Originally Posted by Relinquis
if he dumps it into the net after tilting the racquet forward, as he mostly likely will do, then he will adjust his swing path accordingly to get it over the net next time by swinging low to high slightly. The key is to have an closed racquet face (i.e. tilted forward, not much, only about 10-15 degrees or so, maybe even a bit less). If the racquet face is not tiled forwards at contact, the spin won't be as intense not matter how steeply you hit upwards and will likely come by sacrificing depth.
That's why you hear coaches sometimes say to lead with the edge of teh racquet. It's a cue to ensure that it is tilted properly.
I guess we'll have to agree to disagree. I don't think the key
to generating topspin is to have a closed racquet face. It's never worked that way for me and I can't think of any reason why it would work that way. The angle of the racquet face determines the angle that the ball will leave the racquet. The swing path can have some effect on what racquet face angle you will want, but you're not going to get appreciably more topspin just by tilting the racquet face.
The key to generating topspin is swinging low to high as you said. However how do you swing low to high fast enough to generate large amounts of topspin without some combination of pronation and uppper arm rotation? A gently upward swing path, which about all you can get without pronation and upper arm rotation, will produce small to moderate (at best) amounts of topspin. You're not going to get the kind of spin that you see modern players getting without using modern techniques.