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Muscle Fibers - A guide!

by Vantage Sport Nutrition March 14, 2015

Muscle Fibers - A guide!

Build more muscle with fiber specific training!

The diagram below shows the break down of a single muscle fiber; every time we exercise & take the muscle to failure we cause micro tears & with the right rest & nutrition these tears repair creating a bigger & stronger muscle.

We can increase the size, endurance & strength of a muscle by training each fiber specifically. For example, if you stick to the same amount of sets, reps & rest when you train then it is likely you are only training one muscle fiber type & as a result would not maximize the potential results you could get if you trained all three.

Each muscle fiber will compliment each other, so in theory by training a different muscle fiber each week you can lift heavier, for longer & add more size & definition. Not to mention burn more natural calories by adding lean muscle mass & increasing energy used for repair.

For example, if you build a combination of strength, endurance, power & size over a 1-4 week period, then in weeks 4-8 by theory you should be able to lift heavier weight, for longer, with more power & again build more size.

Skeletal Muscle Fibers

Type I

Type I fibers are also known as slow twitch fibers. They are red in colour due to the presence of large volumes of myoglobin and so oxygen and high numbers of Mitochondria. Due to this fact they are very resistant to fatigue and are capable of producing repeated low-level contractions by producing large amounts of ATP through an aerobic metabolic cycle.

Athletes such as marathon runners have a high number of this type of fiber, partly through genetics, partly through training.

We can specifically target this muscle fiber by completing a higher amount of sets, 20 – 50 reps & 30 to 45 second rest. As mentioned above, this will promote more blood flow to the muscle, an increase in oxygen supply & increased endurance. This type of training can also cause tears as so much blood is flushed into the muscle to supply the aerobic/oxygen demand that is causes cell tears in the muscle & thus can increase muscular size.

Type II a

Type IIa fibers are also sometimes known as fast oxidative fibres and are a hybrid of type I and II fibers. These fibers contain a large number of mitochondria and Myoglobin, hence their red colour. They manufacture and split ATP at a fast rate by utilising both aerobic and anaerobic metabolism and so produce fast, strong muscle contractions, although they are more prone to fatigue than type I fibers. Resistance training can turn type IIb fibers into type IIa due to an increase in the ability to utilise the oxidative cycle.

We can specifically target this muscle fiber by completing a more hypertrophy based rep range between 8 & 12 reps. As mentioned above, type II a fibres are a hybrid of type I & II; this allows us to lift heavier for fewer reps but also take advantage of using aerobic & anaerobic energy & thus allowing for a combination of power, strength, endurance & size to be built.

Type II b

Often known as fast glycolytic fibers they are white in colour due to a low level of myoglobin and also contain few mitochondria. They produce ATP at a slow rate by anaerobic metabolism and break it down very quicky. This results in short, fast bursts of power and rapid fatigue. As mentioned above, this type of fiber can be turned into type IIa fibers by resistance training. This is a positive change due to the increased fatigue resistance of type IIa fibers. These fibers are found in large quantities in the muscles of the arms.

We can specifically target this muscle fiber by completing a more strength & power based rep range between 2 & 6 reps. As mentioned above, these muscle fibres primarily work in fast bursts & fatigue quickly, therefore we want to lift heavier for fewer reps which will ultimately build a lot of power & strength.


Blog Post written by Callum Melly, Previously a Vantage Sponsored Athlete (Twitter, Instagram)

Vantage Sport Nutrition
Vantage Sport Nutrition


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