Quick answer: Face-on: after impact the lead elbow bends and points at the target, with the arm folded in rather than extended.
What it does to the ball
The arc shrinks: less speed and compression, with a recurring weak fade.
Root causes (by frequency)
Compensating for an out-to-in path so the ball doesn't go left
Fear of a full release
A lack of body rotation that leaves the arms no room
How to fix it
Both arms long toward the target after impact: a towel between the forearms shouldn't fall until the finish
Drills that fix it
Towel between the forearms · 15 min · 15 reps
Keep the arm structure and eliminate the chicken wing Hold a rolled towel between both forearms and make three-quarter swings without dropping it until the finish. The arms stay extended and the body rotates to keep up with them. Move to full swings once it survives 10 in a row.
Frequently asked questions
What is "Chicken wing (bent lead elbow after impact)" in the golf swing?
Face-on: after impact the lead elbow bends and points at the target, with the arm folded in rather than extended.
What does chicken wing (bent lead elbow after impact) do to the ball?
The arc shrinks: less speed and compression, with a recurring weak fade.
How do you fix chicken wing (bent lead elbow after impact)?
Both arms long toward the target after impact: a towel between the forearms shouldn't fall until the finish
Sources
David Leadbetter — The Golf Swing
PGA of America — PGA Teaching Manual: The Art and Science of Golf Instruction