A new study of fitness and lifespan suggests that a person's so-called fitness age – determined primarily by a measure of cardiovascular endurance – is a better predictor of longevity than chronological age. The good news is that unlike your actual age, your fitness age can decrease.

The concept of fitness age has been developed by researchers at the Norwegian University of Science and Technology in Trondheim, who have studied fitness and how it relates to wellness for years.

Fitness age is determined primarily by your VO2max, which is a measure of your body's ability to take in and utilise oxygen. VO2max indicates your current cardiovascular endurance.

It also can be used to compare your fitness with that of other people of the same age, providing you, in the process, with a personal fitness age. If your VO2max is below average for your age group, then your fitness age is older than your actual age. But if you compare well, you can actually turn back the clock to a younger fitness age. That means a 50-year-old man conceivably could have a fitness age between 30 and 75, depending on his VO2max.

Knowing your fitness age could be instructive and perhaps sobering, but it also necessitates knowing your VO2max first, which few of us do. Precise measurement of aerobic capacity requires high-tech treadmill testing.

To work around that problem, the Norwegian scientists decided several years ago to develop an easy method for estimating VO2max. They recruited almost 5,000 Norwegians between the ages of 20 and 90, measured their aerobic capacity with treadmill testing and also checked a variety of health parameters, including waist circumference, heart rate and exercise habits.

They then determined that those parametres could, if plugged into an algorithm, provide a very close approximation of someone's VO2max.

But while fitness age may give you bragging rights about your youthful vigour, the real question is whether it is a meaningful measurement in terms of longevity. Will having a younger fitness age add years to your life? Does an advanced fitness age mean you will die sooner?

The original Norwegian data did not show any direct correlation between fitness age and a longer life.

But in a new study, which was published in June in Medicine & Science in Sports & Exercise, the scientists turned to a large trove of data about more than 55,000 Norwegian adults who had completed extensive health questionnaires beginning in the 1980s. The scientists used the volunteers' answers to estimate each person's VO2max and fitness age.

Then they checked death records.

It turned out that people whose calculated VO2max was 85 per cent or more below the average for their age - meaning that their fitness age was significantly above their chronological years - had an 82 per cent higher risk of dying prematurely than those whose fitness age was the same as or more youthful than their actual age. According to the study's authors, the results suggest that fitness age may predict a person's risk of early death better than some traditional risk factors like being overweight, having high cholesterol levels or blood pressure, and smoking.

Of perhaps even greater immediate interest, the scientists used the data from this new study to refine and expand an online calculator for determining fitness age. An updated version went live this month. it asks only a few simple questions, including your age, gender, waist size and exercise routine, before providing you with your current fitness age. (I discovered my own fitness age is 15 years younger than my chronological age - a good number but still not as low as I could wish.)

Thankfully, fitness age can be altered, said Ulrik Wisloff, professor at the K.G. Jebsen Center for Exercise in Medicine at The Norwegian University of Science and Technology, who led the study. His advice if your fitness age exceeds your chronological years or is not as low as you would like? "Just exercise."

Dr. Wisloff and his colleagues offer free exercise suggestions on their website. But he said almost any type and amount of exercise should help to increase your VO2max and lower your fitness age, potentially increasing your lifespan.

In upcoming studies, he added, he and his colleagues will directly compare how well fitness age stacks up against other, more established measures of mortality risk, like the Framingham Risk Calculator (which does not include exercise habits among its variables). They also hope to expand their studies to include more types of participants, since adult Norwegians may not be representative of all of the world's population.

But even in advance of this additional data, there is no harm in learning and lowering your fitness age, Dr. Wisloff advised. "There is a huge benefit," he said, "larger than any known medical treatment, in improving your fitness level to what is expected for your age group or, even better, to above it."

New York Times