When it comes to playing sports like football and soccer, using your head may actually be the best way to lose it - or at least to lose a little bit of your cognitive power.

It's a common scenario: It's the end of the work day and you're struggling with an achy back and sore neck, even though your physical activity for the day hasn't involved much more than sitting at your desk, eyes glued to a computer screen.

When a friend asked Kimberly Zolotar what it was like having Multiple Sclerosis (MS), she couldn't immediately answer. Sharing her thoughts in the "My Turn" section of the Los Angeles Times , Kimberly wrote in 2008, "How could I possibly explain how it feels to have a potentially disabling, progressive and incurable neurological disease? It has been 13 years since my doctor told me I have MS, but the answer to my friend's question changes every day, sometimes every hour."