If you’re planning on using the new heart rate monitoring features in watchOS 4 on your original Apple Watch think again because they aren’t there. Apple Watch Series 0, as it’s now called, can track your heart rate, but the new monitoring options require an Apple Watch Series 1 or newer.
If you have the original Apple Watch (introduced in April 2015 and discontinued in September 2016) you can’t take advantage of heart rate notifications and resting heart rate tracking. Apple hasn’t said why, so we can only speculate is has something to do with the Apple S1 processor used in the original model.
That means if you plan to use all of watchOS 4’s heart rate monitoring features you’ll have to pick up a new model. Apple still sells the Series 1 model, which does support watchOS 4’s heart rate features, and Series 3 models will be available in stores starting on Friday, September 22nd.