Crunches are the most basic abdominal exercises in fitness today. There are countless variations on the theme of crunches. In all of them, you begin by lying on your back with your lower back pressed against the mat or floor, your knees bent, and your feet flat on the floor. Begin by contracting the abdominal muscles and then slowly lift and lower your head, shoulders, and upper back.
You can select your arm position. If you feel tension in your neck, place your hands behind your head with your fingers interlaced or touching. If your neck does not bother you, you can extend your arms straight in front of you or overhead, or you can place them on your thighs and slide them up as you lift your upper body, shoulders, and head. If you are comfortable doing so, you can cross your hands over your chest. Some trainers advise clients to tuck the chin in; others advise to keep the cervical area straight. Lightening your feet off the floor, thus releasing weight from them, as you lift your upper body makes the crunch more challenging. You can feel this effect by alternately raising your right and left toes with each crunch.