The race director for Dick's Sporting Goods Pittsburgh Marathon has one piece of advice for the thousands braving the snow and cold to train for the May 2 race: Register.

More than 13,000 people have already registered for the race, up from the record 10,500 runners who participated in the marathon last year.

But even though this race is larger, it won't be able to accommodate everybody who wants to participate.

"You better jump in," race director Patrice Matamoros said. "You have to get in. You should really consider making a commitment."

Because of the high volume of registrants, organizers announced Thursday they will cap the race at 16,000 runners. Registration is limited because organizers can only support so many runners, both in terms of the number of supplies they can provide and the number of people the course can support.

Last year, the cap was set at 9,000, but procrastinators should not expect the same flexibility this year.

"The cap is the cap," said Karen Fredette, public relations consultant for the marathon.

It's a good problem to have for a race that three years ago did not exist.

Founded in 1985, the race was canceled after the 2003 running before its rebirth last year.

Last year's record number of participants made the Pittsburgh Marathon the 28th-largest marathon in the United States.

The previous record number of runners was 6,500.

Matamoros believes running is more popular in times of economic downturn because, unlike other physical activities, it is not costly.

Dale Schwab, president and founder of People Who Run Downtown, a local running group, said he has not noticed a strong correlation between recessions and running but agreed it is cost-friendly.

"You just buy your shoes, some running shorts and shirts, and out the door you go," Schwab said.

He said the marathon's success is good for the sport in the city. During the marathon's six-year hiatus, turnout at his group, which runs Downtown every Tuesday, had shrunk. But it has increased since the marathon was reintroduced and continues to grow.

"The running community in Pittsburgh supports it quite a bit," he said of the marathon.

And the marathon supports those running groups. A list of groups is available at PittsburghMarathon.com, and Matamoros encouraged people to join so they can start training. Running with a group is important, especially in cold weather, because knowing that someone expects you to be there is another reason to get out the door when everything else is telling you to stay indoors.

The marathon's website offers free training courses and nutrition tips. Matamoros said organizers want participants to learn as much as they can about the mental, physical and nutritional aspects of a 26.2-mile race.

"We take a whole-body approach," she said. "We're not just saying run, run, run, run, run."

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