I cancelled the subscription and kept the chart.
Strava Premium's best feature is one line: Fitness, the 42-day rolling average of how hard you have been training. It is a forty-year-old sports science model computed off data my watch already collects. So it is here now, with the fatigue and form curves that give it meaning, plus everything else the subscription was holding. 4,129 activities, all of it live.
Fitness, Fatigue, Form
Three numbers. Fitness is what you have banked. Fatigue is what you spent recently. Form is the difference, and it is the one that predicts whether today is a good day to race.
Two years of it
Fitness rises slowly and falls slowly. Fatigue does both fast. Every marathon block in here reads the same way: the two lines climb together, then fatigue drops off a cliff in the taper and form goes positive right before the start line. That gap is the whole point of a taper.
Against Garmin's own numbers
The curve above is my computation. Garmin publishes its own acute and chronic load from the same activities, on a different scale and a shorter chronic window. Both are here. If a dashboard only ever shows the version that flatters it, you should not trust the version it shows.
Two years of weeks
Every activity, not just the runs. Strength work counts here even though it never shows up in a mileage total, which is exactly why a mileage total is a bad measure of training.
Where the time actually goes
Ninety days of heart rate, by zone. The polarised training everyone recommends looks like a fat zone 1 and 2 and a thin everything else. This is the check on whether the easy days are actually easy.
The watch versus the chip
Garmin finds the fastest 5K inside any run, including the ones that were never races. Official results start when you cross the mat and include every second of the finish chute. The watch is always faster, and the honest thing is to show both rather than quote whichever is prettier.
Chip times live on the PR board. These are not those.
VO2 max and what the watch thinks I can run
VO2 max is an estimate off heart rate and pace, so read the trend and ignore the day-to-day. The predictions below are Garmin's, generated from it, and they are reliably pessimistic against a real race day.
Year over year
Nine years of it. The mileage went up every year until this one, which is a taper of a different kind.