Once upon a time, any road race worth its weight in Gatorade was a 10K. Large town or small, it didn't matter if the course lent itself to that distance. The 10K was the standard, and the 10K ruled.

Then something not entirely shocking happened: Some of those athletes involved in America's running boom of the 1970s got into other sports (running boom begat tennis boom, which begat breakdancing, which begat ... whatever) or lost interest in the daily fitness commitment.

The 5K grew in appeal: Courses were less complicated, event planners could count on wrapping the whole thing up in a few hours, and casual runners could enter with confidence.

Yet it should come as no surprise that in this day of Extreme Everything (sports, reality shows, breakfast cereal) the pendulum appears to be swinging the other way.

Say hello to the age of half marathons.

"It's definitely a stepping stone," said Dan Albaugh, race director for the Presque Isle Half Marathon July 17 in Erie. "There are so fewer 10Ks anymore and the marathon is too much.

"I think people are looking for something like this. The half marathon is more popular because of that."

This is the 27th year the Erie Runners Club has included a half marathon to its schedule of events; there is a marathon Sept. 11 that also includes a 5K and a half marathon.

Perhaps a 13.1-mile race in the heat of summer doesn't sound as enticing as, maybe, 13.1 miles in November. Still, the official start is at 7:30 a.m. but walkers can begin at 6:30 if they want. The waterside nature of the Presque Isle State Park course helps, too.

"The peninsula juts out into Lake Erie, so there's a nice breeze, and it's close to the bay," Albaugh said.

The finish line is conveniently less than 100 yards from the lake, where runners have been known to take a flying leap after they're officially in the books.

The Presque Isle Half Marathon (www.erie-runnersclub.org) attracts about 400 runners a year, including John Trucilla, a judge in the Court of Common Pleas in Erie.

Trucilla will be competing in an Ironman triathlon the week after Presque Isle, so he'll be skipping this summer's event. But he has run it several times and influenced his wife, Suzanne, to run it as well.

"Of all the distances, I always thought the half marathon was kind of the most pleasant," said Trucilla, also a veteran of Pittsburgh's Great Race. Trucilla said. "Marathons are grueling and painful. Five-Ks and 10Ks are speed races and usually you're uncomfortable the whole way.

"But in half marathons, you can settle into your rhythm."

There are a growing number of half marathons in the Pittsburgh area each running season, including the third annual Chamber Classic Oct. 8 in North Park (www.naccc.com or 724-934-9700). The IKEA-Montour Trail half marathon and 5K is a big event scheduled for Sept. 10. Part of the race's allure is its fast, downhill start and gently rolling course along the Montour Trail (www.montourtrail.org). Proceeds benefit the expansion and maintenance of the trail.

The 28th annual Jefferson Hospital Philadelphia Distance Run (www.runphilly.com) is Sept. 18 at the Philadelphia Museum of Art.

More than 85,000 runners entered the lottery to win a spot in the annual New York City Marathon this year. But anyone can enter the New York Road Runners Club's cool series of half marathons. Beginning in March and ending in October, the Road Runners stage half marathons in each of the city's five boroughs; Manhattan's is Aug. 28 (www.nyrr.org).

Then there are the seaside charms of the Virginia Beach, Va., Rock 'N' Roll half marathon Sept. 4 (www.rnrhalf.com), where 20 local acts stage a battle of the bands along the flat, sometimes-oceanfront course. It's a popular event; registration is limited to 20,000 runners and, according to the race's web site, is nearly a sell out.

And speaking of rock ...

Downloaded any great songs for training? What's the best pre-race music on your MP3 or iPod? We're doing an informal survey of what keeps runners on their toes.

Steelers 5K

Sometimes you win a race and all you get is a T-shirt. But the top male and female finishers in the 17th annual Gatorade/Steelers 5K race win a trip to the Dec. 24 Steelers-Browns game.

Day-of-race registration for Saturday's event begins at 7 a.m. in the Great Hall at Heinz Field. The 5K run/walk begins at 9 a.m.