They grouped the people by fitness, from those who were in the bottom quarter of fitness, to those who were below average, above average or highly fit, essentially in the top 25 percent of fitness.

The researchers also marked off a small group in the top 2 percent or so of endurance and categorized them as having “elite” fitness.

Then the researchers checked death records for the decade after people had completed their stress tests.

They found that some of the men and women had died and also that there strong correlations between fitness and mortality.

The greater someone’s fitness, the less likely he or she was to have died prematurely and vice versa, the numbers showed.

This correlation held true at every level of fitness, the researchers found. People with the lowest fitness were more likely to die early than those with below-average fitness, while those with high fitness lived longer than those whose fitness was above average.

Even at the loftiest reaches of endurance, the advantage held, the data showed. The 2 percent of the people with elite fitness lived longer than those with high fitness and were about 80 percent less likely to die prematurely than the men and women with the lowest endurance.