http://www.youtube.com/watch?v=TrJfOi5rnlU

Mark Rippetoes says that, “the main feature of a squat shoe is heel compressibility. The drive out of the bottom starts at the floor, where the feet start the kinetic chain. If the contact between the feet and the floor is the squishy gel or air cell of a running shoe, a percentage of the force of the drive will be absorbed by the compression of the cell. This compression is fine for running, but when squatting it reduces power transmission efficiency and prevents foot stability….Squatting in running shoes is like squatting on a bed. Many people get away with it for years, but serious lifters invest in squat shoes.”

Here is a great article by Mark Rippetoe and Lon Kilgore explaining more about the different kids of shoes for lifting ranging in price from Chuck Taylors for $40 up to the state of the art Adidas shoe for $200.

Below is R. Plukerfelder (USSR) in a deep split clean. These photos are from the European Weightlifting Federation.

Here is Lopatin, also a Soviet lifter, wearing an early model of the Soviet made weightlifting shoe.  Look closely and you’ll see that he hasn’t laced up his shoes completely for ankle flexibility.  He has even fashioned a crude metatarsal strap with his laces.