Skip the crunches this weekend. Instead, blast your midsection with this lightning-fast 5-minute challenge from well-known trainer Todd Durkin, C.S.C.S.

You'll time yourself performing 15 reps of each of the following explosive exercises: The medicine-ball chop, the groiner, the med-ball squat jump and the floor jack.

Do them back-to-back with as little rest as possible. That's 1 round. Do 3 total. Your goal: 5 minutes.

The four movements work every muscle head to toe, but they call for a blend of core stability and powerful contraction. (That’s a recipe for safety, and here's another: 3 Back-Saving Tips for the Weight Room.)

That means your abs are working the entire time, says Durkin. So go hard and go fast to boost your metabolism, skyrocket your heart rate, and chisel your core. 

Want more? Shred Belly Fat with This Metabolic Complex.

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