I’ve got a post that I put on instagram to illustrate positive and negative power.
The picture illustrating positive power will show a player with a straight spine, their hand under the middle of the ball, and their knees over top of toes. All the lines in their body are pointed at the hoop or straight up in the air. They are creating a lot of positive power.
The picture illustrating negative power shows the player going pigeon toed with one foot, leaning their spine, their hand not under the ball, and their knees caved inwards. The arrows showing directions they are generating power are pointed all kinds of different directions.
When I post this picture I can usually start a countdown to the time someone will point out, “but Harden/Kevin Durant shoot with their knees in, so it isn’t bad”.
My typical reply is that just because a couple of freaks of nature (I mean that as a compliment) are able to compensate for that habit and still make shots doesn’t mean that habit is HELPING them make shots. It is more likely that these players are great in spite of this habit rather than BECAUSE of the habit.
I would list the health of a players knees as another reason to avoid the habit. It was explained to me by a physic-therapist that this habit in youths is the reason a certain muscle under-develops, which then causes knee injuries over time.
Now, a friend of mine that is on staff with an NBA team as a physical therapist did say that caving the knees inward CAN generate more power with ELITE athletes, in a situation where they are trying to jump higher. As we continued the conversation he did say, from a shooting perspective and especially in a youth development perspective, he would never recommend someone do this. Only in VERY specific situations that don’t apply to the average, or even above average, athlete.
So focus on using your legs evenly, in a strong, stable, balanced matter, by keeping your knees over top of your toes as you shoot.