What is the difference between a crunch and a sit-up?

A crunch involves only lifting the shoulder blades off the floor by flexing the spine, while a sit-up brings the entire torso up to a seated position using more hip flexor involvement. The crunch provides better isolation of the abdominal muscles.

Should my lower back come off the floor during crunches?

No, your lower back should remain in contact with the floor throughout the movement. Keeping it pressed down ensures the abs do the work rather than the hip flexors.

Where should I place my hands during crunches?

You can place your hands lightly behind your head without pulling, cross them over your chest, or extend them toward your knees. The key is to avoid using your hands to yank your head forward, which can strain your neck.

Crunch

The crunch is a bodyweight core exercise that isolates the abdominals by curling the upper torso toward the pelvis while lying supine. It suits lifters of all levels seeking targeted abdominal development with minimal equipment.

Muscle group: Core
Primary muscles: abs
Equipment: Bodyweight

How to do the Crunch

Lie on your back with knees bent and feet flat on the floor, hip-width apart.
Place your hands behind your head with elbows out to the sides, or cross your arms over your chest.
Engage your abs and curl your shoulders and upper back off the floor, lifting your shoulder blades a few inches.
Pause briefly at the top of the movement while maintaining tension in your abs.
Lower your shoulders back to the starting position under control.
Repeat for the prescribed number of repetitions without letting your head rest completely between reps.

Form tips

Keep your lower back pressed into the floor throughout the movement to prevent hip flexors from taking over.
Focus on curling your ribcage toward your pelvis rather than pulling your head forward with your hands.
Exhale as you curl up and maintain a consistent, controlled tempo rather than using momentum.

Common mistakes

Pulling on the neck with hands: this strains the cervical spine and reduces abdominal engagement.
Lifting the lower back off the floor: this shifts work to the hip flexors instead of isolating the abs.
Using momentum to swing up and down: this reduces time under tension and diminishes the effectiveness of the exercise.

Sets and reps

For hypertrophy, perform 3 to 4 sets of 12 to 20 reps with controlled tempo, and for muscular endurance, aim for 3 sets of 20 to 30 reps or to near failure.

Track the Crunch in Gym Track

Log every set in seconds, see your last session's weight and reps as you train, and get a new PR flagged automatically. Free on iPhone and Android.

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Frequently asked questions

What is the difference between a crunch and a sit-up?: A crunch involves only lifting the shoulder blades off the floor by flexing the spine, while a sit-up brings the entire torso up to a seated position using more hip flexor involvement. The crunch provides better isolation of the abdominal muscles.
Should my lower back come off the floor during crunches?: No, your lower back should remain in contact with the floor throughout the movement. Keeping it pressed down ensures the abs do the work rather than the hip flexors.
Where should I place my hands during crunches?: You can place your hands lightly behind your head without pulling, cross them over your chest, or extend them toward your knees. The key is to avoid using your hands to yank your head forward, which can strain your neck.

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