Put simply, the golf swing is a big wheel your sternum is the hub and your arms are the spokes. So not only can your arms change the radius of the wheel they can actually ‘shift’ the wheels path left or right resulting in catastrophic shots.
Some shots you can expect from flexed arms are tops, fats, thins, slices and pull hooks. If you hit any of these shots there’s a good chance your arms are miss behaving.
Straighter arms also mean more power so it won’t be just a straighter shot you can expect.
So straighter arms mean straighter and better golf shots, for a right handed player the left arm shouldn’t flex at all until the finish, after the arms pass shoulder height.
So here’s a great drill to work on this.
Hit some balls finishing at a ‘straight arm finish’. What I mean by this is the arms should finish level to the ground bolt straight, almost locked out! The arms throughout the swing should feel straighter even in the back swing, just use the blanket thought of straight arms.
This will be very challenging at first but it will get easier the more you practice it. There is a progression from here but this is the first point of call. Obviously no golfers finish here in real life however they do travel through this vital position.
At your finish position your arms should be almost in the same position as they were at address with your torso turned towards the target. It’s a great practice motion to make, set up then just push through to a straight arm finish with no back swing. This should exaggerate the feeling.
Before anyone asks there should be no ‘roll’ or rotation of the arms, if anything, they should be just squeezed a bit more together.