Think im the opposite to you then. I find running 3 miles so easy but struggle on my UB work although its starting to come together. I recently got back from the Brecon Beacons national park. Had some nice runs and mountain bike rides out there. Whenever I was riding I had quite a heavy backpack on so I think thats contributed to my UB. When I climbed a small mountain (only 620m but not on a trail) I had my mountain bike over my shoulder along with my half stone backpack and it was too easy.
Does anyone know wherebouts the RM train in that area? I heard they go there on either week 24 or week 26 in basic training. There was a small army convoy parked near the top of the mountain. They looked pretty impressed lol
i think that i must do a hell of a lot more training if you find that easy 
