The concept of “lactic acid build up” has been an often repeated myth in the exercise community for many decades now, Lets take a brief look at the myths and the facts of what really causes that post workout muscle soreness.
- What is Lactic Acid? Simply stated the body converts carbohydrates into lactic acid during a strenuous workout which is converted into lactate.
- What does it do? It produces energy for the muscles during a strenuous activity.
- Does lactic acid build up? Actually no, it begins to break down in just a few hours after a work out.
- Does lactic acid/lactate cause muscle soreness? No, in fact there are no studies showing that lactic acid causes muscle soreness.
(Myth) The accumulation of lactate causes fatigue in muscles.
(Fact) Lactate does not cause fatigue, and on the contrary is a useful and efficient fuel source.
(Myth) Lactic acid can be measured in the blood using a lactate analyzer.
(Fact) Lactic acid does not exist in the blood. As soon as it is produced, the substance thought to be lactic acid disassociates into lactate and hydrogen (More on lactate and hydrogen below). A lactate analyzer measures the concentration of lactate (a useful fuel) in the blood.
(Myth) Lactate clearance and lactate tolerance refer to how the body deals with fatigue.
(Fact) Since lactate does not cause fatigue, its clearance from the blood depends on the body’s ability to use it as fuel. The body not only tolerates lactate, but at times prefers lactate over glucose as an energy source.
So what really causes the muscle pain after a work out?
What is it then that causes DOMS for days after exercise? The answer is swelling in the muscle compartment that results from an influx of white blood cells, prostaglandins (which are antiinflammatory), and other nutrients and fluids that flow to the muscles to repair the “damage” after a tough workout. The type of muscle damage I am referring to is microscopic (it occurs in small protein contractile units of the muscle called myofibrils) and is part of the normal process of growth in the body called anabolism. It is not the type of damage or injury that you see your doctor about. The swelling and inflammation can build up for days after a workout, and that’s why muscle soreness may be worse two, three, or even four days after a workout
In summary lactic acid is not the cause of delayed onset muscle soreness, lactic acid does not build up in the body, and it is in fact a valuable source of energy for the muscle during a strenuous workout. Lactate is converted back into glucose and filtered out by the liver and is a naturally occurring chemical in the body.