"People generally look to the old faithful crunches or sit ups as their favorite abdominal or core exercise. I'm more of a fan of something that is way more practical than lying on the ground straining your neck," says Declan Condron, an exercise physiologist for Fitness Builder.
"One of the main jobs of the abdominal or core muscles is to act as stabilizers for the trunk, helping to support while the person is squatting, lifting, or moving about in general. Many studies show that muscle fiber activation rates in the rectus abdominis, transverse abdominis, and internal and external obliques are higher during the squat than during many ‘traditional’ crunch type exercises where the performer is lying on their back."
To do it: Stand with your feet shoulder-width apart, with the barbell on the back of your shoulders. Lower your body toward the floor, sending your hips back and down and bending your knees. Push through your heels to return to start position, keeping your back flat and head up throughout the movement. Try to do 8-10 reps for 3 sets (resting 45-60 seconds between sets).