system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 : Why does travelling make you feel so tired when you've just sat there for hours doing nothing?
gpt
Former flight medic here. There is lots of data on the "stressors of flight" (many of these stressors are also present in automobiles). As the vehicle moves, the sway and direction change cause you  to have to keep yourself upright. These micro movements cause your muscles to be continuously working (even if you don't realize it). The US Air Force has done studies report conistent exposure to aircraft vibrations can lead to fatuige and increased chance of health problems.