Derek Hough -- Lean, Mean Shirtless Dancing Machine

7/15/2011 4:05 AM PDT BY Johnny Lopez
We know what "Dancing with the Stars" pro Derek Hough has been doing during his summer vacation ... working out!

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

Tens across the board.



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