SCIENCE: Why Do Some People Get Fitter Than Others?

Studies indicate, unsurprisingly, that genetics must be involved, since a particularly high or low response to exercise tends to run in families. But less has been known about which genes might be involved, and how those genes actually increase or blunt the body’s response.

Now a new study in rats adds to a growing body of data about how and why bodies respond so differently to exercise. In the study, rats with a particular set of genes responded robustly to exercise, becoming much more fit after a few weeks of running, while rats born with other genes gained little cardiovascular benefit from the same exercise program, apparently because their heart muscles didn’t react as expected.

The results raise questions about whether people who remain stubbornly unfit, no matter how diligently they work out, might want to rethink their exercise routines.

I’m going to go out on a limb here and say yes.