David emphasizes Michelangelo's mastery of human movement is that the subject is not in stationary position or not even in the motion.
He used vast art skills and his art influenced many artists and were often religious.
David could be a biblical character who defeats the enormous Goliath. The figure is neither still nor in movement, and therefore the accurately carved muscles emphasize Michelangelo's mastery of the human type.
Hope it would help !
