There is an important angle in the golf swing called “lead arm adduction,” and it is the angle formed between your lead arm and your shoulders. As you bring your club to the top of your backswing, this angle will naturally reduce. But if you compare the swings of great ball strikers with those of amateurs, you will see an important difference that happens in transition.
What we see with the better players is their lead arm abduction angle actually gets smaller as they start the downswing. Think of it like they are leaving their arms in position at the top even as they start the downswing with the rest of their body… their arms get closer into their chest. This motion stores energy in your arms, giving you a boost in club head speed as they eventually spring through impact.