Kellan Lutz showed off his sexy pecs while at the Muscle Milk Fitness Retreat. We prefer him shirtless, but the Twilight hottie in a tight shirt still does the trick!

Mr. Lutz joined several celebrities for the Beverly Hills retreat which included the Rock Bottom Body class ... known to have helped Cameron Diaz sculpt her fabulous body for the upcoming flick Bad Teacher.

After checking out the latest Oakley eyewear, the hunky actor hit the court for a charity 3-on-3 basketball tournament. See Kellan sitting courtside ... after the jump.