Data-Informed Decisions using HRV
Level 4: All-Star
Welcome Players! I want to give you a real example with real data on how measuring your HRV can actually be used to make better decisions when it comes to your training and recovery.
And as a bonus, the data we will be using is my own!
I’m going to describe the context of my lifestyle, how my biometric data responded, and the decision-making process I used to navigate the environment with the information present. Let’s get started.
Cause & Effect
Context (My Life)
Water in a Bucket
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I measure my HRV every morning upon waking (before getting out of bed) using a 3-min measurement period with a Polar H10 chest-strap.
I record & visualize my data using HRV4Training Pro (from where screenshots are taken below).
HRV4T has the best signal processing that I’ve found of raw ECG data and they also deliver powerful insights in the form of a moving average creating a ‘normal’ or ‘baseline’ range for the individual measuring.
This is the green range in the images below, and requires at least 30 days worth of data to compute. The blue line is the trend line of daily measurement scores for the selected value.
The metrics I personally care most about are Heart Rate (HR), HRV using the metric rMSSD, and Sleep Quantity, which I will refer to more accurately as Sleep Opportunity (SO).
Let’s take a look.
We can see my heart rate get into a normal range between 56-62bpm before lowering significantly between Nov. 20-25th. Starting Nov. 26th it escalates progressively until eventually rising outside normal ranges on Dec. 5th and stayed elevated until the 9th.
My HRV as delineated by rMSSD created a normal range between 80-120ms for the better part of November and stayed within a very manageable range with periodic exposures to the lower range on Nov. 14-19th. Starting Nov. 28th it progressively declined until the 9th where it started to recover. Notice how after the consecutive days of poor scores the average range (green) dropped by almost 15ms (bottom of range on Nov. 27th = ~75ms, bottom of range on Dec. 9th = ~60ms.
I don’t have as much data on sleep quantity, a little under 30 days, but we can see that I average between 8 and 9 hours of sleep opportunity per night. Here my sleep was around the upper range until Nov. 28th from which it was significantly restricted for 2 days before slowly returning to the lower range between 7.5-8hrs until Dec 9th.
I like to look at the correlation between my sleep opportunity and rMSSD. While it’s certainly correlated in my mind (and statistically as well), it doesn’t describe the whole story seeing as from Dec. 3 on my sleep time started to increase without a corresponding response from rMSSD.
Cause & Effect
We see the numbers, but what do they mean? Well, not much yet.
I talked about all the lifestyle factors that can affect HRV scores in this article:
For my personal life, I know that the increase in HR on the 29th & 30th was a result of sacrificing sleep for getting work done late at night on the tail-end of a project. Two nights of increased mental effort and lack of sleep significantly affects my bodies ability to establish a parasympathetic state evident from my rMSSD score on the 30th.
What comes next is what I find so fascinating about HRV and its ability to reflect your resiliency to stress over a period of time and not just at one instance. On Dec. 1st I got adequate amounts of sleep, my resting HR was back within range, and my rMSSD score was improved from the 30th but just below normal range. By all accounts I was much improved compared to the previous day, but taken in context with my 7-day moving average I was actually still continuing to decline.
My autonomic nervous system had not recovered sufficiently to outweigh the negative influence my lifestyle was having over the most recent period of time. Essentially good, but not good enough!
On Dec. 3rd I failed to get an adequate amount of nights sleep (again), and saw my RHR slightly higher than previous day yet still within range and a regular HRV score for once.
We know that stacking consecutive days of positive habits has a synergistic effect where the sum of all habits done repetitively will be more impactful than completing a greater number of habits, inconsistently.
Doing the basics everyday will allow you to recover more quickly than ignoring the basics and doing ice baths, massages, bodywork, float tanks, etc. combined.
From Dec. 3rd on my sleep opportunity was hectic, my RHR steadily increased night over night, and my rMSSD continued to decline.
All this signaling high levels of stress, diminished ability to tolerate that stress, and a complete dysregulation of my system compared to baseline ranges.
Knowing the range that my RHR and rMSSD are in while I live a lifestyle that includes 8+ hours of sleep, a diet limited in processed sugar & grains, 2-3 days a week of coordinated exercise and high levels of natural physical activity lets me evaluate what part of my lifestyle changed leading to the increase of stress on the system during the decline in measurable scores.
Was it the fact that I wasn’t getting enough sleep?
That certainly played a part in it, both subjectively knowing I do not feel as alert and clear-minded when I get less than adequate sleep. The statistical correlation provided by HRV4T gives me some validity in that feeling as well.
But the non-measurables that I know played a large factor had to do with mental stress.
The increase in mental effort I used to finish a project that I was excited about certainly drained some of my energy. I also know that while I enjoy working hard to be proud of the quality of my professional products & services, it is a heavy draw on my vitality.
Water in a Bucket
We can think of our daily ‘energy’ as water in a bucket, the bucket is our life. The faucet that fills our bucket is our lifestyle habits, and there are two holes in the bottom of the bucket. One hole drains from our applied stressors; social outings, personal obligations, training. The other hole is uncontrolled stressors; the way we make a living, fights with a friend, unpredictable events.
If the amount of water flowing in to the bucket is greater than the drainage of water, then we can extrapolate that our life is going well and in balance. Our nervous system is given enough time and resources to restore a parasympathetic state while we expend energy through sympathetic pathways without creeping into a chronically-overactive state. All is well.
But if the faucet slows down (decreased or negative lifestyle habits) or either of the drains gets bigger (increased demands in personal life and/or work), then our water levels will slowly drop until the bucket is empty.
The progressive decline of parasympathetic activity signaling dysregulation in the autonomic nervous system can be measured through comparisons of biometric data to baseline ranges.
Just because I had one limited nights sleep and a low HRV score does not mean my bucket emptied. The faucet slowed down and one drain hole got slightly larger. Luckily I had plenty of water in my bucket where I didn’t notice an effect on my body.
Although my parasympathetic state was having less and less influence over my ANS it had not begun to affect performance.
Over the course of a few days I failed to restore positive lifestyle habits and the applied stressors only got bigger, getting to a point where I would no longer be able to maintain optimal levels of performance. My bucket was losing water fast and I was past the point of return of being able to make a quick fix.
At this point all hopes of plugging the leak and returning to normal performance quickly were far out of reach. The decline in physiological state had reached a point where it was going to take an equal amount of time (in days) if not more to return to previous levels.
From the time of initial decline (Nov. 29) until now (Dec. 9), ten days of decreased values compared to normal ranges for me as an individual.
Ten days I allowed my body to pull from it’s energy reserves without adjusting my lifestyle to ensure I was recovering from stress as much as I was undergoing stress. As I continued to sacrifice effort spent on recovering in lieu of effort spent on forward progress professionally I traded sustainability for speed (of progress at work).
And I will pay the price.
There is no cheating human physiology. What water is not added into the bucket now must be added later at twice the cost.
Had I decided on Dec. 4th that I was going to reverse my habits and pull back on work and make sure to get back to a sustainable lifestyle, I would (hypothesis) be fully recovered by the 9th.
A 5-day decline in physiological readiness as energy was expended from Nov. 29th - Dec. 4th, followed by a progressive improvement in scores as they return to baseline measures when the stressor was removed and care routines were implemented.
Conservation of energy comes from operating at a sustainable capacity at work/obligations and ensuring maximum care taken to lifestyle habits that promote a positive HRV effect. Sleep, nutrition, physical activity, social relationships & comfort.
But since I instead decided to continue to sprint from Nov 29th - Dec 9th, a full 10-days, my bucket nearly completely emptied. I say nearly because a completely empty bucket is burnout, injury, illness, or otherwise non-negotiable negative effect on the body. I believe I was close to that point as evidenced by my subjective energy levels and mood.
Either way, now must begin the journey of recovery. A 10-day decline means I anticipate at least a 10-day recovery period, if not longer. All will depend in how much energy I am able to conserve in work & personal life and how diligent I am at refilling my bucket through positive habits as mentioned.
I’m sure if I was able to completely remove energy expenditure from other obligations I could recover quickly, maybe 5-7 days. It will necessitate a careful balance that ensures I am adding more water to my bucket each day than I allow to be drained.
These are the actions you will be able to discuss when in a long-term goal-based program. Should I keep pushing for the next 3, 4, 5 days? Or should I humble myself on progress for the next 2, 3, 4 days and come back fully recovered and ready to make up lost ground?
Any seasoned athlete will tell you that time spent getting healthy is worth more than time spent improving (if not 100% healthy).
Before biometric technology these decisions were made based off of “external factors” such as training volume, training load, training intensity, etc. Trying to gauge how much time was needed for recovery based on the quantity and magnitude of stress applied to the system.
That model worked well but lacked specificity because it couldn’t account for how each system (person) reacted to the stressors applied. The same training stressor applied to both you and I will achieve different results not because the stressor was different, but because you and I are different!
The individual differences between athletes & all people can account for huge differences in adaptations.
HRV gives us valid data of “internal factors”, which can be used to directly measure our individual responses to an applied stressor.
When used in conjunction with external factors it allows to quantify YOUR response to a specific stressor!
I wish I could tell you that I allowed my HRV to decline steadily so for the purpose of this case-study, but admittedly I did not.
I made a conscious decision to continue to drain resources to finish the ‘race’ (project I was working on). Just as understanding risk-tolerance is important for an investor to make wise decisions, so it is the same for an athletic endeavor. How much are you willing to risk to milk every drop of progress out of a given time period?
Knowing your HRV or other biometric data cannot make decisions for you because the data cannot account for the context of your life.
To use HRV effectively you must be measuring daily as well as learning to understand how your body feels & performs when conditions are optimal, and how performance changes when stressors are applied.
The more you learn your body’s “normal” response the more you will be able to gauge the effect of a stressor and how you will respond should you not intervene. These decisions can be made by you and you alone.
They can be used to know how long you can continue to drain resources, or at what magnitude, before you are bound to crash. And when you do crash, they can help gauge your recovery back to maximal capacity.
Every gray area in-between that exists for unique situations and individual differences can be navigated with a better understanding of YOUR response to stress.
Have a question? Want to share an experience with us so others can learn too?
Disclaimer: This is not medical advice. The content is purely educational in nature and should be filtered through ones own lens of common sense and applicability.