Re: Lower Back Issue
I too felt a tightness and turned out to also be a ruptured disc. Tho I took it to the extreme.
Once injured I continued to train hard, not knowing the severity of the problem. Ended up 1 month bed ridden and learning to walk again.
Thanks to rehab, I can Crossfit now and love it.
My advice: consult a professional ASAP!
Best of luck.