How I Decoded My Apple Watch Metrics: Taking a Look At The Raw Numbers (Part 2)
In Part 1, I talked about the high-level "magic" happening on your wrist. How Apple uses neural networks and math to guess your VO2Max even when you’re just walking around the block. But if you're like me, "trusting papers" isn't enough. I wanted to get my hands on the raw numbers to see the "Prediction Delta" for myself
The problem? When you hit "Export Health Data" on your iPhone, you don’t get a clean spreadsheet. You get a giant, messy folder full of scary XML files.
Here’s how I tackled the two biggest data hurdles in the export: the massive health records and the hidden workout GPS paths.
Streaming the "Heavyweight" (The CDA File)
Inside your export, there's a file called export_cda.xml. This is where the "clinical" stuff lives. For example, the second-by-second Heart Rate and Blood Oxygen levels we will use to compute a VO2Max.
The...
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