I used to have that when I started cycling (after never doing any sports throughout my whole life, not even the required exercises in school) but it was a combi

I used to have that when I started cycling (after never doing any sports throughout my whole life, not even the required exercises in school) but it was a combination of doing too much too quickly with not having adapted the rest of my behavior to support it (sleeping, eating, drinking). As they say, finding the right balance is golden.