Lactic Acid: Friend, Not Foe

Lactic acid is actually a fuel

For years, many scientists thought that lactic acid was just a metabolic byproduct or waste product that was produced during intense exercise, but today we know that lactic acid is a “friend” for athletes, not a foe. Many people associate lactic acid as that “burning” sensation in your muscles that causes fatigue in your muscle as your pushing yourself really hard in the gym. What the newest research has proven is that increases in lactic acid is actually a fuel, not a metabolic waste product. Lactate is an important substrate that can be used during sub-maximal exercise, recovery and at rest. It is the preferred source of fuel for the heart and brain.

Dr. George Brooks, one of leading experts in lactic acid metabolism was quoted as saying. “Lactic acid which is commonly referred to as a metabolic byproduct is one of the classic mistakes in the history of science. The understanding now is that muscle cells convert glucose or glycogen to lactic acid. The lactic acid is taken up and used as a fuel by mitochondria, the energy factories in muscle cells.” In fact, it has been estimated that roughly 75 percent of the lactate produced inside the muscle cells is used in this way, and only 25 percent leaks out into the bloodstream, where it can be measured through blood lactate testing. Lactate production during intense exercise stimulates a phenomenon called mitochondrial biogenesis after exercise. An increase in the concentration of mitochondria inside muscle cells is one of the major adaptations to training that improve endurance performance.  In fact, there are some sports nutrition companies have introduced sodium lactate into sports drinks and there is some tentative support that sodium lactate can improve performance.

Another common myth about lactic acid is that it causes muscle soreness. As discussed in many of Dr. Brooks papers is that lactic acid levels return to baseline within an hour after exercise.  Much of the research to date has shown that lactate has no correlation with muscle soreness.  For example, when subjects perform maximal eccentric contractions, there is very little lactiate produced yet there is considerable muscle damage and muscle soreness following eccentric contraction.

In addition to the benefits listed above, new research suggests that lactic acid may also trigger muscle growth. A new study found that the combination of lactate and caffeine also activated the anabolic signal molecules mTOR and S6K; in conjunction with increases satellite cell activity.  This study was done for four weeks on rats but at the end of the four weeks the rats that had been given lactate and caffeine had built up more muscles than the animals that had only done exercise.

Below are some of the many benefits of lactate metabolism:

  • Results in mitochondrial biogenesis or creation of new mitochondria
  • Stimulates Growth Hormone production from the pituitary which reduces bodyfat and increases lean muscle mass.
  • Can be used as an alternative fuel during exercise for improved performance.
  • May stimulate anabolic signaling pathways and enhance satellite cell