By far the most common resistance exercise known to man for working the abs is the rope crunch. It’s also the ab exercise done most incorrectly. This is because there are two ways to crunch the cable (assuming you’re doing them on your knees, as you should). One way is to pull the weight down by bending at the waist. The other is to lock your hips and crunch your sternum toward your pubic bone by rotating your spine and driving your elbows downward. One way works your hip flexor (psoas)—a muscle you can’t see. The other works your rectus abdominis, the washboard you’re actually looking for.
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Anatomy of the Abs
The rectus abdominis is the main muscle of the anterior trunk. It is a long, flat muscle that extends vertically the entire length of the abdomen, originating at the sternum and inserting at the pubic bone, making up the coveted “six-pack.” The muscle flexes the spinal column, particularly in the lumbar region, drawing the breastbone (sternum) toward the pubis. It also tenses the abdominal wall and aids in compressing the contents of the abdomen.
Tendinous inscriptions create spaces that enable the muscle to bunch up as the distance between the rib cage and pelvis decreases during contraction. These are the little blocks that add up to the six-pack—they are not individual muscles and cannot be targeted separately.
There is also no such thing as a “lower” or “upper” abdominal. It is one continuous muscle split vertically down the center without interruption. The muscle can indeed be stimulated in ways that emphasize contraction nearer the origin or insertion, but there is no anatomical mechanism that allows anyone to isolate a “lower ab” without affecting the upper portion as well.
The relative ease of this exercise compared to the other crazy stuff people allegedly do for abs is deceptive. Because it appears simple, it requires less thought about mind-muscle connection, which in turn avails you of a much brighter shade of pain.
How Pain May Be the Secret to Building a Shredded Six-Pack
This movement is really about finding the upper threshold of what you think you can’t possibly bear and then going past it. For some reason, the rectus abdominis is freighted with nerve endings that produce an incredible amount of searing pain at the upper limit. Taking this muscle deliberately to honest failure, four sets in a row, is perhaps the most grievous route to enlightenment. However, it’s necessary.
The Correct Rope Crunch Form: Step-by-Step Instructions
Find a high cable and clip in a double-ended rope attachment. Place a pad or yoga mat on the floor in front of the machine.
Grab the rope in each hand and kneel down slightly more than arm’s length from the weight stack.
Raise your hands behind your head so your head is positioned between your elbows and the cable angles upward and away from you toward the machine.
Arch your back and completely stretch out your torso, making sure you are far enough away from the pulley so the weight does not rest on the stack.
From this starting position, lock your hips and pull the weight down by flexing your rectus abdominis, as if trying to touch your elbows to your knees. Do not let your femur pivot in the hip joint, and don’t bring your elbows past your face.
With your hips locked, the movement is accomplished by rolling your spine from an arched position into a hunched contraction, completely isolating the rectus abdominis.
Use enough weight to get at least 20 reps, with another five to ten thrown in for masochism’s sake. Pain management becomes a game — see how much you can handle. You’re not going to hurt yourself if the weight is realistic.
