I was really proud of myself because I was riding with my 13 year old and her 12 year old friend, and I pretty much did everything they did (except the 12 year old can jump a course).
Fast forward to today and the old hips are awfully creaky. I'm proud that I don't have muscle soreness, so I'm in good shape. But the joints, well they are not 13 anymore ... Oh well, I'm not going to stop riding! More glucosamine, I guess!