Apple employees were hooked up to breathing masks and exercised in 'climate chambers' to test the Apple Watch

Apple is revealing its rigorous and highly secretive testing process for the Apple Watch in a new “Nightline” documentary, according to ABC News’ Rebecca Jarvis.

It turns out that Apple used Apple engineers, developers, and managers as test subjects to fine-tune the Apple Watch, and it all took place in a top secret lab where volunteers were hooked up to breathing masks as they exercised.

“[The employees] knew they were testing something, but they didn’t know it was for the Apple Watch,” Jeff Williams, Apple’s senior vice president of operations, told ABC News. “We hooked them up with all the masks and so forth, but we would put on an Apple Watch covered up.”

Apple also conducted fitness tests in “climate chambers,” rooms with controlled temperature and humidity levels designed to replicate various outdoor environments around the world.

To test the Apple Watch’s performance in extreme conditions, Apple also traveled to Alaska and Dubai.

ABC News is only teasing its tour of Apple’s secret Apple Watch testing lab for now, but you’ll be able to watch their full report by tuning in to “Nightline” Friday at 12:35 am EST.

In the meantime, you can watch a teaser trailer of the upcoming “Nightline” broadcast over at Yahoo! News.

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