Cable crunch: how to do it, how much weight, and what the crunch studies measured

A cable crunch is a crunch done kneeling at a cable machine. You hold a rope attached to a high pulley and curl your trunk down toward the floor against the weight stack. It trains the rectus abdominis, the long muscle down the front of your trunk, at its main job of bending the trunk forward, with a weight you can add to like any other exercise. It's the gym option for the curl-forward slot in the core workout.

This page covers the setup, what the crunch studies measured, how much weight to use, the standing, machine and home versions, the faults, and the sets. More exercises for the same machine are on the cable workout.

How to do a cable crunch

1. Set a rope on the high pulley and kneel a step or two in front of the stack, facing it, on a mat.
2. Hold the rope ends beside your head, elbows bent and pointing down, hands staying where they are for the whole set.
3. Sit tall on your knees, hips stacked over them. Your hips stay there the whole set.
4. Curl down: pull your ribs toward your hips, rounding your back, until your elbows reach about your thighs. Breathe out as you go.
5. Pause for a moment at the bottom.
6. Come back up slowly until your back is straight again. That's one rep.

Your hips are the test. If they sink back toward your heels as you pull, your hips and arms are moving the weight, not the curl of your trunk.

What the crunch studies measured

No study of the cable crunch by name turned up in a PubMed search for this page. The crunch itself, the same curl without the cable, has been measured, and so have the effects of adding weight:

• The front abs, not the hips. In 14 people testing the crunch, the bent-knee sit-up and seven commercial ab machines, the crunch was among the exercises with the most activity in the upper and lower rectus abdominis and in the obliques. The hip flexor measured worked hardest in the sit-up and several of the machines, not in the crunch.¹
• Heavier weights, more activity, in clear steps. In 13 people doing crunches with loads from 20 to 80% of their one-rep max and at the max itself, the abdominal muscles worked hardest at the max. Activity differed between the loads, but neighbouring loads, such as 20 and 40%, mostly didn't differ.²
• The setup changes the share. In 42 untrained adults aged 28 to 67, 18 men and 24 women, a crunch on a training ball with an elastic band produced more rectus abdominis activity than a seated crunch machine, 104% against 84% of a maximal contraction, and less activity in the rectus femoris, a hip flexor, 27% against 65%.³

All three measured activity during a few reps, not change over weeks. Read together, they say the crunch works the front abs more than your hips, more weight means more work in noticeable steps, and how you're set up matters. The cable crunch keeps the same curl and lets you load it in steps.

How much weight to use

Pick a weight you can curl for 10 to 15 controlled reps, stopping with a rep or two left, the same range the core workout uses for crunches. (How to judge reps left.) Once the top of the range comes easily, move up a clear step. In the load study, its authors advised load changes of more than 20% of a max when progressing a crunch.²

If you can't keep your hips still, the weight is too heavy, however many reps you get.

What it changes over weeks

No trial of cable crunches, or of any weighted crunch, that measured muscle growth turned up in a PubMed search for this page. The training evidence for core work in general is modest: a 2016 meta-analysis of trained people aged 16 to 44 found that core strength training made the trunk muscles much stronger, with only small-to-medium gains in other measures of fitness and athletic performance, and the studies were of low quality.⁴

So the fair case for the cable crunch is a stronger trunk at its curl-forward job, trained with a weight you can track. This page makes no claim about how your midsection will look.

Standing, machine, band and at home

When you want a harder exercise rather than more weight, the next steps on the core workout are the hanging knee raise and a reverse crunch on an incline bench. In 21 healthy men and women aged 23 to 43, a hanging knee raise with arm straps and a reverse crunch on a bench inclined 30 degrees were among the exercises that worked the abs and the internal obliques hardest.⁵ For the abs' other job, resisting an arch rather than curling, there's the ab wheel rollout.

The common faults, and a fix for each

• Sitting back into your hips. Your hips stay over your knees; the movement is in your trunk.
• Pulling with your arms. Keep your hands fixed beside your head, so the rope moves only because your trunk curls.
• Too heavy, too short. If your ribs barely move toward your hips, lighten the weight until they do.
• Letting the stack pull you up. Come up slowly; the way up is half the rep.
• Cranking your neck down. Keep your head in line with your trunk and let it travel with it.
• Training through something that hurts. Sore muscles the next day are normal; a sharp or lasting hurt in your back or neck isn't. Stop, and see a doctor or a physical therapist.

Sets, reps and where it goes

• Two or three sets of 10 to 15 at the end of a session, after your main lifts. The American College of Sports Medicine's 2026 position stand, which covers healthy adults, advises at least two sets per exercise.⁶ Where core work goes in your week covers the order.
• One curl-forward exercise a session is enough, next to a plank or an ab wheel for the arch and a carry for the lean.
• Add reps, then weight. When 15 controlled reps come easily with your hips still, go up a step. (Progressive overload covers the options.)

If you'd rather not plan it alone

The cable crunch is one exercise; deciding how much core work your week needs next to your squats and deadlifts is the part a page can't do. Coaching is the version where your workouts are built around the days you actually have, and a weekly call looks at the week you just had and rebuilds the next one. Coaching to build muscle explains how that works, and here's how to apply. Otherwise: at the end of your next session, do two sets of 12 cable crunches with your hips still, and write down the weight.