Derek Hough -- Lean, Mean Shirtless Dancing Machine
7/15/2011 4:05 AM PDT
Derek Hough -- Lean, Mean Shirtless Dancing Machine
We know what "
Dancing with the Stars" pro
Derek Hough has been doing during his summer vacation ... working out!

The 26-year-old showed off his pumped up pecs and biceps by going shirtless in L.A. on Wednesday.
Tens across the board.