It lacks strength and stamina and speed. It is no longer flexible. And so it is with the mind. Tireless it may be, but in productive as well. It also lacks the mental skills of memory, imagination, problem solving, data processing, retention and recall.
Creativity ebbs away.
The less time I spend in my mental gymnasium, the more I lose in mental function. Unquestionably there is a loss on brain function with age. I don't have the rapid recall I had when I was younger. But I am not running races at the same speed either. Still, the word finally comes, and the race does come to an end.