Allen Rosenberg, an influential if controversial rowing coach who guided an eight-man crew to an unexpected gold medal at the 1964 Olympic Games, died Dec. 7 at his home in Silver Spring. He was 82.

He had Lewy body dementia, a degenerative neurological condition, his daughter Miriam Rosenberg said.

In the 1960s and ’70s, Mr. Rosenberg was called the “genius on the water” for the way he revitalized the U.S. rowing program and introduced revolutionary changes in the sport’s training and techniques.

For years, the United States had dominated the sport’s fastest and most glamorous event, the eight-man crew with coxswain, winning every Olympic gold medal from 1920 to 1956. In the 1960 Olympics, a disappointing U.S. team failed to win a medal of any color.

During the trials for the 1964 Games, Mr. Rosenberg coached an unheralded eight-man crew from Philadelphia’s Vesper Boat Club. His crew had an ungainly, outmoded racing shell, but Mr. Rosenberg’s innovative training methods helped drive his Vesper eight to an upset victory over favored college teams from Harvard and the University of California.

Allen Rosenberg was an influential if controversial rowing coach who guided an eight-man U.S. crew to a gold medal at the 1964 Olympic Games. (Courtesy of Peter Mallory)

Allowing himself a moment to gloat, Mr. Rosenberg said, “A boatload of men will beat a boatload of boys every time.”

At the Olympic Games in Tokyo, Mr. Rosenberg’s powerful crew rowed to a decisive victory in the finals, outracing a strong West German team by five seconds to reclaim the gold medal. The diminutive Mr. Rosenberg — who began his rowing career as a 5-foot-1 coxswain in the 1950s — became something of an oracle of the sport.

He devised what became known as the “Rosenberg style,” in which the legs, back and arms are used in an overlapping, sequential manner.

He also introduced unheard-of practices for the time, such as meditation, weight training and tai chi, to give his rowers a competitive edge.

“He is, by far, the most influential coach of the last 60 years,” Peter Mallory, a five-time national rowing coach and author of a four-volume history of the sport, said in an interview.

But even as the “Rosenberg style” of rowing was gaining supporters, the personal style of Mr. Rosenberg was gaining detractors.

He began his rowing career in his native Philadelphia as a 100-pound coxswain, shouting orders on stroke speed and other tactics to husky teammates who outweighed him by 100 pounds. In 1954, his first year in a boat, Mr. Rosenberg coxed a four-man crew to a national championship. A year later, he coxed an eight-man boat to a gold medal in the Pan-American Games.

By the early 1960s, he had turned from competition to coaching, taking over Philadelphia’s venerable Vesper Boat Club at the urging of four-time Olympic rower John B. “Jack” Kelly, the brother of actress Grace Kelly.

“He was a compulsive student of the sport,” said Dan Spero, a world­ champion sculler in the 1960s who rowed for Mr. Rosenberg in a four-man crew that took first place in the Maccabiah Games, an international competition for Jewish athletes, in 1961.

“A coxswain, because he is so diminutive, has to exude confidence and positive leadership, which can border on pugnacious.”

Two years after his team won Olympic gold, Mr. Rosenberg abruptly left the sport. Supporting himself first as a pharmacist and later as a lawyer, he moved to Rochester, N.Y., where worked as a lawyer for the University of Rochester and as an administrative law judge.

“I admit that I’m a better coach than I am a lawyer,” he said in 1975.

In 1972, the U.S. eight-man crew won the Olympic silver medal under Mr. Rosenberg’s longtime coaching rival Harry Parker, who led the Harvard rowing team for decades until his death in June at age 77.

Parker was not interested in becoming the permanent national coach, so Mr. Rosenberg left semi-retirement in 1974. He promptly led the American eight to a surprising world championship, which made him a revered figure in the sport.

An aura seemed to grow around him, as his un­or­tho­dox training methods produced results.

“I don’t mean it egotistically, but now, after 20 years, I’m willing to admit I really am talented,” he told Sports Illustrated in 1975.

But the magic soon wore off. Mr. Rosenberg’s eight-man crew finished fifth in the world championships in 1975.

A year later, during preparations for the 1976 Olympic Games in Montreal, Mr. Rosenberg was described in the New York Times Magazine as “a bundle of neuroses, contradictions and rowing wisdom packed into a diminutive five-foot one-inch frame.”

His enigmatic coaching methods soon triggered a rebellion in the team — known in rowing circles to this day as “the Mutiny.”

Accounts vary about the nature of the dispute, but three of the team’s top rowers either quit the team or were dismissed by Mr. Rosenberg.

The crew he took to Montreal finished an embarrassing ninth.

It was the end of Mr. Rosenberg’s coaching on the national stage.

Mr. Rosenberg moved to Washington in 1977, worked as a lawyer for the Navy Department and later as a patent attorney in private practice.

Without a college job, his coaching was limited to occasional work with the Potomac Boat Club and Occoquan Boat Club, even as Parker and other coaching rivals continued to maintain a national presence.

“There were two Allens,” Mallory said. “He held grudges and could be unforgiving. He was a tough cookie. I thought he was one of the nicest gentlemen I’ve ever met, but he could be mercurial because he was so competitive.”

Allen Perry Rosenberg was born Nov. 29, 1931, in Philadelphia. After graduating from Temple University in his home town in the 1950s, he practiced pharmacy, then attended law school at night. He received his law degree from Temple in 1964.

His marriage to Ruth Borsuk Rosenberg ended in divorce.

Survivors include his wife of 23 years, Lisbeth Sklar of Silver Spring; six children from his first marriage, Sarah Rosenberg of Atlanta, Daniel Rosenberg of Chicago, Rebecca Rosenberg of Helsinki, Miriam Rosenberg of Tel Aviv, Tziporah Rosenberg of Rochester and Isaac Rosenberg of Arlington; a stepson, Joshua Cohen of Boston; two brothers; and six grandchildren.

“He’s like a genius who can’t find his way around the subway system,” one of his rowers, Dick Cashin, told Sports Illustrated in 1975. “The only time he comes into his own, as a leader beyond belief, is on the water.”