Offseason NFL charity events often consist of bowling, building playgrounds or signing autographs — not rappelling 38 stories down the face of a high-rise.

Extreme philanthropy resonates more with Vikings safety Andrew Sendejo. He will descend down the fourth-­tallest building in Austin, Texas, this weekend as part of the Make-A-Wish “Over the Edge” fundraiser.

The agility and focus required for this sort of stunt was honed long before Sendejo played in the NFL. At age 5, Sendejo began studying martial arts.

“I learned at a very young age about discipline and having a really good attitude and paying attention to the details,” Sendejo said, “and it just so happens that football is made up of a lot of all these small little details.”

Sendejo, at age 8, was required to write a 200-word essay to earn his red belt. He started the task by asking his parents what an essay was. His progress impressed instructors and he began touring with a demo team.

He excelled at Kata, the choreographed pattern of movements from various martial arts, though he preferred the more physical sparring competition. His favorite move was three to four kicks to the belt, then a high kick to the face. “That one worked every time,” he said.

The trophies Sendejo brought home were bigger than he was and, by 9, he reached the ceiling for junior martial arts with a third-degree red belt.

Texas football, the “Friday Night Lights’’ kind, was his new focus by middle school, but martial arts has shaped every stage of his life. In college at Rice he joked with players and coaches that he was a ninja. A year later, Rice’s former offensive coordinator told his players to watch out for Sendejo because “he’s a ninja.”

He no longer owns his gi, the clothing worn by ninjas, or his collection of weapons that included a sword, nunchucks, throwing stars, a bo staff, and sais, “The ones that Raphael has,” referring to the Mutant Ninja Turtle’s pronged batons.

“I was obsessed with ninjas,” Sendejo said. “It was always heavy ninja-themed.”

He has plans to honor his background and childhood hero Raphael by dressing up as the ninja turtle at the charity event this weekend.

Sendejo, 28 and entering his seventh NFL season, joked that he might consider spreading rumors around the NFL that he’s a ninja since it worked in college. But the Vikings coaching staff and front office is impressed enough by his work ethic.

“I have a switch,” Sendejo said. “When I come into work, I have the discipline to flip that switch and go into work mode and get my job done.”

The Vikings rewarded Sendejo this offseason with a four-year contract extension worth $16 million. A year ago, Sendejo’s future with the Vikings was uncertain when coach Mike Zimmer questioned the viability of his options at strong safety next to standout free safety Harrison Smith.

However, Sendejo earned the job and started 14 games, had 61 tackles and an interception. He likely will enter training camp battling for a starting position with free-agent signee Michael Griffin, along with youngsters Antone Exum and Anthony Harris.

Sendejo also plays an important role on special teams, an area he’s excelled at since signing with the team in 2010, special teams coach Mike Priefer said.

“I think [the contract] was just a respect factor. I know he wanted to stay here, and I’m extremely happy he stayed, and I know there are a lot of coaches and players that feel the same way,” Priefer said. “He’s a phenomenal young man. I trust him. He works extremely hard at everything he does. He’s the type of guy that we need on our football team as a leader and as a football player.”

Sendejo leads a players-only special teams meeting every Friday during the season.

Smith, who has built a strong friendship with Sendejo over the past several years, said it’s not hard to notice Sendejo’s discipline.

“He’s regimented, and that has continued throughout his life,” Smith said. “He always knows his assignments. … He rarely makes mistakes. That’s how he always was and I think last year he kind of got his opportunity and just got better and better.”

Smith is convinced Sendejo still owns all his ninja gear and plans to be in attendance at the W Austin Hotel when his defensive partner rappels 38 stories, possibly in ninja attire. Smith will have his camera ready.

“I wouldn’t be surprised if he tried to talk to some people on his way down or stopped in some rooms [in the building],” Smith said. “It will be a lot of fun.”