Compared to our lissome forebears, we are fat, we are unfit and we are downright lazy. The onslaught of statistics about our slide into sloth makes depressing reading, with everything from television to public transport blamed.

Yet a recent study of working adults from the British Heart Foundation suggests that inactivity and its side-effects are less a product of indolence than the fact that some people are so busy trying to stay on the professional treadmill, they don’t have time to work out on a real one. More than half of those surveyed thought work was the principal culprit in preventing them taking up exercise.

This is familiar territory for teachers. In a survey of primary staff carried out by the Association of Teachers and Lecturers last year, 86 per cent felt there were not enough hours in the day to get their jobs done properly. The implications for regular exercise are obvious.

We all know we should take more exercise. We are told continuously that it would transform our lives, helping us cope with stress, boost vitality and gain self-confidence and a sense of achievement. If your body looks better, the argument goes, then everything else falls into place.

But how do you manage to fit this in if, as the ATL found, you’re already burning the midnight oil? First, remember that you don’t need to find a huge window in your diary - 20 to 30 minutes three or four times a week are all it takes. You can slot them into the working day, or tag them on at either end. Here are some suggestions.

Make use of your routines There are things you do every day and barely think about. Introduce exercise as something that is a much of a habit as, say, cleaning your teeth. That way, you don’t have to think about doing it or work yourself up to it. Irregular exercisers constantly have to re-motivate themselves to start up again. Scheduling it at regular times will also help.

Regard exercise as an ally not an enemy If the thought of a jog round the block fills you with dread, it’s going to take up far more time than it should, if only because you’ll spend ages finding 101 reasons for not pulling on your trainers. Instead, focus on the sense of well-being you will feel after the run, rather than your discomfort during it. It’s like jabbing a sharp stick in your eye - lovely when it stops. Alternatively, you could make exercise revolve around a social event.

You can exercise at work Unless you are a PE teacher, that might seem difficult, but there are exercises that can be done anywhere, anytime. Stretching, for example, reduces stress and fatigue, fosters mental alertness, improves circulation and flexibility and prepares the body for other physical activity - and you don’t need to change into a tracksuit to do it. There is also excellent exercise potential in everyday activities: power walk round the campus instead of ambling, for example; climb stairs vigorously. It will all help far more than you think.

Use your journey to or from work Walking, cycling or running are ideal ways to increase fitness at a time when you would otherwise be sitting in traffic. The biggest difficulty is what to do with your clothes and the piles of paperwork you routinely transport between home and work. A running rucksack or cycle panniers may be the answer. See if a colleague who lives nearby could transport your gear to school while you run. If you travel by public transport, get off at an earlier stop.

Don’t waste time off Lunch periods should be the perfect opportunity to get away, but for many it is taken up with meetings and administration instead. That could be set to change. The Government has recognised the importance of exercise in its “Healthy Teachers Healthy Schools” initiative in which it encourages schools to make sure there are opportunities for staff to exercise in the middle of the day. In the evenings, if your normal routine is to cart home a bag full of work, try a swim, run or gym session before you start. Pitch into the evening work immediately afterwards. Or just tag exercise on after the last session of the day. No more work to be done after this point! It makes a boundary between work and relaxation, and stops work encroaching into what should be your free time.

Set yourself targets Teachers have probably heard too much about targets, but exercise benefits from having a few. The choice of target will depend on you and your current level of fitness - it should be challenging but achievable. But beware of setting timescales that are too ambitious. You don’t want to injure yourself. If in any doubt you should check with a qualified instructor. A weekly increase in activity of about 10 per cent is often suggested as a balanced one.

Other factors, such as family circumstances, are bound to have a bearing on individual exercise programmes, but don’t let them become reasons for abandoning one altogether. With a little creativity and commitment anyone can become fitter, however demanding their schedule.

THE KEEP-FIT CURRICULUM

* Vary your exercise to achieve a balance of the three main ingredients of physical fitness: strength, flexibility and cardiovascular efficiency. Some forms of exercise emphasise one at the expense of others. Running, for example, develops heart, lungs and lower body strength but neglects the upper body and limits flexibility. Yoga is great for flexibility but limited in respect of the cardiovascular system.

* To benefit your heart, aim to exercise for 15 to 30 minutes three or four times a week at a level which causes you to breathe more heavily.

* All exercise burns calories, but focusing too closely on the bathroom scales can be frustrating. Much of the immediate weight loss from strenuous exercise is in the form of water and depletion of the muscles’ glycogen stores, both of which have to be replaced.

* To lose a pound in weight requires expenditure of 3,500 to 4,000 calories, and because of changes in the proportion of muscle to fat, some people may find their weight increases in the early stages of an exercise programme. Don’t be discouraged. You will start to look slimmer and feel better.

* You will use almost as many calories walking a mile as running a mile. However, more intensive exercise raises your metabolism for several hours afterwards which means you continue burning calories at a higher rate.

* Activities in which you are supporting your own body weight help to maintain bone strength - particularly important as we grow older.

* If you need others around you to provide motivation, then join a group, class or gym. But if you are happy to work alone you may cut out the time spent making arrangements and travelling. Many solitary exercisers claim that work problems fall into place and new ideas emerge while they are working out alone.

* If you are overweight, have been inactive for a long time or have any history of heart trouble, talk to your GP before starting an exercise programme.