Did you know that the time between each of our heartbeats is a little different with every beat? Whether our heart rate is fast or slow, the precise time between beats varies. Heart Rate Variability (HRV) is a relatively new metric in health and it gives you powerful information about how stress affects your physiology.
That’s because stress triggers two processes within the body.
- First, stress from any source activates our fight or flight system, the sympathetic nervous system (SNS). It boosts heart rate, produces stress hormones, and puts us on high alert.
2. When the stressful situation passes, our rest and digest system, the parasympathetic nervous system (PNS), takes over to relax us and return our body to homeostasis.
The amount of difference in beat timing seems to be related to the activity of our SNS and PNS. When we are rested and relaxed, we have more PNS activity. In this state, our heart rates display a lot of variability in the timing of beats. Picture a dance party: dancers move quickly, then slowly, then faster again, and so on. When we’re rested, our heartbeat dances like nobody’s watching.
If we are stressed out or not yet recovered from our last workout, our SNS dominates. Our heart rates will be less varied and more consistent – more like the metronome from piano lessons, or a ticking clock.
If stress is high, variability in the heart rate decreases. If stress is low, variability in the heart rate increases.
Why does this matter? Because now we can track and use the information to benefit our health. All it takes is a simple heart rate monitor and an app that analyzes heart rate data. Since stress from all sources contributes to SNS activity, we can use the information to gauge our exercise readiness. If our HRV is low, it means we are stressed out, and need the right kind of workout to help us recover.
We can (and should!) exercise daily. Monitoring heart rate variability helps us decide how to exercise – when to go for the HIIT class, and when to choose a low-intensity workout to promote recovery.
To get started tracking your own Heart Rate Variability (and a gazillion other metrics), see this tech guide at Quantified Self.
For more insight into tracking Heart Rate Variability in action, author Ernesto Ramirez takes a fascinating look at his HRV data from a high-stress work day.