In the life drawing session I attend, we usually start off with a continuous movement exercise where the model completes an action. For some reason almost everyone dislikes this part but I have noticed an improvement since doing them so it is obviously worth the while!
I’m not sure how convincing these moving figures are, some are more static than others but the ones where the arms are moving, or over the head go some way to represent an action. The action is not always clear, unless there is a prop involved, for example the hula hoop. If you can get all of the limbs in action then it will resemble a figure that is moving.