the START in topspin forehand
Unloading of the force takes place in the following ways: ● the body starts just before the arm ● the arm is pulled from his shoulder as if it were devoid of power (this mode of movement entails, among other things, the arching of the body).
It is important to understand this point – which is one of the key points of difference between traditional shot and the open stance of topspin: arm (and shoulder) in not exercising topsin push!
The movement of stroke in topspin can be somewhat compared to a whipping, in which the rope may not actually exert any push. The arm can be visualized as a towel hanging from the shoulder (his arm obviously exerts some force component, but not the push of the racket).
See the example of balls hang by a thread that with the rotation movement develop the strength to hit the drum with energy.
It is therefore not the strength of the arm (shoulder) that carries out the racket, but the rotation movement with which the body unwinds from loading performed in the opening (the progress of the arm is due to two components: body rotation + hip advancement). For this reason the movement begins with the body (from the shoulder), then follows his arm pulled from the shoulder.
experiment of the suit that the slap even without having the arm entered
It is good to do an experiment that makes us understand how it is possible to “slap” the ball without using your arm strength: wear a suit without sticking your arm into the right sleeve, and try to hit something that is in front of you (where it could be a high ball) with the empty sleeve.
You will see that it is possible to give a slap to that target if you leap the sleeve with the shoulder.
You’ll also see that to do this you perform all movements of topspin forehand (see next point): the movement starts from the foot that goes to the tip, and then the body is arched exteng itself upwards.
Indeed in the martial arts (particularly Chinese ones, like Bruce Lee teaches) the punch does not push but is due to a whip.
See how Bruce Lee uses Nunchaku, an instrument consisting of a stick attached to the handle with a chain (which therefore can’t possibly do any pushing force except that of a whip). < see video >
In the starting phase of stroke we begin to unload the strength that has accumulated with preparation (opening) with two components: body twisted clockwise (seen from above) and bending of the knees.
To unload the accumulated force the back leg begins to spread out, starting at the ground: the foot is stretched on the tip. Extending the leg the body rise (vertical component of stroke: spin) and right hip moves forward (horizontal component of stroke: push).
In this movement the leg acts as a pivot, so you have the rotation that once your racket will impact the ball will produce the typical spin of the topspin.
The movement of the foot that rises at the tip is a hint of the more powerful movement of the jump, which give a major rotation component to the ball (the problem is obviously that to jump with each shot you must always be able to get on the ball in a very favourable position, and having a physical particularly trained).
you can see again the video of Djokovic:
Another important point: the racket initially did not made a hinge movement such as opening a door (hinged on the shoulder), but you “pull” the racket in the direction of the logo on heel (moves thereby is initially parallel to the body, i.e. perpendicular to the net: only at the last moment the racket rotates by 90° to impact the ball being at that point parallel to the net).