I have no idea! Neither my husband nor myself were ever involved in sports of any kind when we were kids. We were both drama geeks! But I have lots of friends who have kids that are extremely involved in sports. Seems like most of them start at about age 5-7? My kids have not expressed any interest in sports, at least not yet. It’s my impression, though, that the ideal age is pretty much any age where they start really expressing an interest in participating in sports, music lessons, or whatever! Even though it was never my thing, if my kids asked me to put them in sports, I definitely would.