Nearing the crest of a steep, winding hill between the third and fourth miles of yesterday's race, I heard series of groans from President Carter.

They were not the usual pants and grunts of breathlessness that are the common sounds of runners as they battle gravity and themselves. I looked to my left, and suddenly the president began to stagger. His face was ashen. His mouth hung open, and his eyes had an unfocused look.

He faltered. Two runners -- apparently Secret Service men who were part of the contingent accompanying the president either on foot or in golf cart-like vehicles -- reached under Carter's arms and held up his sagging body.

Even though he had collapsed and was no longer making it on his own obviously diminished steam, Carter lunged forward. In mumbled words, he said he wanted to keep going.

But it was clear that Carter, rubbery of leg and gasping, had no choice. He could not go on.

Assisted by the two aides, he shuffled forward. He motioned again that he wanted to push on. Runners passed by and offered friendly encouragement."Keep it going, Jimmy," said one. "Get ready for the next race." said another.

I called out to one of the Secret Service men: "Give him water -- and fast." None came forward.

Either they had no water or the advice was not considered worthy.

When Carter slowed to a walk, he was shuffled out of the pack. I stopped to observe.

The president, his gray shirt beginning to show patches of sweat, was led to a cart. As he sat there passively, watching the line of fellow runners edge by up the punishing hill, a few frightening and tentative moments passed. To me, the state of the president's health was in grave doubt.

I didn't think that Carter was suffering heat stroke or heat exhaustion. The midmorning weather had an early autumn crispness, and most of the course until this point had been through the shaded lanes of the park.

It was not that far into the race. The event, a little more than six miles, is considered a stroll in the forest for experienced distance runners. For many in the field who were in training for upcoming marathons in New York and Washington, six miles is so short a distance that some runners didn't stop at the finish line but turned around to put in some real mileage.

A further factor was that the president's pace was well short of burning. He clocked the first mile at 8:25. This was a slightly uphill mile, followed by a long downgrade. When he collapsed, the president was running at a pace of about 8:45 -- respectable, but considerably slower than the 7:30 pace that the white House has been putting out as Carter's usual speed.

The Thurmont Community Ambulance Service arrived from over the hill. It remained there 10 minutes, until Carter, still wearing a yellow sweat band, was taken away in the back seat of a private car.

I wasn't certain whether the president's doctor, William Lukash, was next to Carter at the moment of the emergency. According to Jeff Darman, a past president of the Road Runners Club of America, Carter's physician was farther ahead in the pack. Darman says he was several hundred yards ahead of Carter and Lukash was near him.

The White House yesterday said that Lukash was in command of the situation.

One physician who did come by when the president was in his initial distress was Dr. Paul Spiegler, a Washington internist.

After the race, I asked for his observations. "The president look gray and ashen," said Spiegler. "I thought he looked bad, very bad, and the possibility of a heart attack was real."

Later in the day, Spiegler said, when Carter came to the picnic area to talk with some of the runners, "I was glad that he recovered so well. He looked fresh and well."

That was surely how Carter began the race. He took his place near the head of the pack, a few yards behind the front runners at the starting line.

I was in Carter's grouping from about the half-mile mark to his callapse. He talked with none of those near him, as runners sometimes do. About the only distinguishing feature was the president's black socks, rarely seen among runners.

Carter, who did some cross-country running in his days at the Naval Academy and who returned to the sport earlier this year, had done some training runs over today's course. The race was delayed for about 15 minutes as the president took his place in the pack.

Carter has a loping style of running. His shoulder turn is a little heavy, but he keeps his hands close to his chest. In the early part of the race, he gave no signs of being in trouble.

About two miles out, as the field turned around and the speed men began coming back, Carter called out "give them room on the right."

In the going and coming of the next several hundred yards, Carter was greeted by a stream of runners dashing past from the other direction. In festive spirits -- which tend to be more festive the fewer miles that have passed -- runners would call out the usual comments of "looking good" or "nice pace."

Carter acknowledged some of this with a wave, but mostly he was silent and intent on conquering the course.

Nearly everyone in the field of about 900 finished, including an 11-year-old boy and a man in his mid-70s.

A few veteran runners were heard grumbling that the president's collapse was bad for the sport and would give rise to still more snickers from the sedentary who think running can be hazardous to one's health.