Saturday, May 6, 2017

Free Throw Deep Dives: The Windup and the Release

Part three of an infrequent series. Click here to go straight to the interactive tool.

In previous free throw deep dives, I used SportVU ball tracking data to examine how launch angle and release spot affect free throw accuracy. In this post, we back things up a bit, one second to be precise, and dive into the specific mechanics of each player's free throw shot.

For this free throw analysis I focused on the motion of the ball (in all three dimensions) for the second prior to the ball being released. One second, while somewhat arbitrary, was chosen so that I'm capturing the natural shooting motion of the player after any pre-shot routine has been completed (e.g. one dribble, two dribbles, Klay Thompson's weird arm tap thing, etc.).

The ball tracking data is messy, and shooting motion will vary from shot to shot, so I built a simple LOESS model for each player, with the goal of teasing out a player's typical shooting motion in all three dimensions. LOESS models are nice because they don't force you to shoehorn your data into a pre-determined type of curve (e.g. polynomial, exponential, etc.).

Here are the results for Kevin Durant's typical shooting form: