TETSUButt-Ups vs Crunch (On Stability Ball, Arms Straight)
The Butt-Ups and the Crunch (On Stability Ball, Arms Straight) both train the abs as their primary muscle. The Butt-Ups are bodyweight-only while the Crunch (On Stability Ball, Arms Straight) uses a stability ball. Here is how they compare and when to pick each.
Side-by-side comparison
| Butt-Ups | Crunch (On Stability Ball, Arms Straight) | |
|---|---|---|
| Primary muscle | abs | abs |
| Body part | waist | waist |
| Supporting muscles | hip flexors and lower back | hip flexors |
| Equipment | bodyweight | stability ball |
| 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.
Crunch (On Stability Ball, Arms Straight) — first steps
- Sit on the stability ball with your feet flat on the ground and your knees bent at a 90-degree angle.
- Lie back on the ball until your lower back is supported and your upper body is parallel to the floor.
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 Crunch (On Stability Ball, Arms Straight) adds an unstable surface that raises core 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 Crunch (On Stability Ball, Arms Straight)?
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 Crunch (On Stability Ball, Arms Straight) adds an unstable surface that raises core demand. Choose based on your equipment and which movement you can progress consistently.
Can I do both the Butt-Ups and the Crunch (On Stability Ball, Arms Straight) 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 Crunch (On Stability Ball, Arms Straight) 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 hip flexors for the Crunch (On Stability Ball, Arms Straight).
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.