MLB and the High-School Baseball Tournament

I am now watching sports news on NHK BS1. MLB players are definitely bigger than their Japanese counterparts. They have more muscles (presumably without using steroids) ... hence more power and strength. I don’t think their physical differences are caused only by genes and diets. My guess is that MLB players have been training more systematically according to sports science. As the high-school baseball tournament is going on in Japan right now, I cannot but wonder how many high-school baseball teams in Japan incorporate sports science into their trainings.