Hi Tim, I have a 14week old collie pup, Cora, who loves being very active, playing a lot in our garden and going for long walks. She came from a long line of working farm collies, both parents working on a farm. I started reading articles that suggested I might be over exercising her and that might cause arthritis later in life. This concerned me. I’ve cut back and been trying to look for scholarly articles with good quality studies on this subject but there seems little out their. Certainly collies are not a breed renowned for premature osteoarthritis.