Originally Posted by luvforty
you need something to coil AGAINST... and here is where the 'friction' comes into play
It's not the friction. It's the ground reaction force. Literally the planet Earth pushing on you. The legs contribute about 20-30 something %, somewhere in the area, of the power IF
you have a well established kinetic chain all the way to the racquet. The energy from the legs has to be efficiently transferred through each link in the chain which means up to the quads, gluts, hips, back, torso, upper chest, back, shoulders, forearm, wrist and then racquet in a coordinated sequential order. Then if you have good rotation and no kinks or hitches or a break in the chain you will get the 20-30 or whatever % it is.
It is not
over 50% of the power even if you're Roger Federer. Therefore MOST of the power does not
come from the legs. It's only one of the major contributors. The torso area contributes more power than the legs if you want to get technical.
I rest my case.