Thanks.

I am 41, and I have a local friend who did her first IM at (I think) 50. I really think I could do it if my knee would hold up, and of course, if I really have the commitment to train for a couple years. That is the question, truthfully. I am going to bike this year for a goal ride I have targeted, and I am going to use swimming for cross training. I am thinking of starting a walk/run thing in the fall and see how the knee goes.

I appreciate the info about the training and the swimming. I understand the Canadian IM has the swimming in a lake, not ocean. My friend trains here in a big glacial lake we have.