This story was originally published on HackerNoon at: https://hackernoon.com/how-i-decoded-my-apple-watch-metrics-taking-a-look-at-the-raw-numbers-part-2.

Learn how to parse Apple Health XML & GPX files. A technical guide to "streaming" large CDA files and extracting workout kinematics using Python.
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Exporting Apple Health data results in massive, messy XML files that are difficult to process. By using a "streaming" parser to filter specific LOINC codes and extracting GPS kinematics from GPX files, I converted 300MB of raw records into clean CSVs. This structured data is now ready to be fed into a custom machine learning model to reverse-engineer VO2 Max.