When I was younger (40s, 50s) and running a lot, I had lower back pain and mild intermittent sciatica. Long story short, after futile medical diagnostics and disastrous chiropractic interventions, a physical therapist uncovered the problem: an asymmetrical very tight psoas muscle. It was literally pulling on my lumbar vertebrae, causing inflammation and compression around the sciatic nerve roots on that side. What I learned is that it’s important to stretch and strengthen a variety of muscle groups that we often ignore (and the muscles supporting the core are key), AND it is imperative to create symmetry. We unconsciously create and reinforce asymmetry in muscle strength and nerve activation, and that can result in a real mess.