Millions of people now consult wearable devices as though they were oracles of the body, trusting readiness scores and heart rate variability metrics to guide their most intimate decisions about rest and exertion. Medical experts are urging a more measured relationship with these numbers, noting that the algorithms behind them often lack the clinical validation that their confident presentation implies. The tools themselves are not without value, but the distance between what a consumer wearable can reliably measure and what its users believe it measures has grown wide enough to cause real har