I hope some dog experts here will answer a practical question. We have a spayed female rescue dog, 4 or 5 years old, who apparently never learned to play. She is anxious, but has overcome initial fears and is affectionate. She performs the play bow and engages in running games outside, but balls and tug-of-war are alien to her. Are there any toys or procedures that might expand her play repertoire, for the sake of her exercise as well as enjoyment?