My Motorola Razr is headed for the tech recycling depot. A couple we know just bought the latest, greatest iPhones and gave us their old iPhone 6s. We're just getting to figure out some of the stuff on them. One app that I find particularly interesting is the Health App which tracks your steps and also calculates how many floors the hills are equivalent to. Neat. Two questions:

1. How does it calculate flights?

2. How do I open the transferred data?

I sent the data via mail to my iMac but, when I unzip the file (using Unarchiver), the documents are gibberish. I was expecting something that would work in Excel. The unzipped file are called export_cda.xml and export.xml

Apple's iPhone Health App does not collect data directly rather it is a repository of data accumulated from the Apple Watch, a variety of third party apps that in turn collect data from glucometers, sphygmomanometers, electronic scales, etc. as well as accumulating and recoding health data from medical providers online patient "portals". Exercise metrics are generated from data and measurements taken by the Apple Watch and communicated to the Health app on the paired iPhone by Bluetooth. The watch data is in turn generated by actual pulse measurements, ECGs, as well as arm and body movement detected through multi-axis accelerometers. You need to tell the watch when you begin strenuous exercise to get accurate credit.

I don't know about calculating flights but various movement metrics are imputed from a combination of physical movements typically associated with a particular activity and the measured pulse rate all taken from the Apple Watch.

As to the data you sent to the iPhone an xml file is not readable by Excel or Numbers. Those apps can read .CSV (comma separated value) files or their own proprietary formats. This article will explain what an XML file is and how to read them as well as a link to a site that will translate XML to CSV. NOTE: be aware that is a Windows-centric site. However how you would get the csv data into the Health app I can't help you other than most of the data can be keyed in manually.

ADDENDUM Since XML is a first cousin to HTML (both are markup languages) some browsers can read XML files. I don't know if that includes Safari or not.

Only partially correct. Yes, data are collected as stated above, but them also collects it directly, to the best of my knowledge. I do not wear an Apple Watch nor have any other active health apps, and the Health app mysteriously knows my steps and flights. Obviously it can track these when I am carrying the iPhone, but that is not always the case.

In the newer iPhones (6 and up?) there are electronics that act like an altimeter. Track little forward progress and a change in altitude and you might have a flight of stairs.

At an Apple support site someone with a similar query as mine got this response: "According to the Health app, a flight of stairs is counted as approximately 10 feet (3 meters) of elevation gain (approximately 16 steps)."