Mountain Biker's Best Friend

We just got a rescue pitbull/boxer mix who's around 1-3 years old and likes to run. I've never biked with my dogs but this one is so good off leash and needs to burn off a lot of extra energy. At first I was taking it easy but soon realized that unless it was a smooth downhill I couldn't get away from him if I tried.

I think this will become a regular thing.  I'm going to need to work on sit-and-stay so I can get some better pictures of him trailside.