"Kids have no fear," she says.

That overconfidence sometimes worries Weil. Although she's convinced her team to wear knee and elbow pads when they practice, helmets are still unpopular.

"They should wear helmets. They don't she says simply.

Luke, who likes to skate in traffic ("It's the adrenaline"), says "I definitely think you should wear [a helmet]. I don't wear it myself, for aesthetic reasons."

Another source of problems have been with bike riders. Nearly every rollerblader has some story to tell about antagonistic bicyclists. Many skaters say that the cyclists resent them for increasing their numbers so greatly and so quickly.

"We get a lot of friction," Weil says. "I've seen bikers intentionally knock skaters down ... and curse them out. I've had people elbow me."

"They go really fast, then they hit you and it's your fault," Thomas adds.

But Luke says tension is wearing off as bikers become resigned to the presence of the rollerbladers. "They've learned to accept it. There's more of us," he says. "People are ignorant of [the sport] until there's too many skaters to handle."

Rollerblade is actually a brand name that has, Kleenex-style, become synonymous with the type of product itself. Those in the know call the contraptions "in-line skates" to distinguish them from their passe cousins, roller skates.

In-lines were originally conceived of by two hockey-playing brothers from Minneapolis who wanted a way to keep in shape during the off-season. Scott and Brennan Olson built the first pair of in-lines in their garage in 1980.

The device enjoyed a limited popularity among hockey players until roughly four years ago, when sales abruptly and somewhat inexplicably skyrocketed. Mike J. Benshoff, Boston area representative for Rollerblade, attributes this lag time to cosmetics. In late 1988, Rollerblade developed a new skate with a flashy neon design, and sales started climbing. "When those went on the wall, things took off," Benshoff says.

Since then, Harvard and other Boston-area students have been among the most consistent consumers of Rollerblades. Benshoff reports that City Sports in Boston has sold over 3000 pairs of blades this year. And the company is still expecting three more years of growth.

Jim Brine, who owns Brine's Sporting Goods in Harvard Square, confirms the popularity of these toys. "There was a dramatic sales increase in 1991," Brine says. "And 1992 was much more dramatic than 1991." Brine says a number of factors help make the skates appealing to so many different types of consumers.

"Some of the people are joggers whose knees can't take jogging anymore," he says. "A lot of young people are playing hockey on them, not rellay for conditioning, just for fun." And in Harvard Square, students are buying them simply to get from one class to another. "You can cover a lot of ground." Brine says.

The demand has been almost too much for Rollerblade to keep up with, Brine says. Competitors like Ultrawheels, Bauer, and Roces are making quick inroads, and, in some cases, turning out a more durable product.