You know you'll feel better once you start exercising, you know you'll look better and, after a brief period of pain, you'll begin to enjoy it. However, it often takes a massive wake-up call (impending nuptials, beach holiday, having to lie on the floor to get into your jeans) before you get up off the couch.

Another encouraging call to exercise is when some miraculous result is promised in a short period of time, particularly if it comes accompanied by a celebrity seal of approval, although not of the Jade Goody My Shape Challenge or the Jayne Middlemiss Love Yo g a varieties. You want to know what celebrities actually doand not what they're being paid to endorse.

Enter Sebastien LaGree, trainer to the Hollywood stars and the man behind Systeme Dynamique, which he's just brought to Ireland.

Combining weights and pilates, it strengthens and tones the body, burns calories and ups the heart rate.

Nicole Kidman, Courtney Cox, Jessica Simpson, Sheryl Crow, Ben Stiller and Mary J Blige are some of the attendees at his LA studio and he is confident about the rapid effects of his classes.

"It depends on the amount of energy you put in but usually you see results within two weeks. It's a very fastforward approach. Everybody who comes to my studio who had done pilates for years said they got more results with me than they did in a few years." Before you presume that LaGree's solution is a magical one, be warned . . . it's quite tough.

LaGree says there is an "awful lot of bullshit" associated with pilates. The exercise form was created by Joseph Pilates during the first world war to help returning soldiers recover from their injuries and was based around certain principles which aim to condition the body through proper alignment, breathing, precision, control, concentration and flowing movement.

For many years it remained a specialised form of fitness, where practitioners had to undergo extensive training.

It has become more mainstream in recent years when a federal court ruled that 'pilates' was a generic term.

The result, LaGree says, was the emergence of trainers without proper qualifications alongside those who remained true to the original principles . . . and thus a lot of confusion as to what pilates actually is.

He came across it after he moved to LA from Seattle to pursue the movie industry. "I had a bit of trouble on the way and I was forced to make a living right away in LA and I couldn't see anything that I wanted to do that would give me the flexibility to go to auditions and I didn't want to be a waiter, " he says.

"I was body-building then and much heavier. People kept asking me if I was a personal trainer and I thought maybe that was a sign. The third person who asked me, I said yes.

So now I had a client."

He rented a place off Melrose Avenue, where he first encountered pilates. Initially, he was sceptical. "There was no music, no seating and you had the trainer smoking with the client after the session . . . it was just weird." He got into it because he liked the principles behind it but didn't believe that it should be as inaccessible or as expensive as it was.

He devised his 'Boot Camp Pilates' circuit training classes . . . traditional pilates with a twist. "Nowadays people want to get strong . . . women want to get strong . . . but they don't want to bulk up. They like the weight training but they don't want to look like Arnold, not even the guys. Being big is not in any more but with this you strengthen the body and you also do cardio."

Courtney Love was his first big-name client. She made him nervous at first but now:

"When you hang out in Hollywood, you go to parties and you see celebrities all the time.

Nicole Kidman talks about my personal life, her personal life. We just chat and then we train. I go around the corner and have my breakfast and there's Robert Duvall having his breakfast. It's LA."

As for his celebrity fans, they want what's going to work and, like the rest of us, often leave it until the eleventh hour. "I have celebrities who come and say, 'I have 20lb to lose and I'm shooting next week.' And I say, 'How long have you known about this?'

And they say six months.

These extreme makeovers are really bad for your body but it's very popular in the US and they're looking for something with quick results and so they come to me. It's very painful but it does work."

'System Dynamique' classes available only at Pilates Plus Dublin, Tel: 01 280 6120;

www. pilatesplusdublin. com