Hey,
I went to the gym today with my little brother. I helped him with his posture and showed him how to squat.
While showing him, I over emphasized the posture (taking your chest out, your butt out-(I emphasized this part to get his motion from his hips and not from his knees) and keeping your abs tight), and I think I over arched my back. (His back seemed nicely straight, and my seems over curved when doing so). And about 1-2 hours later I feel a very weak pain in my lower back. Especially when standing and so.

Does it make sense that I simply over arched my back?, can I solve it by emphasizing the abs?