Wanna come out and play catch?
I think what's also really good about children is the type of movement. They're constantly moving, but never really too extreme and have breaks in between as well. Usually they also socialize a lot with other kids in the village or area they're living in. Nowadays as an adult even if you are a sporty person and move a decent amount, you're usually always moving in an unbalanced way. Most people don't move at all, then there's people who go to the gym where they exert themselves way too much and for too long, but the other time they're also just sitting. Then there's also construction workers or those type of people, they usually mess their backs up and it's also just not a good type of activity. I think the healthiest would be to emulate living like a squirrel - constantly in moderate movement and activity.
The trend for children is definitely very negative. Imagine how unhealthy the average baby in this day will be once they're teens or adults.