I've never had steps counted during Spin Class - three years of owning a Surge, and now an Ionic. This isn't because of the Android app, but the design of your device. It uses an accelerometer, which triggers on impact... footfalls, essentially.
So when you're on a Spin bike, you're not actually triggering this sensor, but when you're on a road bike, you can get step counts every time you hit a bump. I know it's not a satisfactory answer, but it is the technically correct one.
I ended up using a different app that could connect (via ANT+) to the Spin bike computer so I could get cadence and speed and track my Spin sessions. Since both Fitbit app and the other app connect to MyFitnessPal, I use this to track my calories, food, exercise. Again, not the best situation, but it's worked for me for three years now.
Best AnswerI agree. It's the best answer I've heard so far. I had some people try to strap the FItbit to their ankles.
Best Answer@K-Mac I did try that with the Surge, with limited results. Couldn't get an accurate heart rate reading on my ankle because the skin just isn't the right thickness(?), or not enough capillaries to get a good reading. Your results may vary.
Best AnswerI have done this also. I can’t believe it can’t automatically recognize an indoor spin bike. I upgraded from Alta hr to versa 2 bcz I thought it would.
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