New Discovery: Lactic Acid is Muscle Fuel, not Waste Product

How do we miss this stuff? We've all learned over the years that lactic acid is a waste byproduct of anaerobic exercise. Yeah, a waste product. Plus, it hurts. Wrong. All wrong. Lactic acid, in fact, is a preferred fuel of the mitochondria, the little engines in muscle cells.

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. Mitochondria even have a special transporter protein to move the substance into them, Dr. Brooks found. Intense training makes a difference, he said, because it can make double the mitochondrial mass. It is clear that the old lactic acid theory cannot explain what is happening to muscles, Dr. Brooks and others said.

This is why it's so important to employ training variety in your bodybuilding routines. Moderately low reps (6-8) build strength and contribute to muscle hypertrophy, while more reps (9-15) build endurance. Plus, things like interval training (running brief sprints) can really increase the number of mitochondria in the cells and enhance your muscular endurance. Don't fear the lactic acid buildup — covet it! Lactic Acid Is Not Muscles' Foe, It's Fuel – New York Times