Dutch exercise physiologist Dr. Jan Voss was one of the early researchers of muscle fiber types. Performing numerous muscle biopsies on himself as part of his research, Voss noted that the color of the muscle tissue in his gastrocnemius would change from week to week. Sometimes there was a predominance of red (slow-twitch) fibers, and other times white (fast-twitch) fibers. In fact, Voss believed that the changes would take place day to day or even hour to hour depending on such things as temperature, metabolic activity, and so on. (Source: Iron Man Magazine – May 1, 2003)

The apparent take-home message is that you should not pay much attention to muscle fiber type during training. Your body will adapt to whatever stress or demand you impose on it.

However, in a paper titled “Strength training and fiber types” published in the March 1994 issue of Scholastic Coach, Dr. Thomas Pipes starts the article with this statement:

“Effective strength training must take into account the athlete’s muscle fiber distribution.”

According to Pipes, athletes with a very high percentage of slow-twitch fibers should perform higher repetitions and train more frequently; whereas, those with a high fast-twitch composition should train with lower repetitions less frequently. “Failing to act on this information may only cause a lack of achievement,” states Pipes. “It’s also possible that the strength-training program you are using may be worse for the athlete than no training at all.”

In The Elite Trainer, I discuss this concept further and introduce two novel, non-invasive methods of determining muscle fiber type composition – one is an improved strategy to the original Pipes approach, and the other is an interesting technique taught to me by soft-tissue specialist Dr. Mark Lindsay that uses electronic muscle stimulation to map out muscle fiber distribution across the body. Check out pages 27-33 of the book. I think you’ll find the information quite useful.