Thursday, December 2, 2010

Talking Turkey...

So, it’s been a week since Thanksgiving. Still working on any leftovers? We froze much of ours, and most of the rest became a turkey pot pie and turkey-noodle soup this past week. For those of you who prepared some traditional turkey dinner – which parts were most preferred on Thanksgiving day and which were left for the days that followed? ... the “dark meat” (legs and thighs) or the “white meat” (breast)? And what makes them different?

Time for some muscle biology. “Dark” muscle, also often called “red” muscle or oxidative muscle, has a dark color and stronger flavor due to high concentrations of myoglobin (an oxygen storing protein), more blood vessels (to provide more oxygen and remove more carbon dioxide), and more mitochondria in its cells (which can generate more energy in the form of ATP). This type of muscle, therefore, is very well suited for extended use without getting fatigued. It just doesn’t tire out as quickly as the other type of muscle – the “white” muscle (also call glycolytic muscle). This rather pale type of muscle lacks the biochemical mechanisms for long periods of sustained use, and therefore is used for quick bursts of activity – but tires out pretty quickly.

So what do you know about the life style of turkeys and their relatives such as chickens, partridge, grouse, and other related birds? Well, they walk and run a lot, and only rarely fly – and if they do fly it’s only for short distances because the flight muscles (in the breast) can’t sustain long periods of activity. Compare that with another type of bird that is a holiday favorite for some – goose, or perhaps duck. These birds fly long distances during annual migrations, and hence have lots of “red” muscle in the breast – necessary for sustaining flight for long periods of time. If you’ve ever had duck or goose you know that the taste is quite different than that of turkey or chicken; this is partly due to the difference between the “red” and “white” muscles.

If you prefer fish for your holidays you can see similar patterns – lots of strong-flavored dark muscle in open ocean long-distance swimmers like tuna, swordfish, and some sharks, but lots of light-flavored white muscle in less active fishes such as cod, haddock, flounder, and halibut.

Humans, and other mammals, also have different types of muscle cells, but they are interspersed with one another within our muscles – so we don’t have distinct regions of “dark” or “light” muscle. The way that we exercise, however, does influence which types of muscles cells get larger. More aerobic activity favors the darker “red” muscle cells, whereas short periods of anaerobic exercise helps the lighter “white” muscle cells.

Want to learn more? Come to St. Mike’s and take a course in physiology......

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