Mental Exercise

This statement could not be more true.

Walking, running, lifting weights, hiking, biking, swimming, P90X, etc... are all ways to improve your physical health.  For those that are in great physical shape, these exercises are done on a regular basis to keep the body fresh.  If you want muscle strength it is important to challenge your body as muscles do not grow unless they are pushed to their limits.

Reading, writing, blogging, listening, problem solving, creating, analyzing, etc... are all ways to improve your intellectual health.  For those that are in great intellectual shape, these exercises are done on a regular basis to keep the mind fresh.  If you want brain strength it is important to challenge your mind as your mind does not grow unless it is pushed to the limit.  

Are you more physically fit or intellectually fit?  How can you improve on one and still maintain strength in the other?