Hyperkinetic disorder is a form of attention-deficit hyperactivity disorder (ADHD) in which children not only have attention problems but also act impulsively and have difficulty sitting still and controlling their movements. They commonly have increased muscle tension which can hinder normal movement and manifest itself as stiffness, restlessness (as they repeatedly move around to get comfortable) and even poor handwriting. Researchers at the University of Stavanger in Norway studied 24 8-12-year-old boys with hyperkinetic disorder on two separate days. On one day they were given a placebo and on another day they were given methylphenidate (Ritalin). On the day the children were given the methylphenidate they showed temporary improvements on tests of coordination such as throwing a ball or holding a leg in the air, as well as improvements in thumb movement which could lead to better handwriting.