How to do a Crunch
The crunch trains the abs through a short curl of the shoulders toward the hips. Clean form keeps the lower back planted and drives with the abs, not the neck. CalmArms grades your range and control and counts each rep automatically.
Muscles: Rectus Abdominis
Demonstration: Crunch
How to do it with clean form
- 1
Lie back with knees bent and lower back flat on the floor.
- 2
Curl your shoulders up toward your hips in a short range.
- 3
Keep your neck neutral — don’t yank your head forward.
- 4
Lower under control and keep tension on the abs.
Common crunch mistakes CalmArms catches
Pulling on the neck to lift the head.
Turning it into a full sit-up by lifting the lower back.
Using momentum to bounce off the floor.
Rushing reps and losing ab tension.
How CalmArms grades the crunch
CalmArms grades crunches on elbow-based range and tempo, so controlled reps with real ab range score higher than neck-driven bounces.
Variations graded
Grade your crunch on your next set.
Prop your phone and lift. CalmArms counts every rep and grades your form A–F, hands-free — on-device, no video uploaded.