This practice is described at some length on the link. I began at 75 and now I continue at 81. My reflexes are no duller, perhaps a tad sharper.
The Resilience ball requires us to focus on this moment, then the next, like slides in a slow motion movie. We enter a state known in Japanese martial arts as mushin, no mind.
Please be careful in how you practice—easy, careful, free. If you have any concerns or medical issues, please consult your physician. I advise wearing glasses to protect your eyes.
Available on Amazon.
Resilience Reflex Balls come in various shapes and sizes. Here is one inexpensive option. There are others on Amazon.