Maybe for you Bro this true - but between the ages of 38 and 47 I was working as a jobbing gardener - I started off with ramps to get the machinery in the van, after a few months I could lift it all - 60 kilos was the heaviest - and that went on until I ceased being a gardener.
Since I have had a job that is very sedentary - have trouble lifting my coffee cup now.
I don't think that F1 unlike other physical sports has that much of an impact physically, Handling G force is something the body trains to and everything else is ritual gyming to stay toned which a 40+ year old is well as capable of as a 20+ year old.
Maybe eye sight and the peripheral vision and that crud goes a bit......but seriously I think if we look at Michael, he is so fit and for the love of money hope he sticks around for a while yet.
This applies to the entire human race.As you get older your whole body effectively slows down and becomes slighly less effecient.Apart from racing my other hobby was weightlifting.
Even at 55 I could still lift the same weight as could at 25.But I was unable to do it consistently in competition over the course of a day.The problem was stamina levels as my body took longer and longer to recover from each individual lift.
Added to which the continued strain and pressures on my back and knees became unsustainable and then I needed a few days to recover fro my efforts.
I'm not sure physical or mental strength is really the issue. can a driver maintain the strength and ability to keep driving fast in a modern F1 car? Actually, I think they could. The main problem I have found with getting old is all the mental baggage I have accumulated. Whether that is coming to terms with one's own mortality and how that affects one's relationships with family and friends (particularly one's own children) or with all the other things that interest us in life. F1 requires the utmost concentration and I think the baggage takes the edge off of that more than anything.
I would think that with F1 being as safe as it is then someone like Schumacher or Barrichello could carry on quite successfully into their 50's. After all, unlike boxers they're not getting punched in the head at every round. Having said that, there is one other factor to consider.
Every generation has the opportunity to benefit from studying those who have gone before and their accumulated knowledge. It stands to reason that if a young gun learns from a master and then innovates with their own intuition and learning then they will outshine their predecessors. Their elders will naturally become uncompetitive as the rising stars build further on the experience and knowledge that is passed down to them.