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Want some abs like a Dancing With The Stars star? In her second Women’s Running-exclusive Diet Bet Challenge video, former cover runner Karina Smirnoff demonstrates an ab exercise that can be done pretty much anywhere (for her, it’s on a park bench). She recommends 30–40 reps each time, but we say start with however many are comfortable and build up—just make sure to keep your back straight! Tune in next week for Smirnoff’s third video, and follow or join her entire #LoseWithKarina challenge at the DietBet website.