Follow up on Lactic Acid

In addition to having fewer blood vessels, fast twitch muscle fibers express the MCT4 isoform (a protein); such does not allow lactate to be removed from the muscle cells quickly, which helps it to build up in these muscles. Interestingly, slow twitch muscle fibers express the MCT1 isoform, and this allows lactate to be removed from the muscle quicker in order to prevent lactate build up.

Initial research showed that the lactic acid build up in fast twitch muscle lowers the pH in the muscle fiber cells. As a result of this the force of tetanic contractions increases and the recovery of force improves. These effects are largely attributed to lactate counter acting the fatiguing effects of K⁺ (potassium) which is released in the muscle during work. In this sense the lactate is as beneficial as the potassium is detrimental, and the resulting effect on muscle fatigue is minimal. It is important to note that the lower intercellular pH causes by lactate does not affect Ca²⁺ (calcium ions) release in muscle cells.

Further research dealt mostly with lower pH and lactate concentrations in muscle cells being detrimental to muscle function, as this is a subject of some debate. The greatest contradiction to lactate being beneficial are studies showing that higher blood pH creates increased muscle performance by lowering both intercellular and extracellular potassium levels. Studies have also shown that a greater ability to remove lactate and acidity from muscles gained through training is also beneficial to muscle performance. Those who do not believe lactate is beneficial are quick to point out, however, that lactate is not the greatest cause of muscle fatigue, and that its effects are somewhat minor.

The main rebuttal against this view is that lower pH in muscle cells creates hindered uptake of Ca²⁺, which aids muscle performance.

In addition to what I have learned from independent research I have also gained a mass of general knowledge on the subject of body building from my sponsor. I plan to expand upon that knowledge, and to give a more in depth report on it in the future.