The Forgotten Biomechanics of Breathing

April 22nd, 2020
The Forgotten Biomechanics of Breathing

The Forgotten Biomechanics of Breathing: a reminder of our internal breathing mechanism during the time of COVID-19

by Jennifer Norton Graham, MPT

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Breathing Mechanics

On a day to day basis, an adult takes 12-18 breaths per minute. Our breathing mechanism is driven by muscles and joint mobility. With the current COVID-19 pandemic, revisiting our natural biomechanics of breathing could not be more appropriate.  Did you know that you can strengthen your breathing muscles and breathing mechanics?  Just like lifting weights to build muscle, or stretching to improve flexibility, you can complete breathing exercises to help strengthen and lengthen your diaphragm, intercostals (muscles between the ribs) and rib cage.  A tune up of the respiratory system in general, can go a long way especially with our current COVID-19 crisis. 

Normal Breathing Mechanics

Why understand normal breathing? If we understand normal, then we can understand when something is different with our breathing.  This understanding can help set breathing goals.  For example, in normal breathing biomechanics, we can explore the diaphragm muscle, the intercostal muscles, the joints of our rib cage/thorax, and accessory or helper muscles.  

  • Our diaphragm is a large domed shaped muscle. The diaphragm travels down into the abdomen as we take a breath in or inhale, allowing air to travel inward into the lungs. Simultaneously, the external intercostal muscles (muscles between the ribs) contribute to inhalation (breath in) by lifting the ribs up and out, also allowing air to travel into the lungs.  The external intercostal muscles and diaphragm contribute to an increase in the volume (opening) of the thoracic cavity which allows the lungs to bring air and oxygen inward.  

The Forgotten Biomechanics of Breathing

  • As we breathe out, the external intercostals relax which causes the chest wall to relax, and the diaphragm relaxes which allows it to return to it’s domed shape. As we exhale, air leaves the lungs and carries carbon dioxide out of the lungs.  
  • The rib cage provides the site for the muscles to attach which allows the thoracic cage to expand larger during the inhale, or compress the thorax during exhale.  The rib cage also helps to protect our internal organs.  At the back of the body, the rib cage articulates with the 12 thoracic vertebrae (back bones). At the front of the body, ribs 1-7 articulate with the sternum or breastbone, and then ribs 8-10 connect by way of cartilage to the ribs above, whereas the ribs 11-12 are floating at the front of the body. 
  • As we inhale, normally the chest wall will move forward and upward at the breast bone and upper ribs in a pump handle motion. The thoracic spine or back extends or straightens as we inhale, which allows the breast bone to expand further forward. The front to back portion of the rib cage increases in diameter through this mechanism. The side of the rib cage opens up the thoracic cavity in a bucket handle motion, and the lower ribs open in a caliper motion and all mechanics help to increase the thoracic cavity volume. A piston like motion occurs as the central tendon of the diaphragm pulls the diaphragm down into the abdomen.  
  • Normal expiration is a relaxed process.  The diaphragm returns to a dome, the external intercostal muscles rest, the ribs drop back down to a resting state. 

To review, a normal breath in, causes the ribs to move up and out, the diaphragm moves down.  In a normal exhale or breath out, the rib cage and diaphragm relax, allowing the ribs to move back to a downward position, and the diaphragm to a dome shape. 

Did you know that the muscles in your neck can help you breathe when you need help or in cases of illness?

Yes, that is correct.  The neck muscles (see diagram) specifically the sternocleidomastoid, upper trapezius, and scalene muscles do not usually assist during normal resting inhalation.  However, when needed, these muscles can contribute to a deeper inhale during physical activity, and in the case of illness or disease.  If the diaphragm muscle is not working effectively or is weak, then these neck muscles can contribute as primary muscles of inspiration. Breathing with the neck muscles or accessory muscles is not generally what we want in normal breathing, but is important to understand the role that they play, as helping muscles of breathing.  Here is a closer look at the back-up muscles to breathing: 

  • Sternocleidomastoid muscles bring the breast bone up which helps to increase the front to back diameter of the thorax.
  • Upper trapezius muscles bring the shoulders up, which then in a roundabout way bring the ribs upward during labored inhalation.
  • Scalenes help to hold the first rib during normal resting inhalation, and during deep or abnormal breathing they help to bring the first two ribs up which causes an increase of the thoracic cavity if the neck is not moving. 
  • Serratus anterior and pectoralis major and minor are also helper muscles and act by causing the ribs to rise or pull the ribs toward the arms as long as the arms are still. 

Accessory muscles or helping muscles of active expiration or exhalation are important to understand as well.  Expiration or exhalation in a controlled manner, forced or prolonged is assisted by the contraction of the abdominals and the internal intercostals. 

  • Abdominals cause the rib cage to contract forcefully down, which then squeezes the abdominal contents upwards into the diaphragm.  When the abdominals contract, the pressure on the inside of the rib cage increases and pushes air out of the lungs.
  • Internal intercostal muscles pull the ribs down and in, also compressing the abdominal contents and increasing the pressure inside the rib cage causing air to be pushed out of the lungs. 
What happens when breathing shifts off the normal track?

Abnormal Breathing Patterns or mechanics

There is something called Paradoxical breathing, why?  Because the breathing mechanism is a paradox.   In this abnormal pattern of breathing as you inhale, the ribs move down and on exhale the ribs move out. The complete opposite of what was written above when describing the normal breathing mechanics.  Abnormal breathing from a mechanical standpoint can occur when the breathing has become inefficient or is imbalanced.   For example a person uses the diaphragm only, or only their external intercostals or when the accessory muscles or helper muscles have shifted into primary roles.  Or if the mobility of the rib cage, overlying tissues or vertebrae do not move well enough to allow the mechanics of breathing to work at their top ability. Other abnormal patterns of breathing include:

  • Shortness of breath (dyspnea)
  • Rapid or shallow breathing (tachypnea)
  • Slow breathing (bradypnea)
  • Deep fast breathing (hyperventilation)
  • Unable to breathe while lying on your back (orthopnea)
  • Stopping breathing at the end of exhaling (apnea)
  • Stopping breathing in the inhale (apneusis)
  • Periods of deep breathing alternating to shallow breathing (periodic breathing or Cheyne-Stokes breathing)
Physical Therapy can help you strengthen and mobilize for Breathing optimization!

Our physical therapist has a specialized understanding of breathing mechanics (both good and bad) and the effects on overall health and function. At Graham Therapy and Fitness, P.A. traditional physical therapy exercises and other techniques are utilized such as:

    • Diaphragmatic breathing exercises
    • Pursed lip breathing 
    • Intercostal muscle breathing exercises 
    • Accessory respiratory muscle inhibition/relaxation exercises
    • Joint and fascia mobilization techniques
    • Lateral costal expansion
    • Segmental breathing
    • Chest mobilization
    • Cough efficiency exercises 

These techniques work to strengthen or restore the natural breathing mechanisms in our body to create strength and promote optimal breathing motions.   Consider a visit to your physical therapist for a breathing mechanics evaluation.  Physical therapists have the ability to devise a plan to help strengthen and mobilize our bodies to breathe and cough more efficiently.   It can be empowering to learn what each of us already has within us, a functioning respiratory system.  Optimize your breathing mechanics Contact Us today!