Gretchen Reynolds, our Your Move columnist, explains that the calculator measures your “fitness age.” Fitness age is a well-studied scientific concept that uses a few simple health measures to ...

Plug this information into an online calculator and you can see right away if you’re biologically older or younger than your birth years. The idea that we have a “fitness age,” distinct from our ...

This led to the development of a ‘fitness calculator’ in 2013 that took all these factors into account to calculate someone’s fitness age. Other fitness calculators have been invented since ...