I know several people at 85 that are more fit and "lively" than MK was even 5-10 years ago. If you take the average 75 year old man that has no serious diagnosis (other than the typical "getting older" stuff), I find it unlikely that this person would be any less fit than MK is today. But, it's fine. Not everyone ages in the same speed, and someone has to be "below average" in this regard. I had a relative that moved like she was a typical 90 year old when she was 65, but still lived for another 20 years. Not that it was 20 happy years, but still. She hated that she couldn't do all the things she wanted to do anymore, getting tired for nothing, pains and so on. But, there is a lesson in all of this - take care of your body.