Does Correlate need an Apple Watch?

For recovery, strain, sleep and HRV-based questions, the practical answer is yes. Those series have to exist in Apple Health, and the usual source is sleeping with an Apple Watch. The app is iPhone-only (iOS 18). A WHOOP or Oura export can fill history, though live overnight Watch data going forward comes only from the Watch.

Does cancelling WHOOP or Oura mean losing the historical data?

Cancelling does not lose the historical data. Both companies provide official export files (Oura CSV, WHOOP .zip) that Correlate can import and read on the iPhone. The import on the developer’s phone held 197 days of WHOOP Day Strain and 158 days of WHOOP HRV and Recovery. There is no live account link.

Does a result like r = 0.43 at a 3-day lag mean exercise caused the HRV change?

Correlate reports a pattern in the athlete’s own data. The Ask screens say so. A statistically significant p-value and a delay are useful leads for how to train. Treat the result as a hypothesis to explore rather than causal proof.

Does Correlate send data to a server?

Correlate does not send data to a server. Everything runs on the iPhone: recovery and strain scoring, correlation testing, and imports from Oura CSV or WHOOP .zip files. The Ask Your Data footer states this directly. The app requires no account.

Does Correlate work with Garmin?

Correlate reads Apple Health and imports Oura CSV and WHOOP .zip exports. Garmin data reaches Correlate only if it also lands in Apple Health, either via a Garmin phone-app sync setting or a third-party bridge. A direct Garmin Connect link is on the developer’s roadmap rather than in the current release.