What muscles does the ab crunch machine work?

It works the whole rectus abdominis, because the movement brings the ribs toward the pelvis against the machine's resistance. The obliques stabilize the trunk and the hip flexors barely contribute as long as the glutes stay on the seat. The arms do not count: the handles only keep the chest against the pad.

How do you set up the seat on the ab crunch machine?

Adjust the height until the machine's pivot sits level with your midsection, roughly at the navel. Higher and the movement comes from the shoulders; lower and it comes from the hips. Then lock your feet under the supports and check that the chest touches the pad with the back resting before you move the load.

Ab crunch machine or cable crunch: which is better?

Both load spinal flexion with external resistance, so they serve the same purpose. The machine fixes the path and is easier to learn: you only have to curl the trunk. The cable crunch, kneeling in front of a rope, demands more control of the hip position and allows a slightly larger range. If you are just starting, use the machine; once you own the movement, alternate with the cable.

How much weight and how many reps for the ab crunch machine?

Start with a load that lets you do 12 to 15 slow reps, with a short pause in the contraction and a two-to-three-second return. The abs train like any other muscle: once you comfortably reach the top of the range, move up one plate on the stack. If you have to pull on the handles to finish the set, the load is too high.

Ab crunch machine

The ab crunch machine is a seated trunk flexion against an adjustable resistance, designed to load the rectus abdominis with more weight than a floor crunch allows.

ABS · CORE

Ab crunch machine: how the movement is executed

How it is executed

Sit on the ab crunch machine with your back fully supported and feet secured.
Adjust the seat so the machine’s pivot aligns with your midsection.
Grip the handles and brace your core.
Flex your spine by bringing your chest toward your hips, contracting the abdominals.
Slowly return to the starting position while keeping tension on the abs throughout the movement.

Muscles worked: Abs
Primary muscle: Upper abs
Equipment: Machine
Movement pattern: Core
Difficulty: Intermediate
What it is for: Core strengthHypertrophyStabilityStrength
Also known as: Machine crunchAbdominal machine

Watch the full tutorial

Common mistakes

Pulling the handles with the arms. The arms only hold position: the movement is bringing the ribs toward the pelvis by flexing the spine, not pulling with the lats.
Hinging at the hip instead of rounding the spine. If the whole torso comes down with a flat back, the hip flexors do the work. Think about curling down one vertebra at a time and stop where the spine stops flexing.
Dumping the weight on the way back. The controlled return is half the stimulus and it also keeps the stack from banging. Come back over two or three seconds without releasing the abs.

Frequently asked questions

What muscles does the ab crunch machine work?: It works the whole rectus abdominis, because the movement brings the ribs toward the pelvis against the machine's resistance. The obliques stabilize the trunk and the hip flexors barely contribute as long as the glutes stay on the seat. The arms do not count: the handles only keep the chest against the pad.
How do you set up the seat on the ab crunch machine?: Adjust the height until the machine's pivot sits level with your midsection, roughly at the navel. Higher and the movement comes from the shoulders; lower and it comes from the hips. Then lock your feet under the supports and check that the chest touches the pad with the back resting before you move the load.
Ab crunch machine or cable crunch: which is better?: Both load spinal flexion with external resistance, so they serve the same purpose. The machine fixes the path and is easier to learn: you only have to curl the trunk. The cable crunch, kneeling in front of a rope, demands more control of the hip position and allows a slightly larger range. If you are just starting, use the machine; once you own the movement, alternate with the cable.
How much weight and how many reps for the ab crunch machine?: Start with a load that lets you do 12 to 15 slow reps, with a short pause in the contraction and a two-to-three-second return. The abs train like any other muscle: once you comfortably reach the top of the range, move up one plate on the stack. If you have to pull on the handles to finish the set, the load is too high.

Variations and substitutions

Medicine Ball CrunchOther Dead BugBodyweight Lying Bicycle CrunchBodyweight Cable crunchCable Cross-body crunchBodyweight Weighted CrunchesOther Leg-raised crunchBodyweight Lying Leg RaisesBodyweight

Abs exercises Machine exercises Estimated 1RM calculator Back to the library

Put it to work in Kaizer

App for gym trainersSeveral clients on the floor, each with their routine and history one tap away — no paper, no spreadsheets.Kaizer vs KahunasHead-to-head comparison, including what each one does better.Pricing and plansBasic supports up to 3 clients from USD 5 a month.

Glossary and calculators

AutoregulationAutoregulation means adjusting a session's load or volume based on how the person responds that day, instead of following a number set weeks earlier.DeloadA deload is a planned period, almost always a week, in which volume or intensity comes down so the body can finish absorbing the accumulated work.Relative strength calculatorHow much relative strength you have

Program your clients' routines from these exercises, without the spreadsheet.

Start free

Ab crunch machine

Program your clients' routines from these exercises, without the spreadsheet.

Ready to raiseyour standard?