I remember a personal trainer at a gym arguing with me one time about a misconception they had about lactic acid. They believed that lactic acid causes muscles soreness and that stretching the next day helps rid the muscles of lactic acid. This personal trainer was so confident in what they knew, they proceeded to argue this myth as truth.
Misconceptions like this are what lead to incorrect and even observed program design. Even though his trainer would not heed my advice I still believe it is fundamentally important to know what lactic acid is, especially if you are into muscle building.
Lactic acid is the product of anaerobic respiration or glycolysis which in Latin literally means to cleave sugar. The sugars we consume are six carbon molecules. In order to extract energy from these sugar molecules they are split into two three carbon molecules of lactic acid.
As the muscles continue to expend energy, lactic acid is continuously produced until the PH in the muscles lowers to the extent that the actin and myosin protein filaments of the muscle fibers denature and can no longer function until the PH is normalized.
The only way to rid the muscles of high concentrations of lactic acid is by allowing the circulatory system to carry it away. Obviously the better circulation you have the quicker this process is. As a result, certain types of training that pumps or flushes the muscles with large amounts of blood can cause an increase in muscle size simply due to muscle tissue vasculation.
This becomes apparent in training programs of powerlifters compared to bodybuilders. Powerlifers are concerned with strength and therefore have no need to high repetition training, supersets, giant sets, etc. Whereas bodybuilders want to maximize the amount of muscle size they have and take advantage of both types of training. Lower reps will build bigger muscles cells while higher reps will vasculate the tissue.
It is also important to know that lactic acid is not entirely a waste product. Lactic acid is is carried away from the muscles into the blood stream and when it reaches the liver it is converted back into sugar through a biological process known as the Cori Cycle.
Lactic acid doesn’t cause muscle soreness. Regardless of how much lactic acid is produced the body will always shut down before it can damage itself. The burning sensation in your muscles is a natural mechanism that stops you from continuing to produce more lactic acid. As a result the denaturing that occurs in the proteins of the muscle in completely reversible.
But rather, muscle soreness is caused from microtears in the muscles fibers themselves causing extracellular leakage that generates an immunological reaction that results in swelling. Muscle soreness is literally muscle damage.
So stretching has nothing to do with lactic acid removal. This trainer lacked a basic knowledge of human physiology and as a result it lead to observed program design advising clients to stretch when they are sore.