An excerpt from "The Winter Olympics: An Insider's Guide to the Legends, the Lore, and the Games" by Ron C. Judd, a Seattle Times staff reporter.

Cross-country skiers compete on what amounts to snow-covered trails, although the trails are nothing you’d encounter on your own out in the woods: They’re carefully groomed by snowcats and measured to within the millimeter for distance.

Field of Play

Cross-country courses range from 1,500 meters to 50 kilometers. Each course must have equal parts ascending, descending, and flat ground, with the easiest part near the start and the most difficult near the midpoint. Courses less than 30 kilometers long must have a total elevation gain between 600 and 900 meters (just under 2,000 and 3,000 feet) for women, 900 and 1,200 meters (3,000 and 4,000 feet) for men.

As in alpine skiing, courses differ greatly according to topography, altitude, snow condition, and other factors. Unlike alpine skiing, the distance traveled is always the same within one race specialty, that is, a 10K race is always 10 kilometers, but the amount of elevation lost and gained can vary substantially from one course to another.

Format, Rules, and Strategy

The first thing that usually trips up the casual observer of Olympic cross-country skiing is the fact that it has two distinct disciplines: classical, where skiers take straight strides in preset parallel tracks (the common kick, pole, glide stride), and freestyle, in which skiers use a skating stride (think of a speedskating motion on skis), pushing off on the insides of their skis, across a broader, flat track with no preset grooves. Courses for the two disciplines are the same; the snow is simply groomed differently. Skaters use a broad, flat snow surface; classical skiers keep their skis in the preformed grooves, except while passing. The skating style used in freestyle is significantly faster—about 8 percent faster in course tests—than classical and was first allowed at the Olympics in 1988. Since then, individual races have alternated between classical and freestyle, from

one Olympics cycle to the next. Vancouver’s individual races will be in classical style, although races such as team relays and pursuits combine both styles.

The men’s events for the 2010 Olympics are the 1,500-meter sprint and team sprint, 15-kilometer individual start, 30-kilometer combined pursuit; 50-kilometer mass start, and 4×10-kilometer relay. The women’s races will be the 1,500-meter sprint and team sprint, 10-kilometer individual start, 15-kilometer combined pursuit, 30-kilometer mass start, and 4×5-kilometer relay.

Unless a race is designated as having a mass start, the start order is determined by a drawing. Skiers leave at 30-second intervals and, in all races except sprints and relays, race against the clock. If a field of competitors is particularly large, some races will launch skiers two at a time, in dual tracks, at 30-second intervals. When faster skiers overtake slower ones, the slower skier must yield the right of way if an approaching skier yells “Track!” from behind.

The race formats:

Mass-start races begin with skiers lined up across the start line, in rows. The first one across the finish line wins.

Individual-start races begin with skiers released at 15- or 30-second intervals. The fastest time wins.

Sprints are a single-elimination tournament. Skiers start at 15-second intervals, and time trials narrow the initial field down to 16 skiers, who are grouped into four heats. The top two finishers in each heat advance. In the final, four semifinalists compete against one another for the three medals. Sprints were added to the Olympics in 2002.

Team sprints consist of semifinals and final rounds. In the semifinals, 10 or more teams of two skiers (skier A and skier B) alternate to race the relay three times each. The fastest five teams qualify for the final and race to the finish line. This event debuted at the Olympics in 2006.

The combined pursuit, as the name implies, combines a classical and freestyle race. The classical race—usually 10 or 15 kilometers—is first. Skiers stop at the midpoint and change into skating boots and skis. They’re then restarted for the freestyle race—also usually 10 or 15 kilometers—in a staggered start according to their finish times in the classical race. Example: A skier with a 10-second lead at the end of the first race begins with a 10-second head start in the second, hence the “pursuit.” This allows the first skier across the finish line in the second race to be the overall winner, making the race a much more fan-friendly event, especially in the case of close finishes. Note: In the early Olympic years for this race, 1992–1998, the combined pursuit was run on separate days. It then morphed in 2002 into two races on the same day, with a substantial gap in the middle. By the 2006 Turin Games, it had changed to two races run consecutively, with only a short break.

Relay races are similar to track and field relays. One skier finishes and tags the next with his or her hand to send them on their way. The relay has a mass start. The first two stages are skied classical, the last two freestyle.

Race strategy is all about timing, and knowing when to expend energy and when to conserve. Cross-country skiing is a grueling sport, the most aerobically challenging of any in the world. Pacing is the key to longer events, while fast starts and impeccable technique are crucial to sprint races. In longer races, drafting behind competitors until an optimal passing time occurs is a strategy often employed by savvier competitors.

Training and Equipment

Cross-country skiers, particularly the distance racers, are widely considered the world’s best-conditioned athletes. The sport requires incredible endurance, a combination of upper and lower body strength, and abnormal aerobic capacity. Because skiers use their upper bodies in harmony with their legs, they consume far greater quantities of oxygen than, for example, marathon runners or even track sprinters. And there’s another requirement: a substantial and unusual tolerance for pain.

Training usually consists of daily running, cycling, roller skiing, snow skiing, weight lifting, and other endurance, aerobic activities.

The “skinny skis” of cross-country racing are extremely lightweight, usually constructed of a combination of wood and carbon fiber. The skis used for the classical style of cross-country are rigid, with more camber than skate skis, and have a more sharply upturned tip. Freestyle or skate skis have a wider shovel and generally are significantly shorter. In both cases, boots are attached to ski bindings only at the tip, allowing a full striding motion. Classical-style boots are shorter, allowing better ankle movement. Freestyle boots have higher ankle cuffs usually surrounded by a rigid exoskeleton to provide better torsional strength to accommodate the skating motion used in this style of skiing.

Ski racers wear one-piece bodysuits, lightweight hats, and gloves, and use poles made of graphite and/or Kevlar. Skate-skiing poles are typically stronger than classical ones, due to the greater amount of weight placed on them during push-off.

The key to the entire system, however, is something you’ll never see: wax. For classical skiing, technicians apply glide wax to the underside of the tips and tails and a grip wax below the binding. This allows the ski to bite into the snow when the skier places his or her weight on the center of the ski while pushing off. For skate skis, glide wax is applied to the entire ski, because the skier pushes off the edges of the ski, not the flat center of the base.

Just which wax to use under what conditions is the challenge. Many a great ski racer has seen his or her race—and his or her Olympic career—go down the tubes due to a bad wax choice. Once you’ve started, there’s no time to switch, and rules prevent doing so even if you could. The world’s top ski teams protect their wax additives and application rules like closely guarded national secrets. In a sense, they truly are.