The other day I observed a coach work out his team. He had about 13 players and for the hour and a half time I was there he accomplished nothing.
This was not for his efforts, he was actually working hard and the kids were working hard, but not one got better that day.
The problem was that every time the coach would come by, he would show the kid something to fix and then walk away. Everyone has seen this. Its a typical practice for most people.
The kid listened and then repeated his previous swings. Trying to do what the coach said but simply can't. This is because the coach is trying to fix the symptom vs fix the cause.
All flaws are traced back to a cause usually created when a player is trying to use strength to swing and has none. Knowing how the body wants to move and how anatomy works allows one to look for the cause vs the symptoms.
Example when the back shoulder drops it is caused by being over your front foot. When this happens the kid must use his back side abs to swing. Squeezing these abs causing them to contract lowers the shoulder in the process. Fix the legs fix the shoulder.
Know the Why