Glowing spectacles could hold the key to avoiding jetlag after long-haul flights.

Scientists in Australia have developed hi-tech glasses which they say prevents the mental and physical fatigue associated with flying across different time zones.

They believe that wearing the glasses for a couple of hours before and during flights could help the human body clock to adjust to travel more easily.

Bright light is the tool which re-times our body clocks

Dr Leon Lack, Flinders University

According to a report in the Daily Mail newspaper, the spectacles use lights to help stimulate the brain and wind the body clock backwards or forwards.

Light-emitting diodes are fitted on to the frames of ordinary sunglasses and are powered by a battery carried in a pocket. The diodes emit blue and green light.

Light effect

Light plays a key role in helping the human body clock to run smoothly and to decide whether the body should be asleep or awake.

Light triggers the production of hormones in the body which manage the body clock.

Dr Leon Lack and colleagues of Flinders University in Adelaide said the spectacles help to reset travellers' body clocks.

"Bright light is the tool which re-times our body clocks," he said.

He said they should be worn for three hours a day for at least two days before travel and for three hours during the flight.

The invention has already sparked interest among athletes in Australia, who have to travel long distances for international competitions, not least the 2004 Olympic Games in Athens.

Sport spectacles

David Pyne of the Australian Institute of Sport said jetlag can seriously affect athletes' training schedules.

"The glasses would make a big difference because it would minimise the disruption and athletes could maintain their continuity of training from day one, which could have important physical and mental impacts on performance," he said.