Sweat or Water
If you are sweating; or you are swimming with Series 2 or 3, can the liquid on the heartrate sensor affect the accuracy and/or speed of readings?
Apple Watch Series 3, watchOS 4.2, Apple Watch Series 3 - 38mm Case
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Hi
Apple Watch Series 2 and 3 record your heart rate continuously when you record a Pool Swim or Open Water Swim using the built-in Workout app:
Work out with your Apple Watch - Apple Support
Apple advises that performance of the heart rate sensor can potentially be adversely affected by water:
For the best performance from the heart rate sensor, including during any other types of workout, be sure to wear your Apple Watch snugly, but not too tightly, on the top of your wrist:
Wearing your Apple Watch - Apple Support
Apple suggests tightening your Apple Watch band before workouts and loosening it again afterwards. Certain other factors can also affect performance of the sensor:
- Your heart rate. What it means, and where on Apple Watch you’ll find it. - Apple Support
- Get the most accurate measurements using your Apple Watch - Apple Support
Be sure to also clean and dry your Apple Watch, band and wrist after swimming, workouts and/or heavy sweating, in accordance with Apple's handling guidelines: