Physical Exercises to Stimulate the Brain

Practice handstands or floating upside down when you are in a pool.
Take up or practice an activity that requires coordination, such as a racket sport, basketball, baseball, or ballroom dancing.
Next time a small gadget is broken (like a clock radio or a lock) take it apart to see how it works and try to fix it or identify the broken part. Consider working toward an advanced version of this exercise - doing simple servicing on your car, such as changing oil and filter.
Learn to juggle, beginning with just three objects, or learn to tie complicated nautical knots.
Learn basic stretching exercises, especially for those muscle groups that you do not move much, like the toes, lower back, and neck.
"Spin your brain" and stimulate more neural activities by doing tumbling or cartwheels or spinning your body around on one foot.
Revive your jump-roping skills.
Extend the amount of time you can stay underwater without breathing. Diving from the edge of the pool, swim underwater as far as you can until you need air. Do this regularly, each time going a little farther and a little longer.
Walk backward for two blocks (do not forget to look for traffic before crossing the street) and gradually lengthen the distance you can go.