"I STARTED out as a tumbler and an actor -- I never considered myself a dancer," says Russ Tamblyn, the actor and dancer whose rocketing, ricocheting dancing stole several scenes in the movie versions of "Seven Brides for Seven Brothers" and "West Side Story." Tamblyn began preparing for his career by playing Batman and jumping from trees as a kid in Los Angeles, then won several tumbling and gymnastics championships in high school.

Tamblyn's billing has changed several times, along with his professional and personal stature. His first movie, "The Boy With Green Hair," featured 10-year-old Russell Tamblyn. A few pictures later MGM decided he was "Rusty," and he was Russ by the time he did "Samson and Delilah" in 1949. Now Tamblyn is considering going back to Russell.

Tamblyn was under contract to MGM and had just finished "Retreat Hell!" (billed as Rusty) when the opportunity arose to film his first big musical, "Seven Brides for Seven Brothers."

" Choreographer Michael Kidd said he argued with the studio that he wanted to use six great dancers for the picture, and Howard Keel would be the seventh," Tamblyn recalls. "The studio argued that they had all these actors under contract. They finally agreed to let him use four dancers and two contract players, who turned out to be Jeff Richards and me. Jeff Richards never did a dance step in the movie.

"Kidd said to me, 'I hear you're a tumbler.' So I did a back flip for him and he said, 'Great! We can put it in the number!' " Tamblyn wound up ricocheting off planks and logs and stealing the picture. "When I was done, everyone said, 'Where did you study?' " he says with a laugh. Tamblyn is modest about his dancing. An interviewer once asked him, "Who did you study with?" When Tamblyn responded that he never studied dance, the interviewer looked aghast and said, "My God, my boy--Michael Kidd, Jerome Robbins, Alex Romero--you've studied with the masters!"

While still under contract to MGM, Tamblyn made a test for the part of Tony in Leonard Bernstein's "West Side Story." "It was down to Richard Beymer and myself for Tony. When Beymer got that, they offered me Riff, and MGM turned it down. I had to go in to Benny Thau, the head of the studio, and almost beg for that part. It was hard work--we were dancing in New York in summer on pavement. But it was worth it."

Tamblyn was nominated for an Academy Award for his role in "Peyton Place." "Then a strange thing happened," he says. "I had just finished 'Peyton Place,' and the studio said, 'Boy, you're hot now.' Then they called and told me, 'Your next movie is "High School Confidential!" ' Well, I complained like hell--it was a B movie, but I was more or less forced to do it.

"I always thought it was funny that that movie should outlive 'Peyton Place,' " Tamblyn says. Because of his role as a young no-goodnik in "Confidential" (later retitled "Young Hellions") Tamblyn was invited last year to Austin, Tex., to be the guest of honor at the world's first Juvenile Delinquency Film Festival--"everyone came dressed like hoods and j.d.'s," he says with a laugh.

Tamblyn's most recent movie, rock star Neil Young's antinuclear comedy "Human Highway," was his first venture into choreographing for film. Young and Tamblyn were next-door neighbors in Topanga Canyon for a few years, so Young asked Tamblyn to choreograph the film's final sequence, to music by the new wave band Devo. "It was the funniest thing, working with 22 people--most of them non-dancers--Neil, Dennis Hopper, Dean Stockwell. So I put a lot of running into it, nothing too intricate," Tamblyn says. Last year, he choreographed and starred in Eugene Ionesco's "The Man With Bags" in Los Angeles (again with music by Devo).

Tamblyn says he runs and swims to stay in shape, but says he doesn't miss his dancing days, "mainly because I was an acrobatic dancer. You have to be young for that! If people see Russ Tamblyn is in a show, they expect me to come out and do three back flips--and I'm 48! It hurts more now."

He lives in Santa Monica with his wife, country-rock singer Bonnie Murray, and their 9-week-old daughter, Amber Rose. Tamblyn says he occasionally takes on an interesting project, mostly at dinner theaters. Last year he appeared in "Bye, Bye Birdie" with Chita Rivera, and he has just finished a successful week's run of Stephen Sondheim's "Follies" with the Pittsburgh Civic Light Opera Company. "It's a shame that it was only a week, because by the time I was finally having fun with it and feeling back in shape, it was over."