My first bicycle was a hand-me-down with 10-inch wheels, a fan belt instead of a chain, and no brakes.

Training wheels? Surely you jest. I must have been less than 3 when I learned to ride. I bought my fourth bike on a cost-sharing plan with my folks for $50 when I was 11. It was a three-speed “English” bike and was my ticket to the rest of the world. My hometown rests in a bowl surrounded by hills, and so without a bike with gears, my parents knew I wasn’t going outside a 5-mile perimeter. But with my racing green Phillips, I became a two-wheeled explorer without limits as long as I was home by dark and unaccompanied by a police officer.

At 13 a friend and I were allowed to cycle unaccompanied for 300 miles. The 3-day journey included spending one night in a boarding house and another sleeping under picnic tables on the side of the road. I still can’t believe my folks allowed us to go in that era before cell phones and GPS. I think it was a simple miscalculation. They were sure we would be back home before dark the first night.

As an adult I have been a committed bike commuter, and my wife and I prefer to do our European sightseeing from the saddles of our folding bikes. My children all learned to ride bicycles before they were 4. But to them, their bikes were never more than a toy. Ride to school? “Dad, no one does that!” Luckily, we lived close enough for them to walk.

Even so, after a 25-year hiatus during which their bicycles hung from the rafters in our garage, all three of our children have incorporated two-wheel travel into their adult lives. One has become a competitive road racer. One commutes 20 miles round trip in Boston. And one has added cycling to her fitness routine on a regular basis.

Their rediscovery of bicycling is not unique. Here in Brunswick, Maine, biking to school, at least up until junior high, has become “cool.” A bike rack that was once just a rusting reminder outside our K-1 school is now filled, and the second- to fifth-graders’ three racks overflow on the first warm day of spring. In Boston, where I pretty much had a nodding acquaintance with all my fellow bike commuters 45 years ago, the road can be three deep in cyclists at some intersections during rush hours.

Surprisingly, not all young adults learned to ride a bicycle when they were children. It’s not unusual to encounter an adult who can’t swim. But not learning to ride a bicycle? How can that happen? There may be financial constraints. For example, my Dad never learned, but his family lived in a city and couldn’t afford a bicycle. But it is likely that many 30-year-olds found video games, cable television, and other indoor diversions more appealing when they could have been learning to ride. And for many it just wasn’t cool.

I learned in a recent Wall Street Journal article (“ ‘It’s Like Riding a Bike’ Means Nothing to These Adults Trying to Learn,” by Miriam Jordan, July 14, 2015) that while 5% of the population can’t ride a bicycle, 13% in the 18- to 34-year-old age bracket lack the skill. Enough of these young adults are discovering that bicycling could offer them ecologically friendly and cheap transportation as well as a low-impact recreational option that bicycling schools for adults are springing up in cities across the country from Los Angeles to New York to meet the demand.

I worry that the current surge in the coolness of bicycling that we are observing here in Brunswick is a strictly local phenomenon, and the number of children who reach adulthood not knowing how to bicycle will continue to grow. I wonder if our national health might be improved if bicycle instruction for those who don’t know how to ride were included in grade school physical education classes. It might make a lot more sense than teaching archery or badminton.

Dr. Wilkoff practiced primary care pediatrics in Brunswick, Maine, for nearly 40 years. He has authored several books on behavioral pediatrics, including “Coping with a Picky Eater.”