I lead this exploration when students talk about wanting to "stand up straight." We've probably all said or heard this before. It's common to think in straight lines because of the man made objects we look at, with mostly straight lines and flat surfaces. However, the reality of the body is far from straight.
This exploration is to trace the curves in the back of the body. You can do this on your own and it's powerful when done with a partner (exchanging the experience of tracing and being traced). You can trace with one or both of your hands or you can imagine a hand doing the tracing.
Start by sitting or standing upright (notice, I did not say straight!). Find what feels like being most balanced on your sits bones or feet allowing the top of your head to be above your spine.
Then, make contact with the top of the head. Notice the curve there. Notice how far away it is from the surface you're balancing on.
Brush the curve of the back of your head. Register as you pass the back of your head that what you're seeing with you're eyes is processed near there (because the visual cortex is in the back of the brain).
Continue to brush along your neck, noticing the cervical curve of your spine.
Continue to brush along your upper and mid back, noticing the thoracic curve of your spine and the ribs ribs on either side.
Continue to brush along your low back, noticing the lumbar curve of your spine that extends below the ribs to about belly button height.
Continue to brush along your sacrum, noticing how the direction of the curve of your sacrum is similar to the thoracic curve of the spine and the curve of the back of your head.
See if you can have all of the curves in mind simultaneously.
Do this 2-3 times and notice anything new that comes into your awareness about the curves and/or the transitions between them as you trace. This will certainly make you think about the non-linear nature of the body.
To read more about how the body is far from straight lines, check out my blog on "Our Body Concept Matters". This exercise also combines well with another key to mastering the art of being upright explained in "Is there a neck joint?" Also, try this exploration after thinking about the curves of the back of the body (tracing them in your minds eye) in the restorative lying down practice described in the “Alexander Technique For Success: The Five Minute (Un)Fix.”
Images: Spine: maxpixel.net, Head: by GDJ (pixabay.com), Sacrum: BodyParts3D is made by DBCLS [CC BY-SA 2.1 jp