May 6, 2011 at 8:19 AM ET
Fire-walking is a feat few of us want our bare feet to attempt. But should your tootsies traipse over a bed of red-hot coals, scientists have discovered an unusual phenomenon that occurs during it.
A fire-walker's heart rate appears to match the rhythm of his relatives and close friends on hand to watch the offbeat event, a new study finds.
The annual fire-walking ceremony in San Pedro Manrique, Spain, provided an odd backdrop for a unique experiment. In this research, scientists wanted to find out if the social effects of a "high-arousal ritual" such as fire-walking, which brings together large groups of people as either participants or bystanders, could influence people's physiology.
To test this idea, researchers strapped heart rate monitors on the chests of 12 out of 28 fire-walkers (11 were men) involved in the yearly June ritual. In addition, they measured the heart beats per minute of nine spectators who were relatives or friends of one of the fire-walkers and also tested 17 onlookers who did not know the participants. Data was collected several hours before the event and during it.
(Fire-walkers at this Spanish ritual also carry another person on their backs as they cross the coals, but the spectators tested for this experiment were all in the crowd.)
The study, published online in the Proceedings of the National Academy of Sciences, found that the heart rates of the fire-walkers and their related spectators showed a similar pattern: Their pulses peaked in sync as they made their way barefooted across glowing coals reaching temperatures of 1250 Fahrenheit.
But the heart rates of observers who were not family or friends did not resemble the fire-walkers.
"We were surprised to find synchronized arousal between fire-walkers and spectators," says Ivana Konvalinka, a doctoral student at the Center of Functionally Integrative Neuroscience at Aarhus University in Aarhus, Denmark, and the study's lead author. They had very different bodily behaviors at the event, she points out, since the fire-walkers performed the activity, while the spectators watched.
The researchers also had not expected to see such big differences in cardiac effects between the related and non-related spectators. "Both groups had superficially the same experience -- they both merely observed, and had the same information available to them," explains Konvalinka.
She suspects the similarities between the heart rates of the fire-walkers and their related spectators throughout the event because of shared information and familiarity. During a shared emotional experience the related spectators have a kind of empathic mirroring as if they were involved in the actual walk.
"The implications of our findings could perhaps be extended to various forms of collective action, such as corporate team-building, sports, public riots, warfare, and so on," says Konvalinka. "Shared arousal might be one mechanism driving these collective actions."
And in case you were wondering, Konvalinka tells us fire-walking should not cause burns on people's feet since the blood flow in this area tends to carry heat away from the foot.
If you've ever tried fire-walking, please let us know exactly what it was like. If you haven't -- would you?
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