As children we didn't focus on a full-body workout. Though most children, at least when I was growing in up in the 90s are in far better shape than most adults. Sure a 12 kid couldn't help move an oak dresser but they are better overall physical shape. If adults were just active playing sports, I'd suspect obesity and related health issues to decrease with mental health improving.

I know there are many here on HN that will loathe the idea of playing sports.