Apple Watch Series 8 test: Secret additions to a successful watch

Always noticeable accuracy

The main sensors in the Apple Watch Series 8 are known for their accuracy, have not been advanced and still provide very satisfactory results. The heart rate sensor in particular excels at tracking variations, even during interval exercises.

Some deviations can still be observed, but the heart rate curve closely follows the reference curve obtained with the reference chest strap, Polar H10.

GPS tracking is also very good, turns are not cut too often when observing the obtained routes in more detail. The total distance measured during a running or cycling activity corresponds fairly well to reality. However, we would have appreciated seeing the arrival of a dual-band GPS chip on this 8 Series, for better accuracy in challenging environments (city center, woods, etc.).

Note that the Apple Watch Series 8 is able to automatically detect some sports activities like walking, running, and cycling, for example. It takes some time and distance (less than a kilometer by bike, according to our tests), but it’s perfectly workable if you forget to start the activity.

What’s new in watchOS 9

watchOS 9 also brings new features to the purely sports part, especially in running, since we now take advantage of displaying heart rate and strength zones. There is also new data in the Activity Report, such as vertical oscillation, stride length, and ground contact time. Interesting for those who want to go further in analyzing their training and monitoring their progress. However, there is a lack of real interpretation of these results and their consideration in training programmes.

With WatchOS 9, Apple Watches now benefit from better sleep monitoring, including wake detection, deep sleep phases, light and rapid eye movement. Compared to the data recorded with the Dreem 2 sleep tape serving as our reference, the Apple Watch Series 8’s sleep monitoring turned out to be fairly consistent.

There are certainly inconsistencies, some omissions, and less general accuracy, but the phases of deep sleep are generally detected and the other phases are correctly interpreted, making it generally possible to count the number of sleep cycles made during the night. The Apple Watch performs better than the vast majority of its competitors at this point.

Skin temperature to monitor menstruation only

However, with the new skin temperature measurement, the Apple Watch Series 8 stands out. This is currently only used to improve menstrual monitoring, particularly by detecting a slight rise in temperature coinciding with the period of ovulation. To do this, the Apple Watch compares average temperatures measured during the night, which clearly includes wearing the watch while sleeping. However, the results can only be viewed in the Health app and not on the watch itself. We’ll try to determine the accuracy of this new functionality in the coming weeks.

We can’t help but regret that Apple doesn’t use its temperature sensor to detect overheating episodes. However, the high contrast in skin temperature at the wrist may explain why this function is not yet available.