The biomechanics of strokes in tennis
Technique is a movent or a serie of movements through which we achieve the best possible result with the less possible effort without causing any injury and the capacity to repeat this movement consistently.
So, in tennis a good technique is considered the one that enables us hit the ball with high speed, accuracy, repeat this consistently without being injured.
The speed of the ball depends on the speed of the racket head at the moment of hitting the ball and the accuracy on the position of racket head the moment of impact.
The maximum possible racket head speed is mainly obtained through the legs, hips, trunk and shoulders and not through the arm and certainly not at all through the wrist. There must be optimal coordination between the legs, hips, trunk and shoulders so that one limb to transfer its speed to the next and finally the speed that is achieved through all these limbs is transferred through the arm to the racket.
The chain of movement (legs, hips, trunk, shoulders, arm)
We initiate the stroke by pushing the ground with our feet, transferring the weight of the body upwards and forwards in the direction in which our racket is going to meet the ball.
Just before the legs reach their maximum speed, the hips start their movement. They receive the speed of the legs and add more speed to the movement. Next, the trunk enters just before the hips reach their maximum speed, further increasing the speed of the movement, and finally, the shoulders increase the speed even more and this speed is transferred through the arm to the racket.
The arm transfers the speed generated by the whole body to the racket, which accelerates and moves at high speed towards the ball. Since the racket moves away from the pivot point of the body (shoulder) due to the length of the arm and the length of the racket, the speed of the racket head is much higher than the speed achieved in the body. That's why taller players can achieve higher speed strokes.
The role of the arm and hand is to correctly direct the racket head towards the ball to get the shot we want (topspin, topspin, flat, etc.) and to control the trajectory of the ball so that it lands exactly where we want it to. The wrist does not add speed to the ball. It must be stable to avoid swinging the racket, which will affect the accuracy of the ball when it does not touch the sweet spot of the racket.
