Crunch (Arms Down)

Active muscles:

Abdominals:

• Rectus abdominis
• External oblique
• Internal oblique
• Transversus abdominis (or “corset muscle”)

Pelvis (depending on execution):

• Psoas major
• Iliacus

Legs (depending on execution):

• Rectus femoris
• Sartorius

For a six-pack or injury prevention?

Strong abdominal muscles are essential for a strong core and preventing, among other things, lower back pain. In practice, many people primarily perform abdominal exercises for a more attractive abdomen. Often, a flat stomach or six-pack is the ultimate goal. In most cases, you do not need to perform abdominal exercises for a flat stomach or six-pack. These are mainly caused by a low body-fat percentage. You cannot selectively burn fat in the abdominal region, not even with abdominal exercises. “A six-pack is made primarily in the kitchen,” as the old saying goes.

At a low body-fat percentage, abdominal exercises can make a visual difference. Thicker muscle bellies in the rectus abdominis create deeper lines in the abdomen. However, the abdominal muscles are used and therefore trained during many different exercises and daily activities. For most people, a low body-fat percentage is therefore enough for a six-pack. In some exceptional cases, the muscle bellies (the “blocks”) of the rectus abdominis are so flat that they are barely visible, even at a low body-fat percentage. Very superficial tendinous intersections and a linea alba that divide the muscle bellies can also contribute to this. In those cases, it may be useful to perform abdominal exercises for appearance, if a six-pack is your goal.

Training your abdominals for a slim waist?

However, the abdomen can be viewed not only from the front but also from the side. The transverse abdominis draws the abdominal wall inward and thereby prevents the abdomen from protruding. The transverse abdominis is also active during abdominal exercises. Training it as well could therefore make your waist circumference smaller, like a corset being tightened.

At the same time, however, the muscle bellies of the rectus abdominis become thicker. This creates deeper lines when viewed from the front, but also makes the abdomen protrude farther when viewed from the side.

Train your abdominals or legs?

During abdominal training, muscles in the pelvis and upper legs are often also engaged unconsciously. The rectus femoris is one of the quadriceps muscles. It is the only quadriceps muscle that crosses not only the knee joint but also the hip joint.

The rectus femoris brings the thigh toward the pelvis and the lower part of the spine, and vice versa. It is a so-called hip flexor and therefore brings the thigh forward from the hip joint. This also happens when the torso is brought too far toward the thighs during an Ab Crunch, causing it to begin to resemble a Sit-Up. The weaker sartorius assists the rectus femoris in this.

Shorter muscles that connect the pelvis to the thigh, the psoas major and iliacus, also play an important role in hip flexion.

During the Ab Crunch, therefore, focus on rounding the spine (as if you were being punched in the stomach). When you lift the entire torso, you begin to engage the aforementioned muscles in the pelvis and upper legs more. The higher you come, the less active the abdominal muscles also become. This is one of the reasons Crunches have become more popular than Sit-Ups over the years.

Hands on the chest, alongside the body, or behind the head?

The Ab Crunch is often performed with the forearms crossed over the chest or with the hands behind the head. In terms of abdominal muscle engagement, this appears to make little difference. However, with the hands behind the head, you may be more likely to also bend from the neck (bringing the chin toward the chest). Keeping the hands on the chest or placing them alongside the body therefore more readily promotes the correct posture during the exercise.

• Crunches (arms down)
• Sit-Ups
• Crunch Machine
• Cable Kneeling Crunch
• Ball Crunch