DIAPHRAGM FUNCTION FOR CORE STABILITY
By Hans Lindgren DC, 9 Jul. 2011
Dysfunctional breathing patterns
Physical and psychological causes of breathing dysfunction can be hard to separate, and dysfunctional breathing can therefore not be simply defined. Whether the cause is postural, developmental, medical or emotional, the presentation is always very similar. Breathing patterns regarded as dysfunctional include upper chest breathing with decreased or absent lateral expansion of the lower ribcage, with a tendency for asynchronous and paradoxical breathing.
During paradoxical breathing the belly is drawn in and the lower ribcage narrows rather than expands during inspiration (13). Paradoxical movement of the diaphragm has been evaluated using MRI during deep breathing which showed an upward movement of the costal part of the diaphragm when the crural part moved downward during inspiration, and the opposite relationship during expiration.
腹部肌肉不平衡活化伴隨腹內外斜肌、腹橫肌的肌張力減少，在呼吸失能族群中是很常見的。而腹直肌(尤其上段纖維)反呈現高張狀態。呼吸失能的典型特徵為:平躺姿勢下，腹直肌明顯往上抬升而下外側腹壁凹陷空洞。腹部的姿勢肌（tonic muscle)與相位肌（phasic muscle)協同收縮來協助橫膈的呼吸功能。
Postural signs of dysfunctional breathing
The ribcage is often stiff and held in an elevated position which externally rotates the ribs and pulls the costal diaphragm fibres from its normal dome shaped position to a more straight and vertical position. This position reduces the zone of apposition and thereby the diaphragm’s contraction. Spontaneous flaring of the lower ribs is often observed.
Accessory breathing muscles
Muscles including Scalenes, SCM, upper trapezius and Pectoralis are often hypertonic and over-developed from the increased vertical movement of the ribcage and elevation of the shoulders during inspiration. The thoracolumbar extensor muscles are hyper-tonic attempting to stabilize the spine in the absence of proper core stabilization. Every breath involves a shoulder elevation and a back extension. Breathing dysfunction is a common cause for stiffness and pain in the back and neck.
An imbalanced activation of the abdominal wall with reduced muscle tone in the external and internal oblique muscles as well as the transversus abdominis is common. There is usually hyper-tonicity of the rectus abdominis especially in the upper sections. A typical sign of dysfunctional breathing is therefore a marked elevation of the rectus abdominis and concave hollows at the lower lateral abdominal wall in supine. Both phasic and tonic synchronized contractions of the abdominal wall assist the function of the diaphragm during respiration.
Weak abdominals: Abdominal weakness impairs the diaphragm function. If the abdominal wall offers no resistance to the diaphragms contraction it would only displace itself downwards without any distinct increase in IAP. The opposition against the diaphragm contraction performed by the abdominal muscles maintains the important zone of apposition and dome shape of the diaphragm.
Hyper-tonic abdominals: If the abdomen is held too firmly by the abdominal muscles the central tendon cannot descend. Instead, as the diaphragm contracts, it pulls cranially on the lower ribcage which elevates and expands the ribs. If the ribs are completely fixed in place by a strong abdominal muscle contraction the breath will entirely be performed with the upper and middle chest. Abdominal hollowing and a too rigid bracing of the abdominal muscles are therefore counterproductive for ideal diaphragm activation to occur.
Ideal abdominal activity maintains the shape and pressure of the abdominal cavity sufficiently to make the action of the diaphragm more expansive on the lower ribs. The required intra-abdominal pressure is created and maintained by the synchronized activity between the diaphragm, the pelvic floor and the abdominal wall. The eccentric contraction of the abdominal wall during inspiration plays a crucial part in maintaining the zone of apposition and the length to tension ratios between the diaphragm and the abdominal muscles, as well as creating stability and support for the trunk. During expiration, contraction of the abdominal muscles increases the length and dome shape of the diaphragm, allowing for an effective contraction during inspiration
When exercising, the muscles of the abdominal wall are often heavily recruited during late expiration to force air out of the lungs. This forced expiration lengthens the diaphragm fibres prior to the next inspiration contraction and the diaphragm is thereby able to generate more tension which will increase the inspiratory volume.
醫學上：呼氣末肺容積對橫膈膜收縮及肋骨有很大的影響。慢性阻塞性肺疾病（COPD)、肺氣腫、氣喘等問題常與肺部過度充氣有關（FRC functional residual capacity增加）。過度充氣會造成橫膈縮短、減少圓頂弧度及ZOA區域。研究顯示慢性肺部過度充氣造成橫膈尺寸上的改變，此現象特別發生在ZOA區域。
失能的呼吸特徵在一般人占11 % ；占氣喘族群30 %；焦慮族群高達83 %。
Causes of dysfunctional breathing patterns
Developmental: non-ideal development during the first year of life affects the stabilization system and often results in postural changes. Signs of developmental abnormalities affecting respiration can be a short stiff chest (baby-chest), flaring of the lower ribs from insufficient activation of the oblique abdominal chains, and a protruding weak abdominal wall often with a diastasis of the abdominal wall present. The high chest position and weakness of the abdominal wall and markedly reduces the diaphragm’s efficiency.
Medical: The end expiratory volume of the lungs has a great influence on the power of the diaphragm contraction and its effect on the ribcage. Conditions like Chronic Obstructive Pulmonary Disease (COPD), emphysema and asthma are often associated with hyperinflation of the lungs where air gets trapped in the lungs. Hyperinflation results in a shortened diaphragm with decreased dome curvature and a reduction of the ZOA (3). Studies have demonstrated that changes in the diaphragm dimensions produced by chronic hyperinflation occur almost exclusively in the zone of apposition.
The shortening of the diaphragm decreases its power and efficiency. The diaphragm fibres attaching to the lower ribcage end up in a transverse orientation (low flat diaphragm) rather than vertical, and the lower ribs shift from their normal oblique position to a more horizontal direction. When the diaphragm contracts during such circumstances it is unable to lift and widen the lower ribcage and instead the lower lateral ribs are being pulled inwards during inspiration (Hoover’s sign (5)). Hodges et al (4) showed that during respiratory disease the co-ordinating function between the diaphragm and the transversus abdominis was reduced. Heart disease also commonly affects the breathing pattern.
Emotional: Psychological and emotional states often alter the respiratory control. Fluoroscopic studies show that in situations of tension and emotional stress the diaphragm shows signs of hyper-tonicity by becoming flattened and immobile.
Dysfunctional breathing is shown to be present in 11% of the normal population, in 30% of asthma sufferers and 83% in people suffering from anxiety (1).
Increased respiratory demand alters the breathing pattern and often reduces the respiratory muscles ability to perform their postural duties (4).
Additional benefits from proper diaphragm breathing
As mentioned earlier, proper diaphragm breathing allows the diaphragm to perform its respiratory function while simultaneously providing stabilization support for the spine by an increased intra-abdominal pressure (core). Properly synchronized diaphragm breathing also improves the ventilation of the lungs by increasing the inspiratory volume, which increases the level of oxygenation of the blood since the lower lobes expand more, and the majority of the blood sent to the lungs goes to the lower parts.
There is a mechanical effect on the organs in the abdominal cavity when they get pushed downwards during diaphragmatic inspiration - Dysfunctional chest breathing is shallow and mainly expands the top part of the lungs. The posture improves when the lumbar spine properly supported by a sufficient IAP and no accessory muscles (neck, chest and back) are being recruited as in the dysfunctional breathing patterns.
The key to core stabilization is to maximize the diaphragm’s efficiency in performing breathing activity and postural tasks at the same time. Kolar (7) (8) showed that the diaphragm pushes further down into the abdominal cavity during a postural task than during tidal breathing. When the postural tasks become more demanding the diaphragm’s expiratory position is lower than during tidal breathing. In short this means that the diaphragm can be pushed down voluntarily to increase the Intra-Abdominal Pressure (IAP), and provide stabilization support for the lumbar spine. The key to real core stabilization is to maintain the increased IAP while going through normal breathing cycles. This is achieved by the synchronized activity between the diaphragm, pelvic floor and the entire abdominal wall.
The diaphragm then performs its breathing function at a lower position to facilitate a higher IAP. The abdominal wall provides opposition to the diaphragm’s action. When the diaphragm contracts during inspiration the abdominal wall maintains the high IAP through an opposing and slightly eccentric contraction, and during expiration the actions are reversed and the abdominal muscles contract concentrically to compensate for the reduced pressure resulting from the diaphragm’s eccentric upward movement. The opposing activation of the abdominal wall increases the diaphragm’s efficiency of contraction by ensuring the optimal length and dome shape of the diaphragm is maintained. The position of the chest and its effect on the zone of apposition is crucial for proper diaphragm activation.
Core stabilization starts with proper function of the diaphragm!