Muscle · Chest

Diaphragm

Diaphragma

A domed sheet of muscle sealing the bottom of the rib cage, separating the lungs and heart above from the abdomen below. Its fibres rise from the whole lower rim of the rib cage, from the breastbone's tip, and from the front of the upper lumbar spine by two tendinous legs, and they all converge on a tendon in the middle of the dome that is anchored to nothing but itself. When it contracts the dome flattens and drops, air is pulled in, and the pressure below it rises — which is why the founder's document gives it two jobs, not one: breathing AND core pressure regulation. The same document lists it as habitually restricted, and reads shallow chest breathing with stiff ribs as the cause of neck tension and poor core support.