Schmitz's swimmers also go through a structured dry land practice twice a week that focuses on building core strength and athleticism.

WSJ: Missy Franklin: How Not to Ruin a Swimming Prodigy

The process involved smearing hot latex on his hands and arms, allowing it to dry, and then peeling the strips off and wrapping them around the core of the ball until it reaches the requisite size and weight.

ECONOMIST: Sports anthropology