Woke up this morning with lower back pain. So I declared this day my rest day and did slow flow instead.
I suspect it’s the mattress, which I have been using since I arrived in my sister’s house a week ago. You see, I am used to sleeping on hard surface (wooden bed and/or floor). Couldn’t find scientific explanation for this but the best resource I found in the net is an article from Beautiful on Raw.
I wish I could just sleep on my mat in my shalita. Om.