The Breathing Muscles

The lungs are passive extensible organs located within the thoracic cage, the movement of air through them is possible due to the respiratory muscles which drive environmental air in and out the airways.

Indeed, the breathing mechanism can be imagined of as a pump in which the contraction of muscles brings the expansion and compression of the thorax. Thus, changes in the volume of this cavity produce changes in the pressure within it, and as a consequence, this creates the gradient that moves air in and out the cavities. At rest the average adult takes 10 to 15 breaths per minutes, with a volume of about 0.5 litres, producing a minute ventilation of 7.5 l /min.

Essentially, all muscles that attach to the rib cage have the potential to generate a breathing action (figure 1), but we can easily divide these muscles as inspiratory muscles which expand the thoracic cavity causing inhalation and expiratory that compress the thoracic cavity causing exhalation (McConnell 2011).


Figure 1 – Respiratory Muscles from Respiratory Muscles Training theory and practice, McConnell 2013.


Inspiratory Muscles

Figure 2 – Deep Frontal Line from Anatomy Trains, Myers 2001.

The principal muscle of inspiration is the diaphragm, a domed sheet muscle that separates the thoracic and abdominal cavities. It attaches to the lower ribs and the lumbar vertebrae of the spine. When it contracts, the dome sheet moves downward into the abdominal cavity like a piston. This movement increases the volume of the thoracic cavity, creating a negative pressure. Its contraction also induces the lower ribs to move upward and forward, which also increases thoracic volume.

But the diaphragm is also part of the Deep Front Line (DFL) which starts from the underside of the foot, passing up behind the bones of the lower leg and behind the knee to the inside of the thigh. From here the major track passes in front of the hip joint, pelvis, and lumbar spine, while an alternate track passes up the back of the thigh to the pelvic floor and re-joins at the lumbar spine. From the psoas-diaphragm interface, the DFL continues up through the rib cage around and the thoracic viscera, ending on the underside of the viscerocranium (figure 2) (Myers 2001).
As stated by Myers, the DFL plays a significant role in the body’s support especially in lifting the inner arch, stabilising each segment of the legs, supporting the lumbar spine from the front, maintaining the chest while allowing the expansion and relaxation of breathing, balancing the neck and the head.

Other primary inspiratory muscles are the external intercostal muscles located in the area between adjacent ribs. Their contraction moves the ribs upward and outward (similar to the raising of a bucket handle) and also serves to stabilise the rib cage, to make it more rigid, as well as to help in small rotation of the trunk.

Finally, the scalene and sternocleidomastoid muscles are attached to the top of the sternum, to the upper two ribs, and clavicle, to the cervical vertebrae and mastoid process. When these muscles contract, they lift the top of the chest contributing to the inhalation.


Expiratory Muscles

The principal muscles of expiration are the rectus abdominis, the transversus abdominis and the internal and external oblique muscles. When these muscles contract, they pull the lower rib margins downward, and compress the abdominal compartment, raising its internal pressure.
But, is worth to mention that resting exhalation is a passive process brought about by the recoil of the lungs and rib cage at the end of inspiration. Thus these muscles only come into play as breathing muscles during exercise or in forced breathing manoeuvres (including coughing and vomiting).



  • Cover: Thorax and Abdomen of Leonardo da Vinci 1507
  • McConnell, A., 2011. Breathe strong, perform better.: Champaign, IL: Human Kinetics, c2011.
  • Myers, T. W. L. M. T., 2001. Anatomy Trains: myofascial meridians for manual and movement therapists / Thomas W. Myers; forewords by Leon Chaitow, Deane Juha.



The Core

muscles-of-the-abdominal-wallCore is defined as the most important or essential part of something.

Talking about the human body the term core or core box refers to the muscles surrounding the hips, pelvis, and lower back.

Core has been used to refer to the trunk or, more specifically, the lumbopelvic region of the body (Bergmark 1989; McDonald and Lundgren 1998; McGill 2001; O’Connor et al. 2012). Its function is crucial to stabilise the lumbopelvic region and to provide a foundation for movement of the upper and lower extremities, to support load and to protect the spinal cord and nerve roots.

Panjabi defined core stability as “the capacity of the stabilising system to maintain the intervertebral neutral area within physiological limits” (Panjabi 1992).

While Tsatsouline underlines how “without the stable platform provided by the core muscle we are just shooting a cannon from a canoe” (Tsatsouline 2010; McConnell 2011).

The core’s main muscles are:

•          Rectus Abdomins – better known as the six-pack. This muscle runs from the ribs to the pelvis and is responsible for trunk flexion (e.g. crunches).It also provides stability to the spine and pelvis when it works with the other core muscles.

•          Multifudus – the group of muscles that runs between the vertebra in the spine, providing extension and rotation to each spinal segment.

•          Transverse Abdominis – the deepest muscle layer of the abdominals. It’s a belt or brace that runs horizontally attaching itself to the spine, giving a narrow or slim appearance to the waist. It’s  considered to be one of the most important muscles in spinal stabilization.

•          Internal and External Obliques –These muscles run obliquely from the pelvis to the spine and are most effective in trunk’s rotation.

•          Gluteus Maximus, Medius and Minimus – the hip’s muscles that support and stabilise hips and spine.

•          Pelvic Floor Muscles – the muscles that run from the pubic bones on the front to the tail bones on the back. They provide support for the organs in the pelvis.

•          Diaphragm – The main muscle for breathing. It separates the thoracic cavity from the abdomen.  Its insertions are to the xiphoid process along the costal margin, laterally goes into the ribs 6-12 and in the back, muscle’s fibres insert into the vertebra at T12 and into the lumbar vertebrae at L1 and L2. It is the roof of the core box.

To sum up, the core stability maintains a pelvic neutral position while protects the lumbar spine’s section (Stanton et al. 2004). Furthermore the core musculature is believed to play an integral role in the process of transferring energy from the trunk to the extremities (Tse et al. 2005; Abt et al. 2007; Nikolenko et al. 2011). Weak core musculature, paired with strong extremity musculature, could lead to fatigue and insufficient force’s generation that may be detrimental to many aspects of sport performance or exercise (Tse et al. 2005; Nesser et al. 2008; Nesser and Lee 2009; Nikolenko et al. 2011). Furthermore a weak core, especially in elderly people, could entail a fall accident as proven by many scientific studies (Judge 2001; Casas-Herrero and Izquierdo 2012; Dae-Sik et al. 2014; Azizan and Justine 2015; Kwon-Young 2015).

Luckily many researchers and fitness instructors had worked out a huge number of exercises some of them really efficient for train our core muscles.

A short table of some of these exercises is reported here:

Exercise type Example
Traditional core exercises Back extension. Sit-up.
Core stability exercises Prone Plank. Side bridge.
Ball/device exercises Back extension on ball. Crunches on a ball.
Free weight exercises Squat. Deadlift.
Noncore free weight Shoulder press. Biceps curl.

Modified from(Martuscello et al. 2013)


Then, are you ready to start?

Ask your personal trainer to teach you one of these exercises and start build you core!

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Azizan, A. and Justine, M., 2015. Elders Exercise and Behavioral Program: Effects on Balance and Fear of Falls. Physical and Occupational Therapy in Geriatrics,33 (4), 346-362.

Bergmark, A., 1989. Stability of the lumbar spine: A study in mechanical engineering. Acta Orthopaedica,60 (S230), 1-54.

Casas-Herrero, A. and Izquierdo, M., 2012. [Physical exercise as an efficient intervention in frail elderly persons]. An Sist Sanit Navar,35 (1), 69-85.

Dae-Sik, K., Dae-In, J. and Mi-Ae, J., 2014. Analysis of Core Stability Exercise Effect on the Physical and Psychological Function of Elderly Women Vulnerable to Falls during Obstacle Negotiation. J Phys Ther Sci,26 (11), 1697-1700 1694p.

Judge, J. O., 2001. Core concepts in geriatrics. Physical activity…adapted from the American Geriatrics Society’s Geriatrics Review Syllabus: A Core Curriculum in Geriatric Medicine, 4th ed. Clinical Geriatrics,9 (13), 19-30 17p.

Kwon-Young, K., 2015. Effects of core muscle stability training on the weight distribution and stability of the elderly. J Phys Ther Sci,27 (10), 3163-3165 3163p.

Martuscello, J. M., Nuzzo, J. L., Ashley, C. D., Campbell, B. I., Orriola, J. J. and Mayer, J. M., 2013. Systematic Review of Core Muscle Activity During Physical Fitness Exercises. Journal of Strength & Conditioning Research (Lippincott Williams & Wilkins),27 (6), 1684-1698.

McConnell, A., 2011. Breathe strong, perform better.: Champaign, IL : Human Kinetics, c2011.

McDonald, J. C. and Lundgren, K. L., 1998. The progressive dynamic lumbar stabilization program for the treatment of musculoskeletal dysfunctions that contribute to mechanical low back pain. Journal of Sports Chiropractic & Rehabilitation,12 (2), 55-64.

McGill, S. M., 2001. Low back stability: from formal description to issues for performance and rehabilitation. / Maintien du bas du dos: de la description formelle au pragmatisme dans un cadre de performance et de reeducation. Exercise & Sport Sciences Reviews,29 (1), 26-31.

Nesser, T. W., Huxel, K. C., Tincher, J. L. and Okada, T., 2008. The relationship between core stability and performance in Division I football players. Journal of Strength & Conditioning Research (Lippincott Williams & Wilkins),22 (6), 1750-1754 1755p.

Nesser, T. W. and Lee, W. L., 2009. THE RELATIONSHIP BETWEEN CORE STRENGTH AND PERFORMANCE IN DIVISION I FEMALE SOCCER PLAYERS. Journal of Exercise Physiology Online,12 (2), 21-28.


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Tsatsouline, P., 2010. SECRETS OF THE SOVIETS. Men’s Fitness,26 (5), 129-133.

Tse, M. A., McManus, A. M. and Masters, R. S. W., 2005. DEVELOPMENT AND VALIDATION OF A CORE ENDURANCE INTERVENTION PROGRAM: IMPLICATIONS FOR PERFORMANCE IN COLLEGE-AGE ROWERS. Journal of Strength & Conditioning Research (Allen Press Publishing Services Inc.),19 (3), 547-552.