If You Want to Strengthen Your Core, Try Celeb Trainer Gunnar Peterson's 5-Move Workout

This is a killer move for your core, legs, and upper body. When holding elbow plank, be sure your shoulders are stacked over your elbows and your body is in one straight line.

• Start on the floor, resting on your forearms and knees.
• Step your feet out one at a time, coming into a plank position.
• Contract your abs to prevent your booty from sticking up or sinking. Your spine should be parallel to the floor, with your abs pulling toward the ceiling.
• Hold 30 seconds, and work your way up to one minute as you get stronger.