Picture teams of up to 24 skaters performing complex choreography in unison, while moving over the ice in close formation at blinding speed. Synchronized skating resembles a form of group ice dance, with the emphasis on the difficulty and quality of the steps and footwork, the neatness of the formations, the smoothness of the transitions between formations, and speed and ice coverage. Jumps of more than one rotation are not allowed, and it is also not permitted for the choreography to highlight individual members of the team.

The discipline of synchronized skating was invented in the 1950s with the creation of the Ann Arbor Hockettes, a group described as a "crack skating chorus" who performed exhibitions during intermissions at local hockey games. By 1984, when the first U.S. Championships in the discipline that was by then called "precision skating" were held, there were 38 teams competing in five divisions. At this year's competition, being held this week in Plymouth, Mich. -- just down the road from the sport's birthplace -- there will be 100 teams in eight divisions ranging from juvenile to adult. To put some perspective on the size of this event, the total number of athletes involved is about 10 times that for the U.S. Championships in the singles, pairs, and dance disciplines that were held last month in Cleveland.

Although the rules of the sport permit men and women to compete on an equal basis on mixed-gender teams, in practice, nearly all of the skaters who participate in synchronized skating are females, which reflects the gender imbalance of the general population of skaters.

In fact, the growth of synchronized skating is primarily a result of large numbers of girls and women who skate compared to boys and men. Because of their sheer numbers, female skaters have a much smaller chance of achieving any kind of success in singles competition, or being able to find partners for pairs or dance, than do males. As they advance in the sport, many girls find that they lack the talent or interest to learn the difficult jumps that are required for singles skating at the higher levels, or find that they dislike the extreme stress and pressure of individual competition, or become discouraged by seeing that there are just too many other girls competing who are better than they are. Joining a synchronized skating team gives these skaters a competitive outlet and motivation to stay active and continue to progress in the sport, when otherwise they might have simply quit skating entirely.

Skating on a team also brings young people all the benefits associated with participating in organized team sports in general: Learning how to work as a member of a team, learning how to win and lose with grace, and opportunities to socialize with one's peers in a structured activity and to form lasting friendships with them.

Another factor in the growth of synchronized skating in the U.S. has been Title IX, the federal law that requires colleges and universities receiving government funding to provide equitable support for men's and women's athletics. Because of Title IX, many schools have been forced to seek new sports offerings for women. Synchronized skating is becoming an increasingly popular alternative, with more than a dozen schools -- most located in the Midwest -- now offering either a varsity or club program in this sport, and more schools in the process of developing such programs.

In turn, the availability of athletic scholarships and access to high-quality training facilities and coaching have attracted top skaters and made the collegiate teams among the best in the country. The varsity team from Miami University of Ohio, which pioneered synchronized skating as a collegiate sport, is now the defending U.S. champion. In addition to the separate collegiate division, this year four of the 16 teams competing in the championship division at nationals also have university affiliations.

Beyond this week's U.S. Championships, the first World Championships in synchronized skating will be held April 5-8 in Minneapolis. The ISU first accepted synchronized skating as an international sport discipline in 1994, and the World Championships are the next step on the road that many hope will lead to full Olympic status for the sport.

While the U.S. teams have been fairly competitive in other recent international competitions, the real powers in synchronized skating are Canada and, somewhat surprisingly, Finland and Sweden, which don't have strong national programs in the other disciplines of figure skating. Although synchronized skating was invented in the U.S., as it was internationalized it picked up a somewhat more European flavor. Current trends in the sport put more reward on speed and ice coverage than intricate footwork, and choreography that features subgrouping, counterpoint and ornamentation -- as well as continually evolving patterns and shapes -- is the "in" thing.

If you attend a synchronized skating competition, here is what you can expect:

• Junior and senior teams skate a short program and a long program, both of which must demonstrate the five basic elements: circle, line, block, wheel, and intersection. In other divisions, only a long program is skated.
• In its simplest form, a circle element consists of the entire team skating footwork in unison in a circle while maintaining one of the various holds, but at the elite levels one is far more likely to see much more complex variations -- circular formations that travel across the ice as well as rotate, splitting from one circle into two and then rejoining, plus changes in direction, hold and geometric pattern.
• Similar variations apply to the other elements. Line and block moves involve the entire team traveling across the ice in a crisp formation, while a wheel is a rotating pattern with multiple "spokes." Intersection moves are built from the other formations; for example, two straight lines for a simple move, or a line and circle for a more complicated one.
• The best way to appreciate the patterns made by synchronized skating teams is to sit where the judges sit -- fairly high up in the arena, not at ice level. Judging and scoring in synchronized skating is otherwise similar to the other disciplines of figure skating. Most skating fans find that it doesn't take any particular special knowledge of the rules of synchronized skating in order to get a sense of the competition; just watch and enjoy!