You may think you've mastered all there is to know about getting stronger, faster, fitter. But most of the ideas you hear circulating in your local weight room today have about as much basis on scientific fact as the notion that the world is flat. We're calling out these myths once and for all. Class is in session. Are you ready to be schooled?
Lactic acid causes muscle fatigue.
How It Started: Research conducted nearly 100 years ago (on frog muscles, no less) suggested that lactic-acid levels within muscles increased with fatigue.
The Truth: "Lactic acid increases with fatigue because it's fueling your muscle contractions," says Chad Waterbury, a strength coach in Los Angeles. It causes the painful burning sensation in your muscles that makes you want to stop lifting, but your liver is also converting lactic acid into more energy, so it's actually helping to offset fatigue. Muscle fatigue is prompted by an accumulation of protons within the muscles, which is caused by the breakdown of glycogen, the stored carbohydrate that helps to fuel exercise.