Functional Movement Screen for their influence on breathing are shoulder mobility and the active straight-leg raise.
Shoulder mobility is more than looking at range of motion of the shoulder. It lets us know if you actively extend the upper spine. It lets us know if there are restrictions in the ribcage.
It’s the same with the active straight-leg raise. The symmetry and ability to lift a leg in an unweighted situation tells us quite a bit about the pelvis, the core and the way the hips work together.
Restrictions from the neck through the pelvis can interrupt and restrict the natural rhythm we authentically use in breathing. If there’s a restriction, you have to pick another path and use an asynchronous breathing or an inefficient breathing pattern.
As I’ve always said, mobility then motor control, or mobility then stability. The first order of business: Mobility must come first.
You can fatigue the breathing muscles, especially if you’re using the wrong ones. The biggest limiting factor in your next run may not be the endurance in the quads or calves. It may be the endurance in the breathing muscles used inappropriately and inefficiently around poor upper body and trunk mobility patterns.
Crocodile breathing is another way to do that, and gives a different sense of feedback where the belly expands both side-to-side and pushes into the floor, lifting the low back, or the sway we normally have in the low back when we lie on our bellies. We see the back going up and down, which looks much like a crocodile lying on its belly and breathing.
Benefit of this style of breathing is that you will mobilize your thoracic spine and when your thoracic spine can move well - your shoulder will move and function better. The diaphragm and intercostal muscles are integral to the proper functioning of your body.