yeah, it move the rotator cuff, which can get stiff and sore if
   you're just sitting behind a schooldesk all day long. It also
   alternatively works the biceps and triceps - do what Aleph said
   - even a pair of 1-2 lb weights are surprisingly heavy in that
   exercise because it works out some of the lesser used muscles as
   well. In real life, when would you use that motion? Well ,I can
   think of a perverse reason to use it as an adult- but it's
   really bad. "