CONTROLLED CHAOS is how renowned BMX bike rider Mat Hoffman describes Tony Hawk's Boom Boom HuckJam, even though in a recent show Hoffman himself lost control and was knocked unconscious as he tried to land the very difficult "no-handed 900" trick.

Hoffman, 30, who also almost made unwanted contact with a motocross rider 25 feet in the air last month at a Huckjam," says the show gives the best skateboarders, BMX bikers and motocross athletes the stage to attempt crowd-pleasing stunts without worrying about the judging and guidelines used in competitions.

"It's not like we're going to ride around and entertain people doing small stuff. We do the hardest tricks that you train for with people inches away from you, weaving in and out. You have to be very precise or you'll take everyone out with you," Hoffman says. "Sometimes we make it and sometimes we don't. That's the freedom of this tour."

Designed by the biggest name in skateboarding, Tony Hawk, the Boom Boom HuckJam has gathered extreme sport notables, including Hawk, Hoffman, skater Bucky Lasek and biker Dave Mirra, to share the challenging 13-foot halfpipe ramp. The Boom Boom HuckJam stops at MCI Center on Sunday as part of its first-ever, two-month national tour.

With L.A. punk band Social Distortion pounding live on a side stage, the athletes test their mettle against gravity as they perform high-flying ollies, 360 tailwhips, 540s, 720s, 900s, tailwhips, hand plants, McTwists, triple barspins, kick flips and double back flips over the gaps. In many cases, the skilled riders invented the tricks, and the vocabulary. Boom Boom HuckJam, defined by Hawk, means a thrilling show with background music (boom boom); launching into the air ("huck"); and grouping together great talent ("jam"). In April, the riders spent a week trying out routines in an abandoned airplane hangar in San Bernardino, Calif. After figuring out how to structure the show and integrate the skaters, bikers and motocross riders, they came up with a two-hour performance in which they take turns riding solo and in groups, with as many as eight riders rolling on the ramp simultaneously. Part of the show is choreographed, with athletes in groups of two's and three's doing flips and technical maneuvers over and under one another, and part is an open freestyle session where anything goes.

"I'm trying tricks I haven't even made yet," says skater Lasek, 29, making sure to mention that both Hawk and Hoffman have landed the seemingly impossible five 180 degree in-air rotations of a "900" during the tour.

Says Hoffman, "It's such a cool environment with a great band and the best bikers and skaters in the world feeding off each other's energy. So it pulls the best tricks out of everyone."

TONY HAWK'S BOOM BOOM HUCKJAM -- Starts at 7:30 Sunday at MCI Center, 601 F St. NW. (Metro: Gallery Place/Chinatown). 202-628-3200. Tickets, $28-$78, can be purchased from 202-432-7328 or www.ticketmaster.com.

Bucky Lasek skates at a recent Boom Boom HuckJam show wearing a "Devo Energy Dome" hat. Devo performed earlier in the tour.