One thing I always found a bit of a puzzle: it's widely understood, and scientifically backed up afaik, that strength training is healthy and good for longevity. Yet, if you look at people whose everyday jobs look a lot like functional strength training, eg construction workers, my general impression is that their bodies (age 50+) are in worse condition than the average population (who's not in great shape already),…
Try doing bending down and picking heavy stuff up, for 8 hours a day, every working day.