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The  three  main  groups  of muscles  used  for breathing  are the diaphragm, intercostal and accessory. Adopting diaphragmatic breathing  is important for reducing hyperventilation.

The  diaphragm  is a strong,  thin,  flat sheet  of muscle which separates the chest from the tummy and is shaped like the dome of an umbrella. To breathe in, the Medulla Oblongata, located in the brain, sends a message to the diaphragm to move downwards. This creates a negative pressure in the chest cavity, called the thorax, which causes the lungs to draw in air to equalise this negative pressure. The downward movement   of  the  diaphragm   on  the  abdominal   contents causes the stomach to expand a little as we breathe in.

Two activities which result in poor use of the diaphragm are bad posture and mouth breathing.  Mouth breathers  tend to breathe  using their upper chest muscles. Surprisingly, the upper  chest  does  not  expand  outwards  but  rises  and  falls with  each  inhalation   and exhalation.

Switching  to  nasal breathing   is  the  first  step  in  changing   to  diaphragmatic breathing. Poor posture  has  a negative  impact  on breathing and being  slouched  over a desk  all day will not  help. At each workshop, I demonstrate how posture influences breathing.

 

 

Note: This bell jar experiment illustrates the central role which the diaphragm performs during breathing. To breathe in, neurons within  the  brain stimulate  the  diaphragm to  contract (move downwards 1  cm to 10 cm) which enlarges the chest cavity or thorax. This causes a negative pressure (as in the first diagram) resulting in inhalation – until the pressure in the alveoli within the lungs equals atmospheric pressure. At the end of inspiration, the nerves to the diaphragm cease firing and so the muscles involved in respiration relax. This ‘compresses’ the air within the alveoli, and this causes an exhalation. It is the movement of the diaphragm from the relaxed position to the contracted position which  causes the  tummy  to  move  out,  and  that  from  the contracted position to  the  relaxed position which causes the tummy to move in.

 

‘Deep’ versus ‘big’:

The correct interpretation of the word ‘deep’ in this context is breathing  using the diaphragm.  A deep breath means  using the depth of the lungs. There is a misconception that a deep breath is a big breath. A deep breath can be a big or a small breath.  What  is  important is  that the diaphragm   moves. From time to time, I ask people to take a deep breath and the response  is almost  always huge  inhalations  of air – often through  the mouth.  Not only is this breathing  big, it is also shallow as chest muscles predominate and only the top parts of the lungs are ventilated.