Does your phone count your steps if you're holding it?

Excuse me, but I was wondering something about my phone and its fitness tracking capabilities. I've been using it to monitor my daily step count, but I've noticed that sometimes I hold my phone while walking. Does this affect the accuracy of the step count? Will my phone still be able to accurately count my steps if I'm holding it in my hand as I walk? Or does it rely solely on the movement of my body to detect steps?