Here’s why, you are slowly building the worlds strongest and tightest quads and hip flexors known to man. You are also building great vertical strength but zero laterally. Eventually this will tip your pelvis forward making your back tighter and tighter. Eventually your back will go into spasm more often.

Start now, not tomorrow or after breakfast, stretching your quads, hams and lower back. Consider laying off the heavy deadlifts and squats. I know, total heresy but I was so proud I could do 4 sets of 12 reps of 1,000lbs on the leg press on my 40th and countless sets of 405 squats until my back locked up a month later while sipping my morning coffee. Therapist asked, “umm why so heavy?” She just doesn’t understand the gym ego but 20 years out of college ball I sort of asked myself the same question.

Ditched the heavy stuff, replaced with lots of cycling and bodyweight work and back has never felt better. Guess what, I go months without missing a single workout due to soreness, sprains or strains and now look like a DB instead of a RB.

I know, tons of guys lift heavy into their 70s with no trouble, right? My advice is slack off, work hardcore on the flexibility and you just might avoid ruining your back. Good luck.

The S.I. joint theory seems reasonable. My symptoms are mostly consistent with what I’m reading. How long did it take you to recover (squat heavy again) and what did you do to facilitate that?

Hopefully things resolve soon like and you get back to full man-beast status.