This blog is a summary of my Clubhouse room on the 27th of April 2021 (VAGUS rest digest immune room)
Heart Rate Variability (HRV) is besides pulse, the most used biometric data in sports. It is generally used to measure health and recovery. But before I’ll explain about it, I’ll need to answer the questions; ‘Why do we have heart rate variability (HRV)?
The fundamental reason for heart rate variability (HRV) is that the Vagus nerve (10th Cranial nerve https://en.wikipedia.org/wiki/Vagus_nerve) has, among its many other duties, the task of preserving the body’s energy. It has a brilliant system to optimize the distribution of oxygen to the body. When you inhale, the heart rate goes up, and when exhaling the pulse goes down. Simultaneously the vagus nerve is enlarging the oxygen absorbing molecules in the lungs (bronchioles) and fine-tuning your blood pressure to spread the blood to all parts of the body. No piping engineering automation in the world can come even close to this perfect system of energy optimization. But the Vagus is NOT always ‘on’. The Vagus nerve’s energy saving feature is used only when the body ‘has time’ for it. When we are in fight or flight mode (sympathetic activation = high stress), the body does not even try to optimize energy. It is using excess energy for short time survival and hence not bothering to let the heart rate vary. Instead, it lets the pulse rise, opens the bronchioles in full and adjusts blood pressure to max flow regardless of energy considerations. Since heart rate variability is tied to oxygenation, it is also depending on your breathing rate. Here comes ‘modern evolution’ into play. Our current lifestyle cause our breathing to be too quick, it has speeded up our ‘normal’ breathing to an average of 3 seconds inhale and 3 seconds exhale. With this kind of breathing, the vagus nerve, does not have time enough to engage the full energy saving mode and hence HRV is not directly tied to breaths even though it is performing this ‘increase and decrease’ of pulse quite well as long as we are not very stressed. Only when breathing is paced to 5 seconds inhale and 5 seconds exhale, does the Vagus nerve function properly and this ‘inhaling=high pulse’ cardiac/respiratory synchronization is working as it should.
Is optically measured pulse enough for HRV monitoring in sports?
Almost all current sports watches and wearables, measure the pulse with an optical pulse indicator. This is a blinking light on the bottom of the watch which measures the expansion of the blood vessels on your wrist. This measurement is never exact due to the nature of both the technology and blood vessels themselves. Hence optical pulse, for short term measurements (less than one minute) are generally only about +/- 15% right. The frequency of meaningful measurement data is naturally also low with optical pulse measurement. It is though useful and it averages out to be quite precise on longer time measurements (> 30 min or more).
In sports, HRV is today used to evaluate:
- general health of the athlete
- timing when athlete is more or less adaptive to training
- predict when an athlete may perform well or worse on a particular day
- predict if an athlete is more than usual susceptible to injury
My recommendation is that optical HRV in sports is to be used in above cases 1-3 when the optical HRV is:
- used to track ‘general level’ measurement of HRV and health during the persons ‘normal’ breathing – not while exercising.
- used to track longer time changes (weeks) in HRV for instance as averages during one week
- measured during the night to get accurate readings.
The optical HRV limitation are such that they should not be used to evaluate ‘quick’ reactions to training, for instance by measuring ‘before-after’ and evaluating recovery or timing adaption for a specific training session. Anyone using optical ‘passive’ HRV must keep in mind that it is very dependant on the breathing periodicity and in sports it is very difficult to know ones breathing. I also strongly advice against trusting the breathing estimates provided by these wearables. This is because it is based on o a reversed logic from the HRV – which as I told is not exact – and hence the breathing is a not exact breathing approximation of a not a exact HRV short term measurement.
Advantages of using VAGUS® ECG for sports:
The VAGUS ECG gives a more ‘in-depth’ analysis of the persons autonomic nervous system, health, inflammation levels and prediction of performance (see my other blogs about health).
Since we use ECG and a specific fixed period breathing test – the data is very precise and not dependant on changes in breathing cycle. The VAGUS HRV gives an accurate snapshot of the moment during the test. When athletes do the test at specific intervals, the values are comparable and easily applicable for timing and adaption of exercise amount during a specific day. There is also much reason to presume that the test values are good predictors of performance.
How to use the VAGUS® ECG to improve your performance?
To evaluate inflammation levels after a training session, we recommend doing regular and standard timed tests after the session. (15 min and 2 hours). The pre- and post-exercise VAGUS® ECG test is usually done in the locker room (after shower and drying).
In general, I recommend doing the VAGUS® ECG Test 3 times per day – morning, noon and evening. In the morning (before drinking coffee), users normally do the test by the kitchen table before starting breakfast. The noon test is best to do after lunch and the evening test is done before going to bed.
The VAGUS ECG test parameters to track athletes are:
- Pulse (HRmin, HRmax and average HR asp bpm)
- Heart Rate Variability (HRV, both as ms and index 0-100)
- Breathing as calculated from the ECG electrical signal (BRE, 0-100)
- Smoothness of breathing (RSS. Index 0-100)
- Smoothness of heart rate variation (CSS, Index 0-100)
- Timing of heart rate changes compared to each breath. (RSA, 0-100)
- Periodicity when pulse is at its highest compared to maximum inhalation. (RSAsync, 0-100)
- Vagus Health Index as summary index of above values (VHI, 0-100)
The VAGUS® COACHING platform is an easy-to-use tool to track this data and use it to improve performance.
I think the VAGUS® ECG test will enable athletes, amateur sporters and coaches to use its data to be better informed and further optimize training. It is also hopefully used to improve health, reduce inflammations and improve mental wellbeing.
The VAGUS TEST intro video: https://www.youtube.com/watch?v=cVQc6ZVNfe0
Ps: To do the VAGUS® ECG test, users need to perform controlled breathing. Proper diaphragmatic breathing often requires practice. Relax muscles in the neck and shoulders. Follow the timer on the watch and breath in through the nose for five seconds. Then exhale fully during next five seconds. Start again until the 30 seconds ECG recording is finished. Feel how the lungs fill with air and inflate like a balloon while the upper part of the belly and lower ribs move outward. As you get better, the breathing value and most other vagal tones also usually improves.
Pss: Contact me to [email protected] if you are interested in implementing the VAGUS® COACHING platform for your team.
© Gustaf Kranck