Want a strong core? Add this high-energy workout to your workouts and boost fat loss, muscle gain and strength. All you need is 15 minutes two to three times a week and a medicine ball.

 Words/workout: Sam Ly (pictured)  Photography: Jamie Watling 

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1. Straight-arm plank

Lie on a flat surface. Position hands directly under shoulders and legs, shoulder-width apart. Stay on the balls of toes and push the body off the ground into a push-up position. Keep head forward and spine neutral as you contract the core, keeping stomach tight, and hold for 30 seconds.