Turning 40 was a watershed moment for Alan Lawless. He began to dwell on how "incredibly unfit" he was, began a short-lived stint of hitting the gym and then underwent six weeks of gruelling military-style bootcamp workouts.
Then, the Dubliner took a new test designed to show how well a body is working for its age. If Alan was feeling gloomy about his chronological age, his "fitness age" was even more sobering: he was 48.
"This is not good, because it means I'm not doing what I should for my age," says Alan, a training and development director at Oracle, the American software company.
"I'm 14 stone and not that tall. The doctor told me 'you'll never be a skinny whippet' because I'm stocky.
"I've lost half a stone through a combination of bootcamp and changing my diet, such as eating more fruit. But I have a good stone and a half more to lose. I have a three-year-old daughter and she takes a lot of running-around after. I want to be able to enjoy that."
Staring at the mirror each morning reminds us how our bodies are withstanding the march of time, albeit only on the outside. Finding out how well our bodies are ageing on the inside used to require access to an exercise physiology laboratory. But Norwegian scientists have devised a simple online tool that helps anyone estimate their own fitness age without even moving from the sofa.
Researchers at the Norwegian University of Science and Technology developed the test after evaluating the fitness, weight and health measurements of some 4,600 Norwegians between the ages of 20 and 90. As part of the fitness assessment, each volunteer ran to the point of exhaustion on a treadmill to pinpoint their peak oxygen intake, a measure known as VO2 max that shows how effectively the body is delivering oxygen to its cells.
The data from the study was used to create an algorithm that estimates someone's VO2 max. The online tool then compares that figure with the desirable VO2 max for a healthy person, at every age from 20 to 90, to tabulate a person's fitness age. In one instance, the researchers came across a 70-year-old man who had the VO2 max of a 20-year-old, giving him a fitness age of 20.
The researchers say their online calculator is not scientifically exact but that it provides a useful estimate of cardiorespiratory fitness and, for the perpetually unfit, a wake-up call.
Anyone can take the fitness test without huffing and puffing on a treadmill or stationary bicycle. That's because the Norwegian scientists discovered that just five measurements are required to predict a person's VO2 max and their fitness age, namely their waist circumference, resting heart rate, frequency of exercise, intensity of exercise, age and gender.
This new tool is the single best predictor of current and future health, according to Professor Ulrik Wisloff, the director of the KG Jebsen Centre of Exercise in Medicine at the Norwegian university and the senior author of the study on the formula, published in the journal Medicine and Science in Sports and Exercise.
Stephen Carr agrees. As an army sergeant and instructor with Bootcamp Ireland, he is exceptionally fit. When the 37-year-old took the online test for the Irish Independent, it found he had a fitness age of 17. It also showed his VO2 max score was almost the same as a score from a physical test he took last May.
"I'm a member of the Defence Forces and we have an annual fitness test where we do timed runs over certain distances, so we can track our progress as we pass through our career," Stephen says.
"I was surprised at how accurate this new test was. It was nice to hear I've got a fitness age of 17, though how true that is I don't know. I remember doing a fitness test when I was that age and was a young amateur soccer player, but I didn't pay much attention to the results. My cardiovascular fitness is probably the same as it was when I was in my late 20s. But everyone is more prone to injury as they get older."
When Stephen is testing the fitness of soldiers, he often uses the traditional bleep test, as the 20-metre shuttle-run test is dubbed, to measure their VO2 max. This endurance test involves running continuously between two points that are 20m apart to the pre-recorded sound of beeps played at set intervals. As the test proceeds, the interval between each bleep decreases, compelling an athlete to increase their speed over the course of the test for as long as physically possible.
"VO2 max is an excellent measure of fitness," Stephen says. "You can improve it, but you will get to a level where you'll plateau. A soldier or soccer player who is extremely fit won't see the same dramatic improvements in VO2 max as someone who is sedentary."
This measure of peak oxygen intake typically declines with advancing years, but the fitness clock can be reversed with regular exercise and a healthy diet. A favourable VO2 max for your age is associated with a plethora of health benefits, including better cardiovascular function and a lower risk of heart disease and obesity-related health problems.
Jenny Quinn, a 31-year-old civil servant, filled out the online fitness test at her desk at work, inputting her resting heart rate of 70 and waist circumference of 101cm (39.8in). She discovered she had a fitness age of 37, which she wants to further reduce so she can be fit enough to join the gardai.
"I'm not sure how accurate the test was -- I think a fitness age should be based on more stringent criteria," she says.
Until a few weeks ago, when she went on holidays, Jenny was working out twice a week at bootcamp sessions in Dublin's Phoenix Park. Since she signed up to the workouts two years ago, Jenny has dropped a dress size and completed a 10k run during the summer.
"I had been putting on more and more weight, so I started off doing WeightWatchers and then a little bit of exercise," she said.
"When I joined bootcamp, I couldn't even sprint without getting out of breath within two minutes.
"I'm a lot fitter now and I'll probably use my fitness age results as a barometer to get even fitter in the new year."
Take the test How fit are you?
* Click on this link for the fitness calculator.
* Enter your age and gender, as well as your frequency and intensity of exercise.
* You'll need the circumference of your waistline in centimetres. Wrap a measuring tape around the narrowest part of your middle, at the level of your navel.
* To determine your resting heart rate, sit quietly for 10 to 15 minutes, find your pulse and count it for 30 seconds, using the timer on your phone or watch. Double the resulting number to get your resting heart rate and enter it into the online calculator to figure out your fitness age.