Method of executing a tennis stroke

In 1999, Kevin and George Repper were granted a patent (No. 5,993,336) for a "method of executing a tennis stroke". The method consisted of hitting a tennis ball while kneeling on the right knee — that knee being protected by a kneepad.

This raises two questions. First, how did they possibly obtain a patent for this? And second, why did they bother getting a patent for this? Did they seriously expect other tennis players to license this method from them?

I don't know the answer to the first question, but I have a hypothesis about the second. Some googling reveals that George Repper was a patent attorney while his son, Kevin, was on a high-school tennis team. So my guess is that the patent was some kind of father-son bonding experience, with the father showing his son how to obtain a patent. And it seems like the son is also now a patent attorney.