Ms Keohane may be more dedicated than most, but the question of how to remain fit while doing a demanding and stressful job is a familiar one for many teachers. All too often, ideas about "getting fit" bring images of expensive and intimidating gyms, Olympian training regimes and teeth-grindingly physical pain. But when the Government says it wants 70 per cent of the population to be more physically active by 2020, is that what it means?
What is fitness?
Fitness and health are often lumped together and are easily confused.
Clearly, they are related, but they are not the same thing. Whereas health is a broad concept concerned with freedom from disease, and mental and spiritual wellbeing, fitness is more specifically about the body's capacity to do physical work - how far we can swim at a certain speed, for example, or how many stairs we can climb before getting tired. Usually, the fitter you are, the more likely you are to be healthy, but not always - a top-class athlete may be very fit, for example, but could also suffer from a serious illness, such as anorexia.
Physical fitness can be broken down into components, including endurance, strength, speed, flexibility and power. All of these come into play, to a greater or lesser degree, depending on the type of work you're doing, and all can be improved by specific activities or exercises. The ideal is a balanced range of exercise that improves every aspect of fitness.
Most importantly, fitness is a relative term. No one is simply fit or unfit, only fit or unfit for specific activities. The important question is not "What should I do to get fit?", but "What do I want to be fit for?"
Fitness to teach
The minimum level of physical fitness anyone needs is that necessary to carry on their normal daily lives, in particular to do their job. Teaching is one of the few professions in which employers have a specific duty not to employ someone "if he or she does not have the health and mental and physical capacity for the employment". The DfES Fitness to Teach regulations recognise that "teachers need a high standard of physical and mental health... as teaching is a demanding career".
So how fit are we?
In short, not very. The Allied Dunbar National Fitness (ADNF) survey, carried out in 1992, found that 70 per cent of men and 80 per cent of women did too little exercise to benefit their health. And a 1998 health survey of England showed that only 37 per cent men and 25 per cent of women were meeting exercise guidelines (see "So how active should we be?"). It also found that 22 per cent of men and 26 per cent of women lived almost completely sedentary lives, and more than one adult in three did less than 30 minutes of moderate exercise a week.
Inevitably, such inactivity affects fitness levels - the ADNF survey found that almost one in three men and two in three women could not walk up a moderate slope at three miles an hour. Because their knees were too weak, more than half of women aged between 55 and 65, and a third of men between 65 and 74 had difficulty getting out of a chair unaided.
Does it matter?
Yes, if you want to be physically and psychologically healthy. The World Health Organisation said in 2002 that "a sedentary lifestyle is one of 10 leading global causes of death and disability. More than two million deaths each year are attributable to physical inactivity". Inactivity is on a par with smoking, high blood pressure and high cholesterol as a risk factor for coronary heart disease (CHD) and stroke. The Health Development Agency says physical inactivity doubles the risk of CHD and triples the risk of stroke; 37 per cent of CHD cases are attributed to inactivity.
Physical exercise, on the other hand, reduces the chance of both, and helps prevent the other risk factors. Exercise can also help to prevent osteoporosis, non-insulin-dependent diabetes, overweight and obesity, stress, anxiety and mild depression, and it can reduce the risk of colon cancer by around 40 per cent. Being active can raise self-esteem and confidence, and it benefits society - a rise in physical activity could save the economy an estimated pound;2 billion in health costs and lost productivity. It is estimated that 9 per cent of CHD could be avoided if physical activity was increased, potentially saving the NHS pound;144 million.
But we are an increasingly inactive society. The 2001 National Travel Survey showed that the average distance we walk each year has fallen from 255 miles in the mid-1970s to 186 at the end of the 1990s. The average distance cycled has also fallen, from 51 to 38 miles.
So how active should we be?
Physical activity can be considered in terms of frequency, intensity, duration and type. The Department of Health here, and the American College of Sports Medicine in the United States, recommend that adults do at least 30 minutes of moderate physical activity on five or more days a week. That might sound a lot, but "moderate" activity is the equivalent of a brisk walk, not a session in the gym or the pool. As a rough guide, moderate activity should raise your heart rate and breathing slightly as you burn calories to power your muscles, but you should still be able to hold a conversation.
Also, the activity doesn't have to be continuous - you can do it in bouts of 10 or 15 minutes throughout the day and the health benefit will be the same. Indeed, experts recommend regular mild to moderate exercise for a more healthy lifestyle, rather than less frequent, more vigorous activity.
It's certainly better than an infrequent burst of enthusiasm at your local fitness club once every six months.
Again, how much activity you need to get fit, and what sort, depends on what you want to achieve - what you want to be fit for. As Dr Andy Smith, head of the school of sport science and psychology at York St John College, puts it: "Instead of asking how much exercise is good for us, should we be asking how little we can get away with?" The bottom line is that any physical activity is better than none. "Given the huge societal and cultural influences that have stopped us from moving, any physical activity is a health gain," he says. "There is no magic amount of exercise you need to do to get a benefit, the key is to make an effort and persevere. As soon as you move, you win."
What sort of exercise?
The ADNF survey found that 37 per cent of women and 24 per cent of men did no exercise because they didn't consider themselves "sporty types". But "getting fit" is not just about going to a gym and flogging yourself on treadmills and weights machines, although that could be part of it. There are innumerable types of exercise, all with their own benefits and drawbacks, from structured activities (playing sports such as football, tennis and golf, or going to a yoga class), to routine (gardening, using the stairs, walking to school); and from spontaneous (walking, jogging), to planned (cycling, swimming, dancing).
Jeanette Hughes is chair of the Keep Fit Association, the national governing body for movement, exercise and dance. "There is a physical activity out there to suit everybody," she says. "It is not just about the gym. It could be walking the dog, doing salsa, abseiling, or swimming; everyone can find something."
Different types of exercise benefit different components of fitness.
Jogging or cycling help aerobic endurance, weight training builds strength, yoga and Pilates aid flexibility and co-ordination, and so on. Even going clubbing can be beneficial, says Ms Hughes - although, she points out, there are obvious health downsides to certain aspects of the clubbing lifestyle.
"It's all about balance," she says. "Everything in moderation."
But I just don't have the time
For many people, the thought of finding 30 minutes to exercise every day seems impossible. But it doesn't have to be. Jeanette Hughes echoes other experts in recommending simply building more physical activity into your daily routine. "I'd like to see teachers leaving the car at home and walking or cycling to school," she says. "Take the stairs rather than the lift, and go for a walk at lunchtime rather than sit in the staffroom. I'd welcome playground duty just to get out."
There are things you can do at home, too. Stop using your remote control, walk to the shop, or park your car in the furthest bay from the supermarket, hang up washing rather than use the tumble drier, or do the housework more vigorously. Making time is also about making priorities.
According to a survey from the Department of Trade and Industry, UK adults spend an average of 20 hours a week watching television, yet more than half say they would play more sport or take up a new physical activity if they had more time.
How should I start?
Slowly. "Just go for a walk," says Ms Hughes. "Once you get used to that, extend the walk, or do the same distance but walk a bit quicker. The important thing is to get started."
Motivation is important too, so find an activity you enjoy. Try doing something with a friend, do it to music, or in a pleasant environment (a park, by a river), wear comfortable clothes, and vary what you do so you don't get bored. Avoid activities that are intimidating: gyms and competitive sports don't suit everyone. And don't be put off when you get tired. If you exercise regularly you'll get fatigued less quickly. Most of all, be positive: don't focus on what you haven't done but what you have achieved.
Shouldn't it hurt?
Not really. "That 'no pain, no gain' stuff is rubbish," says Ms Hughes. "If it's too difficult to begin with, you will just give up. Start with what's comfortable and work up gradually. You should begin to feel your heart rate quicken and your lungs working, but not feel under strain. Whatever your ultimate aim, even if it's to run a marathon, always build up gradually, so you're aiming to achieve what you want comfortably and safely."
Warming up and cooling down are important too. Don't start at full intensity, but begin more leisurely and increase the work rate slowly.
Before jogging, for example, you might walk for a while, loosen your shoulders, and do some stretching. Do the same at the end to let your body cool down.
What about food and water?
Exercise requires energy, which comes from food. The preferred fuel for muscles is glucose, which comes from carbohydrates. Glucose is stored in the muscles as glycogen, but it burns relatively quickly, and when you run out of it, fatigue sets in. The longer you exercise, and the more intense the activity, the more quickly you use it up. Put simply, the more exercise you do (that is, the fitter you get) the more you should have a diet rich in carbohydrates.
Fluid is also vital. Exercise makes you sweat to keep cool, and that water needs replacing. Again, the best policy is to stay well-hydrated by drinking before, during and after exercise. How much you need depends on how much you lose, but an expert tip is to drink at least a third of a litre 15 minutes before exercise, and at least half a litre afterwards.
Can teaching make you unfit?
Many teachers complain of aching backs from being on their feet all day, bending over pupils' desks and carrying bags full of books. Primary teachers can suffer from sitting on small chairs, reception and infant teachers from knee problems, and all teachers feel the effects of long stressful days. Any exercise can help with stress, especially if you can find time to do it at the end of the day. But relatively simple exercises can help with specific problems.
For lower back aches, for example, you can work on your core stability, strengthening your inner stomach muscles (known as the transversus muscles), which work together with your pelvis and diaphragm to hold the base of your spine. You don't need to do sit-ups or crunches, simply pull your belly button in towards your spine before bending down. It's a gentle exercise and you can do it anywhere - at home, in the classroom, sitting, standing and lying down. Core stability can also help with your breathing and voice projection, and gently easing your shoulder blades back can improve posture.
Similarly, exercise that involves impact - walking up stairs, for example - can strengthen joints and prevent osteoporosis, which is important for older people and women in particular.
What can schools do?
In some ways, teachers have an advantage over other employees in that schools tend to have facilities where staff can exercise - a sports hall or gym, or simply the space of a playground or playing field. And they have each other; for many people "getting active" is easier if someone else is doing it too.
The Keep Fit Association has more than 1,000 fitness teachers across England who take exercise classes - ranging from pure fitness sessions to movement and dance - usually in "community-based" venues such as church halls and colleges. Schools can contact their local KFA branch (there are 66 - see resources) to arrange a lunchtime or after-school session.
Last year, the British Heart Foundation produced a Workplace Health Activity Toolkit to promote physical activity at work. It encourages employers to appoint an activity "champion", suggests how employees can improve their fitness in and around the working day, and includes fitness resources and contacts.
Fit body, fit mind
The benefits of exercise aren't only physical. Fifty-four-year-old Ian Holland, head of the upper school at Weybridge comprehensive, started running in the mid-1970s and has been doing it ever since. This year he entered the London Marathon for the first time. "A teacher's lifestyle is stressful enough," he says. "But the fitter you are physically, the more alert you are mentally."
Like Mr Holland, 49-year-old Cath Keohane believes being physically fit is vital for her job. But it's important to her personally, too. "Teaching is such a stressful occupation that I have to find something to empty my mind," she says. "When I exercise, it's my time; I don't have to think about the school or the children. Afterwards, I always feel like I've done something for me."
Additional research: Sarah Jenkins
Next week: Noise