It's an activity related to the skeletal system. After giving the students some basic vocabulary about the bones (http://www.learningchocolate.com/content/skeleton) we show them the last part of an easy video giving some tips to take care of our bones.(http://www.youtube.com/watch?v=sQmngAicQXs): from the 4:40 minute to the end.
They will have to listen and fill in the gaps.
If they want to know more about the skeletal system and the names of all the bones they can watch the complete video.