JERUSALEM  On a Thursday night early in December, Pinchas Zerbib took off his traditional cotton skullcap. In its place, he put on a polyester one.

“It’s my Under Armour yarmulke,” Zerbib said. “For practice, it’s better. Plus, it’s still kosher.”

As an orthodox Jew, Zerbib, a native of Israel, believes he must always wear a head covering. He spends his days studying in a yeshiva, or a Talmudic learning institution. But three nights a week, he suits up as a linebacker.

“I sit down and learn all day,” said Zerbib, a 27-year-old student. “I love to do this sport and stay healthy.”

Zerbib is not alone in his newfound appreciation of American football. In its fourth season, the full-pads, full-contact amateur Israel Football League, or I.F.L., is attracting a diverse crowd of players from all over the country. Players vary in age, and some are married with children. The league is 80 percent Israeli, with secular and orthodox Jews playing with and against Israeli Arab, Christian, Thai and even Palestinian players. The league has grown from roughly 80 tackle football players to more than 400.