How it works
How it responds when your walking stalls.
GaitGuard runs on your Apple Watch, where the walking happens, and mirrors everything to your iPhone. Here is what it does, step by step, in plain language.
Honest status
The logic below is covered by automated tests on simulated signals. It has not been validated on real patients, and its real-world accuracy is unproven. GaitGuard can miss a freeze and can cue when it wasn't needed.
- 1
It learns your walk
You start with a 30-second calibration walk. GaitGuard checks that you actually walked, measures your pace, and sets your own thresholds from it. It can also suggest a cue tempo that matches how you walk.
Why
People walk differently, so a personal baseline works better than one number for everyone.
- 2
The Watch listens to your movement
The Watch's motion sensor is read 50 times a second, with gravity removed. Every half second it studies the last three seconds and separates two kinds of movement: the steady rhythm of walking, and fast trembling.
Why
Freezing is brief and unpredictable, so the sensing has to be continuous and on the body.[7]
- 3
It waits for walking first
GaitGuard only treats something as a possible freeze if you were walking a moment ago, the walking rhythm has stopped, and trembling-like movement shows up for about a second and a half. It's designed so that gesturing, eating or sitting still shouldn't trigger it.
Why
Starting and stopping are common moments for freezing, but everyday movement shouldn't cause a cue.[1]
- 4
Turns are handled separately
For turns, it only cues when you turn about 70 degrees and your stride slows down while you do. A smooth turn while you're still walking is ignored.
Why
Turning is one of the most common moments for freezing, and it's easy to cue too often if you aren't careful.[1]
- 5
The Watch taps a rhythm
When it responds, the Watch plays a short run of haptic taps at your tempo: 100 beats per minute and four beats by default, all adjustable. If "repeat while frozen" is on, it repeats a few times while the freeze continues. Afterwards it measures how long the freeze lasted and updates your History.
- 6
It adapts to you
After every cue you can tap a tick or a cross on your Watch: did it help? The app becomes slightly more or less sensitive from your answers. There are also modes: Everyday, Exercise (calmer), High alert (more sensitive, and it also cues when walking simply stalls) and Custom.
Why
You know your own walking best, so the app learns from you.
- 7
The steadiness score
The score you see on the dial is built from how regular your stride is and how much of the last ten minutes was spent frozen. It is not a count of cues.
Why
It's a quick way to see how a walk is going. It isn't a clinical measure.
- 8
It looks after the battery
The Watch warns you at 20% battery, and stops monitoring and tells you at 10%.
Why
A cue that can't arrive is worse than no cue, so you're told in advance.