Unused back muscles switch themselves off

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Unused back muscles switch themselves off

19:00 25 August 04

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Slumping in front of the television or computer could deactivate muscles

that support and protect your spine, triggering many otherwise inexplicable

cases of lower back pain.

A European Space Agency study in Berlin, Germany, in which young men spent

eight weeks in bed, showed that an absence of load on spinal support muscles

can sometimes be just as debilitating as a physical injury.

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. Normally 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 between 10 and 15 per cent of cases of

back pain begin with such an injury. For the rest, the cause is often a

mystery.

Restful volunteers

Now a team from the University of Queensland in Australia has shown that the

support muscles of the bed-rest volunteers were inactivated in a very

similar way to those of lower-back pain patients.

Using magnetic resonance imaging, they showed that after eight weeks, the

multifidus muscles of all 19 young male volunteers in the bed-rest study had

wasted and become inactive.

" This is the first study to show that these muscles that protect your spine

are switched off in de-loading, " says Hides, one of the researchers.

Slumping for hours in front of a computer or TV could have exactly the same

effect, she suggests.

Reactivating muscles

The bed-rest study also shows that switching these postural muscles back on

is not simply a matter of getting up and walking around. Some of the

volunteers have been monitored for the past six months and their multifidus

muscles have still not recovered, even in those who exercised.

But people can be taught to reactivate the support muscles using visual

feedback from ultrasound scans. In an earlier study by the Queensland team,

this therapy reduced the recurrence of lower back pain by half (Spine, vol

26, p e243). The work should also benefit astronauts, who often suffer from

back pain.

The conclusions sound reasonable to of the Adelaide Centre for

Spinal Research in Australia. " We know that bones and soft tissues need

physical stresses to maintain vitality, " he says.

Emma Young

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