Hip flexors ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The hip flexors oppose the glutes. They bring your leg forward in running, are obviously important in climbing, contribute to 360 degree pedaling, and more.
As they are overused, they totally screw up mechanics, leading to hip pain, knee pain, and back pain.
To stretch: get down on one knee, keep your torso upright, and move forward. See how I maintain that arch in my back instead of rounding forward? That’s how you get the hip flexors to stretch.