SHOULDN'T THE STANDARD OF HOW ABLE THEY ARE...:

Paralympians have to be assessed by international classifiers before arriving at the Games. But, said Peter van der Vliet, the International Paralympic Committee's chief medical classifier, some 245 athletes here have been deemed borderline -- hovering between one grade and another -- and have been reassessed at the Games. Forty have been moved to different classifications, and eight athletes (in track and field, swimming and judo) have been ruled ineligible and sent home because, he said, they did not meet "the minimal disability criterion."

The classification process is multifaceted and different for each sport. Riders in international equestrian events are observed riding in competition. They also have to undergo face-to-face medical evaluations from two international classifiers, involving a range of movements that tests for strength, coordination and flexibility. The exercises can be as straightforward as touching a finger and thumb together, moving the shoulder, or placing a heel in set spots on the ground.

"They seem like simple tasks," said Dawson, "but when I started doing them I was like, 'Oh, my life -- this is so difficult.' "

The system is meant to focus on the athletes' physical abilities and on the limitations their disabilities impose, not on their riding prowess. But it can anger competitors who believe that they are being forced to compete against people who are less disabled than they are.

"People will say, 'You shouldn't be in grade 1A -- you ride so well,' " said Donna Ponessa, a rider on the United States team. She has multiple sclerosis and is paralyzed from the chest down. She uses a wheelchair and a ventilator, except when she rides. "But I've given up a year and a half of my life for the Olympics," she said -- time almost entirely spent riding, exercising at the gym or working.

Riders with fluctuating conditions like multiple sclerosis are frequently re-evaluated, and athletes unhappy with their classifications can appeal.

"There are two reasons for this," Mr. van der Vliet said. "First, it's a fundamental right that if an athlete believes a wrong decision is taken, he has a right to protest. And with some athletes their default mode is that they will challenge a decision any time they can when they are not in agreement with it."

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