We've been doing crunches since school. But nobody really explained how they work — or why they often don't. So we keep trying harder and getting the same results. Sometimes worse ones.
Most people train their abs for one of two reasons: to get a flatter stomach, or to strengthen the core and take pressure off the lower back. Both make sense. The problem is what actually happens during the exercise.
Who's really doing the work
There's a muscle called the iliopsoas — it runs from the lower spine down to the thigh bone. Its job is to pull the legs toward the torso, or the torso toward the legs. Sounds familiar? That's exactly what a crunch looks like.
When the abs can't engage properly, the body just uses the iliopsoas instead. And it's usually already tight. The result is more tension in the lower back, the pelvis tilts forward, the belly pushes out — basically the opposite of what you were going for.
What's getting in the way
There's a deeper muscle called the transverse abdominis. It wraps around the core like a belt, holds everything in place, and gives the waist its shape. The obliques sit above it. The six-pack — the rectus — is right at the surface.
Here's the issue: if the transverse is weak or not firing, the other ab muscles lose their stable base. The body can't activate them properly. It doesn't matter how many crunches you do.
What actually helps
Two things to focus on:
- Pull the belly in before you start moving, and keep it there. Engage the muscles below the navel, not just the middle.
- The movement should only happen in the upper body. Lower back stays on the floor the whole time. Think about bringing your ribcage toward your hips — not lifting your head toward the ceiling.
If you've been consistent and nothing is changing, it might be worth looking at the transverse — testing whether it's actually working, and helping it if it's not.
That's something we can do in a session: test, release what's tight, activate what's switched off, and give you something simple to keep the progress going at home.
Train well.