Disclaimer: Everything I know about martial arts, I learned from watching television. I apologize if I mix Chinese and Japanese terms. As I understand it, the short burst of sound emitted by martial artists during a fight technique is called a kiai. Obviously, one of its functions is to freak out your opponent. But there is a spiritual function as well. It serves to focus your qi (life force, personal energy or whatever) into the part of your body delivering the strike, thus adding significantly to the force of your attack. There is, of course, no scientific proof of the existence of qi, so it basically amounts to a faith-based religion.
Let's imagine, for a moment, that we truly believed in this qi hooey, and the value of the kiai to force extra energy into our attacking extremity. Ponder with me here...
Anyone who has been observing professional tennis for the past twenty years, from Connors to Sampras to Federer, from Evert to Seles to the Williams sisters, will notice one big non-technological difference between the tennis of the present and the tennis of the past: Where did all this shouting come from?
None of the top players in the 1980's shouted when they hit the ball. McEnroe shouted a lot, but never when hitting the ball. If you watch a professional tennis match today, they all do! Something clearly happened to change the way the game is played.
Monica Seles was the first one I remember. Like a roommate with an annoying habit, I hated her for it. What if... just what if... Monica's trainer was into martial arts and took a trip to the orient to see if there were any ancient secrets that could help Monica become the best, as she did. Monica's kiai's definitely had the proven psychological effects of martial arts kiais. Her opponents found it extremely intimidating. And if you believed that kiais could focus extra life energy into an attack, it would make a whole lot of sense to shout one when striking a tennis ball.
I just wanted to throw that out there. This one definitely goes in the Musings category.
I'll leave you on a humorous note. If kiais really could focus qi, it would make perfect sense to apply it to other sports....like golf. Can you imagine Tiger shouting "KYAAHHH!!" on every drive? Perhaps the youngster that takes his place will...