There are great exercises to work on a more efficient kinetic chain energy transfer. Only thing you need is a plastic pole (like the ones are used in soccer trainings which have a base).
Slalom plastic pole
The first exercise is great to get a better feeling for the rotation of the shoulder axis when uncoiling from a semi-open or open stance. Withholding the pole on the shoulders the upper body rotation is isolated from the movement of the arms and hands. Like that the player is developing a better feeling for the position and angle of the shoulder axis when executing the energy transfer from legs over hips and core, up to the rotation of the shoulders. The shoulders should not turn too early into parallel to net position when contacting the ball.
The second exercise is great to keep both arms in shoulder wide distance working as a unit together. Now the arms are integrated into the upper body unit turn and uncoiling of the upper body. Here the player must bring the right arm in full stretch when uncoiling from semi-open or open stance on forehand and the same when doing so with the left arm on backhand. Lower and upper body start to work in harmony with core of body after a couple of swings.
The third exercise allows the player to improve the nearly stretched arm on contact with the ball and is also perfect for practicing a high racket head acceleration. When the swing is perfectly supported by a sound uncoiling of upper body using the transferred energy of the kinetic chain, the pole makes a loud sound (“Woooosh”).
Implement these exercises when working on the ground strokes on court. They help for a better timing, the use of kinetic chain energy and are fun as well!
Hope to see you using the excercises wisely…
All the best COACH DIMI