My HRV changes a lot from day to day, and I don’t really know what it means. Is that normal, or is something off?
Hey there! Great call out. HRV can change for a lot of different reasons - it reflects how well your body responds to stress, recovers, and adapts over time. Outside of the acute, daily HRV readings that WHOOP gives you, monitoring the stability in your HRV is a great way to know how you are recovering over longer time courses. A very stable HRV means your body is recovering consistently and adapting well to stress, whereas a very unstable or highly variable HRV means your recovery is less stable, possibly due to overtraining, poor sleep, illness, or psychological stress.
This is different from your average - your average can be the same during times of very stable and very unstable HRV. Consider the following HRV values over the course of a 3-day period: 50, 100, 150. This would create an average of 100, but it is highly variable - which could be a bad thing. Consider another set of HRV values: 100, 100, and 100. This would also create an average of 100, but with much lower variability - likely signifying positive adaptation. If you are training, eating, and living normally, and your HRV is more stable than usual, that’s a great sign that your lifestyle is working well!