Journal
HRV: A Guide
Heart rate variability (HRV) is a measure of the variation in time between one heartbeat and the next.
It reflects the balance between the two branches of your nervous system, the sympathetic (“go”) and the parasympathetic (“rest”), and gives you a window into your overall health and wellbeing. Generally, a higher HRV is linked with better health, and a lower HRV with more stress on the system.
Later in this article, we’ll look at 30 factors that can affect HRV, both up and down. But first, let’s make sure you understand exactly what it is.
Three things to know
- HRV is measured in milliseconds (ms).
- It’s the timing between beats. If the time between beats were perfectly constant, that would mean a low HRV. The more it varies, the higher your HRV.
- HRV is highly individual. A high HRV for one person can be a low HRV for another, so establish your own baseline and track what’s relevant for you.
Factors that lower HRV
- Illness (physical stress)
- Ageing (less “rest” tone)
- Stress (the “go” system switched on)
- Smoking
- Caffeine (a stimulant)
- Alcohol
- Poor sleep
- Inflammation
- Chronic pain
- Anxiety
- Depression
- High blood pressure
- Diabetes
- Heart disease
- Obesity
It’s interesting to see the overlap with everyday wellbeing. Another way to look at it: immediate gratification tends to lower HRV.
Factors that raise HRV
- Exercise (improved fitness)
- Sleep (recovery)
- Meditation
- Breathing exercises
- Yoga
- Music
- Cold exposure
- Acupuncture
- Gratitude
- Social support
- Sauna
- Deep tissue massage
- Tai chi
- Time in nature
- Laughter
How accurate are smartwatches for HRV?
Studies differ: some find certain smartwatches reasonably reliable compared with an ECG, and others find them less accurate.
My answer: even if a smartwatch isn’t as accurate as an ECG, it can still give you a valuable picture of how your body is coping, especially when you watch the trend rather than any single number.
How I track it: a real week
Here’s a week of my own HRV readings from when I first wrote this, and what was happening in my life at the time:
- Sunday to Wednesday: working 12-hour shifts.
- Sunday: 250mg of caffeine (100mg more than usual) and a 20-minute jog in 30°C heat.
- Monday: high thirst and appetite. The start of an illness.
- Tuesday: the illness at full intensity. I didn’t go to work.
- Wednesday: improving, but still sick. I went to work.
- Thursday: still sick, but I got some rest.
- Friday: still sick, but improving.
From the Saturday, my HRV was already dropping. That would have been the moment to reduce stress (work) and stimulants (caffeine), both of which lower HRV. I’d say Sunday’s run gave it a boost (80ms on the Monday), but in the end the illness won out: plenty of ticks in the “lowers HRV” list, and very few in the “raises HRV” list.
As I began to feel better, my HRV score reflected it. I’ve seen the same thing at other times too. That’s what makes HRV useful: it often shows you what your body is doing before your mind admits it.
This is general information, not medical advice. If your readings or symptoms worry you, see your GP.
If your HRV keeps telling you you’re running on empty, the free Overgiver Profile can show you where the drain is coming from.