By Chris Collins, CPT
You hear us talk sometimes of fiber. In the wild, crazy world of fitness, fiber often refers to the
fiber you eat. You may already know that soluble fiber absorbs water and helps lower cholesterol; insoluble fiber doesn’t absorb water, adds bulk to your digestive tract, and helps keep you regular. However, there’s another kind of fiber we often talk about, muscle fiber, which is separated into three different types:type l, red muscle fiber, which is slow twitch; type lla, red fibers, which are intermediate; and type llb, white muscle fiber, which are fast twitch and least resistant to fatigue.
For most of us, our fiber types are already set. While it’s true you can somewhat train intermediate muscle fibers to mimic characteristics of type llb, fast twitch muscle fibers while in adolescence, fiber type is predetermined and genetic.
For illustrative purposes, an examination of which types of athletes/populations have which type of muscle fiber is in order. Those people who are good at endurance sports such as distance running, rowing, or swimming likely have a higher ratio of slow twitch muscle fiber to fast. Those folks who succeed at lifting heavy, jumping higher, and sprinting fast have a higher ratio of fast twitch fibers to slow.
While most sports favor fast twitch fiber types, there are pros and cons to having a predominance of each. Folks with a higher ratio of slow twitch might be able to go for hours, but not move as much weight, hit as far, or jump as high one time. Folks who are characteristically fast twitch
dominant might be able to hit hard, lift heavy, or throw far, but they can’t last beyond, on the extreme end, 10 seconds in doing so.
Which fiber type are you? After learning this information, most folks want to know which muscle fiber type they are, fast or slow? While it’s true that outside of performing a muscle biopsy test, you can’t really get a definitive answer, there is another way that can give you a good indication of which muscle fiber type you are.
Here’s the test: For fiber type composition in the chest, triceps, and shoulder, calculate your one rep max on the bench (there’s many ways to do this, charts help), load up the bar to 80% of your one rep max, and press as many times as you can.
Folks who are high in fast twitch composition tend to stay in the four-seven rep range. Folks composed of slower can usually press anywhere from 15-20. On average, most of us will be able to muster around 10. For quadriceps, conduct the same percentage on your squat. For hamstrings perform the same test on deadlifts.
It’s a fun way to determine your muscle fiber composition. Try it out next time you’re in the