I don't remember who posted this, but I thought this was worthwhile...

"Take a small towel, hold it in the hand you Jab with, and snap it 100-200 times, do it as long or as many times as you feel is necessary. I do 100-200 depending how sore I am or whatever, but my trainer came up with this and I thought it was a great idea, the purpose is to get your hand back to the position it started as fast as possible, and in order to make the towel snap you have to bring it back faster than you sent it out. It works the same muscles and it’s a great Idea. Try it"