Hi K.,
ADD/ADHD is considered a sensory integration disorder. These can range from very mild high functioning kids (and adults) to people with pretty severe deficits. There are many apporaches to treatment, including meds, but often the root of the problems comes down to the development of the neurosensory pathways, proccessing outside stimulation (balance, taste, vision, hearing, touch...) and intergrating it into the brain properly allowing for the proper response.
Sometimes kids who are, overactive actually have systems that are overloaded and require more stimulus than the average person to experience the same response in the brain. (hence your son needs to run around to get the stimulus he needs) This can be QUITE complex and I can't really go into the details of testing all the neurosensory pathways here, but it might be something to look into in more detail. Someone who is experienced in working with kids with SID (sensory integration disorders)is your best bet. By doing a very thorough exam, testing neuro pathways with differnt tasks and exercises, they should be able to determine if SID is even an issue for your son and/or what specific areas need work.
My approach for kids with these types of issues involves: nutritional modifications/detox, sensory integration homework/exercises for areas that need work and chiropractic care, as needed, to stimulate the areas of the spine that are involved with those particular parts of the brain. Sorry I can't go into more detail, there is just too much info. If you are interested, please feel free to post again and I'll try to be more specific and send you some resources that you can look into.