Friday, November 7, 2008

KnowAbout Dark And White Meat

Most of you have heard the terms "type one" and "type two" muscle fibers, also known as "fast twitch" and "slow twitch" - but do you really know what those two terms are referring to?

In general, the two terms refer to the two types of muscle fibers present in every mammal, which are responsible for the composition of the muscle. The two types of muscle fibers are as inverse in physiological properties, as they are in the performance that the two yield.

By now you're probably wondering which type of muscle dominates your physique. There is actually a very simple way to tell whether you are made up of white or dark meat...

So, What Are You Talking About?

I refer to the two as white and dark meat because that's actually what the two are! Perhaps one of the main differences is the difference in the rate of full contraction for the two different types of muscle.

"The full contraction rate for a Type One muscle
fiber is about 150 milliseconds..."

It takes about 2½ times longer for a type one fiber to fully contract, when compared to the full contraction rate of type two fibers. The full contraction rate for a type one muscle fiber is about 150 milliseconds, while that of a type two is about 65 milliseconds.

Type Two (Fast Twitch) = White Meat

I will explain a little more about type two muscle (fast twitch) fibers first. Type two fibers are able to exert more force and greater energy, but with much less endurance than type one muscle.

Fast twitch muscle fiber is also more complex than type one. There are actually two different types of type two muscle fibers:

1. Type IIa
2. Type IIb

The only difference between the two is that Type IIa have more endurance than the Type IIb variety.

Nevertheless, no matter what version of type two muscle you are talking about, type two muscle fibers are also larger than type one, and respond better to resistance training than the type one fiber.

This is why many people are able to train and become stronger, but stay literally identical in size. So if you excel at short burst or sprinting type activities, then you are probably a white meat bird.

Type One (Slow Twitch) = Dark Meat

Type one muscle (slow twitch) is not capable of the type of force exerted by type two fibers, but retains endurance well beyond that of the type two (fast twitch) muscle fiber.

Type one muscle is the darker of the two types because of the additional oxygen, mitochondria, and myoglobin (oxygen carrier in muscle) it contains.

These are the three factors (oxygen, mitochondria, & myoglobin) which are responsible for the performance characteristics of the muscle fiber as well. This is also the reason a bird possesses both white and dark meat; they have two types of muscle fibers as well!

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