The January newsletter explained the value of the testing that we have been doing at VQ. Although this battery of tests allows us to characterize several different parts of the athlete’s physiology, the single most important item gained is lactate threshold power. The buzz word lactate threshold (LT) is a point of great confusion among athletes, but what it actually refers to is the point where you are producing enough lactate that your blood lactate level increases by 1 mM over baseline.
The question you should now be asking yourself is, “Why do I care?”
For many years, it was thought that lactate was a waste product generated by exercising at an intensity where the need for oxygen outstripped the body's ability to deliver it. Because there was not enough oxygen, the reasoning went, the cells of the body needed to generate energy through alternative pathways that resulted in lactate production. Since then, scientific experimentation has demonstrated that this is not the case. If there is one thing I can get through to you in this article, let it be this: Lactate production does not equal lack of oxygen.
ATP is the energetic currency of the body. To make this ATP, your body has to burn both carbohydrates and fat. At all times, your body is burning both fat and carbohydrates for energy, but the fuel mixture is determined by the work load. If the workload is light, such as an easy jog, your muscles are not working very hard and your cells are able to meet most of the energy demand through burning fat. You are also burning a little carbohydrate, which is broken down into pyruvate and further processed to make energy as well.
As the workload increases, as if during an interval on the run, you come to a point where you can’t meet the energy demands by burning fat alone and will start to burn more carbohydrates. Burning more carbohydrates leads to greater pyruvate production, which will soon exceed your cell’s ability to process it for energy. It starts to build up and is converted into lactate which is transported out of the cell. The lactate isn’t really a waste product, but is actually a high energy compound transported to the liver, kidneys, brain and heart to be metabolized for energy there. Meanwhile, your body is not “anaerobic,” as many believe; there is plenty of oxygen around and the greater lactate production is simply a result of the necessary change in fuel balance from fats to carbohydrates.
The practical application for athletes is that your exercise capacity and time to fatigue are much greater below LT. Once you go above this level, you begin to tap into your limited carbohydrate storage capacity, which once gone, will result in the dreaded “bonk.” Remember, while your body only contains 2,000 calories of carbohydrate, you will thousands of calories of fat. Thus, for endurance events, it is advantageous to minimize the amount of time you spend above LT in order to save those precious carbohydrates for the times when it is crucial for you to increase the workload to a level that increases carbohydrate requirements.