The Diaphragm in Iyengar Yoga Pranayama and Physical Therapy


Breathing exercises are popular tools with the public and healthcare providers. They are used increasingly in complementary and alternative medicine to promote health and wellness; after vitamins and supplements, they are the most commonly used therapy.
Recent studies show a positive outcome in the application of yoga-derived breathing as a therapeutic method for patients with chronic obstructive pulmonary disease (COPD). To benefit people with breathing challenges, healthcare providers and yoga teachers and practitioners must exchange knowledge.

This article reviews the physiology of the breath (an arena in which healthcare providers are trained) and experiential knowledge (where Iyengar Yoga teachers excel). Both areas are essential in the teaching of breathing techniques and Pranayama.

The Diaphragm: A Muscle and Its Tendon
Two main points about the diaphragm need to be considered: its role in not only inhalation, but also exhalation, and its unique structure.
The active role of the diaphragm in inhalation is universally acknowledged; its role in controlling the exhalation–a central concept of Pranayama–is less well recognized in medical literature. And because this action of the diaphragm is experiential, it can be difficult to understand for those without a yoga background.
Because this action of the diaphragm is experiential, it can be difficult to understand for those without a yoga background.

The muscular portion of the diaphragm that makes this control of the exhalation possible may be compared with the eccentric action of the bicep. When you lift an object and draw it toward you, the elbow bends and the bicep shortens; as you put
the object back down, the bicep is still contracting, allowing you to lower the object without dropping it. The muscular portion of the diaphragm contracts as you inhale, helping to draw air into the lungs. With slow, controlled exhalation, as in Pranayama,
it continues to contract, enabling you to exhale without letting the air rush out and without the chest collapsing.

In addition to this muscular action of the diaphragm, there is a vital but overlooked role played by the central tendon of the diaphragm. Most tendons attach directly to bones. However, the central tendon of the diaphragm attaches to the muscular rim of the diaphragm and anchors it to the spine at vertebrae L1 and L3. This tendon makes up 40% of the central area of the diaphragm.

Elongating and expanding this central tendon is essential to encouraging and controlling the breath; yogaPranayama, as well as yoga asanas, have a vital role. This has profound implications for people with breathing difficulties and should be an integral part of treatment to improve their condition.

Pranayama and Asana
In yoga, deep breathing is part of the practice of Pranayama. In Sanskrit, the ancient language of India, prana is the vital energy or life force; it also refers to respiration. Ayama means length, expansion, and extension, and conveys the idea of restraint, control, and stopping. According to B.K.S. Iyengar, Pranayama also means communication, expansion, or dimension. When practicing Pranayama, one slows down the rate of breathing and expands chest and lung capacity. Pranayama is an integral step in the eight-limbed path of yoga, AstangaYoga, which strives to bring consciousness to mind and body, and finally, freedom.

All breathing is influenced by changes in body position, emotional state, and activity level. These factors long have been considered in yogic breathing practice. Pranayama teaching focuses on prolonging and refining the inhalation and exhalation, which allows the practitioner to control the breath voluntarily.
The ability to breathe deeper and longer requires the physical preparation of the pulmonary and musculoskeletal systems, in addition to developing greater focus on the breath. This preparation of the body and mind forPranayama can be accomplished through the practice of asanas (yoga postures). To better perform these asanas, the support of a yoga prop often is needed to extend and elongate the muscles and soft tissue used in breathing.

This elongation is essential preparation for Pranayama. This is the basis for the Iyengar method's intricate instructions designed to expand and "shape" the breathing, directing the breath with awareness to various regions of the lungs incrementally.

This can be understood better when we review the biomechanics and physiology of breathing.

The Mechanics of Breathing
Breathing is a complex system of communication between receptors within the body (including chemoreceptors in the blood and stretch receptors in soft tissue), controllers in the central nervous system, and the effectors, that is, the muscles of the respiratory system. The desire or need to breathe and the regulation of the rate of breathing is controlled by the central nervous system, based on its analysis of data received from the receptors. A message is sent to the effectors; these tiny respiratory muscles then maintain adequate ventilation for the body's current state.

The goal of breathing is to keep arterial blood gases within acceptable levels to maintain the body's healthy functioning. Air must be moved rhythmically in and out of the lungs. Air exchange is accomplished through the expansion and deflation of the chest wall, which requires the action of a number of skeletal muscles. To understand how this lung-pumping mechanism works, we review below current concepts of anatomy and function of the respiratory muscles.

When air enters through the nose, it passes through the trachea, a tube-like portion of the respiratory tract that connects the larynx (the voice box) with the bronchi and bronchioles, air passageways shaped like small tree branches. Finally, the air enters the alveoli. These small sacs within the lungs resemble tiny folded balloons and have very thin walls full of blood vessels. Here is where the actual gas exchange occurs, as oxygen passes through the walls to enter the bloodstream before traveling to cells throughout the body.

The thoracic region's mechanical ability to expand and recoil depends on the elasticity of the lungs and the muscles involved. Gross muscle weakness may lead to muscle shortness and tightness, which limits the thoracic ability to expand and recoil.

Primary Muscle Activity
During inhalation, the inspiratory muscles contract in a coordinated fashion, creating an intrathoracic pressure gradient that causes air to flow into the lungs. These muscles then relax and air is exhaled because of changes in pressure and the elastic recoil of the lungs.

Deeper breathing in controlled circumstances such asPranayama, or under stressful conditions such as running, may demand the further recruitment of primary and accessory inspiratory muscles. The primary muscles of inspiration, those required during quiet and deep breathing, are the diaphragm and the intercostal muscles, located between the ribs.10
During quiet inspiration, the intercostals assist in elevating the ribs with their oblique attachment from the distal border of one rib to the proximal border of the rib below. The contraction of the external intercostal muscles causes an increase in the lateral and anteroposterior diameters of the thorax.8 Debate persists as to the exact role of the intercostal and abdominal muscles in breathing. Some have suggested that during controlled exhalation, these muscles and the diaphragm help in the "braking" action that slows the static recoil of the lungs and the chest wall. This is how the diaphragm is recruited for slow, controlled exhalation, as during Pranayama.
The diaphragm muscle is composed of three anatomically distinct regions joined and inserted in the middle to a thin central tendon. This central tendon is an often neglected aspect of breath and breath control that we consider below.

The change in the position of the diaphragm and the expansion of the chest during inhalation (left) and exhalation (right).

The costal portion of the diaphragm arises from the upper margins of the lower six ribs and is closely associated with the sternal region. The second region originates from the posterior aspect of the xiphoid process. The third portion, tendinous in structure, is the crural section, which arises from the same region of the anterior ligaments that covers and supports vertebrae L1 through L3. Fibers from all three regions of the diaphragm radiate inward, inserting into the central tendon.

The diaphragm, similar to other voluntary muscles, is characterized by the instantaneous relationship between force, length, and velocity of shortening. Muscles operate with the greatest active force when close to an ideal length (often their resting length). When stretched or shortened beyond this (whether because of the action of the muscle itself or an outside force), the maximum active force generated decreases. The power output of a muscle is the product of force developed and the velocity of shortening. The diaphragm's ability to perform, therefore, is compromised when its muscle and tendinous portion is short. Diaphragm weakness, resulting from both aging and disease, has been ascribed to the shortening of muscles and the central tendon, which influences the diaphragm's strength and ability to descend and slowly ascend.

The central tendon of the diaphragm, its dome, is a thin, strong aponeurosis comprising broad layers of fascia-like tissue with the consistency of thick leather. It is flexible, yet noncontractile, so it is pulled passively by the muscular portion of the diaphragm, to which it is attached. This is important, because different body positions affect the ability of this tendon to move and greatly affect the breath.

When the diaphragm is viewed from the top, a large portion of this central tendon is located ventrally (to the front). Its anterior muscle fibers are shorter than the posterior ones. This is important because different body positions affect the ability of the tendon and the diaphragm to contract. An image may clarify. Imagine this tendon as a circular piece of leather attached on all sides to ropes (that is, to muscle fibers). A group of people is pulling these ropes in all directions; however, because of the ventral placement of the tendon, it is as if the ropes in the back are longer than those in the front. The ligaments that attach the diaphragm to vertebrae L1 and L3–the crurae–also draw this tendon toward the back.
The central tendon of the diaphragm, its dome, is a thin, strong aponeurosis comprising
broad layers of fascia-like tissue with the consistency of thick leather.
This piece of leather must be pulled down as we inhale. Then the ropes must be released slowly to allow for a controlled exhalation.

The Roles of Props
Several restorative asanas, especially Supta Baddhakonasana, elongate the central tendon and enhance its mobility. Placing the body over a prop such as a bolster creates an arch of the lumbar spine from vertebrae L1 through L3. Returning to our image, it is as if the people holding the ropes in the back became stronger and were given longer ropes.
The diaphragm and its central tendon also contribute to the postural control of the human trunk. InSwastikasana for seated Pranayama, as well as in Baddhakonasana, the diaphragm acts as a postural support for the seated position. It is as if the people in the back are still pulling on their ropes. More advanced practitioners can experience a similar action in backbending poses such as Dhanurasana.

Pranayama as a Therapeutic Method
In Pranayama, the focus is on slowing and controlling the rate and duration of the breath, particularly exhalation. "During exhalation, the breath should not be expelled but released," Mr. Iyengar often instructs. Healthcare practitioners long have recognized the importance of slowing down the breath and focusing on exhalation, especially for people with asthma and emphysema who often have difficulty breathing because of the large amount of air that becomes trapped in their lungs.

If healthcare practitioners were to add elements of Pranayama and relaxation using the Iyengar method, it would benefit people with pulmonary distress. The current cardiopulmonary rehabilitation approach to COPD focuses mainly on improving general cardiovascular endurance, strength training, and the use of respiratory devices. There is minimal training in breathing practice itself.
With acutely ill patients, therapists use airway clearance techniques such as postural drainage and coughing. Again, active breathing techniques are used rarely or are given only secondary importance.

There is a need to expand and improve the methods of teaching active breathing for people with acute and chronic respiratory challenges. The application of yoga asanas and Pranayama techniques to breath training will help these patients by expanding the thoracic region's limited mobility, easing the tightness of muscles and tendons (particularly the diaphragm's central tendon), and improving pulmonary function.
Dalia Zwick is a physical therapist and longtime Iyengar Yoga student; she worked with Senior Teacher Mary Dunn in integrating yoga and rehabilitation for people with weakness, poor posture, breathing difficulty, and paralysis resulting from multiple sclerosis, cerebral palsy, spinal cord injury, or developmental delays.


Brooke Myers, Intermediate Junior III, New York, advised on the article; Richard Jonas edited.