low to hi swing is a major component but it's not the only one. There's low to hi swing, timing, angle of racquet face at impact, laid back wrist and racquet in front for leverage, loose arm for max head speed, weight swift, wrist flick (by forearm pronation), upper body rotation etc, new poly strings, an aero pro (which is good for spin although i dont know why exactly), good plow through to dig into the ball before it leaves the strings, some lead at 12 to help accelerate the head. all these things timed precisely come into play. nadal's got it all.