WEST WINDSOR, N.J. — When Joe and Jim Rosa, twins on the West Windsor-Plainsboro High School North cross-country team, were 5 years old, they would compete to see who could stay under water longer in the family pool. “They always had great lung capacity,” said their father, Larry, who swam internationally for his native Puerto Rico and then at the University of Pittsburgh. “We were trembling until they came up. It was scary.”

As the boys got older and played one-on-one basketball in their driveway, they would fight over every point. “Whoever lost,” Jim said, “would usually get mad and throw the ball down the street.”

The boys’ capacity for endurance enhanced by their sibling rivalry has vaulted them to the pinnacle of scholastic running. They are favored to place first and second in Saturday’s New Jersey State Meet of Champions in Holmdel and again the next week at the Northeast regional in Wappingers Falls, N.Y., a qualifier for the Nike Cross Nationals high school championship, Dec. 5, in Portland, Ore. Last Saturday, as a final tuneup for the title events, the boys crossed the finish together, with Jim inches ahead, in their division of the state group meet at Holmdel Park.

In talks about which young Americans could eventually challenge African dominance in distance running, the Rosas lead the next generation with performances that are redefining teenage levels of success, said their coach, Brian Gould. As 16-year-old juniors, Joe has shattered three marquee course records in succession and Jim has been a close second each time. Identical red-headed twins, the boys come blazing across the finish to startled spectators who watch the time clock in disbelief. It takes a practiced eye to tell who the winner is.