One of them is 35-year-old Tetsuya Sotomura. When I met him on a sweltering afternoon earlier this week he was still hard at it in a converted factory building in a north Tokyo suburb, flying high into the air, spinning and tumbling on a massive trampoline.
Back in 2008 Tetsuya placed 4th at the Beijing Olympics, just missing a bronze medal. Since then he's fought injury that put him out of London in 2012 and Rio in 2016. Tokyo was to be his last hurrah, a hometown Olympics to end his trampolining career on a high. But another year is just too much.
"Back in 2008, if the Beijing Games had been postponed by a year I would have thought ok, it's another year to train, another year to grow," he tells me. "But now I am 35. A year feels like a very long time. So, I have decided retirement is the only option."
But there is another reason Tetsuya is getting off the trampoline. He thinks Tokyo 2021 may never happen.
"It's so uncertain. No one knows the probability. If what awaits us next year is cancellation, I would have lost another year for nothing. So that is another reason to go now."
Enthusiasm for the games has plummeted in Japan since COVID-19 arrived here in January. The Japanese government has closed Japan's borders to most foreigners to protect the country from imported cases, and many Japanese people are in no hurry to see them re-open for athletes or spectators.
TV reporters have been visiting the towns due to host various foreign teams and asking locals how they feel. The residents of a town north of Tokyo due to host the Brazilian team were clearly struggling to maintain any semblance of enthusiasm. An opinion poll by the Kyodo news agency found just 23% of people in Japan now support holding the games if Covid infections are still widespread next year.
The latest figures from the World Health Organization (WHO) do not make for happy viewing. More than 15 million infections worldwide, and that number is growing by about a million every four to five days.