What I have personally found is something called Bikerdog. It hooks to the frame of your bike and you can take you dog biking! It's loads of fun, for you and expecailly them! Roxey (she's a husky and has lots of energy too!) usually pulls me for at least a mile before she even begins to slow down! Doing this a couple times a day may be just what you need to calm your little Mollie down!
Here's a pic of Roxey hooked to her bikerdog


and another

she was getting a little pooped, can you tell?!