IOS – How to get Apple Watch 2 to calculate VO2 Max data

Today I wore my Apple Watch on the inside of my wrist while weight lifting. I tightened it one additional notch compared to how I normally wear it during daily activities. Otherwise I had noticed that it would often lose my heart rate, even on the top of my wrist. This usually happened when my arms were vertical and/or the particular exercise required me to twist my wrists.

I am happy to report my heart rate was detected without skipping a beat. The main downside is Activate On Wrist Raise is very finicky. I suppose that is to be expected since the Watch assumes it's being worn on the top of your wrist.

Possibly-relevant piece of information: I am Vietnamese with fairly light skin on the inside of my wrist. Your mileage may vary if you have darker skin.

Also note that I'm only verifying the proper function of the heart rate monitor. I haven't tested distance or step count estimates while wearing the device this way, although I don't see why that should affect those functions.

Edit: I tried again the following day and the Watch lost my pulse on occasion, on either side of my wrist, even when tightened as much as possible. I slid the Watch up my wrist a little and my pulse was detected correctly again. I think this is because when the Watch is too low, movements of your hand tug on the skin and make it harder to measure your blood flow.

I imagine the WATCH will keep as much data as its onboard storage will allow, which is several gigabytes. So, caching Health data really shouldn’t be an issue for most intents and purposes.

Since the title of the question is about the disadvantages of Airplane mode, know that placing your WATCH in airplane mode will preclude you from connecting to the Internet. Therefore, any feature that requires an active Internet connection will not work. Siri comes to mind.

Finally, since the Bluetooth antenna is also disabled, you will be unable to connect a set of Bluetooth headphones, or an external heart rate monitor. Any app that requires an iPhone connection will not work either, meaning all watchOS 1 apps, as well as many, if not most, watchOS 2 apps. GPS via your iPhone will also cease to function.

Enabling Airplane mode thus disables most of the features of your WATCH. On the other hand, there aren’t too many advantages to enabling it. You might see some gains in battery life, though most of that will come from not being able to use your WATCH for a whole lot of things. But if you weren’t using your WATCH a lot to begin with (outside of activity tracking), then battery life is more than adequate to last you an entire day.

Even if you are on a marathon hiking trip, you will defeat much of the purpose of tracking that workout anyway, since the lack of GPS will result in less accurate distance measurements. In that situation, it would be preferable to turn on Power Saving Mode under Apple Watch → Workout.