I would like to respond to Nick's last couple of posts because I figure more than one of you might be wondering where both the relaxation and "substance" exercises lead.
Relaxation: Relaxation is an important aspect of training for individuals in the performing arts. Through relaxation of the body, actors (and dancers for the matter) are more easily able to respond to their surroundings and the people around them (part of given circumstances). It is also easier for you to control your body instead of having your body control you. If you hold tension in your shoulders then all of your character will have tense shoulders, rather than you deciding which do and which don't. It is also integral to the release of emotion. That is why Lauren became emotional. When the tension was released her emotions were free to flow.
That is just the tip of the iceberg of why relaxation is important. See if you can see how tension effects peoples ability to execute the class exercises.
Substance: The substance helps us begin to deal with space and become aware of the way in which our bodies move through it. It is important for actors to be aware of the way in which our entire bodies move through space because our entire bodies can tell stories. You can tell a story with your foot if you want. Therefore you need to be aware of your body in order to be sure that you are telling to story you intend. Giving space (i.e. air) substance helps to make us more aware of our entire bodies.
In conclusion: These are experiential tools, not intellectual tools. Your body sometimes can learn things on it own. Just like an athlete or a dancer who repeats the same movement over and over. I am just giving you a taste of these concepts in this intro class. Part of what you are learning is what actors do and what is important to the craft. These things take years to master and become seamlessly integrated into your work. These exercises have been done by actors for decades. They are a form of training for your mind and body, they are not, in themselves, acting. Chemists learn the periodic chart before they become chemists, actors do these things before they become actors.