How fit do you think you are? According to Dr David Stensel of the School of Sport and Exercise Sciences at Loughborough University, it's difficult to know exactly. Regular exercise - though highly recommended - is only part of the picture. "Genetics plays a big part in fitness too. It's certainly the case that two people of the same age can do the same amount of exercise, but one can be fitter than the other," he says.
What's more, although there is a strong relationship between fitness and health, the two are not synonymous. And, while a bit of exercise might not make much difference to your fitness levels, it can increase your health profile. "The latest advice from the United States is that every adult should accumulate 30 minutes or more of moderate-intensity activity on most if not all days of the week," says Dr Stensel. "This is different from previous advice, which recommended doing three 20-minute periods of continuous exercise each week."
So we challenged five Guardian readers who judged themselves to be reasonably fit and active to undergo a rigorous fitness test. Our guinea pigs included a full-time mother of two who belongs to a health club but rarely gets there, as well as a gym instructor and a personal trainer who keep fit for a living. We took them to the fitness laboratory at Loughborough University, where they were put through their paces to find out exactly how fit and healthy they are - and what the rest of us might learn from their exercise regimes.
Our volunteers started their morning with a questionnaire to make sure they were up for the rigours of what lay ahead - any family history of heart disease, for example, would have ruled them out. Each then gave a blood sample for a cholesterol test, and their blood pressure was measured, as was their height and weight, to work out their body mass index (BMI).
From there it was on to the treadmill for the VO2 max test, which involves checking oxygen output of an exercising individual and the result represents the maximum amount of oxygen the body can use in a minute. The greater the amount of oxygen your body is able to use during a strenuous exercise test, the better; the higher the figure recorded in the test, the fitter the individual concerned.
In order to measure the expired oxygen, each of our volunteers had to run for between 10 and 12 minutes, working from a gentle jog to a heavy pound up a big incline. The grading of the incline was changed every three minutes - so what started out as an easy run on flat ground soon became an uphill struggle. To make it even harder, each was required periodically to breathe, while running, into a mouthpiece so that their expired air could be collected in a bag for laboratory analysis. The reason the test is called a VO2 max is that it takes participants to their maximum physical ability - they run on, at a steeper and steeper incline, until they can run no more. At this point, they are unable to make use of further oxygen to run faster: they have reached the limit of their fitness.
Name: Richard Hart
Lives: Oxford. Married to Jane and father of Ellie, 15, and 12-year-old Jo
Fitness regime: "I'd like to do more exercise, but I'm certainly doing more now than I did when the children were young. I play football and rugby each week, I walk the dog every day and I go for at least one longish run on one of the other days. My daughter Jo is keen on running, so we've started training together; when she goes to the circuit, instead of just waiting for her I've started taking my kit and running as well. Doing sport with my children has been a big incentive to take it up again in the last five years or so: I find I'm happier when I'm exercising regularly. It's quite a sociable thing to go for a run with your children."
Body Mass Index: 26.88
Blood pressure: 125/80
VO2 max: 48.37
Dr Stensel says: "Richard's BMI is high, but that probably reflects a high muscle mass rather than excess fat. His results are impressive and demonstrate that you can still be fit as you get older if you maintain an exercise regime. And rather than watching your children exercise, you should join in whenever you can - it has certainly paid off in Richard's case."
Richard says: "The lab result was much better than I thought. I know I'm not exactly a couch potato, but I don't feel I devote an exorbitant amount of time to exercise. I think my fitness is down to running and to walking the dog, because that's something you always have to do, no excuses. I didn't know I had low cholesterol, so that's an extra boost - but we do eat lots of vegetables, and I try to watch my fat intake."
Moral: Even if you have had a period when you've not done much exercise - such as when your kids were small - taking it up again can reap big benefits. And if you have got older children, exercising with them provides a great incentive for them as well as for you: studies show youngsters who have active parents are more likely to take fitness seriously as they get older.
Name: Katharine Casey
Occupation: Full-time mum to Lili, 16 months, and seven-year-old Daniel
Fitness regime: "I've been a member of a gym for the last two years, and I think I've been there about five times. I'd love to do more exercise but it's really hard when you've got young children. I did exercise more in the past, and after Daniel was born I went back to my gym regime. But since Lili came on the scene, most of my energy is devoted to looking after the children - and I do feel as though I'm on the go the whole time. I try to use the car as little as possible, so we walk most places, and I do a bit of cycling."
Blood pressure: 115/60
VO2 max: 41.74
Dr Stensel says: "Katharine is well within the normal range for her BMI, and her blood pressure and cholesterol are both low. Her VO2 max score puts her in the top 10% of women in her age group, which is very impressive considering she doesn't do any formal regular exercise. What her fitness level shows is that you can stay fit and healthy by incorporating exercise into your daily regime rather than going to the gym."
Katharine says: "I'm delighted at the result. My friends said I had to prove it to all of us that pram-pushing and bringing up young children keeps you as fit as going to the gym every day. I certainly feel I live a very active life, and this proves there are real benefits to using the chances that come along to burn off energy."
Moral: Don't underestimate the amount of exercise you can work into your normal daily routine, particularly if you have young children. Look at your life and try to find as many opportunities as possible to build exercise into your day.
Name: Wendy Powell
Occupation: Personal trainer - runs her own company called No More Excuses!
Lives: Hindhead, Surrey
Fitness regime: I spent about 10 years working in advertising and lived a very unhealthy lifestyle. I drank too much, I smoked, and I didn't do any exercise. When I was made redundant a couple of years ago, I decided to turn my life around: I took up exercise in a big way, and then took it up professionally, as a personal trainer. I had never been sporty in my life, but I took up running and weight training. I watch what I eat, and have lots of wholefoods and vegetables."
Blood pressure: 126/65
Total cholesterol: 5.40
VO2 max: 46.98
Dr Stensel says: Wendy's BMI is on the bottom end of the normal range, and her blood pressure is fine. Her VO2 max puts her well within the top 10% of people for her age group - it would have been very interesting to have put her through these tests two years ago, before she changed her lifestyle, because I think we'd have got very different results. Her fitness is good, and what her case proves is that you can turn your life around relatively quickly when you're still in your early 30s. The only problem for Wendy is her cholesterol, which is high - it should be no higher than 5.2. Cholesterol is strongly influenced by genes, so it could be that Wendy has a genetic propensity to a high reading - and unfortunately exercise often has only a marginal effect on cholesterol levels. Reducing her level of saturated fats should help. Most experts recommend that these fats should supply no more than 10% of your energy intake."
Wendy says: "I do eat full-fat milk and butter, mostly because I'd rather know what the ingredients are in my food, and I don't like additive-filled margarines. But maybe I should think about cutting back on fats. I'm pleased that my VO2 max test was so good - obviously in a job like mine I do get opportunities to exercise and that helps a lot."
Moral: You can turn your life around if you're determined enough. But don't make the mistake of assuming that if you're lean and doing a lot of exercise, you won't have high cholesterol levels.
Name: Tracy Effard
Occupation: Media consultant
Lives: Jarrow, Tyne and Wear
Fitness regime: "I've always been keen on sport, but I've increased the amount of exercise I do over the last couple of years because I really want to avoid middle-age spread and reduced energy levels. I enjoy running best, and I also go to cardiovascular class once a week. I suppose I do four or five exercise sessions each week, and I am quite into nutrition as well. I feel better when I've exercised. It helps my mood to have been out for a run: I have a better day and I feel I reap the benefits throughout the whole day."
Blood pressure: 128/60
VO2 max: 41.94
Dr Stensel says: "Tracy's VO2 max results show that she, too, is in the top 10% for her age group. Her BMI is well within the normal range, her blood pressure is low and she has avoided the weight gain that occur in most people from the mid-20s onwards. Her cholesterol, though, is high, so like Wendy she might think about cutting out some saturated fats. But she's a very fit person, and there's some evidence that lots of exercise has a counter-effect on the damage that high cholesterol can do to your arteries. Firstly, exercise often increases HDL cholesterol (sometimes termed 'good' cholesterol) which is thought to be involved in a process called 'reverse cholesterol transport'. This helps reduce the amount of cholesterol that is deposited on artery walls. Secondly, exercise improves the ability of arteries to vasodilate - open up - when necessary, so enhancing blood flow and oxygen flow which in turn reduces the risk of a heart attack."
Tracy says: "I'm pleased with my VO2 max result, and I might try cutting down on saturated fats. I don't know whether I've a genetic predisposition to high cholesterol."
Moral: Upping the amount of exercise you do around the age of 40 is a sensible step - there's nothing inevitable about middle-age spread, but you do have to work at staying slim and fit.
Name: Jim Faulkner
Occupation: Fitness manager at Esporta gym in Stafford
Fitness regime: "I've always been keen on sport - I was a county footballer and I've also run for Warwickshire. I now work in the fitness business - I teach rowing classes and spinning each week. I play football each Sunday morning for a local pub team, and I train whenever I can fit it in - obviously it's not too difficult as I work at a gym. I reckon I'm pretty fit, and I can't imagine a time when I won't work out. It gives me a lot of energy. My diet goes a bit pear-shaped sometimes, and I do end up having curries with the lads at weekends."
Blood pressure: 120/86
VO2 max: 66.12
Dr Stensel says: "Jim is very fit - he's easily in the top 10% of people in his age group. I'd say his high fitness profile almost cetainly reflects a combined effect of genes and activity. The fittest people tend to be people who have a strong genetic makeup and then are very enthusiastic and train a lot - it's that combination of genes and talent and training that makes great athletes. If you enjoy exercise and do a lot when you're young, there's more chance you'll carry on throughout your life. And it's important that Jim continues to exercise regularly if he wishes to stay as fit as he is now - some studies have shown that being active and fit when you're young does not provide protection from heart disease unless it's continued until middle age and beyond."
Jim says: "I'm pleased with my VO2 max test - fitness is really important to me and I love working out."
Moral: If you do plenty of exercise while you're younger you're almost certainly going to be very fit and healthy. But to maximise the benefits long term, you need to continue your regime on into the future.
The technical bit
Body mass index is calculated by taking a person's weight in kg and dividing it by their height, in metres, squared. Anything with the 18-25 range would be described as normal, while 25-30 is overweight and 30 plus is obese.
Blood pressure is measured in mm Hg. Normal blood pressure is 120/80; a reading of more than 140/90 is considered hypertensive.
Cholesterol is measured in mmol/L. Anything under 5.2 is thought to be healthy.
VO2 max is a test that involves checking oxygen output of an exercising individual during a very heavy exercise test. It shows you how much oxygen that person's body is capable of using in a minute - the higher the figure, the fitter the person is. The value given represents millilitres of oxygen per kilogram body weight per minute.