Performing two hard workouts in a single day, or engaging in hard workouts followed by exposure to cold temperatures during travel, tended to precede colds or flu for Andrew Huberman.

“I have seen for instance if I've ever done two hard workouts in a day something I never do any longer I've tended to get sick after that if I've tended to do hard workouts and then expose myself to cold temperatures while traveling especially traveling overseas that tended to precede those colds or flu”