So far I have just taken my 7 month old Golden Retriever for a few short 1 hr slow, flat rides and he loves it and still has lots of energy to play when we get home. He is about 60 lbs now. I know too much, too soon can cause permanent damage to there hips and heart. Most of my rides are a granny gear climb up a fire road for about 45 min. and a slow free ride descent of about 45 min.including breaks. I cant see it being much more work than playing with his buddies or the 2 hr hikes we have been doing. I think most people (vets) that dont ride think of biking as fast, long xc type rides and I know this would not be the best for a pup. Would my typical slow climb and slow descent be too much right now for my strong, healthy pup.