This video show Bulls star Jimmy Butler performing an insane 50-inch box jump, which is impressive enough. But then consider that Butler did this jump after completing five sets of heavy squats and five sets of heavy cleans.

Jimmy Butler

"He's training so he can still be explosive in the fourth quarter," his trainer Travelle Gaines says.

That is an important consideration for Butler, who led the NBA last season with an average of 38.7 minutes of playing time.

In the summer of 2014, Butler got rid of Internet and cable TV at his house in Houston so he could devote himself to training. The result was that Butler became an All-Star and the NBA's Most Improved Player in 2014-15.

That performance earned Butler a five-year, $95 million contract with the Bulls, which only made him decide to work even harder this summer. Butler went to Las Vegas to train with Gaines, who has worked with hundreds of top athletes.

"He's here at 5 a.m., and then he works on the court with his skills guy, and then he studies film," Gaines says. "He works out all day to get into the best shape possible."

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