Hitting a forehand on the run is a difficult shot for a lot of tennis player because mechanically speaking it’s a little bit different from a traditional forehand.
At 0:10 in the video above, we have a shot of me hitting a normal forehand. What you can see is that once I hit and then follow through, I continue to rotate my shoulders and at the end of my follow through you can see my back. I’ve rotated further around than facing the net, and I’ve gotten myself around so that again, you can see my back.
A running forehand is different because you aren’t able to rotate like this. You simply don’t have any time to really set up for the shot. Because you are running through the ball, the amount of body rotation you can get is very limited. At 0:50 in the video, we have a clip of me hitting a running forehand. You can see that I run out to the ball, and I make contact in a closed stance (my right foot has stepped across my left foot) with my upper body facing the net. Because of the way my lower body is oriented, it’s going to be very difficult for me to rotate my upper body any further around as I follow through. This is why the running forehand is so different from a traditional tennis forehand.
Mechanically speaking, this also means that you now need to swing up more on the tennis ball. You would normally swing more through the tennis ball on a traditional forehand, but swinging through the ball also means that you need to be able to continue rotating your body. Since you can’t do this on the run, your swing path needs to become much more low-to-high. Ultimately, this means that the racket will travel upwards during your follow through, causing you to have to finish with the racket around your head. This type of finish is called the “Reverse Forehand Finish” and it is very commonly used by Rafael Nadal. Rafa hits this type of forehand so often because his game is adapted for clay courts, where he is constantly sliding on the run into the tennis ball. If you watch Nadal carefully when he hits this type of forehand you can see that he never rotates his upper body further around than facing the net.
Years ago, Pete Sampras sometimes had a similar reverse finish, although his stroke mechanics leading up to his follow through were considerably different than those of Nadal.