As Aimad Khelalfa, a senior for the Wakefield High School cross-country team, prepared for the district championships three weeks ago, he knew he had a good chance of qualifying for regionals. His coach had said so, and he felt it in his own muscles.

So Aimad decided to do something radical: He decided to eat on the day of the meet.

It was radical because Aimad, 18, is Muslim, and the holy month of Ramadan had just begun. Each year since he was 11, he has joined millions of Muslims worldwide who take no food or drink from sunrise to sundown. This weekend, they began celebrating the end of the month with three days of feasting.

For many American teenagers, joining a sports team is an integral part of high school, and for new immigrants it can be a good way to find friends and fit in. But athletes who emigrate from predominantly Muslim countries, where sports and other energy-sapping activities tend to be postponed during Ramadan, find that the Western clock does not stop for Islam.

Aimad, whose family moved to Arlington from Algeria four years ago, usually breaks his daily fast at home, starting with dates and moving on to couscous, meat, vegetables and water. Especially water.

"You really get thirsty" during long training runs, he said.

At Burke Lake Park in Fairfax, the best runners from eight high schools would race a three-mile course at 3:15 p.m. on this late October day, long after the pre-sunrise meal had been digested, and Aimad didn't want to falter.

"Only the best four schools out of eight are going to go to regionals," he said, adding that there are circumstances under which one can break the fast and make it up after Ramadan ends. "When you're traveling a long distance, if you're a pregnant woman, if you're sick -- if you have some kind of excuse -- you can break your fast."

Aimad planned to consult an imam about his plan, then try to talk his 16-year-old brother, Mohamed -- known as "Mo," and also on the team -- into doing the same.

"My brother is a little more strict," he explained. "But I think if he breaks fast, he'll do better, and it's better for the team."

Muslims are not alone in having to find a compromise between religion and sport. Sandy Koufax, one of baseball's pitching greats, skipped a 1965 World Series game because it fell on Yom Kippur, the Jewish fasting day. The movie "Chariots of Fire" tells the story of Eric Liddell, a Christian from Scotland who refused to run a qualifying heat in the 1924 Olympics because it fell on a Sunday.

But in recent years, as more American and immigrant Muslims have emerged in professional, college and high school athletics, they have had to find ways to satisfy the demands of the sport without ignoring the demands of the spirit.

Ibrahim Hooper, a spokesman for the Council on American-Islamic Relations, said coaches and teammates have become more sympathetic as they have become more familiar with Ramadan. "With the tremendous flow of information about Islam, many people have picked up at least the basics," he said.

But Meryem Noucair, 15, a sophomore on the Wakefield cross-country team, still finds herself explaining. "People ask if we're doing it because we're being punished," said the native of Morocco. "I tell them no, it's a good thing."

Imam Johari Abdul-Malik, the director of outreach at Dar Al Hijrah Islamic Center in Falls Church, said that Muslims are allowed to take exemptions if their jobs or livelihood requires it and that professional athletes, or those who have scholarships or are trying to obtain them, fit that category.

In the end, the decision is highly personal. "It's your own conscience. There's no one keeping track," Hooper said. Compared with the Prophet Muhammad's time, he said, when conditions on the Arabian Peninsula were hot and dry, "it's not that difficult to play a game and fast at the same time."

That depends on whom you ask. Mikal Baaqee, 22, a middle linebacker for Virginia Tech, does not fast on difficult practice days or game days.

"God is the number one priority, but at the same time, I have a deal with my teammates, and I'm part of the team," he said. "If I can't perform . . . it's going to hurt the team."

After Ramadan and football season are over, Baaqee will have to make up about 20 fasting days, and his mother approves.

"She knows that I want to have a future in the NFL, and I can't be jeopardizing all that," he said.

But what of the powers higher than his mother? "I think God would understand," he said.

In high school sports, the stakes are generally lower, and parents aren't always so understanding -- especially if they didn't grow up with letter sweaters and homecoming games.

Razia Begum, a Pakistani immigrant, has two sons on Wakefield teams, one of whom trains daily with Aimad. He is a lanky boy named Muhammed Fahad Khan, 15, nicknamed T.K. for "Tall Khan," and all this running worries her.

"This morning I said to him, 'Can you stop?' " she said. "He said, 'No, I can do this.' But I'm the mother. I feel bad because all day he's hungry and not eating and not drinking anything. He's very, very tired. It's not good."

Begum is clear about what her son's choice should be. "This one is necessary," she said of fasting. "Sports is not necessary."

For some teenagers who are testing the limits of their bodies and their resolve, fasting while exerting themselves is a challenge they would rather rise to than maneuver around.

Ahmed Dorghoud, 17, a square-jawed senior at T.C. Williams High School in Alexandria, has a fall training schedule that would be daunting even if he weren't fasting: He is on the football, wrestling and lacrosse teams, and he is in ROTC, which involves marching and drills.

Recently he donned a dress uniform for an ROTC ceremony at which he was promoted to captain, then quickly changed into football gear for practice. Boys in red-and- white football jerseys -- including his brother, Sherif, 15, a sophomore -- heaved themselves against tackling dummies and raced across the grass to receive passes, and Ahmed soon was indistinguishable among them.

But his fasting has distinguished him in his teammates' eyes, and he is aware of the awe it inspires. "They think it's a really amazing thing that I'm doing all they're doing" without food or water, said Ahmed, who is from Egypt.

Josh Nesbitt, a beefy middle linebacker for T.C. Williams, concurred. "I'm like, 'Man, doesn't it suck to, like, fast and not drink or eat?' " he said. Ahmed played as well as ever during Ramadan, he said, but that didn't protect him from temptation.

"We're like, 'Ah, doesn't this look good? I know you want some of these fries, Ahmed, don't say you don't,' " Josh said. "But no matter how much you taunt him, he's not going to break."

By the time of championships, Aimad had not convinced Mo that he should break fast. He also had neglected to consult an imam, and he realized that Meryem, the third Muslim from Wakefield competing that day, was fasting. So, to be safe, Aimad fasted after all.

Before they left for Burke Lake Park, the teammates passed around a can of spray paint and customized their hair with their school color, green. Their coach, Bob Strauss, a tall man with a handlebar mustache, sprayed his white hair green, too. As they warmed up, he didn't mention the fasting. Better not to let them obsess, he said.

The gun went off. The boys sprinted through the trees. Teammates and spectators screamed from the sidelines.

"Yeah, Apache! Move up!"

"Come on, Mo!"

Aimad only had to finish in the top 15. The top 15 runners would go to regionals, no matter how the rest of their team did.

It was a long three miles. He didn't think about his empty stomach or his dry mouth or the fact that he had lost 15 pounds in two weeks of fasting. But he couldn't ignore his legs. They felt incapable of propelling him as usual. And toward the end, there was a incline.

He crossed the finish line in 16th place. The runner in front of him had finished one second earlier.

"Weak, weak," Aimad mused. "It was my best time, but I could have done better if . . . " He managed a wistful smile.

Mo was 19th. Another Muslim runner, who attends J.E.B. Stuart High School in Falls Church, came in ninth. He had not fasted.

Strauss told Aimad he had done remarkably well, considering that he had been training, going to school and waiting tables at a restaurant, all on an empty stomach.

"It depresses me that he didn't make it, having so much on his plate," Strauss said. Then he caught the look on Aimad's face and reached out with his thumb to tip the boy's chin up. "But that's okay, we love him anyway."

A week later, they were back to root for the girls' team, which had made it to regionals. Heavy rain was falling, and afterward, squelching through the mud and shivering from the cold, Aimad, T.K. and Meryem headed to Dar Al Hijrah to break their fast.

By the time they arrived, it had been dark for 20 minutes. Prayers were over and the dining area was packed. Meryem tied a scarf over her head, they quickly prayed, then they heaped plates high with rice, breaded fish and spicy stew. They sat with friends and slid to make room for Imam Johari. They talked about the indoor track season, which the boys start Wednesday.

But not Meryem. She's trying out for the basketball team tomorrow.

And it won't help a bit that she won't be fasting anymore, she said. She will be too nervous to eat.

Sherif Dorghoud, like his brother, Ahmed, fasted despite a grueling football schedule.Aimad Khelalfa, kneeling, prays with Muhammed Fahad Khan before breaking his fast after a cross-country event.Mohamed Awad abstained from food and drink for much of the daytime despite his ROTC drill training at T.C. Williams High School in Alexandria.