The Mystery of Muscle Fibre Types

We often hear about fast and slow twitch muscle fibres. They are often whispered about in the gyms or talked about by the know it all bodybuilder in the locker room. Well, what the heck are they and do I really care?

Lets go through both types and how they impact your training.

Slow Twitch Muscle Fibres. (Type 1 Muscle Fibres)
These muscle fibres are better at using oxygen when you train therefore are better at continuous, extended muscle contractions. Slow twitch are given this name because they do exactly that... fire slowly, enabling then to last longer before they fatigue.
So if you are a long distance runner then you are realying heavily on this type of muscle fibre.

Slow Twitch Muscle Fibre Features:

• smaller in diameter
• red in color
• depend on oxidative phosphorylation for their ATP supply
• are highly vascularized (more veins for better blood supply)
• have more mitochondria
• more myoglobin

Fast Twitch Muscle Fibres. (Type 2 Muscle Fibres)
These muscle fibres are actually anaerobic in function and are responsible for the speed at which a muscle fires. The fast twitch response is the mechanism that rapidly contracts the muscle fibre over a sort distance or period of time.
These muscle fibres are great for explosive movements such as sprinting.


Fast Twitch Muscle Fibre Features:

• larger
• white
• glycolysis is the source of ATP
• less vascularized
• less mitochondria
• less myoglobin

Everyone has a mix of these muscle fibres in varying amounts. This is why some people are born better at different types of sports such as distance running compared with sprinting. Some of us a build for speed and power and others for distance and stamina.

Cheers,
Bouncelife.