Gunnar Peterson worked out the 14-time Grand Slam champion for over a decade. (Getty)

Pete Sampras was one of the greatest players to ever take the court, racking up 14 Grand Slam wins, 286 weeks at No. 1 and six consecutive year-end No. 1 finishes. Every great athlete needs a great team, and for a decade, Sampras was led in the gym by Gunnar Peterson. 

Based in Beverly Hills, Peterson has trained everyone from the Los Angeles Lakers to Hugh Jackman to the Kardashians to word champions like Sampras. 

"Honestly one of my favorite people," Peterson says. "Pete Sampras' work ethic, second to none."

On a recent episode of the TENNIS.com Podcast, he explained that whenever he showed Sampras a new move in the gym, like a one leg dumbbell deadlift, his first rep would look much like anyone else's.

"It's a new movement, you're learning the mechanics of it," Peterson says. "By the second set, it literally looks like the guy invented the move. His athletic learning curve, second to none... I loved the hours he was in there."

The hours were memorable for another reason. Sampras liked to work out in the heat, so leading into his sessions, Peterson would turn the air conditioning off. The other clients had to adapt. 

"I'm not going to compromise, this is Pete Sampras and he's training for something in particular," Peterson says. "I want this to be the way he wants it. We used to call it 'Pete Heat' and the gym was roasty, toasty, that's for sure."