Lower abdomen got hard as a rock

I was surprised when I felt my lower abdomen got hard as a rock yesterday morning while I was laying in bed. It was not painful though. I called hubby right away coz I got nervous and thought something might be wrong with my baby but he said it is just normal to feel that way sometimes. My fears went away after hearing what he said to me. I also called mom and told her about it and she got excited and teased me that my baby is probably doing some exercises inside my womb. She told me some of her experiences when she was pregnant of hubby and how her tummy got hard also especially when dad rubbed her tummy.

That was the first time I felt my lower abdomen got hard and I searched about it and found out that it's called "braxton hicks".