RMSSD, SDNN, LnRMSSD — your wearable picks one and doesn't tell you which. Here's what HRV actually measures, how Oura, Garmin, WHOOP, and Polar each capture it differently, and why your baseline matters more than any single number.
Your wearable data contains a hidden signal: the ultradian rhythm. We're building a system that reads it — predicting your best focus windows from sleep data, then refining in real-time with a heart rate monitor.
Looking for the best app for a Polar H10 chest strap? Here's what to look for if you care about heart rate, RR intervals, HRV, ECG, guided readiness checks, and long-term trends.