I bought the 265s about 6 weeks ago. I have started to notice that the only time my fitness age changes is if I enter my weight. Even if my weight is exactly the same, my fitness age will change immediately after I enter it. I'm a female, 5'9" tall, with a weight that hovers between 137lbs and 138lbs, so my BMI is usually around 20.3, which is a very healthy weight for my height and age (61). Despite the fact that my V02 max has been consistently improving, when I entered 138lbs 2 days in a row, my fitness age went from 54 to 55. The following day I entered my weight again, which was 137.6 (clearly a water weight difference), and it immediately went back down to 54. Not once have a I seen it change when my V02 max changes, only when my weight changes. Seems very odd to me. I would expect an improved V02 max with a balanced HRV would lower fitness age, but they don't. Whatever algorithm they're using for fitness age seems very arbitrary.
