Most people who exercise regularly have heard about the problems lactic acid build-up in major muscles can cause. Muscle fatigue, cramping, and reduced performance have all been tied to increased levels of lactic acid in the affected muscles. This week in SciTech Watch we take a look at the results of new research on lactic acid's role in metabolism and exercise. It seems lactic acid can be your friend.

Exercise physiologists tell us that lactic acid is a by-product of metabolism in muscle cells as they do work. When lactic acid, also known as lactate, builds up to too high a level the muscle's functioning is impaired or performance reduced. Lactic acid is considered a waste product that must be flushed out of the muscle to keep its performance at high levels.

Now results from 30 years of metabolic research at the University of California, Berkley are painting a strikingly different picture of lactic acid's role in metabolism. The two methods which a muscle uses to do work have been found to be linked together rather than being two distinct methods, as thought previously. The two methods, anaerobic metabolism and aerobic metabolism are now believed to be linked together and the link is lactate.

When muscle cells convert carbohydrates to energy they do so in an oxygen-free cycle called the glycolytic pathway. This method produces lactate as a by-product. The lactate is flushed out into the blood stream for reuse or disposal. During intense exercise, a second energy production method, the oxidative pathway, becomes active. This method uses oxygen and lactate to provide more energy for muscle work. Thus the lactate produced by the glycolytic pathway is used by the oxidative pathway as fuel to produce additional energy.