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When fitness expert and Instagram sensation Kayla Itsines offered to demo some of her best moves for getting washboard abs here at the InStyle offices, the answer was an obvious yes.

Enter the weighted straight-leg jack knife. It may be a mouthful, but even just after a rep or two, you fee the burn. If you want a stand-out six pack, this exercise is definitely for you. And if you don't feel comfortable using a heavy weight, not to worry, Kayla demos a few different modifications depending on your fitness level. She recommends doing 10-15 reps of this move every day for best results.

Watch the full video tutorial above and get those summer-ready abs you've always dream of!