Why 'strengthen your core' is lazy advice — and what the assessment actually looks like

If you’ve ever had back pain, someone has told you to strengthen your core. Your doctor probably said it. Your trainer said it. The article you read said it. Everyone says it, and almost nobody explains what they mean or what muscles they’re referring to, or how to actually test whether yours is weak.

“Core” is one of the vaguest words in fitness. Let’s break it down properly.

The core is not just abs

When people say “core,” they usually mean rectus abdominis — the muscle you can see. That’s a small part of what actually stabilizes your spine. The real team includes:

• Transverse abdominis — a deep muscle that wraps the midsection like a corset
• Multifidus — small segmental stabilizers along the spine
• Diaphragm — yes, your breathing muscle; it co-contracts with the others to pressurize the abdomen
• Pelvic floor — bottom of the cylinder, closing off the abdominal pressure system
• Obliques and quadratus lumborum — rotational and lateral control
• Glutes — especially gluteus medius for pelvic stability in single-leg tasks

Doing 100 crunches a day targets essentially one muscle in that list, and not the one most correlated with back pain prevention.

What the assessment actually measures

When someone comes to me with back pain and “weak core” on their referral, here’s what I actually test:

• Diaphragmatic breathing — can you breathe into the belly and lower ribs without the shoulders rising? Most people with chronic back pain cannot. Breathing is the foundation of stabilization.
• Transverse abdominis activation — can you draw the lower abdomen in without holding your breath or bearing down? Tested with a biofeedback cuff or palpation.
• Single-leg stability — stand on one leg, hold 30 seconds, eyes closed. Most people fail this long before their spine is the limiting factor.
• Hip hinge pattern — can you load the hips posteriorly without rounding your lumbar spine?
• Glute activation timing — when you extend your hip, does the glute fire first, or the hamstring?
• Anti-rotation control — resist a side-pulling band for 30 seconds without your torso rotating or your ribs flaring.

The results usually show that “weak core” isn’t really the issue — the issue is specific weaknesses or timing failures in one or two of these components, usually combined with compensations that have been running the show for years.

Why generic core programs often don’t help back pain

Planks, crunches, and sit-ups can be useful movements for some people. For others, they reinforce the exact compensation pattern causing the back pain — particularly if someone has poor diaphragm control and is bracing by holding their breath and flaring their ribs.

A program built on a proper assessment fixes the specific deficit. One I’ve used many times: someone whose “weak core” turned out to be poor hip extension timing. We spent three weeks on glute activation and diaphragmatic breathing — no crunches, no planks — and the chronic back pain they’d had for two years resolved.

The real ask

“Strengthen your core” as advice is about as useful as “eat healthy.” The value is in the specifics: which muscles are underperforming, which movement patterns are inefficient, and what the graded program looks like to correct it. That’s what a movement assessment is for — and it takes about 60 minutes to do properly.