Arms swing and heads bob. Chests heave and hips weave. The sweat runs in rivulets across faces twisted with determination.

It's two days after the body of a second runner was found sprawled in the weeds near Dulles International Airport, killed by Washington's oppressive heat and humidity. And in Washington, people are still running.

"And did you read about the wreck on the Beltway the other day?" sneers Dan Shae, one runner on Memorial Bridge at noon yesterday. "Charlie Pride got caught in an airplane wreck yesterday," Shae says. "People die in all kinds of ways."

Shae is an Army chaplain. He speaks for many runners.

Most believe, as Shae does, that the reason Henry Kronlage and Patrick Reiley died last Sunday in Herndon's 10-mile race was simple carelessness. Neither man, the runners say, should have been in the race.

These runners, who tramp miles of Washington's foot paths in 90-degree heat under a searing midday sun, say Kronlage and Reiley "didn't know their bodies."

"If I heard of 15, 20 people dyin', it wouldn't make any difference to me," said 40-year-old Elmer Barnes, an Air Force chief master sergeant running yesterday near the Lincoln Memorial. "What's good for one, isn't good for another."

Runners take a lot of heat. Not from the sun, but from relatives, friends and people who just hate running. What many regular runners fear most about the Herndon tragedy is not that the same thing might happen to them, but that the incident wil provide more ammunition for those who like to knock running.

"One thing I am concerned about," said Phil Stewart, president of the D.C. Roadrunners Club, "is that there will be a huge overreaction to this. There have been a lot of heat-related deaths due to the heat wave this summer, and here we have two that take place in a running race and they will receive a lot more scrutiny."

The number of runners in Washington appears to have thinned some in recent weeks, apparently because of the heat. But few seem to be running scared because of Sunday's tragedy.

"Most of the people you see out here run regularly," said Holton Foster, a 34-year-old attorney for the Securities & Exchange Commission, running along the Mall near Independence Avenue. "No one has really stopped running.

But most people," said Foster, "recognize that you can't do what you normally do when the temperature is 95 or 100 degrees. Yesterday I ran a fifth of what I usually do. I cut my time back 30 percent. You have to change your pace."

Some, such as Joni Mazer, a film editor for WJLA-TV, are running earlier in the day. "We're not going to run if we feel bad," Mazer said, having completed a five-mile course yesterday morning along the George Washington Parkway south of Alexandria. "I think it's just being aware of yourself and how far you can push yourself."

"People who race in addition to running for conditioning know what stage they are in," said R. H. Williams, a Navy commander running a course between the Pentagon and the monument grounds in preparation for the Marine Marathon this fall. "I was stationed in the Philippines for three years," Williams said. "I became very aware of what it's like to run in hot weather."

There are indications Kronlage and Reiley may have not have been fully aware of what could happen to them running a 10-mile race in temperatures approaching 90 degrees.

Reiley, a 31-year-old from Reston who taught mathematics and physical education in Arlington, was running in his first long race. Relatives said he was an "occasional" runner, who had been out dancing and drinking beer the night before the race.

Experienced runners say the beer and a lack of rest before the race could have left Reilly unprepared and more likely to push himself beyond his physical limits.

Kronlage, a 49-year-old IBM engineer who lived in Fairfax County, had run the annual Herndon race before. Relatives described him as being 5-feet 7 inches tall and weighing 170 pounds. They said he had beenrunning three miles "almost everyday" and that prior to the race he stepped up his routine to five miles a day.

He went into the race determined to run it in 80 minutes, more than 10 minutes faster that he ran it last year. Runners interviewed yesterday agree with officials of local running organizations that Kronlage's eagerness to break a personal record might have led to his death.

"A woman would never have done that," insisted Joni Mazer. "Women are the kind that will stop. Guys have that killer instinct, they're really competitive."

"We all have an ego problem," said Williams the Navy commander, "You go out to run and then stop to walk a while you get in trouble with your own mind."

In the case of both Kronlage and Reiley, medical experts say it is likely neither drank enough water. Inexperienced runners, they say, can't rely on being thirsty to know when the need more water in a race.

And though the dual deaths amount to one of the most tragic incidents in local foot-racing history, most runners are confident it will have little effect on sport.

"One of the reasons you choose this sport," said Jeff Darman, past president of the Roadrunners of America, "is because you can do what you want to go."