Spending too much time in constant and comfortable temperatures lowers the body's resistance to illness. Bettina Levecke reports.

It's warm and cozy indoors - the heating system keeps temperatures constant. Car interiors are temperature-controlled and room temperatures at workplaces are pleasant, too. Nevertheless, many people are suffering from colds at the moment.

"Our bodies are pampered," says Ulrich Betz, director of the Institute for Physical Therapy, Prevention and Rehabilitation at the University Medical Center of the Johannes Gutenberg University Mainz. "Over time, the lack of exposure to natural stimuli weakens the immune system."

Inuring oneself to cold can strengthen the immune system, which Betz compares to athletes toughening themselves up during sports training.

The more often the body is exposed to cold, the less sensitive to cold it becomes. In other words, it becomes acclimated.

The concept of physical toughening appeared in literature on naturopathic medicine as early as the 18th century. The natural scientist and physician Johann Georg Kruenitz (1728-1796) defined "Leibes-Abhaertung", or "body toughening", as "acclimating the body so that it can withstand the effects of the elements and other hardships or so that it doesn't feel them".

The sundry methods of physical toughening - air and sun baths, cold showers, going barefoot, sauna visits - were developed in Europe from England to Switzerland and in various ways came to be part of contemporary naturopathy.

Why does exposure to natural stimuli improve health?

"The impact of warm and cold on the body is, above all, stress," notes Rainer Brenke, head physician in the naturopathy department of the Hufeland Clinic in the German spa town of Bad Ems.

As soon as the body registers the difference between body temperature and ambient temperature, it works to keep the former at a normal level.

"This boosts blood flow and the entire body is invigorated," he says.

How this strengthens the immune system remains unclear.

"Preliminary scientific findings indicate, however, that regular cold-water applications increase the number of white corpuscles," Betz says.

The cardinal principle of successful physical toughening is regularity.

"The body only becomes acclimated through repeated, long-term measures," says Wolfgang May, a physical medicine specialist in the German town of Schwangau.

A second principle is: Toughen yourself up only when you are healthy. Brenke mentions a third principle: "Don't overdo it. Start slowly and increase slowly, too."

There are many ways to fortify your body's defenses. One simple and effective method is to take a cold shower in the morning. First, you douse your legs and arms, and finally your torso. It is time to stop when the cold starts to sting.

For frigophobics, Betz outlines encouraging prospects.

"The sensitivity decreases day by day," he says.

Afterward, the body is pleasantly flushed and you feel alert and fresh.

As an alternative, the whole family can take a barefoot walk in the garden in the morning.

"But if you're going to walk on dew or snow, you've got to make sure that your feet are warm before you start, and that you warm them up again immediately afterward," May says.

Warmth can be provided by thick socks or a warm, ankle-deep foot bath. Small children can participate as well, May adds.

In addition to reducing susceptibility to colds and flu, stimulation therapy helps lower high blood pressure and alleviate nervous disorders. It also strengthens blood vessels and the cardiovascular system.

"Treading water as advocated by Kneipp strengthens the veins and helps in cases of varicose veins," May says.

A weekly visit to the sauna improves lung and skin function. The general rule applies here, too, Brenke says - that is, "Cold must follow heat, otherwise the contrast stimulation won't occur."

You can start toughening up your body anytime.

"The possible health benefits are as varied as the possible methods," Brenke says, adding from personal experience: "You feel better in your own skin."

German Press Agency