A student where I taught high school once asked my age and I told her. She insisted I was not that old, and so I showed her my driver's license. She was amazed and replied, "You're an official Geezer!" I was about 53 back then. Old is in the age of the beholder.
I run a lawn maintenance outfit/ like the Dolph Lundgren movie, "Army of one" I hired people in the past (18-25) years, always failed. Nobody could put up with going full bore for 14 hrs a day. One guy almost had a heart attack from the over exersion. I remember in the 2016 season, I worked 110 days straight/ 90+ hrs a week, never got tired/ fatigued, or needed an energy drink. My secret, get proper sleep, eat well, drink a few cold ones when slogging it out in the hotter days. Few years ago, the local firefighters held an iron man competion, civilians where allowed to go up against them. In the pushups event, their champion did 120, I ended up with 150
Its all in how you feel. I am very active from April to December, I walk an average of 300 km a week. However, when I start lifting weights again in December, I can only manage 70 percent of my max. ability. Hence, I lost of lot of muscle strenght over my 8 months of doing lawn work. At this point I am back to lifting max. weights. The fountain of youth is basically working out/ lifting weights/ for the brain health its reading/ collecting coins. Not good being a "couch potato". Also, I put down 6000+ calories a day, yet my waist size is better then highschool....29!