By racket head speed I'm talking literal racket head speed. Not in relation to hitting a ball. Just how fast you can physically swing a racket.
Say you swing a racket into a concrete wall and the concrete wall can somehow detect how much force you supplied on decimating the racket. You're a rec tennis player but a rec tennis player with a history in elite strength training. You threw javelin for your country. And you're up against Nadal.
My guess is that Nadal is going to hit the concrete wall about 5 - 10x harder than you with his racket.
What do you think?
First of all, almost no pro hits the ball as hard as they can. They don't swing out of control and neither does a rec player.
Depending on the rec player you see guys hit 100-115 mph serves. Contrast that with the upper tier pros, which is 150 mph or so. So roughly a 50% increase in pace. I'd say thats about the difference in fhs or bhs as well. If a guy hits at 60mph, a pro will hit the same ball at 90mph.