To produce energy for movement, the muscles primarily use fat and carbohydrate for fuel. When carbohydrate, which is the sugar based fuel source, breaks down, lactic acid is produced in the muscles. As it seeps out of the muscle cells and into the blood, hydrogen ions are released and the resulting salt is called “lactate.” As the intensity of exercise increases, the amount of lactate also increases. At low levels of production, the body efficiently removes and recycles lactate. Even while you are reading this blog, lactate is appearing in the blood, but is rapidly removed.
The level of exertion at which the body shifts from aerobic (light breathing) to anaerobic (labored breathing) is marked by such rapid lactate production that the body can’t keep up with its removal, and lactate begins to accumulate in the blood interfering with energy production and muscular contractions thus causing fatigue. This type of fatigue occurs in very short, high-intensity races such as sprint triathlons, and then only during near-maximal efforts such as a finishing kick or a short hill climb.
This is not a major cause of fatigue in most multisport races. If, however, you compete primarily in short events, it may be a limiter for you. The way to improve both the body’s ability to remove lactate and your tolerance of it is with short, high-intensity efforts followed by long recoveries.
Daryl Conant, M.Ed