Those sexagenarians can decide to be old. I'm not. I walked/ran a 10K last weekend and have a half to prepare for in a couple of weeks - different from that 63YO German guy, but same principle. He's older than them but able to walk circles around them because he decided to do the work it took to get where he is, physically (and mentally, the two are not unrelated).
No one is guaranteed tomorrow, not a 90YO, not a 60YO, not a 10YO. That matters less than what you do with what you have and are.