@TheGhostOfAgassi raised a good question.
don't know why the thread was deleted instead of being moved over here.
leaving aside the entire discussion that happened there, with arguments that Serena's serve speed is as fast as men speed, and at some selected tournaments women clock faster groundies of the combined tournament, and how many pull-ups and push-ups an average man vs average woman can do, I think it boils down to total energy that the player can induce to the ball.
this energy is being split between the sheer pace and spin.
from my observation, women tend to play with light-weighted frames.
also, correct me if I am wrong, women on average have less weight, which means that there will be less energy to be transferred to the ball.
in comparison, a top light-weight boxer might generate an astonishing power while hitting, from sheer speed and technique, but a top heavy-weight will still be able to top it up.
Now when we combine this, and compare the pinnacle of the ATP vs pinnacle of WTA, will this explain why men hit "heavier" groundies?
if player A has bigger mass, uses it well and plays with a heavier frame, and probably with a higher SW, should we wonder that player A generates heavier groundies.
what do you think folks?
what other factors result in men hitting "heavier"?