Paul and Gail dennison have written a small, paperback book, Brain Gym.  In it is an exercise called "gravity glider."  It not only helps with reading comprehension, it's good to do after sitting at the offie all day and before playing in a sports event like baseball or soccer.

Sit on a chair or sofa.  Cross your ankles.  keeping your knees relaxed, bend forward and reach out in front of you with straight arms.  Let your arms glide down toward your feet as you exhale.  Glide arms up as you inhale.  Repeat, moving arms to the left and up, right and up, and then center.  Change your legs and repeat.  For most people, their body feels lighter and more relaxed.