You may be interested in learning more about the Qi Gong exercises as part of a practice in Kung Fu which these Shaolin monks demonstrate in this video which you may already be familiar with as you mentioned you're already practicing martial arts. They appear to require much discipline and effort but appear to be highly effective as well, as far as strengthening and protecting the weakest and most vulnerable areas of the body.
This is not physical, but I will share anyway in case you haven't considered it, but there are education iOS apps such as Peak and Elevate which help you to train your brain with daily workouts in the areas of focus, mental agility, memory, problem solving, and language--within 30 days you should observe a marked improvement in your cognitive function.
And of course there are health supplements on the market designed to promote brain function. Again, not a physical fitness exercise, but I just wanted to attack the problem from as many fronts as possible in order to help you see results. Good luck and stay safe.