https://www.cnet.com/news/apple-watch-now-has-an-ive-fallen-and-cant-get-up-mode/

To detect falls and trips in real time, Apple says the Apple Watch 4 is trained to recognize telltale signs. Aside from basic falling (fast up to down drops), the device notices diagonal movement forward (trips), and abrupt halts (slips). These events also have specific arm motions related to them as well, such as jerking forward to break forward momentum, and windmilling backwards to regain balance.

The latest smart watch from Apple though is quite a sophisticated piece of hardware, especially from a health monitoring perspective. Paired with the Health app, and running the latest Apple Watch 5 OS, the gadget tracks heart rate plus takes ECG readings. It track sleep, physical activity and exercise too. And as previous Apple Watches, this model can count and breakdown swimming sessions into duration and the type of strokes employed.