What is HRV?
HRV is the measure of the variation among the intervals of your
Why is important?
The value for HRV, typical values between 20-100, can indicate your overall health and fitness, and also tell you how ready you are for future strenuous exercise. A higher number indicates that your body is very healthy and ready for more challenging workouts.
What factors influence it?
The amount of sleep, amount of training, stress, dehydration, smoking, alcohol, and if you about to get sick, are all things that can influence your HRV.
How to use HRV to better your fitness.
The best way to use HRV is
Good resources to learn more details about HRV.
Article by EliteHRV: What is HRV
Article on HRV4Training site: A Deep Primer
Apps to monitor HRV
Devices used to measure HRV

Arguably the best and easiest devive for keeping track of your HRV.
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Thom Rating: 5 star because I think this should be a tool every serious athlete needs to take advantage.