The fourth step of the one-handed backhand is to step across your body with your inside foot and transfer your weight to that foot. At the same time, the tennis racket drops down behind you and your hitting arm straightens out. The previous three steps of the one-handed backhand were part of your preparation, but in this step we transition to the swing.
At 20 seconds into the video we look at the completion of my preparation. All the weight is on my outside foot and my tennis racket is all the way back. Also, my shoulders are completely sideways. From this position, I step across my body with my inside foot and transfer my weight to that foot. As I do this the heel of my inside foot comes up. I drop the tennis racket down and straighten my hitting arm out.
It’s critically important that you straighten out your hitting arm as the racket drops down behind you. All pro tennis players that hit with a one-handed backhand do this. Also, during this step I’ve kept my non-hitting hand on the tennis racket. You don’t let go with this hand until later in the shot.
At about 1 minute into the video I shadow the motion from the front. From the completion of my preparation, I step across my body with my inside foot and transfer my weight to that foot. As that happens, the racket drops down and my hitting arm straightens out.
1 minute and 15 seconds into the video we watch Andrej Loncar from the completion of his preparation. As he transitions into his swing, he steps across his body with his inside foot and transfers his weight to that foot. At the same time, he drops the tennis racket down and straightens out his hitting arm. Both hands are still on the racket. He won’t let go with his non-hitting hand until the next step.
Note: In the video I say that the tennis racket drops down behind your back. This is not entirely correct. The racket drops down but it is not behind you. It’s an unfortunate verbal slip up. Sorry!