&#x27;Maximum&#x27; heart rate is an urban myth. It&#x27;s a calculated expected maximum which many people can go above. It&#x27;s like the speed of a car, rather than the RPM with its redline failure meltdown.<p>Various things affect HR, for example race-day HR is usually 10BPM higher than normal. For this reason HR is more of a helpful secondary metric for an sport with &#x27;real&#x27; metrics like speed&#x2F;distance&#x2F;weight.<p>Did the fitbit put her at risk? Only if she ignored all other signs of overexertion or danger, like chest pains, dizzyness, pounding heart beats, etc.