Years ago i used to get a mild throbbing headache when i ran. that hasn't happened in years but does anyone have an idea what could have caused that?

Exertional: Headaches from exertion are present in a small % of people. These are often self-limiting and come on for no apparent reason and some weeks later depart the same way. Despite research, neuroscientists are still uncertain of the cause(s). Migraine and muscle tension or even temporo-mandibular joint troubles are possibilities too. Glad they've resolved. Hope you're still exercising