The 41 year old will race for Aston Martin in the 2023 season after impressing many with his pace last season, despite his age.
He did so well, in fact, that it led many to question where age really was any sort of limiting factor to racecar driving at all.
However, Alonso has revealed that keeping up at the top level definitely takes a toll and he is having to work harder and harder to keep up.
"I've had to change many things," he said.
"The moment of my career now, the physical aspects, I have to change a few of my training routines, my travelling, events.
"Formula 1 is very demanding on energy off-track as well, so I have to really be more efficient on more of the things that I do on the weekends or in the weeks.
"On the physical aspect, for sure, I have to do much more than what I'm used to because I'm not 20 anymore."
Alonso is a relative elder statesman among the current grid in Formula 1 but he still has a long way to go to break any records in the sport.
Louis Chiron is the oldest driver to have started an F1 race at 55 years, nine months and 19 days old. Alonso would have to keep racing well into his 50s to even make the top 10.
In fact, even at 41, he is only 92nd on the list but will move into the low 80s by the end of this season.