Lactic Acid – The Good, the Bad, and the Ugly

During a recent discussion with some co-workers, we determined that lactic acid, the bane of an athlete’s existence, is responsible for everything wrong in this world. It burns! It creates muscle soreness; it causes tight muscles, lack of strength and lack of power. Much like “Global Warming” gets blamed for any bad or unexplained climate change, lactic acid is the “Global Warming” of the exercise physiology world. If there is any negative response or discomfort during exercise, chances are that lactic takes the blame.

Well, we are here to tell you that lactic acid is not all bad. It serves several important functions and is an essential component of human metabolism. Let’s take a closer look to dispel some of the myths that surround this mysterious substance and give you a better appreciation and understanding of its function.

As most of us know, when you are exercising very hard your body requires immediate energy. This energy comes in the form of Adenosine Triphosphate (ATP). Two of the body’s energy systems can provide this ATP quickly, but at a cost. These systems Acidaburn are, the immediate phosphate system, which uses high-energy phosphates for energy, and the glycolitic system, which brakes down sugar for energy. The phosphate system, also called the ATP/phospho-creatine system, can provide immediate energy for a few seconds, however if high intensity exercising continues, the glycolitic system becomes the predominant source of fuel. Without turning this into an advanced physiology lesson, after several more steps it produces a by-product that affects the cellular environment. This end by-product is lactic acid.

Lactic acid is a strong acid that accumulates during heavy exercise. Like all other acids, it readily disassociates (i.e. breaks down) into other compounds. In this case, lactic acid disassociates into lactate and a hydrogen ion. The result of giving up hydrogen ions is the lowering of the pH of the cellular environment. That is, the cellular environment becomes more acidic. It is through this mechanism that lactic acid gets much of its nefarious reputation. You see, this reaction is responsible for that “muscle burn” you feel when you continue high intensity exercise.

Remember that lactic acid is always being produced, even while you read this article. However, as you read this article, you are able to use and/or remove all that you produce. If you start to walk you will make more, and again, you will use it as fast as you make it. Now, if you begin to run at high speed, your production of lactic acid will start to increase rapidly. It will increase so rapidly, you won’t be able to dispose of it as fast as it accumulates in your body. This point is often called lactate threshold, anaerobic threshold or onset of blood lactate accumulation (OBLA). The hydrogen ions released now begin to spill into the circulating blood. This increased hydrogen level and resulting low blood pH causes that familiar burn. If you want to continue running at this pace, you will have to tolerate the very uncomfortable feeling. The peak of this build-up will hit at about 2-3 minutes. At this point, the high levels of lactic acid will drop your internal pH so low you WILL slow down. Perhaps, you will even stop and gasp for air! The normal amount of lactic acid circulating in the blood is about 1 to 2 millimoles/litre of blood. The onset of blood lactate accumulation (OBLA) occurs between 2 and 4 millimoles/litre of blood. In non- athletes this point is about 50% to 60% VO2 max and in trained athletes, around 70% to 80% VO2 max. These numbers can be significant as it is this Lactate Threshold VO2, or “LTVO2” that is a main limiter in performance, and not VO2 max.

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