The TFL works with the gluteus medius to stabilize your pelvis and knee during single-leg work. It also assists in hip flexion. It's often overactive in people with tight hips. In calisthenics, it's engaged in side planks, pistol squats, and any lateral movement. Stretch and strengthen it in balance. A weak TFL contributes to poor knee tracking. Train it with lateral leg raises, hip hikes, and banded walks.