Ab Crunch Machine
The seated ab crunch machine loads a crunch against a chest pad or handles on a weight stack, with your back supported and the path guided. It trains the abdominal wall, mainly the rectus abdominis (the six-pack muscle), and suits loaded, higher-effort ab work with little set-up or skill.
Also called: Machine Crunch, Seated Ab Crunch, Seated Ab Crunch Machine, Selectorised Crunch · Equipment: machine · Pattern: pull
Step by step
- Set the seat height so the chest pad or handles sit at the top of your chest and the machine's pivot lines up roughly with your mid-torso. Hook your feet under the foot rollers if the machine has them.
- Sit with your back against the back pad and hold the handles lightly, elbows bent and close to your sides.
- Choose a load you can move with your trunk alone, keeping your arms as passive links to the pad.
- Breathe out and curl your ribcage down towards your pelvis, rounding your spine from the top down. Keep your hips still on the seat.
- Pause for one second in the fully curled position and squeeze your abs.
- Uncurl under control over about two seconds until your spine is upright again and the stack is just short of touching down.
- After the last rep, return fully upright and let the stack settle before releasing the handles.
- Curl your ribs down towards your hips
- Hips stay planted on the seat
- Arms stay passive, abs move the pad
- Breathe out as you curl
- Pause and squeeze at the bottom
- Two seconds back to upright
In VALDA, these cues are one tap away on the exercise while you train.
What it trains
| Muscle | Role | Evidence |
|---|---|---|
| Rectus abdominis: upper | Prime mover | B |
| Rectus abdominis: lower | Secondary | C |
| Obliques (internal/external) | Stabiliser | C |
| Transverse abdominis | Stabiliser | C |
Evidence grades: A = strong research base · B = good · C = limited · D = coaching consensus.
What goes wrong, and the fix
Hinging at the hips instead of curling the spine
Fix: Keep your hips fixed on the seat and curl your ribcage down towards your pelvis.
Pulling the handles with the arms
Fix: Hold the handles lightly and let your trunk move the pad.
Letting the stack slam between reps
Fix: Take two seconds to uncurl and keep the stack just clear of the rest of the plates.
Jerking the weight with momentum
Fix: Pick a load you can curl smoothly and pause for one second at the bottom.
Seat set too high or too low
Fix: Adjust the seat so the pad sits across the top of your chest.
What the research says
Muscle growth · first choiceStrengthRehab & prehabGeneral fitnessEndurance
- Load and effort — Research finds muscle growth is similar across a wide range of loads when sets are taken close to failure. Taking every set to true failure appears to add only a small extra benefit, so many lifters finish ab sets one or two reps short.
- Rep ranges — Ab machine sets are commonly performed for 10–20 reps, with the stack raised once the top of the range comes easily. Lighter, higher-rep sets tend to favour muscular endurance.
- Volume — Research links more weekly sets for a muscle to more growth, with diminishing returns. Around 10 or more hard sets a week has been associated with more growth than fewer than 5.
- Tempo — Studies show growth is similar across rep durations of roughly half a second to eight seconds, so a controlled one-second pause and two-second return fits well within the researched range.
Swap it mid-workout
- Cable Pull-Down Crunch
- Cable Crunch
- Kettlebell Sit-Up
- Medicine Ball Dead Bug
- Medicine Ball Overhead Throw
- Medicine Ball Rotational Throw
With VALDA Pro, FLEX offers alternatives like these when you swap an exercise mid-workout.
Log the ab crunch machine in VALDA, with these cues one tap away while you train and your history for it in one place.
General information about exercise technique, not medical advice. If you have an injury or a health condition, your healthcare provider is the right person to ask.