Go riding. It's the new yoga

When I started learning to ride three months ago, I was hoping simply to have fun. I'd always depended on going to the gym and taking yoga lessons for exercise, so the fitness question wasn't uppermost in my mind. Besides, I'd always thought of the horse as the one burning up the calories, not its rider.

However, after my first full-length riding lesson at the Lea Valley Riding Centre near Walthamstow, I went home drenched in sweat and barely able to walk for five days. As the weeks progressed, the muscle pain wore off, all the stiffness I'd recently been experiencing in my hips vanished, my legs became noticeably stronger and my occasional backache ceased. I also began to realise how relaxed and happy I felt after an hour on horseback, and started looking forward to Saturday mornings in a way I hadn't done for years.

Riding has numerous health benefits. It's fantastic for co-ordination, and sitting correctly in the saddle is one of the best ways to stretch your legs and improve bad posture. Moving in time with a horse loosens the lower back and opens up the pelvis, and tuning in with the animal requires a meditative focus that blows stress clean away.

Before horses were replaced by trains, planes and automobiles, doctors ordered convalescing patients to saddle up if they wanted to regain their health. And, although riding is classified as a low-impact exercise along with cycling, walking and weight-training, it's a very effective way of maintaining general fitness and working isolated body parts, particularly for slightly older people.

One of the riders at Lea Valley claims that her asthma has improved since she started keeping her own horse in the stables, while another horseman says that riding was, in combination with various therapeutic measures, fundamental in helping him to recover from multiple sclerosis because the horse's movement requires the rider's body to respond in ways it cannot do on its own.

Lea Valley instructor Denise Corbett believes that the psychological benefits of riding are just as important as the physical, and her lessons have a similar essence to yoga classes with a big emphasis on breathing and relaxing. She stresses that subtle but firm signals are vital to good attunement with the horse, and that control is all a matter of feel.

"People expect riding to be a lazy man's sport," she says. "Or they're just far too physical. But the less aggressive and violent you are, the more a horse will hand itself over to you as its protector. If you let them down, they take themselves back. It's all about learning to relate without using words and learning to balance in a completely different way without using your hands too much." The holistic aspect of riding is surprisingly powerful. Horses are far more aware of a rider's body than the rider is and can read someone's mind and emotions through the subtlest of somatic flickers. They can sense fear and lack of confidence and they won't respond to an unassertive human being.

My biggest learning curve with riding has definitely been about fear and trust. Following a scare from a disgruntled horse one week and my first tumble the next, I felt paralysed and too frightened to canter. But I worked through it by booking three private lessons, and in beginning to learn how to communicate effectively with half a ton of horse, I have learned a valuable lesson about myself which I would never have got from the gym or the yoga studio.

Where to ride in London

Riding is not the most obvious way to keep fit in the capital, but there are a surprising number of schools to choose from, and most group lessons are cheaper than a Pilates session. Lunge lessons, where the instructor holds a special set of reins and the rider has nothing to hold on to, cost the same as normal, private lessons and are particularly good for the body, stretching and lengthening every muscle.

Once you've reached a certain standard you can go hacking and, if you really feel like a break, several companies, such as Equitour (01865 511 642) offer riding holidays in Britain and abroad, although foot-and-mouth disease has closed many bridleways and rural areas until next spring.

For the best tuition, choose a riding school approved by the British Horse Society (01926 707 700). Make sure you have a hat which meets the required standards (some schools hire them out) and a decent pair of boots. Wear soft trousers or chaps if you don't have long boots, as jeans will rub the skin of your legs against the stirrup leathers. Finally, although riding is wonderful for mind and body, it is a risky sport. Horses are unpredictable, so it's wise to be insured before you settle in the saddle.

Lea Valley Riding Centre, 020 8556 2629.Trent Park Riding School, Cockfosters, 020 8363 9005. Ealing Riding School, 020 8992 3803. High Beech Riding School, Epping Forest, 020 8508 8866. Hyde Park Riding Stables, 020 7262 3791.Wimbledon Village Stables, 020 8946 8579. A group lesson will cost around £18-18.50, although Hyde Park charges £34 to learn in a group of five. Private lessons, lasting 30-45 minutes, cost £24.50-£32.50 and lunge lessons cost the same.