Is it normal for an 80 year old to be in better shape than much younger people?

Is it normal that I have an amazing neighbor that is an 80 yr old (actually he's almost 81 as of this year - 2017) that is fitter than more people I know under age 30? This guy is ex-Navy, maybe that's got something to do with it? He chops wood, maintains his house in excellent shape, builds stuff, still works, and logs his daily exercise miles on his FitBit (he does way over the 10k per day suggestion). This guy is so cool!