Human balance is partly derived by "feedback" signals that travel to the brain from nerves in the feet.

Many people lose some of the feedback as they get older, which makes them wobbly and vulnerable to a fall.

Boston University biomedical engineer James Collins and colleagues tested the idea of reviving the nerve response by stimulating the soles of the feet.

They set up two gel plates implanted with three small vibrators that delivered undetectable low-frequency noise to the soles of the feet.

The gadget was tested on 15 young people, whose average age was 23 years, and 12 older people, aged 73 on average.

The guinea pigs had to stand on the plates for 30 seconds with their eyes closed, then get off and do three random walks, during which they were measured for how much they swayed.

Both the youngsters and the elderly benefited from a quick blast from the sole vibrators but the old ones especially so. Their motor control and stability improved significantly when they walked.

Collins suggests the idea could be turned into a plastic insole that would be inserted into shoes, giving the wearer a random vibration from time to time to perk up the foot nerves and enhance the feedback.