How fit are you, really?
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How fit are you, really?

How fit are you, really? Usually, finding the answer requires a time-consuming and expensive test: People run until they're exhausted on a treadmill in a lab, wearing a mask that measures their oxygen consumption. Meanwhile, physiologists measure their peak oxygen intake (also known as VO2 max), the body's top ability to take in and use oxygen. It's perhaps the best measure we have of overall fitness, and one that's closely tied to general cardiovascular health.

Researchers in Norway set out to find an easier way to determine a person's fitness. To start, they brought in more than 4,500 volunteers and had them do the treadmill test, measuring each person's VO2 max. Every volunteer also provided a wide range of other data, including age, height, weight, body measurements, resting heart rate, exercise habits, cholesterol levels, and more. From the peak oxygen intake data, the researchers determined what a standard VO2 max might be for a healthy man or woman at every age, all the way up to 90. They then looked to the other data to figure out what data points best predicted VO2 max so that people could get a good estimate of how fit they were without having to run themselves ragged in the lab.

They found that age, how often and intensely someone works out, the size of the waistline, and the resting heart rate were the best predictors of VO2 max. The Norwegian team built an online calculator anyone can use to find out his or her 'fitness age,' or where the VO2 max falls on that standardized spectrum. (You can try it here.) If you don't like the number you see, the good news is that you can change it: Work out harder or more often or lose a couple inches from your waist, and you can get younger – in fitness years, at least.