10 Things to Know About Muscle Fibers

Bonus content for paid subscribers! Learn how your muscle fibers work, so you can identify the best way to train for your goals.

Arnold providing an excellent example of tonus - how muscles remain in a state of semi-contraction after frequent use.

Tone or Tonus?

A common goal when starting an exercise program is to ‘tone up,’ the term commonly used to describe muscle definition. The term tone comes from ‘tonus’ which is the technical term for a state of contraction of a muscle fiber. Performing strength training repetitively will leave muscle fibers in a state of semi-contraction, creating the definition that many are working towards. When all of the fibers within a muscle are trained properly, they create the shape we commonly associate with a well-defined muscle.