As of Monday, the United States has new federal physical-activity guidelines. The new guidelines, which represent a scientific consensus about how much and what types of physical activities we should complete for good health, bear a strong resemblance to the existing, 10-year-old governmental recommendations. But they also feature some important updates and expansions, including the first-ever federal activity parameters for 3-year-olds, as well as a few surprising omissions.

And they offer a subtle, admonitory reminder that a substantial majority of us are not moving nearly as much as we should.

The idea that the government might suggest how much we need to exercise is relatively new. The first federal exercise recommendations were released in 2008, after several years of scientific background study.