Google Health 5.09 started rolling out on September 25, and it counts Garmin, Apple Watch and other third-party workouts toward Cardio Load, Gadgets & Wearables reports. The one condition is heart-rate data. Before this, a hard Garmin run showed up in the app and did nothing to the number, which was a real pain if you train on a Garmin and use Google Health for everything else.
Google isn't importing Garmin's Training Load or Apple's training metrics. It takes the synced workout and works out its own figure. Garmin data arrives through Health Connect on Android or Apple Health on iPhone, and its HRV, VO2 max and lap detail still don't come through. The same update carries the blood pressure and insulin resistance trends Google announced for the Pixel Watch 3, 4 and 5. Google's support page still says Cardio Load uses only first-party data. It just hasn't caught up.