People begin to lose their balance in their old age just as their bones get more fragile, a deadly combination that can lead to crippling or fatal falls. The elderly grow wobbly in part because their nervous systems become less sensitive to the changes in foot pressure whenever they lean one way or another. No one keeps perfect posture--everyone sways at least a little--and the brain needs the cues from the soles to stay balanced.

Foot massages could help those who have balance problems. Research led by bioengineer James J. Collins of Boston University shows that gentle stimulation of the feet helps elderly study subjects. The key is that the vibrations must be random--or, put another way, noisy. Usually, noise interferes with the main signal--think of static drowning out a television picture or attempts at conversation in a crowded room. Under the right circumstances, however, noise can actually boost weak signals. The effect is known as stochastic resonance, and it occurs in electronic circuits, global climate models and nerve cells. To see how it works, imagine a frog in a jar: by itself the amphibian might not be able to jump out, but if the jar is in a rumbling truck the frog might get the boost it needs to make it. In the same way, a faint background of random pulses could amplify weak signals sent from the feet to the brain.

This article was originally published with the title Shake, Waddle and Stroll.

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