The Fitness Trends report has had a couple of enhancements. First, the colours are now easier to differentiate and the points showing actual fitness values behind the trend lines are more clearly visible. Second, a slider control has been added to the sidebar that enables you to choose the degree of smoothing for the trend lines. At the lowest level of Smoothing the trend lines follow the actual fitness values closely:
At the highest value of Smoothing a macro pattern of Fitness over the course of each year is plotted:
You can experiment with different values of Smoothing according to whether you want a general overall picture of your yearly Fitness trend (high smoothing) or a more detailed comparison of Fitness at each point of the year (low smoothing).
To compare the same day in different years numerically you can toggle the hover control that is represented by the two left-pointing bars icon at the upper right of the chart from its default value of Show closest data on hover to instead Compare data on hover:
When you do this and then hover over points on the chart you can directly compare the Fitness values for the same given day in every year:
The boxes that have a whole number for day_of_year show the actual Fitness value for that day whereas the boxes that have a fractional day_of_year show the corresponding trend value. For example, the screenshot shows that on day 179 in 2020 (blue box) the athlete had Fitness of 100 whereas in 2015 (red box) at the same time of the year the athlete’s Fitness was 81. In both cases the trend values were slightly below the actual values on that date.