Should You Trust the HRV Values Your Wearable is Giving You?

My experience as an athlete

As a 53-year-old health coach and fitness trainer, I place huge importance on the optimization of my health. I also love to challenge what I call the conventional stupidity approach to health, fitness, and life. I do things a bit differently than most triathletes, marathoners, and personal trainers. 

I fundamentally believe that we need to rest more, reduce chronic stress, and connect more with what’s going on in our bodies. I use a wide range of subjective measures in relation to my health and fitness.

Subjective measures include how I feel, my energy levels, my bowel movements, my mood, my ability to think and make decisions, and of course, how I feel when I am at the gym, in the pool, or on the track or bike. Some people place a lot of importance on objective metrics and numbers and tend to avoid subjective measures. 

I think it’s vitally important to have a good balance of both. I recently found this to be important when I started looking at biometrics. I was looking at my RHR, O2 saturation, respiration, and HRV, all from a nocturnal measurement lens.

 I found there was a trend for my HRV to be quite low, and I mean low – 32, 41, 35 – and it did not vary much regardless of whether I had a 5-hour training day or a rest day. It also didn’t vary much based on my RHR or how I felt. 

I felt very confused. I was worried, starting to think that something was wrong. There was a huge disconnect between the subjective rating I would give myself for my state and the objective numbers provided by the HRV tool I was using.

I even tried several different HRV devices/applications and tools, but they all seemed to show the same result. I was desperate for a deeper understanding of what was going on.

My experience with Biostrap

So why is this so important? Well, I am a serious AG athlete. Last year, I raced in the 70.3 Ironman World Championships. I train about 13 hours a week – I am serious about my sport. This was important to me. I also feel that recovery is one of the key pillars of health and fitness. 

The last thing I want to do is cause further stress to my body that would impact my ability to recover, i.e. doing a solid training session when not fully recovered. I started looking at a system for biometrics that appeared to be more focused on HRV than simple fitness tracking. It also provided the ability to do a 2-minute biometric scan. I decided to give this a trial.

It’s called a biostrap

I had been hearing a lot about the fact that nocturnal HRV readings for elite athletes weren’t effective due to a phenomenon called “parasympathetic saturation”. 

My understanding is that this has been reported in high-level ultra-marathoners, triathletes, and endurance athletes, who are more susceptible to it in the supine position simply because they’re in a more rested or relaxed state where the heart is not being challenged to overcome gravity, pump blood upward, and so forth. When you already have a very low RHR, lying down makes it even worse.

Andrew Flatt PhD, CSCS

Andrew is a highly qualified practitioner in this field and writes fantastic content around biometrics. Flatt explains in more detail:

“Parasympathetic saturation, the results of would be having decreased heart rate variability despite having a very low resting heart rate, which is counter-intuitive because typically, the lower your resting heart rate, the higher your heart rate variability is.

There tends to be an inverse relationship there. But what’s happening kind of physiologically is that the acetylcholine receptors on the heart that respond to vagal stimulation, the vagus nerve is going to release acetylcholine which will bind to the muscarinic cholinergic receptors on the heart, and that tends to slow the heart rate down.”

So after reading all this one morning before training, I decided to conduct a sitting biometric scan.

“Kiviniemi et al. (2007) provides a very thorough explanation of why HRV might be better measured in a standing position as opposed to seated or supine. Essentially, HRV is susceptible to saturation of the parasympathetic nervous system in subjects with low heart rates.”

Yes, this is me, with a 36-41 RHR. I got excited – maybe I had found the reason why my nocturnal HRV was so low. He further explains:

“Mourout et al (2004) saw decreased HRV in overtrained athletes compared to not overtrained athletes in the supine position. Similar results were found when HRV was measured after 60-degree tilt. The non-OT group always had higher HRV in the standing position and saw greater reactivity to the postural change. Therefore, pick a position and stick to it 100% of the time for your values to be meaningful. Switching positions from day to day will provide skewed data.”

Endurance athletes and athletes with low resting heart rates (yes, that’s me) are probably better off measuring HRV in a standing position. We understand that when elite athlete has a very low RHR, they are more likely to be in a state of parasympathetic saturation. Andrew Flatt Explains this as follows:

“This is when vagal HRV markers (e.g., lnRMSSD) are low despite a low resting heart rate. This has to do with excess acetylcholine within the myocardium that maintains inhibitory actions on the SA node and thus limits the typical arrhythmia observed from respiration. See below.”

“There are several potential explanations for the decrease in HRV with increasing parasympathetic effect. If with increasing blood pressure there is higher-frequency vagal discharge and inspiratory suppression is maintained, then there must be a persistent parasympathetic effect during inspiration despite the suppression of vagal nerve discharge.

In in vitro preparations, the dose-response curve to acetylcholine has a rapidly rising portion and at higher concentrations is flat, displaying a simple saturation relationship. High-intensity vagal nerve discharges during expiration may release enough acetylcholine to result in saturation of the parasympathetic effect during expiration.

If acetylcholine concentrations during expiration are high enough, the expected decline in acetylcholine concentrations in the region of the sinus node during inspiration may not be enough to significantly diminish the parasympathetic effect. Alternatively, it is possible that with increasing blood pressure, there is loss of phasic respiratory changes in vagal nerve discharges, resulting in a loss of phasic effect and a decrease in HRV. It is unclear which mechanism is operative in humans.”

Goldberger, J. J., Challapalli, S., Tung, R., Parker, M. A., & Kadish, A. H. (2001). Relationship of heart rate variability to parasympathetic effect. Circulation, 103(15), 1977-1983.

About the Author

Andre Obradovic

Andre Obradovic is an ICF Leadership PPC Level Coach, A Primal Health Coach, a Certified Low Carb Healthy Fat Coach, & a Certified Personal Trainer. Andre is also a Founding member of the Dr. Phil Maffetone MAF certified Coach. He is an Ambassador for the Noakes Foundation, and a regular subject matter expert lecturer for the Nutrition Network (a part of the Noakes Foundation) Andre has completed 16 x 70.3 Ironmans and in 2017 he competed in the 70.3 Ironman World Championships. He has completed 18 Marathons and over 30 Half Marathons. Andre currently focuses his athletic competition on Track and Field with the occasional Marathon.

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