All work and no play makes Jack a dull boy. But it's not often your boss tells you so. It may come as a shock that the Government and businesses are encouraging workers to take a stroll, have a stretch and put their feet up.

January is usually a masochistic month, when we wake up after the festive season and decide to do something about our slothful bodies. But not this year, it seems. In a survey by Canon of 1,500 office workers, only one in 20 said they would join a gym this year, while one in five were planning to do no exercise at all. Once upon a time this was between us and our girdles; not any more.

In October, the Department for Work and Pensions published a report on health and well-being in the workplace. It estimated that sickness costs Britain £12bn a year, and 40 million lost working days. The correct light exercise can do a lot about that, helping beat stress and depression, and fending off occupational health problems like repetitive strain injury. And keeping fit helps to get the best out of your working day, too. Which is why the boss is paying so much attention to your bulge.

Lucky souls working for the top companies in the UK can already expect a wellness programme arranged by management to help them look after their health. Goldman Sachs launched its award-winning programme in the late 1990s as a recruitment draw. At their offices in Fleet Street they have a range of services, including a gym, professional health team, recreation team, children's centre and regular seminars on keeping fit. "These are building blocks to help people lead a healthy, balanced lifestyle," says Neil Snowball, global head of wellness at Goldman Sachs. "A healthy workforce is a more productive workforce."

For most of us, though, a gym at the office is a distant dream, and busy schedules, or laziness, makes a run after work unattractive. "When you're fitter, you feel better, and you're more able to concentrate in the office, but not everyone can get to the gym," says David Smith, marketing director at Canon. "We wanted to look at what people can do at work to improve their health." They consulted physiotherapist Amanda Ursell, who drew up an exercise agenda for the office, the Alternative Office Workout.

Ursell found that even just taking the stairs, meeting colleagues instead of e-mailing them, and going to get a round of teas once a day can help you keep fit and focused, and burn up nearly 400 calories a day (the equivalent of a light brunch).

Keeping moving is not just a way of keeping trim; it is also important to ward off the blight of the modern office worker, repetitive strain injury (RSI), which affects more than a million of us every year. Long hours in front of the computer as a web journalist left Richard Ayers with crippling upper body pain. "My grip opening jars was like an old woman's," he says. "I thought, I'm 30, I shouldn't have this." Ayers was diagnosed with RSI and referred to a physiotherapist, who taught him that it is easy to avoid RSI with the right exercises. "It's all about stopping the problem before it starts, not just when the aches start," he says. Now Ayer treats RSI like a sporting injury, warming up before he goes to work and through the day with neck, arm and back stretches.

Bronwyn Clifford is a physiotherapist who runs London company Physio at Work. She treated Ayers, and says stretching at your desk is always a good idea, but most important is to keep moving. "The main thing is to walk around," she says. "Your body likes movement and keeping active, otherwise muscles weaken and stretch, and getting your blood pumping releases endorphins and helps stress."

Clifford reckons you should be up from your desk at least every hour. "Anything that takes your body out of a static posture is good," she says. "People complain about those who put their feet on the desk, but it's good for you to change your posture."

So the next time the boss takes you to task for slacking off or popping out for a ciggie, put your feet up and remind them that a little play does Jack a lot of good.

The Alternative Office Workout is at: