Boppard, Germany - Hardly anyone lies voluntarily on a bed of nails or runs 40 kilometres without stopping. Fakirs and marathon runners can put the pain out of their minds. One need not be a holy man or top athlete to use mind power to block out pain, though.

"Pain is an emotional reaction to an evaluation in one's head," said Ruediger Fabian, president of German Pain Aid, an organization based in the town of Gruenendeich. Anyone can control this evaluation, he said.

The sensation of pain is subjective, which the pathway taken by a pain stimulus helps make clear. As explained by Professor Rolf-Detlef Treede, president of the Boppard-based German Society for the Study of Pain (DGSS), sensory receptors transmit the signal to the spinal cord. The central nervous system then passes it on to the brain, which processes it in any of various ways.

"The brain has to decide what's important and what's not," Fabian noted. Pain is a protective mechanism of the body, he said, and a pain stimulus on its way to the brain always takes precedence over other stimuli.

But a pain stimulus can be waylaid before it gets there, for example by medication. Anyone who goes to the dentist's knows that. "Local anaesthesia prevents the pain stimulus from reaching the brain," Treede said.

More important, however, is how the brain processes a pain stimulus that has arrived. "The brain can learn that a certain pain isn't so important," Treede explained. If someone scrapes an arm, he said, the injury often looks bad but the injured person knows it is harmless.

The brain can also grow accustomed to pain, Treede said - "at some point it gets used to the hot cup of coffee in the morning, for example."

Through training, people can influence how their brains evaluate pain, according to Professor Walter Zieglgaensberger from the Max Planck Institute of Psychiatry in Munich. Pain sufferers need to take an active part in this process.

"The brain has no delete key," Zieglgaensberger said, noting that every pain leaves tracks in the brain. After drug treatment, therefore, it is important that patients do things that they used to avoid because of pain, he advised. This causes the brain to overlay old memories of pain with new, positive links.

"The fear of pain is worse than the pain itself in such cases," he said.

Fear not only plays a role in pain perception in chronic illnesses, however. With children in particular, fear is often greater than the pain itself. When they injure themselves, their reactions to pain depend in part on their parents' behaviour, explained Ulrich Fegeler, a member of the Cologne-based Professional Association of Children's and Young People's Physicians (BVKJ).

"The louder and shorter a child cries, the more harmless the injury usually is," Fegeler said.

Hence parents should not react with panic when their child gets hurt, Fabian advised.

"Calmness gives a child the feeling that the injury isn't serious," which often lessened the pain considerably, he said.

In truly extreme situations, the body itself provides the strongest pain killers. Marathoners manage to switch off their pain. Their brains release endorphins and adrenalin, Zieglgaensberger said. These chemicals, called neurotransmitters, produce a "runner's high" in trained runners and make them insensitive to pain.

The body reacts to serious injuries in a similar way. "After a traffic accident, for example, endorphins enable a person to move a broken leg to get out of the car," Zieglgaensberger noted.

But neurotransmitters are not only released in extreme situations. Taking a placebo, which has no pharmaceutical effect, can also alter a patient's perception of pain. "Then it's a matter of the affected person's conviction," he said.

Conversely, amputees often feel phantom pains in missing limbs. "The brain remembers and perceives pain," Zieglgaensberger said. Genes play a role in pain too. "Some people feel no pain at all from birth onward due to a particular genetic predisposition," he said.

The body's own pain inhibitors are not only released in marathoners - anyone can trigger them with mind power. According to Zieglgaensberger, people who want long-term influence over their perception of pain should learn not to fear it, and should not see it as being worse than it really is. "Anyone with initiative and an alert mind can do that," he said.