Jackie Jahelka used all her might and tried to dodge her way to the cage. She was stopped by a defender who not only was taller, bigger and stronger but who also was whacking her in the arms with a styrofoam pool noodle.

Hey, big brothers don’t exactly take it easy on their younger siblings.

“Poor Jacqueline,” Stephen Jahelka said of the lacrosse workouts he put his sister through before her freshman season at Adelphi University two years ago. “She’s 135 pounds soaking wet having to go against me, and I’m pushing her around and stuff. People were walking by like, ‘What are you doing to this girl?’ ”

What he was doing was further preparing her for the college level. At the time, Stephen was entering his second season as a defender on the Harvard lacrosse team. As his sister approached the cage, he treated her as if she were a fully grown man in a Yale uniform — but with a pain-free pool noodle instead of a stick.

“It was very beneficial,” said Jackie, who, along with her brother, is a graduate of Garden City High School. “It’s not like I’m going against a 6-foot, 190-pound person on a women’s lacrosse team. It made me go as hard as I could and try different ways to get around him. It helped me become fearless.”

And feared.

Jackie scored two goals in Adelphi’s 13-4 win over Le Moyne on Thursday in Denver to put the Adelphi women’s lacrosse team one win away from a third straight Division II national championship. The Panthers face Florida Southern in the title game on Saturday.

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“It would mean the world to every girl on this team to come home with a third championship,” Jackie said.

A large part of the reason they’re in position to create another dynasty — Adelphi also won three straight from 2009-11 and has seven overall — has been a relentless and balanced attack led by Rachel O’Brien and Jahelka, the team’s leading point-scorer.

“This season, one of my goals was to be a little more well-rounded,” she said. “Most of my damage has always been on goals because I’ve been more of a cutter than a distributor. So I definitely wanted to start creating opportunities for other girls.”

That hasn’t come at the expense of her own scoring ability, though. Jackie, who was named Northeast-10 player of the year and, on Wednesday, was selected as a first-team All-American, already has set career highs in goals (79) and assists (24).

She’ll have a chance to add to those totals, and her brother will be in the stands watching.

“It’s the worst feeling in the world, my anxiety,” Stephen said with a laugh. “I’ve been lucky enough to play on a lot of big stages. State championships, world championships when I was on the Under-19 team, gold-medal games. And I was so much less nervous in those games than watching any of Jacqueline’s games.”

In February, news broke via a series of text messages in the Jahelka family group chat, which includes Jackie, Stephen and their parents. That led to a three-way phone call. The watch list had been released for the Tewaaraton Award, which honors the country’s top men’s and women’s college lacrosse players. The only name listed twice was Jahelka. Both Jackie and Stephen had made it.

“It was a very big surprise to me that I was on that list,” Jackie said, “but I wasn’t surprised to see him on it. I’m sure it’s happened before with the brother-sister combination on that list. But it’s something my family is never going to forget.”

Added Stephen: “It was a cool, unique moment where, at one point in time, you and your sister were eligible for the player of the year award in college lacrosse.”

For Stephen, Newsday’s 2011 boys lacrosse player of the year, his collegiate lacrosse career ended earlier this month as Harvard fell to Yale in the Ivy League Tournament. He’ll graduate from Harvard next week with a degree in economics. During the Major League Lacrosse Collegiate Draft in March, he was drafted 14th overall by the Denver Outlaws. He was traded to the Long Island Lizards in April.

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“The goal when you start anything is to try to reach the highest level,” he said. “I’ve been fortunate to play at a very good Garden City program and a very good Harvard program. Professional lacrosse is about as high as you can go.”

With Stephen back in town, will those pool noodle workouts between a soon-to-be professional lacrosse player and a potential soon-to-be three-time national champion resume?

“Yeah, definitely,” Jackie said. “I’m the type of person where I really have to be pushed. He’s the kind of person who will push me to the best of my ability. We’ll both go as hard as we can and hopefully not kill each other in the process.”