Were lockdowns in the US so hard that the kids were not allowed to leave the house during the time or is it more a problem of their own doing in the sense that they actually could have done sports (running, cycling, hiking, bodyweight exercises if the gym is closed,...) if they had only wanted to? Scheduled activities would have made it a lot easier to overcome one's weaker self of course.

For context: having a walk or doing sports on your own were allowed even during lockdowns here in Germany, while I know that Australia had implemented very strict measures for example.