, a blood sample is taken from either the fingertip or the ear lobe at the end of each stage and run through a lactate analyzer.
A plot of lactate concentration vs. percentage of V02 max is produced and the lactate threshold is identified as the point of inflection, as demonstrated in the graph. Highly trained endurance athletes will reach their LT at around 80 to 85 percent of their V02 max. It is important to note that a true LT test involves taking a series of blood samples. If you only have your exhaled air analyzed, than this is a ventilatory threshold test, which is related, but certainly different from an LT test.
Why should people get tested?
Although V02 max is a clear measure of physical fitness, it provides little useful information for training by itself. The LT, however, provides a definitive anchor point for training. If the test is done correctly, you will be given a heart rate range at which your LT occurred. You can use these values to train at, or just above your LT. There is no guesswork involved, and that is a great benefit to you as an athlete.
Why do I suggest that some athletes not get tested?
Both of these measures are variable and obviously they will improve with training. Being tested just once might be a waste of money because it is only a single snapshot in time. If you use your LT value from pre-season as your benchmark for training the entire season, you won't get much faster. Also, LT varies with environmental conditions and stress. Alterations in hydration, nutrition, hormones, sleep, and the time of day that testing occurs can all dramatically affect the final results.
If you choose to be tested, make sure to be assessed at least three times during the course of the season, i.e. beginning, middle, and end, and under the same conditions. Most reputable testing facilities will sell package deals that include a series of tests at an affordable price. Finally, make sure that the person testing you understands what these tests mean. If they can't describe how to interpret the results any better than what you have read, find another place to spend your hard-earned money.Test your fitness at a triathlon.
Dr. Alexander Hutchison has a PhD in Kinesiology from University of Houston and is currently a research fellow at the University of Texas Health Science Center at the Houston Division of Infectious Diseases. He is also the owner and operator of the Highlander Triathlon. You can email Alexander with your questions at firstname.lastname@example.org.
This article was originally published in USA Triathlon Life magazine. USA Triathlon is proud to serve as the national governing body for triathlon--the fastest growing sport in the world - as well as duathlon, aquathlon and winter triathlon in the United States. Visit usatriathlon.org.