My guess is that "elbow above the hand" relationship can still exist, at least to some extent, even without TE.
It would be useful to view a serve with a neutral thoracic spine. This is a common scenario as many/most club players are unable to perform much TE.
In my experience just trying to achieve this elbow relationship results in better serves. Even if the actual position is never achieved.
e.g. Just improving from (elbow slightly below hand) to (elbow even with the hand).
THROW YOUR ELBOW AT THE BALL
Before striking the ball, all great servers share a few key things in common.
One often-overlooked element is the role of the elbow on the hitting arm.
In order to gain racquet-head speed, the elbow precedes the racquet in moving upwards into the serve. The elbow should transfer from below the racquet to just above the racquet, all prior to contact, creating torque and helping accelerate the racquet up to the ball. In more common terms, by “throwing the elbow” at the ball, the racquet hand is left behind, allowing it to accelerate up into the ball. The more distance the elbow covers, the greater the torque on the swing. Focusing on “throwing your elbow up at the ball” can help relax your grip on the racquet.
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