Racing headlong into danger on a skeleton sled demands the fortitude of a thrill-seeker.

How do you take the spontaneous fun out of a childhood pastime? For a start, you could turn it into an Olympic sport. For many of us, sleds conjure images of long-lost carefree days, when any significant fall of snow was the signal to head to the steepest available hill and slide down it. No training. No planning. No rules.

Childhood ends, and most of us move on. My own sled has largely gathered dust for a quarter of a century; its only use has been to transport occasional loads of winter firewood.

But some adults can never quite relinquish the joys of childhood. In the late 19th century, in Switzerland, sledding was reinvented as the sport of tobogganing (the pioneers were a bunch of aristocratic English tourists with too much time on their hands). Rules were drawn up to provide the veneer of serious endeavor, though at heart the primary motivation was to recapture the juvenile thrills of sledding.

A convenient hill was not enough. Purpose-built tracks were created, with banked corners and horizontal loops (the most famous was the Cresta Run at St. Moritz). By 1883, the humble sled had evolved into the luge, on which the rider lies on his back, zooming down the course feet first, steering by subtly transferring his body weight from side to side.

Traveling on your back at 85 mph is certainly exciting, not to mention dangerous, but for overgrown schoolboys there is a simple way of magnifying the exhilaration (and danger): Lie on your stomach and go headfirst. This new variant of the sled was called the skeleton.

In 1897, the bobsled was devised, enabling up to four people to ride together. To this day, there remains some mystery as to why four people need be involved. The front man steers, the rear man brakes, and the two middlemen sit there for no apparent reason. The fundamental absurdity of bobsledding was captured by the movie Cool Runnings, the true story of the Jamaican Olympic bobsled team, who trained in an old bathtub on a Caribbean hillside.

In recent decades, the final ounces of improvisation and exuberance seem to have been extracted from Olympic sledding, replaced by year-round training and phenomenally expensive equipment. A top-end bobsled costs $50,000, while sledders must wear high-tech speed suits and Space Age crash helmets.

Despite the modern strictures, the kernel of childhood thrill-seeking endures. Skeleton provides it in its purest form. The skeleton itself is a sled stripped to the basics: two steel blades and a fiberglass plate. Handles on the sides allow the racer to grip the craft while making the running start at the top of the run.

The trickiest moment comes when the racer, sprinting at full speed, leaps into a prostrate position on the skeleton. The success of the run depends on executing this transition perfectly. And now, with body taut, feet pointing backward, arms pulled in tightly on each side, the racer hurtles down the course.

The tiniest misjudgment could result in a crash, and once committed to the course there is no way out. A racer who comes off the skeleton is condemned to slide to the finish with only the bodysuit for protection (physical pain is compounded by disqualification for not completing the run on the skeleton).

Why do skeleton racers expose themselves to such ludicrous risk? Because, when all goes right, and they are hurtling at high speed with their faces inches off the ice, the burdens of the world slide away - and they are young again.