Muscle · Core

Transversus abdominis

Musculus transversus abdominis

The deepest of the four sheets of the abdominal wall, and the only one whose fibres run straight around the waist like a belt. It is not a mover: pulling a horizontal band tight cannot bend or twist the spine, it can only compress what is inside it. That is the whole point — transversus abdominis raises the pressure inside the abdomen and tensions the thoracolumbar fascia behind it, and the lumbar spine gets stiffer as a result. The founder's document lists it as the core bracing muscle, and puts it on the WEAK list for this region: it is the muscle that is supposed to switch on before you lift, and the one that most often does not.