Always remarkable precision
Renowned for their precision, the main sensors of the Apple Watch Series 8 have not evolved 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 follows very closely the reference curve obtained with our reference chest strap, the Polar H10.
Heart rate curves during an interval rowing session: in purple, that obtained with the Apple Watch Series 8; in red, that obtained with the Polar H10.
The GPS tracking is also quite good, the turns not being cut too much when you observe the routes obtained in more detail. The total distance measured during a running or cycling activity corresponds rather well to reality. We would nevertheless have appreciated seeing the arrival on this Series 8 of a dual-band GPS chip, for better precision in difficult environments (city center, forest, etc.).
Note that the Apple Watch Series 8 is able to automatically detect certain sports activities such as walking, running and cycling, for example. It takes a little time and distance (less than a kilometer by bike, according to our tests), but is quite practical if you forgot to start the activity.
What’s new with watchOS 9
Version 9 of watchOS also brings new features to the purely sporting part, especially in running, since we now benefit from a display of heart rate zones and power. There are 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 a real interpretation of these results and their consideration in training programs.
With WatchOS 9, Apple Watches now benefit from better sleep monitoring, including detection of wakefulness and deep, light and REM sleep phases. Compared to the data recorded with our Dreem 2 sleep band which serves as our reference, the sleep monitoring of the Apple Watch Series 8 turns out to be rather consistent.
There are certainly discrepancies, some omissions and less general precision, but the phases of deep sleep are generally detected and the other phases are correctly interpreted, which generally makes it possible to count the number of sleep cycles carried out during a night. The Apple watch is doing better than the vast majority of its competitors on this point.
A skin temperature for menstrual monitoring only
However, it is through its new skin temperature measurement that the Apple Watch Series 8 stands out. This is currently only used to improve menstrual monitoring, in particular by detecting the small rise in temperature coinciding with the period of ovulation. To do this, the Apple Watch compares the average temperatures measured during the nights, which obviously involves wearing the watch while sleeping. However, the results are only viewable in the Health app and not on the watch itself. We will try to determine the accuracy of this new function in the coming weeks.
We can only regret that Apple does not use its temperature sensor to detect feverish episodes. The high variability of skin temperature at the wrist may however explain why this function is not yet available.
