This is a nation of goose-necked children hunched over their electronics in front of a TV. They will turn into goose-necked adults with vitamin D deficiencies, the result of spending their sunny hours downloading songs in darkened rooms. Obesity will plague many of them.

Clearly, America would do better health-wise (and health-care-spending-wise) if people went outdoors once in a while and moved themselves. But how does one do so in a society that has engineered exercise out of even opening a garage door?

Some grown-ups do have the gumption to maintain formal exercise programs, but not many. The health-club business assumes that a third or more of those who join in a burst of enthusiasm will be gone in a year.

Home fitness equipment gets converted into racks for extra shirts or folded towels. Shiny machines rapidly become drab. The owner thinks, “I really should jump on the treadmill, but oooh, my apps need updating.”

When exercise becomes a byproduct of doing something else — getting to work, mowing a lawn or picking up a quart of milk — that’s when it becomes a reliable fitness tool. Those who commute by bus know that whatever little else they do that day, they will get in that walk to the stop.

Play is supposed to be the daily work of children. That used to mean getting thrown out of the house and being told to be back by dinner. But parents don’t push their kids into the neighborhood as they once did. One reason is fear, much exaggerated, of strangers harming their little ones.

A more serious problem is the utterly car-oriented design of many, especially newer, neighborhoods. Children would have to cross wide streets and often in front of harassed drivers who regard pedestrians as a wrench in their busy schedule.

But real or imagined, these concerns are not all that’s keeping children indoors and glued to video. After all, a drive through most suburban neighborhoods will reveal fenced backyards with swing sets and no children on them. A sports reporter friend notes the many empty baseball fields he passes on perfect afternoons. If adults don’t organize the sports, the kids don’t play them.

The plain truth is that free-form play out in nature is no longer part of many children’s lives — or their parents’. And children do love their electronics, in part, because they want to be like Mom and Dad. That’s why laptops, cell phones and digital cameras are among the top-selling toys, even for preschoolers.

Walking or biking to school used to be part of an American childhood. But parents now drive their kids to even close-by schools. Forty years ago, 90 percent of children living within a mile of school biked or walked there. Now less than half do.

Many communities ruined the prospect of students’ getting to school on their own power by building mega-schools far from the more densely settled areas. Six-lane roads often cut the schools off from all but vehicle traffic.

What to do? There’s a TV ad for an indoor bike attached to a video game. By pedaling, the child activates the game. The faster he or she goes, the more exciting the game gets. The appeal to parents is obvious. Here’s a way for kids to get exercise and play a video game.

This is healthier, one supposes, than lying in front of a bowl of Doritos and playing “Assassin’s Creed II.” But one imagines that bicycle-powered video game going the way of Mom’s Thigh Master as the kids realize that they, like their parents, can amuse themselves while curled up on a couch. Perhaps someone will invent an exercise pill.

Froma Harrop is a Providence Journal columnist. Her e-mail address is fharrop@projo.com.