After back injury, people need to re-learn how to use their muscles naturally

Professor William Marras, Ohio State University

They were wired up to devices which recorded electrical activity in the back muscles - the signature of whether the person is using them or not.

These "electromyagrams" were compared with those from an uninjured person.

Low-back pain patients used many more muscles, and ended up exerting much more force on the spine, to which they are all anchored.

Protection team

Instead of employing the powerful back muscles themselves, many patients use abdominal or side muscles to try to make up the shortfall.

They are doing this to protect the muscle which was originally injured.

Professor William Marras, an expert in "systems engineering", said: "When people apply all those extra muscles, it's as if they're pushing down on the short end of a seesaw, and trying to lift something on the far end.

Professor Marras takes readings from patient (picture courtesy of Ohio State University)

"They exert more force, and to little effect."

Over time, extra force on the spine can lead to more serious, and permanent injuries, such as disc degeneration.

Professor Marras suggests that physical "retraining" of patients may be required to correct the problem.

"After back injury, people need to re-learn how to use their muscles naturally."

Job problems

Employers should also face stricter rules about protecting employees who have suffered a back injury from further harm.

They should never be allowed to lift heavy objects - even if they are relatively pain free, he says.

In addition, he recommended that patients with back injuries should make every effort to lose weight.