Josh George (David Frank / The New York Times)

Josh George is a world champion wheelchair racer who has qualified to represent the United States in seven events at the Paralympic Games in Beijing this September. He will file occasional diary entries through the Paralympics. Today he writes about the U.S. Paralympic track-and-field team trials that took place in Tempe, Ariz., last weekend.

Trials had begun three days earlier, in the heat of ­Sun Angel Stadium at Arizona State University. This stadium has been home to a horde of track and field’s best.

It is my first trials for a track team. When I made the team that went to Athens the rules were different. If, over the course of the spring, you hit the time set by US Paralympics as their “elite” standard, you were entered into the selection pool. The fastest three racers in each event made the team.

Trials are different. There are still time standards that athletes must hit, but in this system they only have one chance to hit their standard, and in doing so must they finish in the top three. The system is harsh, and the fastest racers over the course of the year can miss the cut if they are having a bad day.

During the warm-up lap before one event I’m entering, the 1500 meters — the last event of the trials — my nerves finally caught up to me. This was the last chance. Not for me — ­I was one of the fortunate ones who already secured a spot on the team — ­but for Aaron, my teammate at University of Illinois Wheelchair Racing. Aaron is a young racer with the potential for world dominance. (We call him Conan, as in the Barbarian, because, among other reasons, he is 6-3 and ripped). It was also the last chance for another young racer named Jordan, with equal potential.

Swinging around to the start line I hear cheers from the stands, from fellow athletes like April Holmes, a single amputee who can churn out 100 meters faster than any female amputee in the world and many with two legs. I also hear Jerome Avery, a guide runner for blind sprinter Josiah Jammison and an Olympic hopeful himself who qualified for the Olympic trials at this very meet. When I settle on the line the tension emanates from the bodies surrounding me.

This is the last chance to make the team.

It is the standards and the coaches who ultimately select the team. But it is the athletes who sometimes know best who should make it, and we can sometimes use our influence on the track. I’ve already made the team, so my role is to be the workhorse in the race. We athletes know that we need Aaron and Jordan on the team, and it is my job to pull them around to a qualifying time. Wheelchair racing, much like cycling and auto racing, makes wonderful use of drafting. Athletes racing tucked behind the leader work an average of 20 percent less while going the same speed.

At the gun the race started smoothly with me setting the pace for Lap 1, but after that, smooth turned to rough. After a split-second lapse in concentration, Jordan crashed into a guardrail. In an instant, one of our fastest young racers was out.

I resumed my pull in front for the remaining three laps, needing to keep the pace up, needing to help Aaron hit the time standard. I was beginning to get excited. We were on pace, I was feeling strong enough to pull us through, and Aaron was in a good position behind our coach and fellow competitor, Adam Bleakney.

Then came the crucial final lap. With 300 meters to go I glanced back to see Adam coming up on my outside. Aaron should be right behind him, I thought, keeping the pace steady. Coming down the homestretch, though, I looked back again, trying to will Aaron across the line, but I couldn’t find him.

The back of the pack had exploded into their finishing sprint and Aaron had fallen off the back of the pack and out of the draft. His time was 1.4 seconds slower than the standard he needed. In this case, the best efforts of the athletes failed to get those who needed to be on the team, on it.

We were greeted at the banquet hall by a pair of Chinese lions, replicas of the ones found in numerous gateways in the Forbidden City — a reminder of the Beijing Paralympic Games we’re headed to. But the faces of some of the chosen athletes were a bit sad, a contrast to the elation you’d expect to see from those who’d made the U.S. National Team. It is a bittersweet process, the Parlaympic trials.