Originally Posted by Ash_Smith
My understanding of the relationship between path angle and speed comes from a biomechanist and coach I worked with for many years from France who worked for the FFT and ATP and also from my own empirical evidence from years of working with players on court. Essentially for the same swing path (assuming the same contact point on the ball) a more closed face will create a lower launch angle than a vertical racquet face.
Obviously as Tight Lines says, all three variables are inter linked, but in my experience racquet face determines launch angle and path determines spin (that is to say has a greater bearing over).
Here comes the (not very) science bit..!
If a ball hit with heavy topspin hits your racquet which is stationary and in a vertical (neutral) position the ball will leave the racquet above the angle of incidence due to the spin. If you hit said ball with a low to high path bit maintained the racquet face as neutral you would impart counter spin, but the launch angle is still higher. Repeat with a closed racquet angle and the launch angle is lower.
As for tennispeed - happy that he has "proven" that the pro's have a closed face at contact. Not convinced he has proven that this factor is the major contributor for topspin production, at least above racquet path.
When getting into the weeds of this--which I think is unnecessary in the context of playing better topspin tennis--it is important to point this out: By maintaining the same swing path, and only changing your racquet face, your are actually changing the part of the ball you're hitting/interacting with.
And I agree; the tennispeed article is underwhelming to the point of being worthless.