Ahh, atlatls! A subject fit for an archaeologist. In days of old (12,000 years ago, more or less) they served to bring down mammoths. I saw a recent study that concluded that an altatl, or spearthrower, increased the force of the spear about 60 times. It is basically an extension of the arm which leverages the force, something like those gadgets that folks use today to throw tennis balls for their dogs. I believe they are outlawed in the major leagues, even for outfielders.