One coach, all your data: why five fitness apps stall progress

The serious self-tracker does not have a data problem. They have a fragmentation problem: the watch knows the sleep, the lifting app knows the squats, the run app knows the tempo, and nothing knows all three. The person is the integration layer, and the person is tired.

Load is only meaningful in total

Tim Gabbett's work on the acute-to-chronic workload ratio made a simple point that the industry has spent a decade proving: injury risk rises when this week's load spikes relative to the last four, regardless of the absolute number. A ratio above about 1.5 was associated with a sharp rise in injury in the original cohorts.

The ratio only works if the load is complete. A heavy leg day counted by the lifting app and a tempo run counted by the run app are, to each app, moderate weeks. Added together they are a spike. No single-purpose app can see it, so no single-purpose app can warn you.

Recovery signals are cross-domain too

Yesterday's squats depress today's HRV. Tonight's short sleep will make tomorrow's threshold run harder than the plan assumes. The lifting app never sees the HRV; the run app never sees the squats; the sleep app sees neither. The question a coach is actually asked, can I train hard today?, needs all of them in one place.

Why the fix is not another app to log into

Adding a sixth app that asks you to re-enter what the other five already know is how most "unified" products fail. The data already flows: Samsung Health, Garmin, Whoop, Oura and Polar all write to Health Connect on Android; Hevy and Strava have APIs. The missing piece is a reader that sits on top, not another logger.

What PeakU does with the whole picture

PeakU reads sleep, HRV, resting heart rate, steps, weight and workouts from Health Connect, strength sessions from Hevy and runs from Strava, and reconciles them into one timeline with duplicates removed. Load is computed across everything on one scale, the ACWR is shown with its drivers, and the coach answers in terms of your actual week: your HRV is 12 ms under baseline and you squatted heavy yesterday, so keep the session but drop the squats. You keep logging where you already log. PeakU is the one place you go to understand it.