NATIONAL SPRINT champion Anton Quist was out in front, so why did he come to a complete stop midway through the race and look back at the competition? On a fixed-gear track bike that goes forward when the pedals go forward and backward when the pedals go backward? With no brakes, both feet strapped tightly to the pedals and balancing on tires three-quarters of an inch wide?

That's professional bicycle track racing, and the best place in North America to see it is the Lehigh Valley Velodrome in Trexlertown, Pa., 175 miles from the Beltway. T-Town, as it's known worldwide to racing cyclists, has hosted more international and national championships than all the other 20 velodromes -- steeply banked bicycle race tracks -- on the continent combined. T-Town is also BYOB, so do bring your own bike, because the track at the Olympic training facility is open to the public when not in use for races or training, usually early and late Saturdays and all day Sundays. Any kind of bike is fine. And even off the track, the bicycling in the Mennonite farmland of the Lehigh Valley is spectacular.

"I stopped riding in the middle of the race because track bike sprinting is a tactical event, and there are advantages to being in the back," says Quist, a 37-year-old Arlington resident who raced for Harvard as an undergraduate. "You can see your opponent and conserve energy by riding just behind his wheel. So we fought for the back, balanced on our bikes. It's cat-and-mouse." When the mouse jumped, the cat pounced -- zero to 40 mph in eight seconds, pedals at 160 rpm. "With the advantage of that rear position, I won by the inch it takes," he says.

Professional bicycle track racing is the fastest human-powered acceleration in sport. The juice to jump to 40 mph comes from legs and lungs. Physical contact on the track can make roller derby look mild-mannered. And because track racing is as much about conserving energy for that final sprint as it is about strength, the race goes generally not to the fastest rider, but to the cyclist who rides the smartest race.

In the summer, pro races start at 7:30 and end about 10 on Friday nights. Six bucks gets you a place on the track rail, a foot from the riders, close enough to see the muscles on their muscles. "On any given Friday," says Gwen Hoover, a cycle mom whose kids love to watch the races and compete themselves, "you'll see dozens of Olympians, world champions and national champions." (Racers from the American, Australian, New Zealand, German and Argentine national teams battled it out in T-Town one recent Friday night.) After the races, spectators head to the track infield to talk to the cyclists and marvel at their machines -- a pro track bike can cost $15,000 and weigh as little as 14 pounds.

Track cyclists have the same kind of rich vocabulary for using their bikes as weapons of fast destruction that Eskimos have for snow. "Sweeping" sounds tidy but can leave the course littered with cyclists, as a racer carves out a four-foot-wide swath by madly jerking the handlebars from side to side. "Hooking" is swerving to cut off a competitor. The list continues: head butts, shoulder butts. The physical contact is at 35 mph, with riders spaced so close "you could cover three of them with a beach towel," says Mike Whitman, a T-Town enthusiast from Sterling.

Pumped from the pro races, I was at the track early one recent Saturday. I had it almost to myself -- not all that unusual during public access time. I did 20 laps around the flat infield lane, each time edging closer to the banked track. But from the bottom up, I saw a 23-foot wall of smooth concrete, and couldn't make the leap. I asked Bob Biese, a velodrome cycling coach who was giving a class at the facility during my visit, about the chance of simply tumbling down the bank. "The bank is only 28 degrees," he said. "As long as you keep forward pressure on the pedals, zero to none." A few nervous laps later, I had roller-coaster thrills flying up and down those steep walls.

T-Town is a regular destination for cyclists at all levels from the Washington area. Gaithersburg resident James Brannan and American University student Tan Liu train together Saturdays on the track. Brannan used to commute by bike but stopped when he changed jobs. "When I gained 35 pounds," the 37-year-old says, "I decided to start biking again, but this time I wanted something more fun, a fixed-gear track bike. At the amateur level out here, it's a friendly culture with an emphasis on skill development and safety. I ride for health. I've lost 30 pounds."

Liu got hooked when he watched the event on TV during the 2004 Summer Olympics in Athens. "I thought it was the coolest thing I'd ever seen and decided I'd race at the 2008 Olympics in Beijing," he says. "It's a long shot, but this is the best place to make it happen." And if he doesn't get to Beijing? "Racing and training have become part of my lifestyle. I can't imagine what my life would be like without it."

A T-Town weekend is a bicycle adventure in an area where the bicycle and the horse and buggy are still means of transportation. Across from the velodrome is Rodale Cycling and Fitness Park, a friendly place for people on the move, with separate lanes for pedestrians, roller-bladers and cyclists along a shady one-mile loop. Great birding. No cars. And if you like riding with large, competitive groups, the park is the starting point for the Derby, a 35-mile training jaunt through Mennonite farmland that the pros and anyone cocky enough to join them make every summer Sunday morning at 10. The regulars genuinely welcome outsiders, though they wait for no one. Ride time is less than 90 minutes. If you can keep up, tell your friends. If you can't, tell your friends you've been training with Olympians, and enjoy the beauty of the rolling hills on the ride back to T-Town.

LEHIGH VALLEY VELODROME -- 1151 Mosser Rd., Trexlertown, Pa. 610-395-7000. Admission free except for pro races, which generally run adults $6-$8, seniors and children $3-$4, children 7 and younger free. Check public access times on the Web site. The track is too slick to ride when wet. Racing usually resumes after a thunderstorm when the track dries. With persistent rain, Friday night racing is canceled or postponed until Saturday. If the pro race is canceled, you'll still see elite training and racing at the track throughout the weekend so long as the track is dry. Visitors interested in exploring the Lehigh Valley area by bike should check out the Lehigh Valley Wheelmen Web site at{tilde}lehighwheelmen/index.htm. The site includes a schedule of public rides for cyclists of all abilities and "cue sheets," or ride directions, for those who want to go on their own; free maps and cue sheets are also available from the Lehigh Valley Convention and Visitors Bureau at 610-882-9200.

Trexlertown, Pa., is about three hours from the Beltway. Take Interstate 95 north toward Philadelphia to I-476 north. From I-476 north take Exit 56 (Lehigh Valley). Follow Route 22 west to Exit 49A (Route 100 south). Follow Route 100 south to the fourth traffic light (Route 222 south). Make a right turn onto Route 222 south, follow for 0.2 miles and make a right turn onto Mosser Road. It is 0.1 miles to the Lehigh Valley Velodrome.

The Lehigh Valley Velodrome in Trexlertown, Pa., hosts many pro races on its banked bicycle track. When it's not in use, amateurs can practice there.For professional riders such as Anton Quist, bicycle track racing is about tactics.