Jane Fonda's fitness tapes -- We talk with the star about the release of her new exercise video, ''Lean Routine''

”We do this because we want our guys to find us attractive,” says Jane Fonda, explaining her fanatical affinity for fitness. ”I mean, I love it when my boyfriend says to me, ‘I can’t believe what good shape you’re in,”’ admits Fonda, who lately has been spending a lot of time on the arm of cable magnate Ted Turner. ”It’s kind of fun for women to be, at least in one area, faster or stronger than their boyfriends or husbands.”

If you think her boyfriend is happy, you should see her producer; theequeen of lean has sold 5.5 million copies of her 11 workout tapes. Her 12th, Jane Fonda’s Lean Routine (Warner), adds nutritional tips to a ”low impact/ high energy” exercise routine. It’s her most expensive video to date, with a budget of close to a half-million dollars. Fonda, 52, who has been known to chomp a brownie to get her energy up before shooting her workouts, uses some MTV-type moves to give this vid a hipper look than her past endeavors. Filling out a fishnet leotard, she aerobicizes across a rooftop set (”à la Janet Jackson or Paula Abdul,” says choreographer Monica Walsh) adorned with city lights, skylights, and a chain link fence.

Fonda’s fitness obsession stems from years of suffering from bulimia and fatigue. ”I ate almost nothing to maintain my weight,” she says. ”It wasn’t until 12 or 13 years ago when I started doing aerobic exercise that everything changed. I could eat a normal meal. It changed my relationship with food.” She decided to parlay her expertise into money for a left-wing political fund, produced Jane Fonda’s Workout in 1982, and profited from millions of fitness- crazed Americans with new VCRs. Today her doctors tell her she has the heart of a 20-year-old. Up at 5 a.m., Fonda jogs with her golden retriever, mountain-bikes, or swims every day.

A week of rehearsals last June went off as planned, but then Fonda abruptly postponed the actual shooting for a month. ”I’d been having a hell of a time during rehearsals,” she says. ”I didn’t realize it, but I had two broken ribs. I don’t know how it happened, but I think they had been broken for three weeks and I didn’t know it.”