Core · Beginner
How to Do Crunches (Proper Form Guide)
The crunch is the go-to move for the abs: a short, controlled curl of your upper body that targets the rectus abdominis — the muscle behind the "six-pack." It needs no equipment and only a small patch of floor.
- In the app
- Form guide (not counted yet)
- Muscles worked
- Rectus abdominis (abs), Obliques, Hip flexors
- Equipment
- None (bodyweight)
- Also called
- ab crunches, stomach crunches, reverse crunches, bicycle crunches
How to do crunches with proper form
- 1 Lie down and set up. Lie on your back with your knees bent, feet flat on the floor, and hands lightly behind your head or across your chest.
- 2 Curl up. Tighten your abs and lift your head and shoulder blades a few inches off the floor, curling your ribs toward your hips.
- 3 Squeeze at the top. Pause and squeeze your abs at the top of the movement without yanking on your neck.
- 4 Lower with control. Slowly lower back down until your shoulder blades touch the floor. That's one rep.
Popular variations
Reverse crunches
Instead of lifting your shoulders, lift your hips and curl your knees toward your chest. Reverse crunches hit the lower part of the abs and take strain off your neck.
Bicycle crunches
Alternate bringing each elbow toward the opposite knee in a pedaling motion. Bicycle crunches are one of the most effective moves for the obliques (the sides of your waist).
Oblique crunches
Crunch up and across toward one side, then the other, to target the obliques and carve the sides of your midsection.
Muscles worked
Primary
Rectus abdominis (abs)
Supporting
Obliques, Hip flexors
Common mistakes
Pulling on your neck
Yanking your head forward with your hands. Keep your hands light and lead with your abs, not your arms.
Going too fast
Bouncing off the floor with momentum. Slow, controlled reps make the abs do the work.
Full sit-ups by mistake
Coming all the way up turns it into a sit-up and pulls in the hip flexors. A crunch is a short curl — only your shoulder blades leave the floor.
Holding your breath
Tensing up and forgetting to breathe. Exhale as you crunch up, inhale as you lower.
How many reps & sets
Abs respond well to higher reps: try 3 sets of 15–25 crunches, resting 30–45 seconds between sets. Mix in reverse and bicycle crunches to hit the whole midsection. Remember that visible abs come mostly from lowering body fat through overall training and diet — crunches build the muscle underneath.
Crunches FAQ
What muscles do crunches work?
Crunches mainly work the rectus abdominis — the front ab muscle that forms the "six-pack" look — along with the obliques and hip flexors as helpers. Reverse crunches emphasize the lower abs, and bicycle crunches target the obliques.
Do crunches burn belly fat?
Not on their own. Crunches build and strengthen the ab muscles, but you can't spot-reduce fat. Visible abs come from lowering overall body fat with full-body training and a sensible diet, which then reveals the muscle crunches build.
How many crunches should I do a day?
A few sets of 15–25 reps a few times a week is plenty. The abs are muscles like any other and grow best with quality reps and recovery, not endless daily crunching.
Does REP RUSH count crunches?
Not yet. REP RUSH counts standing, camera-facing moves like squats, lunges, high knees, curls, and presses. For a quick counted core-and-cardio hit right now, high knees are a great choice.
REP RUSH doesn't count crunches — yet
This one happens down on the floor or against a bench — angles a webcam can't track reliably. REP RUSH focuses on standing, camera-facing moves it can count cleanly. Here's what it counts for you today — free, in your browser, with nothing uploaded.
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