In and out bowing action

In and out bowing action

If we use the forearm alone when playing in the upper half, the bow stroke will be crooked.

The upper arm should come forward slightly at the end of the down-bow and back at the beginning of the up-bow.

Stroke your hand along a broomstick to mimic a whole-bow stroke and you will notice how the upper arm naturally moves in and out.
In the upper-half détaché the upper arm is always passive, that is, it responds to the forearm action.
This action is mainly used when playing at a slow or medium tempo, it becomes cumbersome at fast speeds.
This action is more apparent in those players with shorter arms.
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