To Straighten or not to Straighten

Hi guys. I noticed on a lot of your topspin shots, you don't straighten your arm in the backswing. Is this an advanced technique to save time? Also, what do you think are the advantages/disadvantages of straightening? I know in tennis, my backswing stayed bent, but I straightened at contact. Thanks--Tom M. 

Hi Tom,

The more time you have and the more power you want to generate the straighter you can have your arm.

The forearm action is where a lot of speed is generated so starting with the arm straight allows more forearm movement during the swing. For more control you can keep your arm bent.