Two to four times a week, Holly Perkins works with "Entourage" star Adrian Grenier, putting him through sets of lunges and stepping exercises to keep him buff.

When director Chris Weitz is filming a movie, as he is now in Canada with the "Twilight" sequel, "New Moon," Perkins sends him workouts on DVDs.

Celebrities like Grenier and Weitz have the means to dish out big dollars for Perkins' workouts - she charges $150 for a 1½-hour private session - but you can access her fitness know-how free of charge on Exercise TV.

Perkins, who once worked in cardiac rehabilitation at Beaumont Hospital in Troy, Mich., is now one of dozens of celebrity trainers - including Jillian Michaels of NBC's "The Biggest Loser" - who make shows for Exercise TV, available through Comcast's On Demand or online at www.exercisetv.tv.

"I wish everyone in the world could have a personal trainer," says Perkins from her home in Los Angeles. "So I really try to personalize it like a private training session with me and you in your living room."

Founded by Jake Steinfeld of "Body by Jake" fame, the Exercise TV channel and Web site feature hundreds of workouts that can be viewed and streamed without charge.

For anyone who doesn't have the money for a gym membership or for those who "have kids and want to get a workout in early in the morning or late at night, we're good news," says Steinfeld from his offices in Brentwood, Calif. "We get thousands of e-mails from women around the country who are absolutely wild for Exercise TV because they're able to have a life."

Unlike workouts on linear cable shows, users treat Exercise TV like a personal fitness library, selecting a specific type of workout at any given time. They can pick from trendy, innovative exercises like "Power Bhangra," which is based on Indian dance, to core fitness routines that focus on abdominals and arms. Other categories include yoga, Pilates, kickboxing and strength training, and range from one minute to one hour.

Steinfeld started the channel three years ago; it rotates in 100 new shows each month.

"There's really no limitation if you want to work out," says Chris Mansolillo, general manager of Exercise TV. "You can do it online or on your portable device or at home. The only thing you can't do is have the trainer fly out to your house. But they're pretty much there anyhow."