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 deeply 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 more deeply at biometrics. I was tracking my resting heart rate (RHR), oxygen saturation, respiration, and HRV (heart rate variability), all from a nocturnal measurement perspective.
I found that my HRV values were surprisingly low, and I mean low — 32, 41, 35 — with minimal variation whether I had a 5-hour training day or a rest day. It didn’t change much based on my RHR or how I felt.
That was confusing. I started to wonder if something was wrong. There was a huge disconnect between how I felt and the numbers my wearable was giving me.
I tried several different HRV devices and apps, but they all showed the same pattern. That’s when I knew I needed to dig deeper.
My Experience With Monitoring my HRV
Why did this matter so much to me? Because I’m not a casual athlete, I’m a serious age group triathlete, competing at the 70.3 Ironman World Championships and training around 13 hours a week.
Recovery is one of the key pillars of my performance and my coaching philosophy. The last thing I want to do is overload my body and impair my ability to recover.
I started looking for a biometric system that prioritised HRV, not just fitness tracking. I came across Biostrap, which offered the ability to perform a two-minute biometric scan. Naturally, I decided to try it. (Note that I no longer use Biostrap as they do not support a consumer product any longer. I now use Hume Health Band and Oura Ring as my tracking devices).
Around that time, I began hearing about something called “parasympathetic saturation”, a phenomenon reported among elite athletes whose nocturnal HRV readings often appear artificially low.
What Is Parasympathetic Saturation?
Dr. Andrew Flatt, PhD, CSCS, a leading expert on HRV, explains:
“Parasympathetic saturation results in decreased heart rate variability despite a very low resting heart rate, which is counterintuitive because typically, the lower your resting heart rate, the higher your HRV should be.”
He explains that this is due to the acetylcholine receptors in the heart, which respond to stimulation from the vagus nerve. When vagal tone is extremely high, common in elite endurance athletes , the receptors can become saturated.
This means that even though your body is in a highly recovered, relaxed state, your HRV reading may appear lower, not higher.
This pattern often occurs when HRV is measured in a supine position, such as during sleep, because the heart isn’t working against gravity. For athletes with very low RHRs (like my 36–41 bpm), the effect is even more pronounced.
Sitting vs. Standing HRV: Why Measurement Position Matters
After learning this, I decided to conduct my HRV scan while sitting upright.
Kiviniemi et al. (2007) offer a clear explanation of why HRV might be better measured in a standing position rather than lying down:
“HRV is susceptible to saturation of the parasympathetic nervous system in subjects with low heart rates.”
Similarly, Mourout et al. (2004) found that overtrained athletes showed lower HRV in the supine position, while non-overtrained athletes demonstrated greater variability when measured standing.
The takeaway?
Pick a position and stick to it. Switching between sitting, lying, or standing will skew your data and make trends meaningless.
The Science Behind It
Goldberger et al. (2001) explored this mechanism in detail. They described how high concentrations of acetylcholine within the heart muscle can maintain inhibitory action on the sinoatrial node (SA node), limiting the normal respiratory variability in heart rate.
In simpler terms:
If your vagus nerve is already firing at high capacity, it can suppress HRV fluctuations even when you’re well-recovered — a false low reading.
My Key Takeaways
For endurance athletes, these findings change everything. If you have a low RHR and rely solely on nocturnal HRV, you may be misreading your recovery state.
Here’s what I’ve learned:
- HRV is an excellent tool, but only when interpreted in context.
- Measurement posture consistency is crucial.
- Always compare HRV trends with subjective wellness indicators.
- A single low HRV reading doesn’t mean you’re unwell — look for patterns.
- Your body’s intuition often tells the truth before the data does.
As I emphasize in my coaching and book, the body is the world’s most sophisticated data system, if you know how to listen to it.
FAQs About HRV Accuracy and Recovery Tracking
1. Why is my HRV so low even though I feel great?
If you’re a well-trained endurance athlete with a low resting heart rate, your HRV may be artificially suppressed due to parasympathetic saturation. This is a sign of strong vagal tone, not poor recovery.
2. Should I measure HRV lying down or standing up?
Consistency is key, but many athletes with low RHRs find that standing or seated measurements give a more accurate reflection of recovery readiness.
3. How can I use HRV data effectively?
Look at trends over time, not single-day readings. Combine HRV data with subjective markers like mood, sleep, digestion, and training motivation.
4. Are wearables like WHOOP, Oura, Gamin accurate?
They can be, but accuracy varies by device and method. Most rely on nocturnal readings, which may not suit athletes prone to parasympathetic saturation.
5. What matters more — HRV or how I feel?
Always trust your body first. HRV supports your intuition, but it should never override how you feel physically, mentally, and emotionally.
Key Insights Summary
- HRV readings can be misleading in athletes with very low resting heart rates.
- Parasympathetic saturation may create false low readings.
- Measurement posture dramatically affects HRV data accuracy.
- Always combine objective metrics with subjective awareness.
- True recovery is a balance of physiology, mindset, and rest.
Take Charge of Your Health Today!
References
Blalock, A. C. E., Brown, J. E., Vondrasek, J. D., Cross, B. L., Grosicki, G. J., & Flatt, A. A. (2025). Associations between morning heart rate variability and ambulatory blood pressure characteristics in young adults. Chronobiology International. Advance online publication. https://hrvtraining.com/
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. http://circ.ahajournals.org/content/103/15/1977.full.html
