1. PHED 1 Applied Physiology Mechanics of Breathing
AS PE
PHED 1
Applied Physiology
Mechanics of Breathing

2. The mechanics of breathing
Breathing is the first stage in supplying oxygen to our body cells
Breathing is also called external or pulmonary respiration

3. Inspiration
When you breathe in the intercostal muscles (which are laced between the ribs) contract and draw the rib cage upwards and outwards
The chest expands
At the same time the diaphragm contracts to flatten out
The lungs increases in size as the chest expands and so the pressure decreases

4. Breathing
diaphragm = sheet of muscle, which forms the internal floor of the chest
External intercostals muscles = are found between the ribs and they control rib movement.

5. Expiration The intercostals muscles relax
The ribs move downwards and inwards under their own weight
The chest gets smaller
The diaphragm relax
The lungs decrease in size, as the chest gets smaller
They are squeezed by the ribs and the diaphragm

6. Expiration
The pressure of the air inside the lungs has increased and is higher than the external (atmospheric) pressure
This squeezing effect forces the air out via the lungs and nose or mouth, the same route by which it was drawn in

9. Our breathing and sport
When the body is at rest the movements of the diaphragm alone are enough for breathing
Breathing is automatic

10. Our breathing during exercise
As soon as we start exercise we use our external intercostals, sternocleidomastoid, scalenes and Pectorialis muscles to increase the depth of inspiration
Abdominals and Internal intercostals are used during expiration
We breathe in and out about 16 times a minute at rest
We take in about 0.5 litres of air in each breath

11. Our breathing during exercise
If we exercise at a high intensity, breathing rate can increase up to 50 times a minute and
the amount of air taken in can exceed 2.5 litres in each breath.
Therefore the amount of air breathed in can increase from 8 litres to 125 litres a minute