VO2 Max

The Pixel Watch 3 fitness score had an average error of 8.65%, with gaps too large to trust as a precise personal result. The score estimates VO2 Max, how much oxygen your body can use during hard exercise. A study in *PLOS One* tested the watch against lab measurements in 34 people. They completed a treadmill test at their hardest effort. Lab equipment measured the gases they breathed, while a chest strap tracked heart rate. The watch’s fitness estimates came from use in daily life. Across the group, watch scores averaged just 0.53 units below lab results. But that small average gap hid much larger differences between people. The estimated range of agreement ran from 12.56 units below to 11.50 above. These units measure oxygen use per kilogram of body mass each minute. A close group average does not mean a close personal result. Errors in opposite directions can cancel each other out. The authors concluded that these scores were not precise enough for individual health care decisions. They may still have value for tracking health across groups. For BioSocial members, this puts the source of each number in focus. A watch estimate and a lab result are not interchangeable. When comparing notes, sharing the device and test method gives your numbers more context. This study also did not show whether the watch reliably tracks personal fitness changes over time. How has your watch’s fitness score compared with a lab result or your experience during workouts?