As you watch, think about what the coach is telling the student and how she responds. When he tells her to sing from her toes, think about that, and empathize. Feel it in your toes. How could THAT change the way you sing? What's going on with the mind/body?
The video's roughly nine minutes long and worth watching:
Here's a post from last year where I talk about a video of a trombone master class. The coach is helping the student give a more convincing performance of a trombone part from Wagner's "Ride of the Valkyrie."