Start swings short and build length through the session
The coach recounts a practice tip his dad suggested for controlling arm-swing length: instead of the usual pattern of starting long and trying to get shorter, start with very short swings and gradually increase the length as the session goes on. He says that after 20-30 minutes of short shots hit hard from a small distance, each longer position (chest high, then ear or head high) felt bigger, and it was the day he could finally control his arm swing to the top.
Channel: PorzakGolf
Watch official source at 11:37