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Dara Torres, great genes, and fast-twitch muscle fibers

Posted Dec 19 2008 12:03pm
Jim Lampley: “Do you think you rewrote the rules of career tenure for all swimmers, or did you only really rewrite the rules for Dara Torez because of unique gifts that the universe gave you?”

Dara Torres: “I am very fortunate to have great genes, and I do have real fast muscle twitch fibers, and I think it is easier for a sprinter to come back than it would be for a distance swimmer.”

That is an interestingly worded question and an interesting answer.

Regarding genes and fast twitch fibers:


You are born with a genetically determined composition of fast and slow twitch fibers. Most people have a pretty even mix of fast-twitch and slow-twitch fibers. If you are blessed with a greater portion of fast twitch fiber you will never be a good distance runner, but you could turn out to be a good sprinter. If you are blessed with a greater portion of slow-twitch fiber you will never be a sprinter, but you might turn out to be a good distance runner. Cheetahs are the fastest animals but can only sprint a distance of a few hundred yards; their muscles are predominantly fast-twitch.

Regarding it being easier for sprinters to come back than it would be for distance swimmers:

She clearly demonstrated that. Sprinters rely primarily on fast-twitch muscle fibers. Fast-twitch muscle fibers that were once strong can regain that strength quickly – for an extreme example see pictures here. This ability to regain lost strength has been referred to as muscle memory.

Interestingly strength gains once attained are more lasting that endurance gains. From this study, Enzyme adaptations of human skeletal muscle during bicycle short-sprint training and detraining:

" A long interruption in training has negligible effects on short-sprint ability and muscle anaerobic potential."

In the study cyclists detrained (they stopped exercising for several weeks.), and their blood was taken to determine levels of aerobic enzymes and anaerobic enzymes. Each week the level of aerobic enzymes dropped, while the anaerobic enzyme level did not change.

The upshot: sprinters gains are likely to persist longer and once gains are lost they are likely to come back quicker once training resumes.

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