To really build functional strength in the core, you need to do exercises that simultaneously engage the arms and legs. That's because in real life, it supports the spine while the limbs are in motion, like when you’re running. Enter: the deadbug, an exercise that trainers are increasingly relying on to strengthen the core as the arms and legs move. It's easy enough to integrate into any workout, but it functions especially well as part of a dynamic warm-up, suggests Julie Wandzilak, a Tier X coach at Equinox Columbus Circle in New York City. Aim for 2 to 3 sets of 16 reps (8 per side), but cut sets short if your form falters.
Lie face-up with arms extended toward ceiling, directly over shoulders, and knees bent 90 degrees over hips, calves parallel to floor. Keeping shoulders down, feet flexed, and low back pressed into the floor to protect your spine, engage your core and extend right arm and left leg away from you. Tap heel to floor and return to center. Immediately repeat on the opposite side (left arm; right leg). Continue alternating sides.
Keep your arms still and focus on your lower body, extending one leg down to floor at a time. Once you feel stronger/more comfortable, add upper body in.
Keep a stability ball braced between your raised knee and hand throughout the entire movement, squeezing your core as you alternate sides to keep the ball in place.