Your Back Is Doing Your Hip's Job. Here Is How a Phone Camera Sees It.

I spent three years treating my back. Stretching, core work, a better chair, every routine YouTube had to offer. Then a physio watched me bend forward for about fifteen seconds and said the sentence that ended it: your hips barely move, so your lower back rounds to get you down there. Every time. You never feel it.

That sentence is the whole idea behind Previa. The part that hurts is rarely the part that stopped moving. Physiotherapists have a name for this, regional interdependence: a restriction in one region shows up as a complaint in another. We call it borrowed movement, because that is what it looks like on camera.

What Borrowed Movement Looks Like

Raise one leg out to the side. Say your hip gives 53 degrees and your brain wants 80. Your trunk tilts 27 degrees the other way, and there is your 80. From the front it looks like a clean leg raise. The extra 27 degrees came from your lower back and your obliques, and they pay that bill every time you do it.

That was one real person in our data. Most people do a version of it. The body is very good at reaching a number, and it does not care where the movement comes from. It takes it from whatever is nearby and flexible, which for most of us is the lower back and the neck.

This is why stretching the part that hurts so often does nothing. You are working on the lender. The borrower is somewhere else.

How a Phone Camera Sees It

Four movements, about five minutes, phone leaning against a water bottle two metres away. The camera tracks 33 points on your body, on the phone itself, and nothing leaves it. For each movement we compute two angles. The apparent angle is what you would measure with a protractor on a photo. The corrected angle subtracts what the trunk, the neck or the other leg contributed. The gap between the two is the borrowed part, in degrees, per joint and per side.

From range, stability, left-right symmetry and how much is borrowed we derive one number: your movement age, the age your movement profile matches. A 31-year-old who borrows a lot moves like 38. The seven years in between are the part you can change, because they come from a pattern and a pattern can be retrained.

What 600+ Measurements Show

We have run more than 150 full assessments, over 600 single-test measurements. Of the people who told us their age, 92 percent moved older than they are. The median gap is seven years.

The patterns behind that number repeat from person to person:

Nobody on that list feels any of it while it happens. The borrowing is silent until the bill arrives as a stiff morning, a neck that needs cracking, or a back that "just does that sometimes". These are people who chose to test themselves, and we publish the numbers as they grow.

The earlier write-up, what 250+ body scans revealed, has the full breakdown by test.

Why It Changes

Borrowed movement is a routing decision, and the body keeps routes that work. As long as your back delivers the range, your hip has no reason to show up. Give the hip its job back, a few minutes a day, and the route shifts. The degrees come back to the joint they belong to.

You can watch it happen. Retest in three to four weeks, same camera, same four movements. The borrowed angle shrinks, the movement age drops, and you have the one kind of proof that means something: the number, measured twice.

Nobody wakes up with bad mobility, and nobody fixes it in a day. Both happen one rerouted movement at a time.

What to Do With Your Number

The free result shows your movement age, the biggest angle your body borrows and the joint it borrows from. The Protokoll builds a 14-day routine around exactly that pattern, exercises in the order your pattern needs, and books your retest. Measure, give the stalled joint its work back, measure again.

If you track sleep, steps and heart rate and have never measured how you move, this is the missing number. We wrote about that gap in the health metric nobody tracks.