When I came to the realization that a mismatch between my diet, lifestyle, and training was negatively affecting my health I immediately started to look for ways to quantify the impacts it was having.
Working with a practitioner and getting data from blood work, urine, and stool tests were great in providing clues into what was happening inside my body but it was only feasible to get them done once a quarter at most. What I really wanted was something I could use on a daily basis that could tell me how my body was doing.
Around this time I started hearing about a device called the Oura Ring that measured a metric called heart rate variability, or HRV, and that heart rate variability could be used to determine how recovered you were from the prior day’s training.
I had heard of HRV before, but prior to the Oura Ring, getting an HRV measurement required you to wake up, put on a chest based heart rate monitor, and take a measurement with an app on your phone. To me, adding that extra step to my already busy morning was a huge barrier to measuring HRV, so the fact the Oura Ring could do it automatically was a game changer for me. I thought I could finally quantify my recovery status and better regulate my training and therefore improve my health.
Well it was not quite as simple as I thought it would be. I ultimately found that my HRV score on my Oura Ring was quite good no matter how hard I exercised. While this might sound quite disappointing, and it was at the time, it forced me to learn something more valuable. It forced me to listen to my body. I had to learn to look for the signals my body was sending me indicating that I might need to back off on the training. Learning this skill was far more valuable than any gadget to measure recovery that I could imagine.
However, this does not mean HRV is not useful. Not only do I still measure my HRV daily, I now use a chest based heart rate monitor to do so. I will explain why I made the switch a little later on in this blog post, but before we get there let’s take a look at what HRV is, how to measure it, and how to interpret the data.
I am going to use some clips from a recent podcast from Dr. Mike T. Nelson on HRV to structure this post, but I will also add some of my own insights and useful pieces of information that I think can be useful to someone looking to use HRV.
HRV is measuring the variability of time between heart beats.
As Dr. Mike explains, most people think (or assume) the time between heartbeats is supposed to be the same, however that is not the case, there should be slight difference in the time between heartbeats.
To understand why this variability in time between heart beats is good, we need to know what controls your heart rate. The frequency at which your heart beats is controlled by your nervous system. Your nervous system has two branches, a sympathetic branch that reacts to stressful situations and increases your heart rate, and a parasympathetic branch which reacts to more relaxing situations and decreases your heart rate. The variability between your heart beats, or your HRV, is due to the two branches of your nervous system sending signals to speed up and slow down your heart rate simultaneously.
When your nervous system is balanced, meaning you are not too stressed or too relaxed, both branches are pulling your heart rate in both directions so you see a high amount of variability, and therefore a high HRV. When one branch is more dominant, you see less variability and that can result in a low HRV.
One thing to keep in mind is that HRV is usually talked about in the context of athletic recovery. While it can be useful in that context, it is not just impacted by exercise. Yes, training and exercising are stressors for sure, and yes, a day off from exercise can be quite relaxing as well.
But it’s not that simple….
What if you are having a very stressful day at work? Your easy 30 minute trail run at the end of the day might be a welcome relief from the stress….even though it is also providing a training stimulus.
What if you have a scheduled rest day but suddenly you get a call from your child’s school saying they need to be picked up because they are sick while at the same time you have a big work presentation to give the next day? Even though you didn’t train that day, you still had a high amount of stress in your life that day.
In other words it’s not just training that impacts HRV, it’s any kind of stress, whether that’s training, social stress, stress from an email, a car ride, your bank account…anything.
HRV can also be affected by your interpretation of a situation. Someone getting up in front of their peers and giving a presentation can be the most stressful thing they could ever imagine, but for someone else it might be no big deal.
All of this is important to keep in mind as we discuss how to interpret your HRV data.
There are a number of ways you can go about measuring HRV, it seems like every wearable these days gives you an HRV measurement. The first thing to keep in mind about measuring your HRV is that consistency is important. Pick a method, time, situation, app to measure your HRV and stick with it. You cannot compare HRV measurements from different apps, methods, or times of day to each other, the only fair comparison when it comes to HRV is a measurement done exactly the same way, at the same time each day, using the same device and app.
The tried and true method to measuring HRV is with a chest based heart rate monitor and an app. My preferred heart rate monitor is the Polar H10. Polar has proven time and time again to be the most accurate chest based heart rate monitor . My preferred app of choice is iThlete.
It may not be the nicest or fanciest looking app out there, but it allows you as a user not only to capture your resting heart rate and HRV, but also input subjective measures around sleep, stress, training, fatigue, mood, and diet, all of which can contribute to your overall HRV score.
When doing a single point measurement of HRV with an app like iThlete you want to do it seated (except in some specific cases) first thing in the morning after waking. Basically wake up, use the bathroom, take a seat, put the HR monitor on, and do the measurement. You want to avoid doing anything else before taking the measurement as it could impact the measurement.
My other choice for measuring HRV is with the Oura Ring. With the Oura Ring the HRV measurement is done automatically while you sleep. This is both an advantage and disadvantage. The advantage is you don’t need to do anything and it takes the inconsistency factor out of the equation (for the most part). The disadvantage is that most of the research done around HRV is done around a single point measurement as you would do with an app and a chest based heart rate monitor. That doesn’t mean that the HRV reading you get from Oura is bad, but it’s hard to make direct comparisons between research on HRV and the score Oura gives you.
Of course with the Oura ring you also get additional metrics like sleep data, resting HR, body temperature, respiratory rate and activity, so there are more benefits to an Oura Ring other than HRV.
I use iThlete and have an Oura Ring, and from my own experience and the experience of others, the two measurements line up most of the time. However, I find that iThlete will reflect more acute stressors such as those from training, while those tend to not show up in my Oura HRV reading. I will explain why that is likely the case in a bit.
Personally I do not trust watches and other wearables that give you an HRV score for two main reasons.
- Most wrist based heart rate monitors are not accurate enough to give an accurate measurement.
- You don’t know when the measurement is being taken. For example, what if it takes a measurement when you are in the middle of giving a work presentation? I would expect that measurement to look pretty bad at that moment, but that’s not an accurate measure of your overall stress state. Have I mentioned how important consistency is yet?
When interpreting your data, the ideal state that shows you have the right HRV balance is one where your heart rate is well below your HRV score.
Below is a screenshot from a client of mine who uses iThlete. This snippet from their HRV graph shows a very good HRV score (light blue line with green dots) with a nice low heart rate (red dotted line).
Occasionally you might see a reading like the one below where you have a one off bad HRV score surrounded by some fairly good scores.
In this screen shot you see an outlier in the HRV trend where the HRV is low and resting heart rate is very high. Clearly this shows a stress response, but it may not mean you should not train that day and stay in bed. Most of the time these situations are caused by some acute stressor like a late workout, late meal, alcohol, poor food choice, a stressful social situation, a bad night of sleep, or something similar. As long as you feel fine on days like these, I think it’s fine to train.
Trends in HRV are really the key when it comes to making training decisions. Here is an example where I ended up modifying my client’s training due to their HRV.
You can see a clear decline in their HRV score, plus a rising resting heart rate, which should set off some alarm bells. In addition to the heart rate and HRV trends, the client also told me they felt like garbage as well. I also knew they had just completed a grueling endurance event a few days before this trend started plus they had just moved….talk about stress! I immediately scrapped their training and told them to just walk for a week. After a week off, everything normalized and they were back to training the next week.
When making training decisions based on HRV, look for trends and tie it to life stressors as well as subjective feelings. If they all point to you being overly stressed, it’s time to focus on rest and relaxation to restore HRV balance.
I have alluded to a few times in this post that Oura did not pick up training stress for me, now that we know more about HRV, how to measure it, and how to interpret it I can finally explain why.
I could literally destroy myself with exercise and my Oura HRV score would not budge. Other stressors could however send my HRV to the floor. Things like alcohol, eating crappy food, or a late meal would constantly negatively affect my HRV score. It wasn’t until Dr. Mike explained the concept of parasympathetic saturation to me that I understood why this was the case.
And yes he is talking about me in this clip, and I think it’s the only time my name will be mentioned in the same sentence as Lance Armstrong 😂.
If you notice your resting heart rate is really low, in the 30s particularly on an Oura Ring measurement, and your HRV does not tend to respond to your training intensity, your HRV measurement might also be affected by parasympathetic saturation.
What can you do to solve this problem?
You want to add a little bit more stress when taking the measurement. To do this all you need to do is take your HRV measurement standing. The little added stress from standing removes the parasympathetic saturation and allows other stressors from training to show up in your HRV score.
Unfortunately, you can’t add this “extra stressor” when using something like an Oura Ring because the measurements are done at night while you are sleeping. This is why I have switched to using a chest based heart rate monitor to measure my HRV.
Finally you are probably wondering what things outside of training might impact your HRV?
As I have already mentioned it could be anything YOU VIEW or YOUR BODY VIEWS as a stress. The most common stressors for most people are sleep deprivation, changes in diet, or social stressors.
Of course this is highly individualized for each person. Some people can be unaffected by alcohol while someone else might be completely destroyed by it. Some people can get in an argument with their spouse and be fine while someone else might take days to recover from it.
This is a question I hear a lot of people ask, but unfortunately there is no one answer. First you can’t compare your HRV score to someone else, even when using the same device. If your score on your Oura ring is in the 90s and mine is in the 120s, that doesn’t mean you are worse than me, it’s just that our variability is different. However if you constantly have a very low score you might want to investigate why.
Obviously your body is perceiving some kind of stressor, but that could be a lot of things.
I have heard people with unknown food intolerances eliminate foods from their diet and see their HRV score skyrocket.
I have also heard people with unknown infections also see their HRV score skyrocket once they clear it up.
People with undiagnosed sleep apnea also see improved HRV scores once they address it.
These are very complex situations to figure out and diagnose, so it can take time and work to get to the bottom of them.
One common thing I see from time to time in people with low HRV scores is inadequate aerobic fitness. If you avoid cardio like the plague and the thought of running a mile sounds like the worst thing you can imagine you might want to spend some time working on your aerobic fitness.
Why does improving aerobic fitness improve your HRV?
You are building more resiliency into the system, you can better handle stress and that improves HRV. Everything we do from walking, to cleaning the house, to grocery shopping, to lifting weights can be helped by having better aerobic fitness, so it’s a win no matter what you are doing in life.
I hope this post gives you a better idea of how to use and interpret HRV to better inform your day to day training decisions. While this technology is great to have, we need to remember that our ultimate barometer of our stress are the signs and signals our bodies send us. Instead of using HRV as a replacement for listening to your body’s signs and symptoms, you should use it as a way to reconnect to your body. When you have a low HRV score or one that has been trending in the wrong direction you should then ask yourself how you have been feeling? Can you pick out anything that you might be able to correlate to your declining HRV score? Is your sleep worse? Has your energy been lower? Has your mood declined? Has your hunger changed? Has your motivation to train declined? Once you know what signals to look for you will be better equipped to know when you might need to take a break and rest before it is too late.
Providing information to better inform your health, wellness, and exercise through an ancestral lens forms the foundation of my health coaching practice. The best way to keep up to date with all the content I produce is to sign up for my newsletter where each week I send out a handful of emails with actionable information you can use to achieve your goals or overcome your greatest obstacle. Use the form below to sign up for my newsletter and get everything delivered to your inbox on a weekly basis.
- (2019, April 8). Accuracy of wearable heart rate monitors in cardiac rehabilitation. Retrieved August 27, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6603497/ ↑
- (2016, October 13). Day-to-Day Heart-Rate Variability Recordings in World … – PubMed. Retrieved August 27, 2021, from https://pubmed.ncbi.nlm.nih.gov/27736257/ ↑