Peachtree's world's largest 10K title at risk

"I think our community might celebrate it, like, Wow, cool, you guys did 55 (thousand runners), and the people who run the race might feel pride about the fact that ‘I was a part of that,'" Bosley said. "But I guess the caveat would be we'd be excited about it if we deliver the same first-class race we've been delivering."

Race officials in Boulder are planning for 55,000 entrants in their Memorial Day race in its 32nd year, the same number that the Peachtree has accepted since 1998. Running USA, a non-profit that promotes the running industry, has given the Peachtree its title as world's largest 10K since 1990.

"We're very aware of their participation growth," said Atlanta Track Club executive director Tracey Russell, before kiddingly adding a dig. "We're also aware that they take registration through race morning and we fill quickly. I think it's a friendly kind of checking in on each other."

Last year, in fact, the Boulder race nearly toppled the Peachtree. It had 49,814 finishers, just 153 behind the Peachtree's 49,967. (Running USA ranks races by number of finishers.)

Russell does have a point, by the way. Where the Peachtree caps the field at 55,000 and last year turned away 8,000 applicants, the Boulder race accepts entries even after the race starts.

"Peachtree, if they want to end the discussion, they'll just say, ‘OK, now we're taking 60 [thousand],'" said Bosley, a past participant and fan of the Peachtree. "We're not under the illusion that's something we're controlling."

Like the Peachtree, the Boulder 10K has grown steadily since 2,700 ran the first race in 1979. It broke 20,000 finishers in 1988, 30,000 in 1992 and 40,000 in 2000 and has advanced on 50,000 since then.

Also like the Peachtree, it's a family-oriented event and cultural institution. Among its traditions is the finish at the 35-yard line of the University of Colorado's Folsom Field. Participants stay in the stadium to watch the elite race, which is run after the masses finish, on the stadium video board.

"There's people that look as if they're sprinting past you gunning for the win as opposed to those pulling up the rear and just happy to be out there," said Amanda Charles, general manager of a Boulder running store along the race route.

Another distinction is its wave start. On Monday, runners will be sent off in about 90 groups of 500-800 between a minute and almost three minutes apart to ease congestion. It extends the race -- the last runners cross the start line 2 1/2 hours after the first group, about an hour later than the Peachtree last year -- but prevents logjams. Atlanta Track Club officials, in fact, have been out to Boulder to get ideas for the wave start that they will introduce in July.

How the Peachtree's wave start works could determine if the track club expands its field again in 2011. Depending on what happens Monday, it might be necessary to re-take the No. 1 spot from the BolderBoulder.

Said Russell, "It's a tradition here in Atlanta to embrace and feel really proud of Peachtree [being the largest] and what it does for the Atlanta region, but we certainly feel like safety comes before size."