They have been playing together since they were about 8 years old. When they could have been outside and playing other sports, they spent many springs and summers together honing their hockey skills under the watchful eye of former North Stars forward Mike Fidler.

He stressed skill development and playing aggressive. First to the puck, positioning, tape-to-tape passes, stickhandling. It wasn’t easy and a few players came and went. But a core group of 17, all born in 1999, endured. Their combined résumés of high school and national team competition include awards, honors and gold medals racked up along the way. Now they are bound for Division I college hockey.

Eight of them will compete on four teams this week in the girls’ hockey state tournament at Xcel Energy Center. They weathered an intense training program that helped shaped their careers while forging a lasting bond and earning praise from hockey observers who laud these players as catalysts among the 1999 birth year group — one of the state’s deepest and most talented collection of players.

Edina, No. 1 seed in Class 2A, features Lolita Fidler, Anna Klein, Emily Oden and Sophie Slattery. The Hornets could see No. 4 seed Eden Prairie, led by Naomi Rogge and Crystalyn Hengler, in the semifinals. In Class 1A, Joie Phelps leads No. 2 seed St. Paul United in scoring while goalkeeper Emma Polusny anchors No. 4 seed Mound Westonka.

“It was so nice to grow up with them, play with them and against them,” Lolita Fidler said. “It’s really helped us develop into the players we are today. I don’t think any of us would be as good as we are if we didn’t play together as kids.”

The group shares support via text messages, but the mood changes when they line up for games.

“We’re like sisters, but we’re really competitive, so when it’s time to compete against each other, we do,” Oden said. “But when it’s time to play with each other, we know how to bring it in.”

Commitment. Competitiveness. Camaraderie. Those shared attributes made them almost unstoppable during spring and summer tournaments, first as the Minnesota Made “99 Girls Machine” and later at Velocity Hockey Center in Eden Prairie.

Mike Fidler said his teams played hard and trained harder. They traded more time in the sun for at least 100 hours of practice each offseason. As a result, the team rarely lost in tournaments when playing against older girls, or in 3-on-3 non-checking leagues against boys.

“Anything Mike tells you, it might sound odd, but it’s true,” said Noel Rahn, owner of Velocity Hockey. “Those were unbelievable teams.”

Except the first one. Formed in the spring of 2008, the “99 Girls Machine” lost every game. Worse, Fidler and Tom Oden, who advertised their training program in Let’s Play Hockey Magazine, feared they were losing the team.

“One day I came home and had to tell my wife, ‘I said something to one of them and everyone started crying,’ ” Fidler said with a laugh. “I wanted to treat them like the boys, to be aggressive about what we do and how we do it.”

Training was unconventional at times through the years. Players skated to the blue line, dropped to their knees and kept count of who, as they slid forward on the ice, could alternate thrusting their knees upward the most before crossing the far blue line. Other times players kept their hands and stick on the ice and skated, an arduous exercise that developed edge work and balance.

Phelps said former players still joke about the hours spent on three-man passing drills. And weekly hockey homework included shooting a certain amount of pucks and required a parent’s signature to verify completion.

“There were times where it was like, ‘Wow, I don’t know if I like this,’ ” Emily Oden said. “But he definitely pushed us to the next level and got us where we are today.”

There were lighter moments. Phelps said, “When Coach Fidler called the ‘quarters’ drill, we’d skate to our water bottles because it sounded like ‘water’ when he said it in his thick Boston accent.”

During the trying first season the team scored only one goal, one that drew “this screech on the bench like I’d never heard before,” Fidler still recalls of his team’s reaction.

Then success followed and the team began dominating tournaments. Fidler and Oden kept egos in check, refusing to name a most valuable player. If tournament officials objected to his team-as-MVP request, Fidler said, he told them to keep the trophy.

“You couldn’t even think of being selfish with the puck,” Slattery said. “It wasn’t an option.”

The next step in the players’ maturation came when Fidler moved the team to Velocity Hockey and played in 3-on-3 non-checking leagues against boys.

“The girls were skating around the boys like they were pylons,” Rahn said.

But the girls also saw the need to improve their stickhandling and shooting, Rahn said, and rose to the challenge. The team often took first through the first half of the season and then moved up to play older boys’ teams. Phelps credited the experience for getting her team to another level. That was Mike Fidler’s goal all along.

“I wanted to prepare them for college hockey,” he said. “It’s sad that this week is the end for most of them as high school players, but I can’t wait to see them in college.”