Seems like every celebrity is doing Pilates these days. It's portrayed as a miracle cure-all - filmstars say it keeps them thin, Tiger Woods says it's his secret weapon.

So what is so special about PIlates?

In a nutshell, Pilates strengthens and tones muscles. Toned muscles look leaner than flabby ones - so yes, if you do Pilates you'll look slimmer. Toned muscles work more efficiently and are easier to control - so yes, Pilates can help your golf swing or your dance moves.

Pilates tones and strengthens the core muscles - around your abdomen and pelvis - in particular.  Those muscles hold you erect, so if you do Pilates, you'll stand straighter - which means you'll look thinner, because your belly won't be sagging and your butt won't be sticking out. You may even gain an inch or two in height, depending how much you slouched before!

Pilates is valued by sportsmen and dancers for two reasons. Strengthening the core provides a solid foundation to move in any direction without strain or injury. And the slow, controlled movement improves body awareness - what individual muscles are doing and where you are in space - leading to greater power and grace.

Dancers and athletes also turn to Pilates when recovering from injury - but not because PIlates is the best exercise for sore or injured muscles. That's a myth!

Pilates exercises in their standard form, as taught in a group class, are no more suitable for people with injuries than any other exercise.

When Pilates is used for rehab, the exercises are carefully chosen - and modified if necessary - to give the patient a thorough workout while protecting the affected part.

For instance, when I herniated a disc in my neck, the instructor designed a routine I could do whilst keeping my neck safely supported. If I had just joined a group Pilates class, I could have caused myself pain and even made my injury worse - because most ordinary Pilates exercises involve lifting and holding the head off the floor without any support.

So if you have an injury or muscle problem (like back pain) and are considering Pilates as rehabilitation, see an instructor for some one-on-one sessions. You can't expect an instructor in a group class to modify exercises to suit injured individuals - especially as there may be several in the class, thanks to the misconception that "PIlates is good for rehab".

The secret of success in Pilates is to do every exercise very precisely. Correct positioning and correct breathing are so important that if you go to your first Pilates class and the teacher doesn't take time to teach them to you in detail, you may as well walk out! The exercises won't give you much benefit, and you may even hurt yourself.

Positioning is not as simple as sucking your tummy in or relaxing your neck. It takes time and patience to learn.

It's obvious that Pilates takes a lot of concentration. Every moment of the class, you must be thinking not only about the moves you are doing, but also about your positioning and breathing. At first, it seems impossible to keep your mind on all those things at once! If you want the benefits of Pilates, though, there really is no alternative. Approaching Pilates like an ordinary stretch class - watching and copying as best you can - will do almost no good at all.

If your primary goal is to lose weight, I don't recommend Pilates. There is no magic about Pilates that will make you lose weight (though as I said, it may make you lose inches). To lose pounds with Pilates, you must do what you'd do with any exercise - get out of breath and sweat!

Now as you know, to work up a sweat you must move reasonably fast. Move fast when you're just beginning Pilates and you won't be able to maintain that precision and control we talked about. Perform fast Pilates and you may lose some weight, but you won't get the toning and strengthening benefits, and you may even injure yourself - so you'd probably be better off weight training.

You can do Pilates at home or at the gym with no equipment at all, apart from a mat to lie on. However, go to a proper Pilates studio and you'll find a whole range of equipment which can provide faster results as well as making the workout more interesting.

At the core of the Pilates system is the Reformer Bed (see pic on right). It's unique to Pilates, unlike many of the other pieces of equipment. Its pulleys and ropes make it look like an instrument of torture (which it can be, sometimes!), but it's my personal favourite. I thoroughly recommend taking a Reformer class (where each class member has their own bed) if you can find one.

Pilates teachers also use a variety of pieces of small equipment including exercise balls, Therabands, padded cushions and wobble boards.

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All text copyright Marisa Wright. Photo of reformer bed courtesy of Ramer on Flickr. Photo of "Golf Pilates" courtesy of SFSlim on Flicker