Here’s another exchange from my Instagram Stories Q&A, plus a bit more exposition:
Q: Would you instruct to use the breath to lengthen the spine? Â Is this possible?
A: I generally do not give this cue unless the nature of the pose specifically calls for axial extension, which reduces all three of the major curves of the spine. And yes, any spinal action involves many of the major respiratory muscles.
“Lengthen the spine” is a very common cue given in yoga class that is strongly associated with safety and proper alignment. I believe that – for the most part – when a yoga teacher gives that cue, their intent is to keep the spine in neutral meaning: “don’t collapse into flexion or over-arch into extension.”  In fact, a neutral spine can be relaxed without being collapsed, and is a component of many asanas, including: Sirsasana, Chaturanga Dandasana, Adho Mukha Svanasana.
Anatomically it is not possible to lengthen your spine. The action of axial extension, in which all three curves of the spine are flattened and stabilized, can make you a bit taller – temporarily.  It is not a state you can live in forever, and you wouldn’t want to. It would be exhausting, and likely adversely effect digestion (acid reflux, anyone?).
Axial extension is present to various degrees in a number of asanas such as Tadasana, Virabhadrasana III, Dandasana, Malasana/Upavasasana and Mahamudra, as well as any pranayama in which strong bandhas are engaged. In fact, the muscular action that creates axial extension is, by definition, the action of the bandhas:
- Mula Bandha flattens the lumbar curve;
- Uddiyana Bandha flattens the thoracic curve; and,
- Jalandhara Bandha flattens the cervical curve.
All these actions both reduce the ability of the spine to articulate and reduce the freedom of respiratory shape-change. In other words, the result is spinal and breath stability (sthira). As I said before, this is not something you want to hold all the time.
Bottom line: unless I’m teaching one of the practices in which axial extension is specifically called for I do not refer to “lengthening the spine.” Â You can find more detailed information about spinal actions in many of the major asanas in our book Yoga Anatomy.
