Crunches
The baseline abdominal movement: lying on your back and rolling your shoulder blades about 10 cm off the floor while your lower back stays pressed down. It trains the rectus abdominis through a short, honest range — and its reputation suffers mainly because most people perform it as a sloppy half sit-up and expect it to reveal a six-pack.
Own the movement
Set up first, then execute. Every cue below is something you can check on your next set.
Before the first rep
- Lie flat with your knees bent to about 90 degrees and your feet flat on the floor, or resting on a bench.
- Rest your fingertips lightly at the sides of your head, elbows pointing out. Never lace your fingers behind your skull.
- Press the small of your back into the floor and keep that pressure for the whole set.
- Set your chin so there is roughly a fist of space above your sternum, and hold that angle from the first rep to the last.
Every rep
Breathing & tempo — Exhale on the way up and keep exhaling through the one-second squeeze at the top; inhale as you lower. Two seconds up, one-second hold, three seconds down.
Sets, reps & load
Where to start, and what to change when it stops being hard.
Start with bodyweight and a strict tempo. When 25 clean reps are comfortable, hold a 2.5-5 kg plate on your chest and drop back to 12-15 reps rather than continuing to add reps. Next steps in order of difficulty: plate on the chest, then arms overhead, then plate held overhead, then a decline bench.
What goes wrong
The errors that show up most often, and the cue that fixes each one.
Move your fingertips to your temples, or cross your arms over your chest and remove the option entirely. Keep a fist of space between chin and chest for every rep.
Pause for half a second in the bottom position of every rep so each one starts from a dead stop. Cut the rep target in half while you rebuild the tempo.
Stop at the point where the shoulder blades leave the floor. If you want the sit-up range, programme sit-ups deliberately — do not let a crunch drift into one rep by rep.
Cap the set at 25 and add resistance instead: a plate on the chest, arms overhead, or a decline bench. Fat over the abs comes off through your overall energy balance, not through rep count.
Why bother
The rectus abdominis has one job: pull your ribcage toward your pelvis. The crunch is that job and nothing else, which is why the useful range is only about 30 degrees of spinal flexion. Everything past the point where your shoulder blades leave the floor is hip flexors dragging your torso up, and it neither loads the abs harder nor gets you anywhere.
Unloaded crunches stop building anything once you can pass about twenty-five clean reps. Past that point the set is an endurance test for a muscle that already works all day, and the only honest progressions are a plate, a cable or a longer lever — not another fifty reps. Treat 25 as the ceiling and add resistance the way you would on any other lift.
Where it fits
At the end of a session, two or three times a week, for a few sets in the 12-25 range. Do not put it before squats or deadlifts — a fatigued trunk is exactly what you do not want under a loaded bar. If your programme already includes hanging leg raises or ab rollouts, this is optional accessory volume rather than a requirement.
If this one isn't it
No kit, too hard, or too easy — here's where to go instead.
Same job, different kit
Start here instead
When this gets easy
Asked and answered
Should I anchor my feet under something?
No. Anchored feet give the hip flexors something to pull against, and they will happily take over the moment the abs tire — which turns a crunch into a half sit-up without you noticing. Leave the feet loose on the floor or on a bench. If your feet lift off as you curl, that is a sign you were coming up too far, not a sign you needed a strap.
Do crunches burn belly fat?
No. Spot reduction does not work: the fat used for fuel comes from all over your body, not from the skin above the working muscle. Crunches build the muscle underneath. Whether you can see it is settled by your overall body fat.
Are crunches bad for your back?
For most healthy people, done in the short range with the lower back pressed down, they are fine. Repeated end-range spinal flexion under load is what irritates some people, particularly with a history of disc problems. If crunches hurt, swap to dead bugs and planks — the abs get trained without the flexion.
Crunches or sit-ups?
Crunches if you want the abs; sit-ups if you want hip flexors involved too. The sit-up's extra range comes almost entirely from the psoas pulling your torso upright, which is why it lets you do more reps and feel it less in the abs. Neither is wrong — just know which one you chose.
Why does my neck hurt more than my abs?
You are pulling your head forward with your hands, and your neck flexors are failing before the abs get tired. Put your fingertips at your temples or fold your arms across your chest, and keep the chin angle fixed so your head rides along with the ribcage rather than leading it.