Your spine spends 16 hours a day getting compressed. The routine going around is 5 minutes of paying it back, and the reason it works is buried in your anatomy.
Start with the diaphragm. Most people think of it as a breathing muscle floating in the chest. It's anchored to your skeleton by two tendon straps called the crura, which bolt directly into the L1 to L3 vertebrae. That's the same region where most back pain lives. You take about 20,000 breaths a day, and every shallow, tense one tugs on those exact bones. This is why every position in the routine pairs with long exhales.
Each pose unloads a different structure. Legs up the wall lets your psoas go slack, the deep hip flexor that runs from your lumbar spine to your thigh and spends all day shortened in a chair. The extensions and twists move your vertebrae through ranges a chair never asks for. And lying flat unloads your discs for the first time since you stood up.
The disc part is the strangest. The core of each disc, the nucleus pulposus, is about 80% water and has almost no blood supply. It feeds like a sponge. Compression squeezes fluid out all day, and only when the load comes off can it pull water and nutrients back in. You're about 1-2 cm taller in the morning than at night because your discs refill while you sleep.
Now the exhales. Long, slow exhalation stimulates the vagus nerve, the main brake line of your nervous system, and your heart rate measurably drops on every breath out. The vagus signals your brain that the threat is over, and back muscles that spent the day clenched around irritated nerves finally get permission to release.
A tense diaphragm and a tense back feed each other through the same vertebrae. Break either one and the other lets go.
Have you ever noticed that the save icon is a floppy disk, even though they became obsolete twenty years ago?
That's called a "skeuomorph" - when something new takes on the appearance of what it replaced.
And once you start to look, they're everywhere...