Bolster. The abdominal muscles and gluteal muscles (especially the gluteus maximus) help to regulate your lower back and pelvic situation when running. Weak spot as a result of both (or the two) will have a tendency to lead to your lower back excessively arching along with your pelvis tipping forwards, https://www.theorthopaedicandpainpractice.com/lower-back-and-buttock-pain/