What Is the Psoas Muscle? The psoas (pronounced so-ezz) muscles are two large muscles in your lower back. You have one on either side of your spine. They're the main muscular connection between your ...

For many runners, tight or achy hip flexors pop up at some point during training. But you shouldn’t just ignore them, as it’s often a sign your muscles need some TLC. Your iliopsoas is one of the ...