The Physiology of Yoga

    Breath: The Incognito Master of Balance


Have you ever been struggling for balance in the middle of class, with your foot burning and eyes shifting, as your teacher delivers the cue, “Don’t forget to breathe!” In the midst of your frustration whilst trying not to topple over in natarajasana (dancer pose), you’ve probably formed a (silent) rebuttal along the lines of “Of course I’m breathing! It’s my darn leg that’s the problem!” While it is indeed very likely that you’re experiencing muscular fatigue in your leg, the breathing cue nonetheless carries more weight than you might think.

Many yogis are probably already familiar with some of the philosophy 10463728_10100192994948456_7742401807369315323_o(from both a spiritual and physiologic standpoint) behind the importance of breath in yoga practice. The breath, or manifestation of prana (which translates as “life force”), is a powerful tool that can be utilized to both calm and ignite the mind and body. By focusing on the breath, we are able to take a vacation from the constant chatter in our minds, as well as to activate the parasympathetic nervous system (more on this in a later post) to bring our physiologic processes into a more restorative state. While these are important aspects of breathing, they still overlook the role that the actual act of breathing can have on our balance.

On a macro scale, the act of breathing has been shown to influence our postural sway. As we breathe, our chest cavity expands and retracts rhythmically, slightly shifting our center of mass. Our bodies then compensate for this shift by adopting a slight sway. Several studies (1,2) have demonstrated that an increased rate of breath results in increased postural sway, a compensatory mechanism that maintains balance. Therefore, by slowing down and controlling our breath as we do in yoga, we shift our center of mass less often and thus decrease our postural sway.
Balance is controlled on a micro scale in our bodies as well. While there are several factors that play a role in this, a central player, known as the vestibular system, is located inside the ear. The vestibular system is a series of fluid-filled canals that control the way we perceive and orient ourselves in space. Intricately connected to the brain via a cranial nerve, the shifting of the fluid of the vestibular system lies in close proximity to the Eustachian tube, a small canal made up of both bone and cartilaginous material that connects the nasal cavities to the ear.

The influence of the Eustachian tube on the vestibular system and our sense of balance has been highlighted in several scenarios. In one study (3), Eustachian tube injury was linked to the development of vertigo in SCUBA divers. Similarly, another study (4) identified patients with Meniere’s disease (a disease which causes periodic episodes of vertigo) had decreased Eustachian tube function when compared to healthy individuals. While these studies are observatory and do not offer a physiologic explanation as to why Eustachian tube defect and balance are related, investigation into the anatomy of the nasal and ear cavities provides a logical explanation, as the proximity of these two structures allows for interaction between the systems. When we practice deep, slow breathing (especially
ear-anatomyujjayi breathing which constricts the back of the throat, shunting air towards the nasopharynx cavity) we are able to generate a pressure gradient which can travel from the nasopharynx cavity, down the Eustachian tube to the ear, and thus exert a pressure on the outside of the semicircular canals, providing some stabilization to the fluid inside. This stabilization prevents random, rapid motion of the fluid and has a subtle effect on the brain, resulting in a more stable and balanced neural input from the cranial nerve to the brain’s balance centers. 

A useful visual of this system is to imagine a half-filled plastic water bottle. If this water bottle is placed on its side on a counter and shaken, the fluid in the water bottle will move rapidly from side to side because of the pressure difference the water and air inside the bottle create.  However, if this water bottle is submerged underwater in a bathtub and then subjected to the same disturbance, the fluid inside will shift around less violently because the external pressure generated by the water in the tub provides a stabilizing, inward pressure on the bottle. This system also exists in our bodies, with the breath exerting an external pressure on the middle and inner ear to stabilize our vestibular system.

To bring this back to the mat: When we are struggling in natarajasana, frantically shifting our hips back and forth, that deep breath just might help incite a subtle change that will settle our bodies and minds. While the breath has other profound effects and the vestibular system is not the only physiologic process that affects our sense of balance, the application of mindful breath as a means of steadying the vestibular system can be utilized to help us in our yoga practice.

So go ahead and take a nice, deep inhale—that breath will help in more ways than you think.

For more information about Jessica, please scroll down to the previous post, or visit her bio HERE. 

References 
1. Kitajima N, Sugita-Kitajima A, Kitajima S. Altered Eustachian Tube Function in SCUBA Divers  
    with Alternobaric Vertigo. Otology and Neurotology 2014; 35 (5): 850-856
2. Park JJH, Luedeke I, Luecke K, et al. Eustachian tube function in patients with inner ear
    disorders. European Archives of Otto-Rhino-Laryngology 2013; 270 (5): 1615-1621.
3. Hunter IW, Kearney IE. Respiratory Components of Human Postural Sway. Neuroscience
    Letters 1981; 25(2):155-159
4. Byung YJ. Respiration effect on Standing Balance. Archives of Physical Medicine and
    Rehabilitation 1991; 27(9):642-645

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