Here's a challenge for anyone who wants a go. The idea is very simple and is a great workout if your accuracy is off.
Throw a single tennis ball against a wall 10 times in a row as fast as possible. You don't necessarily have to catch it each time but thats much faster than picking it from the ground.
Distance can be whatever you like, but 10-15m works best for me. Obviously the closer you are, the less time the ball is in flight. But you also have less reaction time for the catch. For any "official" time, I would say no closer than 10m.
Time is measured from the moment of release to the moment you touch the ball on the return bounce of the 10th throw.
On the off chance anyone would like to compete, I threw 29.02 seconds from 15m today. Finally broke 30 seconds haha
Here's the video
https://youtu.be/DmMoDZwFjrM?si=ldfu72bccRca1mxuYou can also just see how many you can catch in a row without letting the ball hit the ground.