I cant tell if my dog is angry/stressed when we play?

So sometimes in the house I randomly like to play with my dog. One of the things I like to do is start running and she'll chase after me. When she catches me, she licks me and shows no signs of aggression or anything. However during the chase she barks. My dog NEVER barks except when we play this game. She is by far attached most closely to me amongst the people in the household. Since she hardly ever barks I cant tell if this is an angry bark or just something dogs do when they play around.