According to Hodges and Gandevia (2000) the activity of the human diaphragm is coordinated for both respiratory and postural, although a principal muscle of inspiration; Hodges Butler, McKenzie and Gandevia (1995) suggest that the diaphragm is also active when attempting to control forces of the spine when thrown into a state of agitated confusion by reactive movements of a limb (Park and Wang, 2012)
Brumagne, Polspoel, Troosters and McConnell (2010) add to this by highlighting that with a sustained challenge to the posture of the trunk by repetitive movement of an upper limb the diaphragm is still modulated to maintain respiration but also develops tonically at the frequency of limb movement, suggesting that that there may be are at least two drives to diaphragm motoneurons during limb movement, one related to inspiration and the other to the movement and synergistically assisting in the mechanical stabilization of the spine via increased intra-abdominal pressure (Gandevia, Butler, Hodges and Taylor, 2006). This correlates to Lindgren (2011) findings who states that
1. The diaphragm is under voluntary control.
2. The diaphragm can still perform its stabilization task independent of breathing
3. The diaphragm can perform its breathing function at a lowered position to be able to provide spinal support while still breathingThe question is how can we train the diaphragm? the next part will explain this.