TETSUButt-Ups vs Machine Seated Crunch
The Butt-Ups and the Machine Seated Crunch both train the abs as their primary muscle. The Butt-Ups are bodyweight-only while the Machine Seated Crunch uses a machine. Here is how they compare and when to pick each.
Side-by-side comparison
| Butt-Ups | Machine Seated Crunch | |
|---|---|---|
| Primary muscle | abs | abs |
| Body part | waist | waist |
| Supporting muscles | hip flexors and lower back | obliques and hip flexors |
| Equipment | bodyweight | machine |
| Steps in our guide | 6 | 6 |
How each one starts
Butt-Ups — first steps
- Lie flat on your back with your knees bent and feet flat on the ground.
- Place your hands by your sides, palms facing down.
Machine Seated Crunch — first steps
- Sit on the leverage machine with your back against the pad and your feet secured under the footpads.
- Place your hands on the handles or the sides of the seat for support.
Full step-by-step guides are linked below.
Which should you choose?
The Butt-Ups need no equipment and scale through leverage, tempo and reps. The Machine Seated Crunch fixes the movement path so you can push close to failure with less skill demand. If your gym has both options, neither is a wrong choice: pick the one that feels strongest through a full range, and swap after 6 to 8 weeks to keep the abs adapting.
Full form guides
Common questions
Are the Butt-Ups better than the Machine Seated Crunch?
Neither is universally better — both train the abs as the primary mover. The Butt-Ups need no equipment and scale through leverage, tempo and reps, while the Machine Seated Crunch fixes the movement path so you can push close to failure with less skill demand. Choose based on your equipment and which movement you can progress consistently.
Can I do both the Butt-Ups and the Machine Seated Crunch in the same program?
Yes, but usually not in the same session — they overlap heavily on the abs. A common setup is one as your main movement and the other on a second training day, or alternating them block by block.
Do the Butt-Ups and the Machine Seated Crunch work the same muscles?
The primary muscle is the same: the abs. Supporting muscles differ slightly — hip flexors and lower back for the Butt-Ups versus obliques and hip flexors for the Machine Seated Crunch.
Track it in Tetsu
Tetsu tracks both movements separately, keeps your PRs per exercise, and tells you which one is actually progressing. Free to start.