Gabe Mirkin, M.D.
Weightlifters compete by lifting the heaviest weight possible only once. Why then do they have to lift heavy weights repeatedly in practice to become very strong?
Muscles are made up of thousands of individual fibers. To become very strong, you have to strengthen as many fibers as possible. The first time that you life a heavy weight, you lift only around one percent of your fibers. As you continue to lift the weight over and over again, you bring in more fibers. Then lactic acid starts to accumulate in muscles, causing a burning in your muscles, and fewer muscle fibers to contract at the same time. Weight lifters have to train by repeating multiple repetitions with heavy weights to strengthen as many fibers as possible. In practice they lift heavy weights, three times, six times and even 15 times in a row, even though they lift heavy weights in competition only once.