All I know is my about to be 11 year old is in dance and gymnastics 6 hours a week and she can run like the wind. At least when she doesn't have a broken toe.
My 11 year old daughter is also in dance and gymnastics, and the strength and conditioning they do is wonderful. She starts a strength and conditioning class at school this week and I look forward to seeing her do more push ups and situps than the football team.
She has zero interest in running, however.
The tangents are moot.