This summer, my 13 year old lefty son picked up what I though was a bad batting habit. I took a video of him on July 31 in the batting cages - his last day of baseball before he starts his Fall break from baseball - and I noticed he is now lifting his back foot off the ground when he swings. Never did this before. I thought of pointing this out to him as a potential flaw, but I did some research first and to my surprise found that lifting the back foot off the ground is actually not that uncommon. See the image below of Ruth’s and Harper’s swings, with the back foot lifting off the ground (Canseco and others did it too). I was very surprised, to say the least.
I don’t know where my son picked this up, as I’m his only batting (and pitching) coach. But this is something I’ve never heard of or read about before, and I try to read a lot! Any thoughts? Is this something a 13 year old should be doing? This just seems to run counter to much of what I’ve read about batting.