Sitting at computer 'can switch off back muscles'

A group of Australian researchers found that if certain muscles in the back were not used frequently enough they could effectively be "switched off", leading to the kind of problems more readily associated with heavy lifting.

The findings followed a European Space Agency study carried out in Germany where 19 Male volunteers spent eight weeks in bed to simulate the effects of weightlessness in space.

A team from the University of Queensland in Australia studying the impact on the bed-rest volunteers found that the support muscles in their backs were "inactivated" in a very similar way to those of lower-back pain patients. According to an article appearing in the New Scientist today, the effect could be "just as debilitating as a physical injury."

One of the researchers, Julie Hides, suggested that slumping for hours in front of a TV or computer could have a similar effect.

Support muscles

According to the New Scientist article ultrasound studies have shown that in most cases of lower-back pain, either the lumbar multifidus muscles, which keep the vertebrae in place, or the transversus abdominis, which holds the pelvis together, or both, are inactive. Under normal circumstances the muscles work continuously to support and protect the lower back.

Heavy lifting, whiplash or other injuries can damage and inactivate these support muscles. This increases the risk of long-term back pain, as people are then more likely to suffer sprains, or damage to the discs or other tissue in the back.

However, only around 15% of cases of back pain begin with such an injury, with the rest having an unexplained cause.

Using magnetic resonance imaging, the Australian researchers showed that after eight weeks, the multifidus muscles of all 19 young male volunteers in the bed-rest study had wasted and become inactive.

No simple recovery

"This is the first study to show that these muscles that protect your spine are switched off in de-loading," said Julie Hides.

Worryingly, after six months of monitoring some of the volunteers still had not recovered, even those who exercised. However, people could be taught to reactivate the support muscles using visual feedback from ultrasound scans, said the researchers.

Such therapy had been shown to reduce the recurrence of lower back pain by half, they added.

Robert Moor, of Australia's Adelaide Centre for Spinal Research, said the findings made sense. "We know that bones and soft tissues need physical stresses to maintain vitality," he said.