The TFL is an active muscle in so many sports – lunging, squatting, and running and cycling also.
It has multiple roles in the gait cycle which is one reason why it can easily become overused or abused.
During the heel contact phase, it serves to counteract the posterior pull of the glute max, which has vast attachments along the posterior aspect of the IT Band.
During the swing phase, it assists the iliacus in flexing the hip.
It can become a dominant flexor of the hip if either the psoas or illiacus is weak. Since its an internal rotator of the hip, if either of the aforementioned functions becomes dominant, it can produce increased internal rotation of the hip on a single leg, which could lead to a compensatory increase in foot pronation.
The bottom line: it’s a busy muscle and deserves good care! 🙂