A frequent source of lower-back pain comes from two muscles you might not have heard of—and that makes sense since you rarely see them on those medical posters of human anatomy in doctor's offices.

The four main muscles of the deep core—transverse abdominis, multifidus, pelvic floor and the diaphragm—work together to keep ...

Tight hip flexors, especially a deep muscle called the psoas, can silently stress your spine. Here's why this muscle deserves more attention—and how to strengthen it. Lower back pain is often blamed ...