Marine Lance Cpl. Robert Cordrey brightened otherwise dismal circumstances for runners struggling through the Marine Corps Marathon yesterday.

As the competitors passed the 20-mile mark at East Potomac Park, some smacking into the invisible but infamous "wall," Cordrey yelled that the American hostages in Iran had been freed.

Cordrey's report was at least premature, although negotiations are continuing, but the runners welcomed the information with cheers, clenched fists, and shouts of "All right!" and "Fantastic!"

The news served as diversion for what might be considered the toughest part of the race: the 18-to-20-mile stretch that for many is the longest distance encountered.

A runner hitting "the wall" encounters a drop in energy and the onset of fatigue and pain. "It's when the muscles use up more energy than they produce," explained Terry Hassler, a third-year student at Georgetown Medical School.

Hassler and classmate Jim Cain were manning the medical facilities at the checkpoint.Across the road, marines and girl scouts were hawking water and a fluid that helps replace substances lost during exercise.

The first wave of runners to round Hains Point had done this before. The runners' faces were as stoical as when they had passed the seven-mile mark. A little later, however, some pain was obvious. And much later, it looked like the Bataan death march.

The runners became walkers. Then limpers. With the grimaces and grunts, it was hard to believe these people chose to do this.

Hassler, who worked the race last year, said the runners suffered mainly from blisters, cramps and exhaustion. Ambulances -- 10 were on duty -- were summoned to attend runners who showed signs of disorentation or dehydration. No serious injuries were reported.

For most, the goal was just to finish. Stuart Ruch, 55, a podiatrist from Pekin, Ill., did. It was his first marathon, and his time was irrelevant. "It's fantastic," he exulted.