Hey Claire,
Be careful on the hills, especially going down. Doing too much and too fast can cause shin splints especially when going down hill. Put your effort into the climbs and let your body rest on the downs especially when you're focusing on a hill day.
Okay disregard, because I just realized you were biking and not running....
Hahaha was wondering what this was about?!?! I don't have any pain running.