By Dr Chris Riley in Star City, Moscow

The Italian cosmonaut who flew with space tourist Mark Shuttleworth last month is completing an experiment that could have major implications for the way we treat osteoporosis sufferers.

Flight engineer Roberto Vittori is back at Star City near Moscow this week attempting to shake the strength back into his bones using a simple vibrating plate which he stands on to exercise.

Bone wastage is a big problem for anyone who spends even just a short time in orbit - and would certainly blight any manned trip to Mars unless researchers can find a way to counteract it.

Vittori's work should help doctors find the solutions they need to better prepare long-flight space crews. The experimental results should also feed back into the treatment of ordinary, osteoporotic people who live on the surface of the planet.

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New bone

Even in their short 10-day trip into space, the Soyuz crew's bone mass will have dropped by 0.3-0.6% - in a kind of accelerated ageing. And despite a rigorous exercise programme on board the International Space Station (ISS), the Expedition Four crew they have left on board could return to Earth next month after over five months in space with the first stages of osteoporosis.

Vittori at work: The experiment has big spin-offs

The long duration flights on Mir in the 1990s caused irreversible 20% bone loss in one cosmonaut.

Such levels of bone wasting are among the greatest stumbling blocks to a human flight to Mars, says Vittori, who hopes to be on a future Mars mission.

But if the vibration therapy being tested works, these potentially debilitating conditions incurred on long-duration space flights might soon be cured.

For just a few minutes a day for two months before the flight, Roberto trained on the plates which shake his leg bones at between 20 and 55 hertz. The vibrations create a so called "hypergravity" environment which seems to encourage new bone to grow.

Sheep and rats

"Bones are dynamic," says Filippo Ongaro, the European Space Agency doctor leading the study. "Osteoblasts build bone and osteoclasts destroy it. This happens in perfect balance most of the time on Earth - but in space the osteoblasts stop working and bone mass decreases," he explains.

Now he is back on Earth, Roberto's rehabilitation is being speeded up by training on the plates again. Ongaro thinks that the vibrations are triggering the osteoblasts to start working overtime again - replacing the bone lost in space.

Ironically, this discovery tumbled out of studies on the harmful effects of vibration on the body, when certain frequencies of shaking were found to have beneficial effects.

An attempt to impact the heel of a German cosmonaut on Mir to simulate the strains of walking for 10 minutes a day managed to fend off a 7% bone loss during a 140-day flight in 1995. And further studies on sheep and rats in the last year have shown just how much extra bone mass can be encouraged to grow by subjecting bones to vibrations.

Optimum frequency

This latest cosmonaut study comes off the back of a recent trial of the technique by Ongaro iwith 11 osteoporotic women in Rome.

Mark Shuttleworth (r) is the control in the experiment

"We turned their bones from osteoporotic back to a healthy bone density in four months," declares Ongaro. "So we wanted to see if the technique could also help our astronauts, too."

Ongaro has found a way of selecting the optimum frequency for subjects by measuring the electrical output of the leg muscles during their exercise on the plates.

"The right vibration frequency seems to encourage extra muscular activity too, and when the muscles are working hardest that is the vibration frequency we apply to the bone. It turns out to be 30 hertz for Roberto."

New trials

He believes the shaking stimulates not only the bone, but muscles, blood vessel growth, and nervous system health as well.

Roberto's recovery will be compared with control subject Mark Shuttleworth, who flew the same mission length without the benefit of vibration therapy. These first experiments back on Earth will be followed by parabolic flights in the autumn to see if the technique works in microgravity, too.

If it still looks promising, the team hope to fly one of the plates up to the ISS next year - to fend off the effects of microgravity-induced osteoporosis for later crews.

Back on Earth, vibrations have already been used in Manchester, England, to strengthen the bones of children with cerebral palsy and a clinical trial of 200 osteoporotic women is about to begin in the United States.