Heart Rate Variability: Reading the Trend and Training by It
Heart rate variability promises a window into your recovery and readiness—but it's noisier, more personal, and easier to misread than the apps selling it would have you believe.
Sleep trackers
Sleep Tracker Accuracy: Trust Total Sleep and Doubt the Stages
Your wearable confidently reports last night's deep sleep down to the minute, but the gap between that number and laboratory polysomnography is wider than the app lets on — here is how to read your data honestly.
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