Crunch

What is the Crunch?

The crunch is the classic bodyweight abdominal isolation: lying on your back, you curl your shoulders and upper spine off the floor through a short range of motion. It targets the rectus abdominis directly and, because it isn’t a full sit-up, it keeps the work on the abs rather than the hip flexors.

Muscles worked

Primary: Abs

The rectus abdominis is the prime mover, contracting to flex the trunk and curl the ribcage toward the pelvis as the shoulders peel off the floor.

Stabilizers

The deep transverse abdominis braces to keep the lower back flat against the floor throughout the curl.

How to perform the Crunch

1. Lie on your back with knees bent, feet flat on the floor, and hands crossed on your chest or lightly cupping your ears without pulling on the neck.
2. This is spinal flexion, not a hip hinge: the goal is to curl the ribcage toward the pelvis, so keep the lower back pinned to the floor throughout.
3. Exhale and peel your shoulder blades off the floor by rounding the upper spine, driving your ribs down toward your belt line.
4. Rise only until the shoulder blades clear the floor (roughly a thirty-degree torso lift), since going higher hands the work to the hip flexors.
5. Pause and squeeze the abs hard at the top, feeling the distance between your sternum and pelvis shorten.
6. Lower under control by reversing the curl one vertebra at a time until the shoulder blades touch back down, keeping tension the whole way.

Suggested working range: 15–25 reps. Default progression: double progression.

Mechanics

A short-range trunk-flexion isolation: only the upper spine leaves the floor as the ribs draw toward the hips, and the lower back stays down. Because the hips never move, the effort stays on the rectus abdominis rather than shifting to the hip flexors the way a full sit-up does.

Form cues

• •Curl the spine segment by segment. Lead with the ribs toward the pelvis rather than yanking the head and neck up.
• •Keep the lower back pressed into the floor so the movement stays a short trunk curl, not a hip lift.
• •Rest your hands lightly by your ears or across the chest instead of pulling on your neck to hoist yourself up.

Common mistakes

• •Pulling on the back of the neck with the hands so the chin jams toward the chest instead of the abs doing the work.
• •Turning it into a sit-up by lifting the whole torso, which shifts the load onto the hip flexors.
• •Yanking up with momentum and bouncing off the floor rather than curling the spine under control.
• •Keeping the neck rigid and leading with the face instead of curling the ribcage down toward the pelvis.

Variations & alternatives

• •Cable crunch: the same trunk flexion loaded on a rope so you can progressively overload the abs.
• •Bicycle crunch: an alternating knee-to-elbow version that adds a dynamic, oblique-involving twist.
• •Sit-up: the longer-range cousin that carries the trunk all the way up to the knees.

Cable Crunch

Abs · Cable

Hanging Leg Raise

Abs · Bodyweight

Machine Crunch

Abs · Machine

Decline Crunch

Abs · Bodyweight

Ab Wheel Rollout

Abs · Bodyweight

Programming: sets, reps & when to use it

Train the crunch for higher reps, roughly 15–25 per set, since it’s a short-range bodyweight isolation where controlled tension beats momentum. Slow the lowering phase and squeeze at the top rather than chasing rep speed.

Frequently asked questions