Diaphragm function & core stability
DNS testing and assessment
By Hans Lindgren DC, 10 Aug 2011
Proper diaphragm function is fundamental for proper core stabilization. As previously described in “Core Stability from the Inside Out” proper core stabilization is achieved by the simultaneous activity of the diaphragm’s two functions of respiration and stabilization.
Postural assessment can be very indicative of the quality of the core stabilization. As described in “Diaphragm function for core stabilization” the position of the chest and pelvis affect the synchronized activity of the diaphragm and pelvic floor. An elevated chest position reduces the zone of apposition between the diaphragm and the lower ribcage, and impairs the contraction of the costal part of the diaphragm.
The combination of an elevated chest and an anteriorly tilted pelvis is a common posture that severely compromises the ability to achieve proper stabilization. Ideally the diaphragm and pelvic floor should be parallel to each other for maximal effect to occur.
The DNS program contains a series of tests to properly evaluate the function of the diaphragm and the individual’s ability to create proper core-stabilization.
1- Diaphragm function test sitting– Subject sits with a straight spine. Examiner places fingers along the lower ribs and in the intercostal spaces, feeling for a lateral expansion of the ribcage and widening of the intercostal spaces during inspiration. An upward movement of the ribcage is a sign of dysfunctional breathing. There should also be activity of the muscles of the postero-lateral abdominal wall (eccentric contraction) and there should be no thoracic spine flexion. Instruct the individual to widen the thorax laterally when breathing in.
2- Diaphragm function supine - Ask the individual to breathe normally and observe the movements of the ribcage. Cranial movement of the ribcage and an inward movement of the abdomen during inspiration are dysfunctional as there should be an expansion of the lower ribcage and abdominal wall in all directions. Place the hands on the lower lateral ribcage and feel for lateral expansion of the ribcage and activation of the muscles of the posterior-lateral abdominal wall. When only the anterior part of the abdomen is expanding during inspiration, the breathing stereotype is dysfunctional. Additionally, activation of the pectoralis and neck muscles when breathing is another dysfunctional breathing pattern.
3- Diaphragmatic function supine - once the diaphragm is properly activated the next step is to force the increased intra-abdominal pressure caused by the diaphragmatic contraction all the way down into the lower abdominal cavity. Place the hand on the lower abdomen centrally and laterally (just above groins) and feel for a pressure increase during inspiration.
If the diaphragm’s respiratory function is properly activated, the next step is to test its function of stabilization. Kolar et al showed that the diaphragm has both a postural function, and is under voluntary control. As previously mentioned, the diaphragm can perform its two functions simultaneously, and that is what we will test for next.
4- Intra-abdominal pressure test supine - Place the person in a supine position with flexion of knees and hips, and the lower legs supported. The hips should be slightly outwardly rotated and in a slight abduction, which corresponds to the width of the shoulders. Bring the individual’s chest in to a caudal position, and remove support from the legs. The individual is asked to actively hold the position while the examiner assesses both the activity of the abdominal wall and the movement of the chest. Signs of good intra-abdominal pressure are if the chest is maintained in caudal position and the lower chest widens during inspiration. There should be a proportional activation of all parts of the abdominal wall. The lower abdomen should have a full rounded appearance, and not a central ridge with concavities at the lower lateral part of the abdomen, which indicates a Rectus Abdominis dominant activation with insufficient intra-abdominal pressure. Rectus dominant activation can also be detected by observing the movement of the umbilicus, as upwards movement indicates an over-activity of the upper rectus abdominis muscle. Other signs of poor activation of intra-abdominal pressure are if the chest lifts to a high position, and if there is little or no activation of the latero-dorsal aspect of abdominal wall. Anterior tilt of the pelvis, and hyperextension of L/S and T/L junctions due to hyper-activity of the paravertebral muscles indicates instability due to insufficient intra-abdominal pressure.
5- Intra-abdominal pressure test sitting - Individual sits with a straight spine. Place thumbs on the lower lateral abdomen (the concavity prone area) and ask the individual to push against the fingers. This gives an opportunity to assess the individual’s ability to create an increased intra-abdominal pressure in the lower part abdominal cavity by voluntarily contracting and pushing the diaphragm downwards. The chest should be kept in a caudal position and there should be no compensatory spinal movements during the activation. Watch for activity of the abdominal muscles. The pressure should come from the inside out and not through activity of the abdominal wall. Inwards movement of the abdomen or an umbilical movement in a cranial direction are signs of dysfunctional activation. There should just be an even expansion of the lower abdomen with the appearance of the area above the groins filling out. This test can also be performed with the individual lying on their back. The individual can push against their own fingers for a great self-monitored exercise when proper activation has been achieved.
The next step is to combine the two functions.
6- Intra-abdominal pressure while performing normal respiration - once the individual can use the diaphragm properly both to “breathe” into the lower abdomen and to push the diaphragm down to increase the intra-abdominal pressure, the two functions should be combined and tested. Ask the individual to breathe in and to push against the examiners fingers placed at the lower lateral abdomen, and to maintain that pressure while going through normal respiratory cycles. During this activity the diaphragm is performing its respiratory task at a lower position whilst simultaneously maintaining an increased intra-abdominal pressure. This test can and should be tested when sitting, standing and lying on the back.
This combined activity is the key to proper core-stabilization.
Once the simultaneous activity of the diaphragm’s dual functions has been properly established we perform tests when moving the neck, arms and legs while assessing the ability to stabilize the core.
7- Trunk and neck flexion test supine -The individual is lying on the back and performs a slow neck and then trunk flexion. The activity of the abdominal muscles is assessed and there should be a balanced activity of all the sections of the abdominal wall with no concavities at the lower lateral abdomen. The chest should be kept in a lowered position and there should be no excessive bulging of the lateral abdominal wall or flaring of the lower ribs. The Thoraco-lumbar and Lumbo-sacral junctions should be stable. This test also gives an opportunity to assess the deep neck flexors, since their weakness will produce a forward poking of the chin when lifting the head.
8- Arm lifting test in supine - Test for the individual’s ability to maintain the position of the chest with a proper breathing pattern and an increased intra-abdominal pressure, while lifting the arms up above the head and down again. Repeat the movement slowly several times and look for proper activation. There should be no cranial movement of the chest and the entire abdominal wall should be evenly activated. There should be no over-activity of the rectus abdominis with an upwards movement of the umbilicus and concavities at the lower lateral abdomen. The lower ribs should expand slightly during inspiration. Pay close attention to the postero-lateral abdominal wall and make sure there are no ante-version of the pelvis and hyper-extension of the Lumbo-sacral and Thoraco-lumbar junctions. This test can also be performed with the individual standing up.
9- Leg lifting supine - Hips and knees in 90 degrees flexion. Initially the individual’s legs are supported while the proper activation of the increased intra-abdominal pressure is established. The individual then supports the weight of the legs and moves them down to touch the floor alternately, whilst maintaining the core stabilization pattern during normal breathing. Watch for chest movement and activation of the entire abdominal wall. Concavities in the lower lateral abdomen are indicative of poor stabilization and so is hyper-extension of T/L and L/S junctions.
10- Sitting hip flexion test - Individual is sitting with a straight spine with the legs slightly apart and hanging freely. The examiner sits behind placing the fingers on the spine at the T/L junction and on the lateral abdominal wall. The individual is instructed to lift one knee. Assessment is made of the stability of the T/L junction and the activation of the abdominal wall. There should be no side shift of the Thoraco-lumbar junction and no spinal movement in flexion or extension. There should be an activation of the abdominal wall. Hyper-activity of the paravertebral muscles at the T/L junction and side movement of the trunk are common signs of dysfunctional stabilization.
11- Sitting hip flexion test -Another method of testing the stability during hip flexion in sitting involves the examiner being in front of the individual and placing the thumbs at the lower lateral abdominal wall. Ask the individual to push against the fingers while lifting one knee by flexing the hip. Watch for the activation of the abdominal wall. There should be an even expansion of the entire abdomen with no excessive contraction of the Rectus abdominis, which is apparent by the upward movement of the umbilicus and concavities appearing in the lower lateral abdomen. Lifting of the chest and an inward movement of the abdomen are other common signs of poor stabilization. Proper activation of the core from the inside is felt as a constant pressure against the thumbs and should allow for hip movement to occur with a stable pelvis and spine. Flexion, extension, rotation and lateral movement of the spine are all signs of poor stabilization. In this test a slight resistance can be added to the lifted knee to further assess the quality of stabilization.
12- Core stabilization during movements of arms and legs simultaneously - should also be assessed. The individual must be able to maintain intra-abdominal pressure and proper breathing throughout the movement of the limbs. In supine this is the basics for all different versions of “dead-bug” exercises.
Each of the tests will give us valuable information regarding the individual’s ability to develop and maintain a proper IAP and keep the spine and supporting joints stabilized and centred. The result of these tests will greatly affect the selection of exercises and determine level of loading able to be used. Each of the tests can also be used as an entry level to stabilization exercises. Once the person can activate the proper pattern they can be used as home-exercises.
These tests should be performed prior to assessments of other movement and stabilization patterns, since the inability to activate the core from the inside out will affect all other stabilization patterns in the body.
Signs of improper activation of core-stabilization during movements are:
Elevation of the chest - brings the diaphragm away from ideal position for maximal activation
Breath holding when performing tasks
The inability to maintain the intra-abdominal pressure during the normal respiratory cycle
Imbalanced abdominal activity with excessive contraction of the rectus abdominis, and lack of activity of the lateral and posterior parts of the abdominal wall
Belly breathing pattern where only the front of the abdomen expands
Concavities at the lower lateral abdomen
Hyper-activity of the Thoraco-lumbar paravertebral muscles
Excessive movement in Thoraco-lumbar and lumbo-sacral junctions
Once the core has been properly activated, the controlled increased intra-abdominal pressure during normal breathing should be incorporated in all exercises and they all become core exercises!
If you are performing core exercises with the chest lifted and there are concavities at the lower lateral part of abdomen, you are probably wasting your time!
Next section will cover activation and training of the core.