Crunches
Crunches are the classic bodyweight ab exercise: lie on your back, curl your shoulders a few inches off the floor, and lower back down. It's a short, controlled movement rather than a full sit-up, which keeps the tension on your abs instead of your hip flexors. It's one of the simplest ways to train your abs anywhere you have a bit of floor space.
Why it works
Your abs' main job is pulling your ribcage toward your pelvis, and a crunch isolates exactly that motion without involving your hip flexors the way a full sit-up does. Keeping your feet on the floor and your knees bent takes your hips out of the position they'd otherwise use to help lever your torso up, so the short lift you're left with comes almost entirely from your abs contracting.
Set up
- Lie on your back with your knees bent and feet flat on the floor, hip-width apart.
- Rest your hands lightly across your chest or behind your head, without lacing your fingers.
- Press your lower back gently into the floor before you begin.
How to do it
- Curl your shoulders and upper back a few inches off the floor, leading with your chest rather than your chin.
- Keep your lower back in light contact with the floor throughout the lift.
- Pause briefly at the top and squeeze your abs.
- Lower back down with control until your shoulders touch the floor again.
- Repeat for the full set without resting at the bottom between reps.
Form cues
- Lift your chest toward the ceiling, not your chin toward your knees.
- Keep a fist-sized gap between your chin and chest the whole time.
- Small range, real squeeze; height isn't the goal.
- Exhale hard at the top of every rep.
Breathing: Exhale as you curl up, and inhale as you lower back down.
Common mistakes
Yanking the head and neck forward to gain height.
Fix: Keep your hands as light support only, and let your abs pull your ribs up instead of your arms pulling your head.
Turning the crunch into a full sit-up.
Fix: Stop the lift once your shoulder blades clear the floor; going further shifts the work to your hip flexors.
Rushing through reps with no pause at the top.
Fix: Hold the top position for a beat so your abs do the work instead of momentum carrying you through.
Letting the lower back arch off the floor.
Fix: Keep a gentle brace in your abs throughout so your spine stays in contact with the floor.
How to program it
- Crunches are light enough on recovery that most people can do them daily or near-daily without it eating into other training.
- 2 to 3 sets of 15 to 20 reps is a reasonable starting target for most beginners.
- They work well as a warm-up activation move or at the end of a session, since the fatigue they cause rarely interferes with other lifts.
- Once 20 smooth reps feels easy, add a slow tempo or move to a variation like hands overhead or a weighted crunch instead of just chasing higher rep counts.
Safety notes
- Stop if you feel the movement in your neck instead of your abs; that usually means your hands are pulling instead of resting.
- If you have a lower back condition, keep the range small and stop the set the moment you feel discomfort rather than pushing through it.
Exercise profile
- Force
- Pull
- Mechanics
- Isolation
- Category
- Strength
Frequently asked questions
How many crunches should a beginner do?
2 to 3 sets of 15 to 20 reps is a solid starting point. Focus on a controlled squeeze at the top rather than rushing to a higher number.
Can I do crunches every day?
Yes, for most people. Crunches are light enough that daily or near-daily practice usually doesn't interfere with the rest of your training, as long as your form stays clean.
Crunches vs sit-ups: which is better for abs?
Crunches keep the movement short and isolate your abs more directly. Sit-ups move through a longer range and pull in your hip flexors, which makes them more of a full core exercise but less of a pure ab isolation move.
Why do crunches hurt my neck?
Your hands are likely pulling your head forward instead of just resting behind it. Keep your elbows wide, relax your neck, and let your abs do the lifting instead of your arms.