Crunches isolate your abdominals to help you strengthen and define your core.
Crunches are an effective core workout to isolate your abdominal muscles. You can control the speed at which you do your crunches as well as the time of hold and contraction at the top of the movement to target your entire core.
Begin with your back flat against the ground, your legs up and knees bent at a 90-degree angle, and hands at your head with your elbows out to the side.
Activate your core muscles, bringing your nose up towards your knees.
Keep your legs in place to ensure you target your core.
Slowly return back to the starting position.