Jackknife Try this exercise to tone and strenthen your core:1. Lie flat on your back with your arms extended straight back behind your head and your legs extended.2. Bend at the waist while simultaneously raising your legs and arms to meet in a jackknife position. Pause, then lower your arms and legs back to the starting position.3. Repeat for the desired amount of reps.Words and workout by Nichelle Laus, model: Shannon Prasarn, photography by Dave LausNEXT: Check out our collection of amazing ab workouts
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