Originally Posted by terrymorse

I disagree, you can glean some useful information from changes in resting heart rate.
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1. Reduction in RHR over weeks of training indicates increased fitness.
2. Increase in RHR from one day to the next may indicate fatigue, overtraining, lack of sleep, or dehydration.

If I see a rise in my RHR from one day to the next, I interpret that as the need to take a recover day.