Bela Karolyi, the famed gymnastics coach who guided athletes to champion status in a decades-long career, died Friday, the Associated Press reported, citing USA Gymnastics. He was 82 years old.

The cause and manner of death has not been specified, the AP reported.

Mr. Karolyi and his wife, Martha, began coaching gymnastics in their native Romania and trained Nadia Comaneci, a five-time Olympic gold medalist. Comaneci posted a tribute to Karolyi on Instagram, stating that he had been “a big impact and influence” on her life.

The Karolyis, who defected to the United States in the early ’80s, were known for contributing to the United States’ international rise in gymnastics and for helping to cultivate young athletes such as Mary Lou Retton into household names.

A commanding personality, Mr. Karolyi was sometimes criticized for controversial coaching tactics. He came under scrutiny amid revelations that Larry Nassar, the doctor for the U.S. gymnastics team, had been sexually assaulting young gymnasts at the Karolyi Ranch training center in Texas. As accusations against Nassar mounted, victims have questioned when the Karolyi family first came to know about the assaults. The couple denied having knowledge about the misconduct as it was happening.

“I don’t feel responsible,” Martha Karolyi said during a 2018 interview with the TODAY show, “but I feel extremely hurt that these things happened.”

Dominique Moceanu, a retired U.S. gymnast who competed as one of the “Magnificent Seven” at the 1996 Summer Olympics in Atlanta, called Bela Karolyi’s influence on gymnastics “undeniably significant.”

“He was a complex individual, embodying a mix of strengths and flaws that left a lasting impact on those around him,” she wrote in a social media post, adding: “His harsh words and critical demeanor often weighed heavily on me. While our relationship was fraught with difficulty, some of these moments of hardship helped me forge and define my own path.”

Throughout their 30-year multinational career, the Karolyis produced 28 Olympians and nine Olympic Champions, according to USA Gymnastics. The athletes they coached include Julianne McNamara, Phoebe Mills, Betty Okino, Kristie Phillips, Kerri Strug and Kim Zmeskal, all of whom have been inducted into the USA Gymnastics Hall of Fame, alongside Retton and Moceanu.

In a memorable TV moment, Mr. Karolyi was shown carrying Strug to the victory podium amid roaring cheers after she injured her ankle then still performed the vault that allowed the U.S. team to win gold at the 1996 Games.

The Karolyi Ranch, a 2,000-acre compound that was the official training center for the national women’s gymnastics team from 2001 to 2017, later became a site of controversy, with some athletes criticizing the facility’s maintenance, spartan environment and lack of safeguards.

Olympian Aly Raisman called conditions there unsanitary and “disgusting,” and filed a lawsuit against the U.S. Olympic Committee and USA Gymnastics in 2018, alleging that the organizations “willingly” refused to “implement appropriate safeguards” there, including ones that would have helped protect against Nassar.

The media has also at times characterized Mr. Karolyi as an affectionate man outside the gym, who was known for bear hugs and raising farm animals. In a humorous speech, he once recalled his early years in the United States and his fumbles learning English.

“Nothing in the world [you] can get without sacrifices – especially when you want to get something, which is the best in the world,” Mr. Karolyi said during a 1990 interview. “Gosh, you have to put the most out of you. The most. More than anybody else. That’s the name of the game.”