All aboard for a flat stomach and a pain-free back

Core-stability exercises hold the key to a well-balanced life. Sam Murphy checks out the methods and muscles involved

You have probably heard of it, but perhaps you are still not sure what it is, or, more importantly, whether you have got any. So, apart from being the latest buzz-word in fitness, what is core stability all about? "The basic idea is that if the abdominals and back are strong, everything else will follow," explains John Brewer, head of the Human Performance Laboratory at Lilles-hall National Sports Centre. "A strong, functional 'core' is believed to protect the spine, enhance posture, minimise the risk of injury and improve sports technique and performance."

But before you head off to the gym in search of core stability, read on. "Core stability has now become something of a marketing term meaning "trunk strength'," says Ben Coffey, a physiotherapist at the West End Physiotherapy Clinic in London. "That's a misconception. In fact, many of the muscles we work in traditional strength-training exercises won't improve core stability at all. For example, a sit-up might strengthen the rectus abdominis, the 'six-pack' muscle, but it won't address existing weakness in the core stabilisers."

In other words, you might have a midriff worthy of Adonis, but it doesn't mean you have got an ounce of core stability. Time for a quick anatomy lesson: the abdominal region has four main muscles. There's the rectus, which runs vertically along the front of the tummy, and acts to flex the trunk. Then there are the internal and external obliques, which run along the sides of the trunk on the diagonal – these serve to rotate the trunk and bend it from side to side. Finally, there's the transversus muscle. This travels horizontally from front to back, rather like a corset. It is this deep-set muscle that provides stability for the trunk.

The key to understanding core stability is acknowledging the role or function of a specific muscle. For example, the rectus is a "prime mover". It gets you from lying to sitting (the getting-out-of-bed muscle). The transversus muscle, however, doesn't have much of a role to play in moving the body. Rather, its role is to stabilise the trunk when other parts of the body move – and to protect the spine. "The stabilising muscles should be recruited first before the 'power' muscles kick in to initiate the movement," explains Coffey. "If the stabilisers don't fire when they should or without sufficient strength, the result is poor technique, potential injury and muscular imbalance."

Little of what we do on a day-to-day basis serves to strengthen the stabilising muscles, however. For example, we sit all day, often with poor posture, or we constantly repeat poorly executed movements, such as running with bad technique. "When the stabilisers lose strength or aren't recruited at the right time, they are no longer able to provide support. Slouching doesn't require any stabilising at all."

So how do we go about strengthening these often weak and lazy stabilising muscles? "True core-stability training needs to be performed with low load, against gravity and with the body in good alignment." says Coffey. "In contrast, most gym-goers are working off-alignment with a high load." But before you can work your core stabilisers, you are going to need to find them. Try this: place your fingers firmly on the inner edge of your hip bones. Now pull your tummy in. Feel the way the muscles "pop out" at you? That's wrong. Now relax, and gently pull in the lower part of the tummy, simultaneously pulling up the pelvic floor. You should be able to feel a more subtle contraction under your fingers. That's the transversus contracting. "Theoretically, the transversus muscle works all day long to stabilise the trunk," says Cherry Baker, whose video The Abdominal Revolution addresses core stability. "But usually, we slouch or get supported by chairs and the muscle doesn't have to do its job. Simply doing more sit-ups isn't the answer, though – the muscle needs to be targeted with specific exercises."

So, which exercises? The first step is simply to repeat the exercise outlined above, in order to get used to locating and recruiting the muscle. Then, progress to holding the contraction for longer, say 10 seconds. Coffey recommends doing the exercise 10 times, twice a day, every day. If you suffer from back pain, you'll be surprised how much difference this can make. "A couple of months of daily exercises is usually what it takes to restore normal function and strength," he says.

As you get the hang of it, the exercise progresses to keeping stable while moving a limb. "Once the transversus becomes stronger and can be recruited more efficiently, the benefits carry over to everyday movements, such as sitting, standing, walking, running and sports," adds Coffey.

But be patient – don't expect results overnight. And while it is possible to learn core-stability exercises from a book or video, it is wise to go to a physiotherapist who can assess your specific weaknesses and show you how to locate the correct muscles. "The majority of people have an imbalance," points out Coffey. Personal trainers are beginning to be more aware of core stability – but beware those who wax lyrical about strengthening the core and then prescribe two dozen sit-ups.

If you can't trust yourself to work on core stability at home, core training is beginning to filter into studio classes. In Reebok's new Core Training class, the core stabilisers are targeted by taking common exercises and sports actions (such as throwing or kicking) on to a round platform which wobbles as you stand on it. "You have to recruit the stabilising muscles even just to step on to the board and remain stable," says Reebok Master Trainer Lorna Malcolm.

You might be wondering why, if it's not going to firm up your six-pack, you should even care about core training. Well, there is some aesthetic payback. "Standing in proper alignment, which involves using your stabilising muscles, usually results in an inch or two height gain," says Coffey. "Improved posture can make you look healthier, younger – and slimmer, too. In particular, the transversus will flatten and pull in the tummy." On top of that, you should reap the benefits of improved sports performance, better posture and less back pain.

The West End Physiotherapy Clinic's Fitness Check will assess your core stability, posture and alignment. The assessment costs £38. Call 020 7734 6263 for an appointment. Reebok Core Training is available at selected Cannons Health Clubs across the UK. Call 080 305050 for details. The Abdominal Revolution video (£14.95, Energy Unlimited) is available by mail order: for details, call 0161 445 3908