Primary Muscles
Rectus abdominis (upper and mid abs)
Core
Crunch
The go-to isolation move for the rectus abdominis — effective with good form, neck-straining with bad.
3D animation — watch the full movement
Secondary Muscles
Internal/external obliques, hip flexors (minimally)
Equipment
None (mat optional)
Location
Home / Gym
Difficulty
Beginner
How to Do It
- Lie on your back. Bend your knees to 90°, feet flat on the floor, hip-width apart.
- Place your hands lightly behind your head — no pulling — or cross your arms over your chest.
- Exhale and lift your shoulder blades off the floor. Think 'chest toward knees', not 'head toward knees'.
- The range is small: only your shoulders leave the floor, lower back stays down. Feel the upper abs contract.
- Lower back down with control (2 s eccentric). Maintain a stable lower back throughout the set.
Common Mistakes
- Yanking the neck forward — neck muscles work, not abs. Hands are contact only.
- Doing a full sit-up — no need to go past 30°; excessive hip flexor activation.
- Speed + momentum — muscle control is lost, tendon stress rises. Slow the eccentric.
- Lifting the lower back off the floor — hyperextension and disc pressure. Keep it grounded.
- Holding your breath — increases intra-abdominal pressure. Exhale on every rep.
Beginner Tips
- 12-15 reps × 3 sets is ideal. If you need more, add resistance rather than reps.
- Feel neck discomfort? Pause. Try a wall-supported head position to learn the pattern.
- Crunch shouldn't be your only abs exercise — pair with plank, leg raise and oblique work.
- Visible abs (six-pack) come from lowering body fat percentage via diet — exercise builds strength.
Frequently Asked Questions
Will crunches give me a six-pack?
Crunches strengthen and build the abs. But visible six-pack requires low body-fat percentage — achieved through caloric deficit and nutrition. Spot-reduction via exercise over a specific area is not scientifically valid.
Crunch vs plank — which is better?
They do different things. Crunch contracts the rectus abdominis (movement). Plank trains the transversus abdominis and stabilisers (stability). A well-rounded core programme includes both.
How many crunches should I do?
For hypertrophy: 3×12-15. For strength: 4×6-10 with added weight. For endurance: 3×20+. The popular 100-crunches-daily challenge risks overtraining and neck stress.
Related Exercises
Plank
The most evidence-backed isometric exercise for core, lower back and shoulder stability.
Leg Raise
The most direct way to load the lower abs — works hip flexors and the lower fibres of the rectus abdominis.
Russian Twist
The classic oblique isolation move — rotational core strength and the V-cut taper.
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