Chapter seven
Principle number five: “The hypothenar adhering to the end part of the grip, acts as fulcrum and pivot of the dynamic mechanisms of the racket.”
The adherence of the hypothenar to the butt of the racket handle is an essential reference to analyse the correct grips and it represents the second of the two factors which determine the dynamic mechanism of the racket.
The hypothenar, which acts simultaneously as fulcrum and pivot, allows to obtain a “quick acceleration of the string face”, compared to the handle, with all the different angles of the push line passing through the barycentre axis of the racket.
The adherence of the hypothenar is to be analyzed separately, and in close connection with each of the two points of greater pressure of the hand on the handle described in principle number four.
The hypothenar acts as a fulcrum with the flexion and relaxation of the wrist joint which utilizes the push line of the area of greater hand pressure; this action is more effective on a forehand whereas it is minimal on a one-handed backhand because of the limits imposed by biomechanics.
(figure showing the wrist leverage in the forehand topspin and forward movement of the string face towards the point of impact with the ball – hypothenar/fulcrum)
Besides, with the superposition of the radius on the ulna during the pronation, which means turning the forearm so that the palmar surface is directed downwards, the hypothenar acts as a pivot.
(figure showing the hypothenar acting as a pivot in the forehand topspin and the side rotation of the string face compared to the handle)
In the kick serve, therefore always with the forward spin of the ball like with topspin rebound shots, by changing the type of grip, the two functions of the hypothenar act by exchanging the dynamic effects transmitted to the racket and, therefore, the forward movement of the string face towards the point of impact with the ball and of the lateral rotation of the string face compared to the grip.
(figure showing the wrist lever in the lifted serve and the lateral rotation of the string face compared to the grip – hypothenar/fulcrum)
(figure showing the hypothenar acting as a pivot in the flat serve and forward movement of the string face towards the point of impact with the ball)
At this point a very important clarification is necessary. In the forehand topspin the barycentre axis of the racket forms an angle of 135 degrees with the barycentre axis of the arm-forearm lever and, at the moment of impact with the ball, the string face is positioned on a vertical plane parallel to the plane of the player’s shoulders.
(figure showing the correct reference points at the moment of impact, with the arm-forearm lever which moves away from the player’s side forming an angle of 45 degrees forwards and sideways, and the angle of 135 degrees between the barycentre axis of the racket and the axis of the arm-forearm lever)
If there is no perpendicularity between the barycentre axis of the racket and the axis of the arm-forearm lever, the pronation would cause the string face to lose its orientation.
(figure showing the lack of perpendicularity)
(figure showing the loss of orientation of the string face due to the pronation, with the arm-forearm lever stopped at an angle of 45 degrees forward and sideways compared to the player’s side)
In this way the dynamic effect transmitted to the ball would make it rebound on the ground before reaching the net.
This does not happen, because the arm-forearm lever utilizes the centrifugal force with the shoulder joint acting as a fulcrum and pivot thanks to the abduction (from the latin abducere, to move away) and to the rotation of the humerus. In this way, the arm-forearm lever moves forward, upwards and towards the player’s other side with the movement which brings the grip hand to draw a semicircle in the air.
And so the lateral rotation of the string face on the grip takes place on a vertical plane and parallel to the plane of the player’s shoulders while keeping a correct orientation of the string face.
(figure showing the humerus and ulna in abduction and rotation, with a correct lateral rotation of the string face compared to the grip and to the two vertical and parallel planes).
The forearm can flex on the arm after the arm-forearm lever has moved with a rotation angle of at least 15 degrees from the point of ball-racket impact , as at that point, the ball has surely already left the string face. In this way, the movement is smoother and the centrifugal force action is utilized fully, saving energies to the advantage of sensitivity.
On the other hand, if you want to exaggerate the ball rotation when executing a forehand in lifted rebound, as you often see Rafael Nadal do, then you abandon the movement of the arm-racket lever towards the other side and you move directly forward and upwards on the same side, bringing the arm higher above the head; only the string face reaches the other side to end up behind the player.
In this case there is no rotation but only the abduction of the humerus.
(the figure shows the exaggerated rotation movement when executing a forehand in lifted rebound)