The Thrill Of Victory And The Agony Of Defeat......so France You Shut Your Mouth!!

It's a combination of things.

The Speedo LZR Racer suit.
Weight training.
Vegetarian diets...quite a few are on one.
Altitude tent/room for sleeping.
revolutionary changes in stroke technique...example: Phelps butterfly, breathes every stroke. This used to be a cardinal sin.