[ksaj]

There are also theories about suddenly becoming active again after a year and a half of relative lack of exercise, compounded with constant psychological stresses.

I would not be surprised if what Israel sees as a Pfizer issue and the US thinks of as a Moderna issue, an interesting contradiction, that this is what is actually happening. Especially since it seems to be over-represented in young active males.

[Barrin92]

the suspected rate is one case in 3k-6k vaccinations according to the article, which is a prevalence 5x-25x higher among the vaccinated than in the average population. Change in exercise regimen does not explain that. I'm not even sure that is associated with myocarditis.

[sjg007]

It's also been seen in the active duty US military so fitness level is likely independent.