Muscle Fiber: What Type Are You?

Muscle Fiber: What Type Are You?

Have you ever wondered why you see some people that look like they’ve been working out for a lifetime, when in fact they’ve never even lifted a weight?  Genetics plays a big part in this and the type of muscle fiber you’re born with will often determine the type of sports you will excel in and even the type of physique you will eventually be able to build.  Muscle is made up of bundles of fibers called slow twitch and fast twitch muscle fiber.  Genetically, some people contain more of one type of fiber over the other.  Slow twitch and fast twitch muscle fiber work in different ways.

Slow Twitch Muscle Fiber

Slow twitch fibers, also known as Type I fiber or red muscle fiber, are efficient at using oxygen for muscle contractions over long periods of time.  This type of muscle fiber fires slowly helping the muscles endure longer periods of activity before fatiguing.  People with a majority of slow twitch muscle fiber both enjoy and excel at lower intensity exercises that require higher endurance such as long distance running or bicycling.  Typically, a person with a majority of slow twitch muscle fiber tends to have a leaner body type with less muscle mass.

Fast Twitch Muscle Fiber

Fast twitch fibers, also known as Type II or white muscle fiber, are anaerobic meaning they work without oxygen.  This type of muscle fiber fires rapidly making them efficient at contracting quickly for short spurts of strength but they also fatigue at a faster rate.  Because fast twitch muscle fibers generate a lot of force, athletes such as sprinters contain more white muscle fiber than red muscle fiber.  Fast twitch muscle fiber is also the muscle fiber used in weight training so a person with abundant fast twitch muscle fiber will generally be able build more muscle mass quickly as well as lift heavier amounts of weight.

Although you can’t change slow muscle fiber into fast muscle fiber, you can train the body to be as efficient as possible to achieve maximum results when it comes to strength training and building muscle.  With the right strength training program and proper nutrition, a person can improve both their athletic performance and physique for a stronger more toned appearance.   

For more information on muscle fiber, weight training, eating healthy, and general fitness and wellness, or if you’ve been thinking about hiring a personal trainer, contact us.