Crunches are a waste of time for a defined core. Instead, try this dynamic move. From a high plank, engage your abdominals and keep your back flat. Rapidly drive your knees towards your chest in an explosive, alternating motion. This targets your entire core, including deep stabilizers. 🔥 Send this to a friend who's still doing 100s of crunches. . . . #fitness #coreworkout #mountainclimbers #abworkout #hiitworkout #corestability #plankvariation #fatburningworkout