The nerves to your hand originate in the cervical vertebrae. Look at the new training and see if you are not putting a new stress on your neck and shoulders. One of the first things I learned from Yoda is that I held the club too tight but this caused problems in my elbow not my hand. I personally don't like the impact bag for most people because it is such and abrupt conclusion to a motion that should be full and free flowing. I usually have to work with people on their form, when they insist it helps their game,The sheer knowledge that you will 'hit' the bag can cause you to ceaze up in your shoulders and that is a reaction that difficult to overcome.
Make sure you didn't start reaching to create the "thump"and thereby straining your neck and shoulders. You may have to practice a few swings in front of a mirror or take a video of yourself to really break down your swing action and then work backwards to correct the dis-ease that has developed in your hand.
Let me know what you find. There are certainly exercises to correct the developing problem.
Hybrid Mode
