Go into almost any gym and you’ll see people doing exercises like sit-ups and leg raises. They believe these are the best exercise for abs. But they’re not — it’s crunch exercises.
Here’s an experiment. Stand up and hold onto something for balance. Put your other hand on your abs. Now, raise your knee up in front of you. Notice the ab muscles are not activated. They don’t attach to the legs.
The muscles that raise the legs are the iliopsoas or hip flexor muscles. They run from the lower back across the top of the pelvis and attach to the front of the thigh. The sit-up is just the mirror image of the leg raise.
The legs stay in place and it’s the torso that lifts up, also making use of the hip flexor muscles. The role of the abs in these exercises is simply to act as stabilizers. They do not contract over a range of motion, which is what is needed in a primary ab exercise.
Let’s look at the abs and what they do. The abdominals attach between the pelvis and the rib cage, and their function, in addition to being stabilizers, is to pull these two body parts together in a “crunching” movement – where the torso rolls or curls forward as if into a ball.
The major abdominal muscles are as follows:
The abdominal muscles sit on the front and sides of the lower half of the torso, originating along the rib cage and attaching along the pelvis.
The Rectus Abdominis muscle is commonly known as the “six-pack” muscle of the abs. Thin bands of connective tissue give it that appearance.
The Transverse Abdominis (also known as the Transversus) is the deepest muscle of the core (meaning it’s underneath all the other muscles). It wraps laterally around the abdominal area.
The fibers of External and Internal Obliques run diagonally on the body, allowing for angled movement.
Although you can feel more or less stress in different areas of the abs doing different movements, there are no different exercises for upper and lower abs. The principle of non-contiguous innervation tells us that motor neurons do not stimulate specific muscle fibers in limited locations or groups but innervate muscles over widespread areas. So the upper and lower abs pretty much work as a single until. The basic variation in the effect of an ab exercise comes from whether you contract your abs though a full range of motion, or only a partial range and how much resistance you subject these muscles to.
Lie on your back on the floor, your legs resting across a bench in front of you. Put your hands behind your neck. Curl your shoulders and trunk forward and upward toward your knees. Don’t try to lift your torso, just roll forward. At the top of the movement pause and squeeze your abs to get a full “peak contraction.” At this point slowly lower your torso, under control, back to the starting position.
2 of 6
Syda Productions
Twisting Crunches
Perform as above, but do one rep as you curl forward twist so that your left elbow comes toward your knees doing the movement. When you do the next rep, twist the other way so your right elbow comes toward you knees.
3 of 6
Chad Zuber
Reverse Crunches
In this exercise, the pelvis comes toward the rib cage rather than the other way around.
Lie on your back where you are able to reach above and behind you and grab something to hold onto — the end of a bench, for example, or the uprights on a barbell bench press bench, or anything else to stabilize you.
Bring your knees up to your chest. This is the starting point of the movement. Roll your pelvis upward so your knees come up to the forehead. Pause, then lower the pelvis back to the starting position with your knees near your chest.
4 of 6
Serghei Starus
Hanging Reverse or Vertical Bench Crunches
This movement is actually too difficult for bodybuilders with really massive legs.
Hang from an overhead chinning bar or place yourself on a vertical bench with your elbows and forearms on the padding. Bring your knees up toward your abs. This is the starting point of this exercise.
From this position, curl upward so your knees come up to your forehead. Pause, then return under control to the starting position, knees near your chest. If this is too difficult, do regular reverse crunches instead.
5 of 6
novak.elcic
Scissors Crunches
In this exercise, the pelvis and the ribcage both move toward each other at the same time.
Sit crossways on the edge of a bench. Lean your torso back and extend your legs. Crunch forward with your upper body and bring your knees up toward your chest at the same time. Pause at the top, perform a peak contraction by squeezing the abs, then return slowly and under control to the starting position.
6 of 6
GaudiLab
Machine Crunches
There are many machines which purport to provide primary ab exercises, but many of these hit the hip flexors instead. When you are using an ab machine, just pay attention to whether the rib cage and pelvis are being squeezed together though a full range of motion, or if the muscles involved are more like hip flexor exercises like sit-ups.
The fact that your abs get tired doing certain exercises don’t mean you are correctly contracting them through a full range of motion, pulling the rib cage and pelvis toward each other. Even acting as stabilizers, they still get fatigued.
