HOW DO BABIES BREATHE? PART 1
Have you ever wondered how babies breathe during the first six months of life?
There is a common misconception that in order to use the thoracic diaphragm efficiently the ribcage should remain fairly still as the abdominal wall around the navel expands resulting in belly breathing. This was taught in my yoga teacher training in the late 1990’s and is still commonly taught by both rehab providers and movement teachers. The most common reason given is that “this is how a baby breathes”.
Pictorial Human Embryology by Stephen G. Gilbert
The ribs of the human fetus are comprised of cartilage as well as areas of bony development called ossification centres as shown in this beautiful illustration by medical illustrator Stephen G. Gilbert. At birth only 30% of the spine has ossified. The pliable, largely cartilaginous ribcage, allows for distortion as the fetus passes through the birth canal.
Babies are born with a few major differences that change during ontogeny or the growth process:
Newborns have a horizontal rib cage with the ribs meeting the vertebrae at almost 90 degree angles
The ribcage diameter is nearly equal front to back, and side to side in the newborn compared to the elliptical or oval shaped ribcage in the adult.
Newborns have a horizontal or flattened thoracic diaphragm. The diaphragm is domed in the adult, sits higher in the thorax and works more efficiently.
The abdominal visceral contents of newborns are proportionately more substantial than in the adult restricting the inferior movement of the thoracic diaphragm. The abdomen is broader than it is long. In adults it is longer than it is broad.
Newborns have low abdominal tone. In the adult, abdominal tone counteracts the intra-abdominal pressure change that occurs with the descent of the diaphragm. Abdominal tone increases the work of the thoracic diaphragm. In adults the thoracic diaphragm is the major muscle of breathing doing 80% of the work. In newborns the diaphragm is not as strong and they are forced to belly breathe using shallower and faster breaths. The nervous system continues developing after birth and by the age of 2 the child has 58% Type 1 (slow twitch fatigue resistant) muscle fibres in the thoracic diaphragm.
In a nutshell the newborn’s ribs are horizontal, elevated and largely cartilaginous and they need to use their abdominal wall in order to facilitate the descent of the thoracic diaphragm during an inhale.
By the age of 10 the ribs are angled obliquely and the ribcage has the ability to expand in an anterior / posterior direction. The ribs and sternum continue to ossify, although not completely until 25 years of age.
In the adult, the thoracic diaphragm is obliquely angled and the abdominal wall has developed tone. All of these changes result in the inferior movement of the thoracic diaphragm during inhalation, accompanied by a three dimensional expansion of the ribcage and thorax, rather than the belly expansion present during an inhale in the newborn.