Friday, April 17, 2009

Fast-twitch, slow-twitch, dark meat, white meat...

At Easter supper, DF-i-L explained to DS that the dark meat from the turkey he was consuming is from slow-twitch muscles while white-meat is from fast-twitch muscles (or at least that's the way I remember it). DGpJ said he didn't think DF-i-L knew what he was talking about, so I was asked to look it up and settle the controversy.

DF-i-L is correct.


Slow Twitch (Type I)
The slow muscles are more efficient at using oxygen to generate more fuel (known as ATP) for continuous, extended muscle contractions over a long time. They fire more slowly than fast twitch fibers and can go for a long time before they fatigue. Therefore, slow twitch fibers are great at helping athletes run marathons and bicycle for hours.

Fast Twitch (Type II)
Because fast twitch fibers use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed than slow muscles. However, they fatigue more quickly. Fast twitch fibers generally produce the same amount of force per contraction as slow muscles, but they get their name because they are able to fire more rapidly. Having more fast twitch fibers can be an asset to a sprinter since she needs to quickly generate a lot of force.

A turkey or chicken stands on its legs all the time but doesn't do much more than that. It needs slow, endurance-trained, efficient muscles in its legs. The dark meat in the legs contains lots of blood vessels that the muscles need for near-continuous operation.

The white meat (breasts in a turkey, for example) muscles require quick bursts of activity, but not much in the way of the oxygen-carrying myoglobin necessary for long-term usage.

By the way, flying birds (dove, pigeon, wild geese, etc.) have dark meat in pretty much all of their bodies. If you like the white meat of fowl, you'll have to look for chicken, turkey, pheasant, etc. If you like dark meat from fowl, you'll find leaner meats in geese (not domesticated; avoid the skin where all the fat is stored), duck (not domesticated; avoid the skin where all the fat is stored), or other migratory game bird.


Jennifer said...

I didn't think about the reasons why certain birds have light vs. dark meats. That's interesting. Did you know in humans women tend to have more slow twitch muscle fibers, while men generally have more fast twitch fibers? Historically, women did the endurance activities of walking long distances for gathering and domestic chores while men used short powerful bursts for hunting.

deborah said...

So does that mean the mean and woman have both white & dark meat? And looking at Jennifer's addition do woman have more dark meat then men?