Take a deep breath and relax

Image 1

The diaphragm with its two crura and dome-shaped muscle fibers joining into the central tendon.

The lung is attached to the walls of the thorax via a thin layer of liquid and a vacuum, which gives it its shape. On the sides, the thorax is surrounded by the ribs and it is separated from the abdomen by the muscle plate of the diaphragm. The diaphragm, in turn, is attached to the lumbar spine by its two so-called 'legs', the crura diaphragmatis, and to the ribs surrounding it. Strong muscles stretch up from this circular basis. In the centre, they meet to form a dome-shaped plate of tendons (centrum tendineum, Image 1).
The diaphragm is our strongest respiratory muscle. For this reason, it should be the main driving force of our breathing movements in all kinds of healthy respiration, be it relaxed abdominal respiration or energising respiration with bandhas.

Image 2

Relaxed abdominal breathing on inhalation: the diaphragm contracts, moves the central tendon downward and lets air flow in.

Deep abdominal breathing brings relaxation

When the diaphragm contracts, the sides of the dome shorten, i. e. the dome itself becomes flatter. If the costal arches, to which the basis of the diaphragm is attached, remain mostly motionless in the process, the diaphragm pulls down the central tendon plate. This causes a vacuum in the thorax, air is sucked in through the windpipe (trachea) and the lungs fill. Moving downwards, the tendon plate pushes down the abdominal organs and the abdominal wall bulges visibly (Image 2).

Image 3

Relaxed abdominal breathing on exhalation: the oblique abdominal muscles support the organs moving back toward the diaphragm.

Exhalation is possible by a mere relaxation of the diaphragm. The air escapes because of the elasticity of the lungs and the central tendon plate is pulled back into its initial position. The abdominal organs follow and the abdominal wall likewise moves in again. This movement can be actively supported by the oblique abdominal muscles (musculus obliquus abdominis externus and internus) by dynamically pulling in the abdominal wall and thus pushing the abdominal organs upwards. The diaphragm relaxes and is thus raised and extended. Further air escapes (Image 3).

In this way, the diaphragm moves between thorax and abdomen, with a downwards movement on inhalation and an upwards movement on exhalation. Inhalation is actively promoted by the the strength of the diaphragm, exhalation happens passively and is caused by the elasticity of the lungs. Conversely, however, exhalation can also be actively promoted by the strength of the oblique abdominal muscles, whereas passive inhalation is possible due to the elasticity of the thorax.

Image 4

Paradoxical abdominal breathing: the diaphragm contracts, but the rib cage is drawn inward and no air flows in.

Paradoxical abdominal breathing

For this type of relaxed abdominal breathing to succeed, the thorax must remain as stable as possible during the breathing process. If the thorax was not to remain stable, not only would air be sucked in on inhalation, but the costal arches would likewise be pulled inwards. Similarly, on exhalation, air would not be pushed out, but the costal arches would merely be lifted. Obviously, this so-called 'paradoxical breathing' is not efficient. Even though the diaphragm and possibly also the abdominal muscles work, only part of the energy spent is used to suck in air. The other part of the spent energy only causes a change in the shape of the thorax (Image 4).

This function is fulfilled by the intercostal muscles (inhalation: mm. intercostales externi, exhalation: mm. intercostales interni). Paradoxical breathing can be observed in people with strong paraplegia. This is the case because the intercostal muscles are controlled by nerves in the marrow of the thoracic spine, which here have lost their function. The diaphragm, in contrast, is controlled by the phrenic nerve, which originates directly in the brain and is still able to fulfill its function.