you'll probably know this as a chiro
I do crossfit.. which tightens the hip flexors.. to the point at the back of the hip it feels like tooth ache in glute.. then whatayaknow goes down back of IT band.. all the way to calf and sometimes numb foot..
only what i've been told, however probably not.. the worst thing is it plays up after surfing.. the movement of sitting on the board irritates it..
but you are right about yoga and that.. need to work on the range of hip motion.. PMO lol.. as well as stretch regularly.. I've never had it properly diagnosed, but crossfitters often tell me what it is

