"Recovery for me is tougher than it used to be. My body just doesn’t absorb everything like it used to," he said.
Age catching up
Whitlock won pommel horse and floor gold at Rio 2016 aged 23.
But, he says he is trying to adjust his body to the rigours of training four years on at 27.
"As I get older, I find an extra day off is not the worst thing," Whitlock wrote. "This is all so much harder than it used to be. I’m still learning what’s best for my body."
Whitlock is set to be the oldest man on the British team this year if selected.
Whitlock isn't considering an end to his sporting career just yet, however.
"I feel I have plenty of life left in me gymnastics-wise and that will be the same after Tokyo," he wrote.
"I do want to continue to Paris in 2024 and make it four Games, but I know to do that I’ll have to take a six-month rest after Tokyo.
"When I got into the sport I was always thinking about the here and now. But it is different now and I have my eye on four Olympics."
In the immediate short-term, Whitlock will compete at the English Championships and the British Championships, which will act as selection events for Great Britain's Olympic team.
He is considering skipping the European Championships in Paris at the end of April.
"It is a hectic year and I need to keep myself fresh for the big one in Japan."