There has always been a discussion whether to use one or the other vibrato, but it has never been clear what they refer to. The movement from the so-called arm vibrato actually comes from the shoulder and the elbow in different degrees, depending on the position of the violin. The wrist vibrato has its variations, as it can be done with one group of muscles or another depending on its initial position. What it is said repeatedly by many physiotherapists is that by making the same movement consistently it will provoque injuries to the tendons, joints and muscles. The best way to avoid this is to alternate between different types of vibrato. I made a computerized analysis of Vengerov vibrato and the results are very interesting.
In the video we can see marked the angle of the wrist, the line of the knuckles and a reference point on the middle phalange of the second finger to get an idea of the range of movement in the axis of the hand mainly generated by two joints (the elbow and the wrist) .
At 0.25x the original speed, one can appreciate more clearly the way the movement of the vibrato is made. We can differentiate four stages:
1) He starts the vibrato downwards with an external rotation of the shoulder and an extension of the elbow creating a passive flexion of the wrist:
Vengerov´s tendency is to start with a narrow vibrato that produces a bigger effect when doing a crescendo. The opposite is done when doing a decrescendo, moving from a wide vibrato to a narrow one.
2) The wrist follows the movement of the arm until it reaches a neutral position where the hand and the forearm are aligned:
When articulating fingers, it is very important to keep the wrist in a neutral position. In this way, the tendons of the wrist will not get to hyperflexion or hyperextension. This could cause an overuse of them, losing the dexterity of the fingers almost completely.
3) Here starts the opposite movement of the arm and forearm:
This is the moment when the exact opposite occurs as Vengerov starts the upwards phase of the vibrato. His shoulder rotates internally, the elbow flexes and, as a result of all this, the wrist extends.
4) Alignment of the hand and forearm. Neutral position of the wrist as the vibrato will continue to phase 1.
The whole arm goes back to the initial position to start the whole process again. Small variation might happen as the execution of the movement is not completely perfect.