Always remarkable accuracy
Accurately known, the main sensors of the Apple Watch Series 8 have not evolved and still provide satisfactory results. The heart rate sensor excels at tracking variations, especially during interval training.
Some deviations can still be observed, but the heart rate curve follows very closely the reference curve obtained with our reference chest strap, the Polar H10.
The GPS tracking is also very good, the turns are not cut too much when you observe the routes taken in more detail. Total distance measured during running or cycling activity corresponds to reality. However, we would have appreciated seeing this Series 8’s arrival of a dual-band GPS chip for better accuracy in difficult environments (city center, forest, etc.).
Note that the Apple Watch Series 8 can automatically detect certain sports activities such as walking, running, and cycling. It takes some time and distance (less than a kilometer by bike, according to our tests), but is very practical if you forget to start the activity.
What’s new in watchOS 9?
WatchOS version 9 brings completely new features to the sports area, especially in running, where we now benefit from the display of heart rate zones and power. The activity report also includes new data such as vertical oscillation, stride length and ground contact time. Interesting for those who want to go further in analyzing their training and tracking their progress. However, there is a lack of actual interpretation of these results and their consideration in training programs.
With watchOS 9, Apple Watches now benefit from better sleep tracking, including wakefulness and deep, light, and REM sleep stages. Compared to data recorded with our Dream 2 sleep band, which served as our reference, the Apple Watch Series 8’s sleep tracking was more consistent.
Of course there are inconsistencies, some flaws, and less general accuracy, but the phases of deep sleep are usually detected and the other phases are correctly interpreted, which usually helps to calculate the number of sleep cycles in a night. At this point the Apple Watch outperforms most of its competitors.
Skin temperature for menstrual monitoring only
However, the Apple Watch Series 8 stands out with its new skin temperature measurement. It is currently only used to improve menstrual monitoring, particularly by detecting small rises in temperature with ovulation. To do this, the Apple Watch compares the average temperature measured during nights, which 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 be testing the accuracy of this new functionality in the coming weeks.
We might regret that Apple didn’t use its temperature sensor to detect fever episodes. The high variability of skin temperature at the wrist may explain why this function is not yet available.