Two physios say the idea that back pain is a result of a weak "core" is wrong and must be corrected to better manage the complaint affecting thousands.

The fitness industry's obsession with building "the core" has caused unnecessary fear about our spines and may be adding to the problem of chronic back pain, say two world-leading physiotherapists.

Our spines were designed to move, not be stiff, and the problem is too many core building exercises require no movement at all.

In fact, years of core strength exercises could be making a person's chronic back pain worse, says musculoskeletal physiotherapist Professor Peter O'Sullivan from Curtin University.

He says people with back pain are already too rigid. Their muscles have tensed up as a protective response to the pain and core strength exercises can be counterproductive.

"The common belief around tensing up a structure that's already tense doesn't really make sense," Prof O'Sullivan said.

Relaxing your muscles around your trunk when you have back pain is actually more helpful, he said.

According to physiotherapist Professor Paul Hodges, from The University of Queensland, the myth that core stability equals a stiff spine needs to be corrected to better back care.

He says too many people "wrongly" believe that a weak core leads to back pain.

It's a fear that has been fuelled by those in the fitness industry who heavily advocate core building exercises as a way of managing the common pain complaint.

While core stability exercises are easy to teach, they involve very little movement of the spine, says Hodges.

"The common assumption in gyms is that people assume core stability means that you stop the spine from moving."

"The Plank" exercise for example involves a person on their elbows and toes while holding their body stiff for a period of time. Many pilates studios also involve people lying still on what is known as a reformer bed while holding their spine rigidly in place.

That's not what core stability means, says Prof Hodges.

"Core stability is getting the balance between movement and stiffness.

"If you think about most functions, they actually need the spine to move," he said.

This blanket idea that exercise should just be about stopping people from moving their spine is only half of the story.

Prof Hodges says some people do move too much and need to be controlled a little more and vice versa. However different functions need different solutions and just doing a routine, "one-size fits all" approach isn't appropriate.

"A lot of fitness programs are designed for healthy people to function, to get fitter. What's a problem is if someone's got pain just doing a conventional program may not be the right thing, you need to have it specifically changed."

Back pain is very common, most people will have it once in their lifetime. With one in six Australians suffering from chronic back pain it does need to be managed properly, say both Prof Hodges and Prof O'Sullivan.

They recommend that people with back pain be individually assessed by a professional - because everybody has a unique movement signature - to work out exactly what exercises and treatment is needed.