We have been asked by the UK Government to test the hypothesis that HRV may be a powerful diagnostic tool for Covid-19. This article will explain the relationship between HRV and Covid, focusing particularly on the implications for people who exercise regularly and contains a call to action for how you can help make this a success.
Those of you that have been monitoring your heart rate variability (HRV) for a while will know that it is a great general barometer of the stress your body is experiencing. This stress can come from multiple sources including:
- Physical stress i.e. physical work & training
- Chemical stress e.g. poor nutrition, alcohol
- Mental & emotional stress
The Total Load caused by the sum of all these stresses needs to be balanced in the form of recovery from good quality nutrition, sleep and relaxation. We can use HRV as a tool primarily to detect when physical stress from training is out of balance with our ability to recover, and the body is starting to break down.
Why might HRV be able to tell us about COVID-19?
What is not so well known is that as well as showing when someone is stressed, HRV can also tell us about the body’s reaction to sickness caused by bacteria and viruses and in particular about the level of inflammation. That’s because the vagus nerve, responsible for controlling the changes in heart rate via the so-called parasympathetic or ‘rest and digest’ nervous system also controls the body’s immune reaction (via the cholinergic anti-inflammatory pathway).
Put simply, when an invading microbe (bacteria or virus) is detected, the body produces cytokines which mobilise the immune response consisting of B cells, and the appropriately named ‘killer T cells’ which latch on to the cells the invader has occupied and literally explode them.
Left unchecked, cytokine production can go crazy, causing more damage to the body than the invading pathogens. This is known as the cytokine storm, and the resulting inflammation is what often kills very sick COVID-19 patients, rather than the virus itself.
The vagus nerve determines the strength of the immune reaction, and by measuring the vagus nerve using HRV, we can see how strongly this is going on. Our earlier blog post discusses this more, but in short, higher HRV = less inflammation, lower HRV = more inflammation.
The body’s nervous system can detect small increases in inflammation, and some previous research has shown that HRV changes may be able to predict regular colds several days in advance of when the person becomes sick.
It does seem as though some athletes are getting what starts as mild to moderate cases of COVID-19, but by carrying on training near the start, they actually draw out the symptoms for many weeks, if not months. At the end of May, the Royal Society of Medicine gave an online webinar on the dangers of novel coronavirus for athletes, where it was explained that bad cases could lead to heart muscle damage (myocarditis) requiring up to 6 months rest from sports participation as well as long term consequences such as Chronic Fatigue Syndrome.
Let’s look at some examples
This chart shows the course of a short, but reasonably intense viral illness – likely caused by one of the 4 corona viruses already in existence before COVID-19 came along. You can see from the red dots and emojis that this athlete became sick quite rapidly, and their HRV dropped for a period of 5-6 days before recovering above their baseline (the thick blue line). You can also see that their resting heart rate started to rise after their HRV had dropped, and that they stopped training (sensibly) whilst their body was fighting the infection. The drop in HRV, before raised HR or symptoms presenting, allowed this athlete to reduce his training, focus on eating and sleeping well in order to give his body a head start on fighting off the virus.
HRV and COVID study
This and similar reports led us to apply for a UK Government grant program funding short term projects intended to help mitigate the effects of the COVID-19 pandemic. We are supported on this project by some specialist physiology researchers and an experienced medical statistician.
What we intend to discover is whether changes in heart rate variability are able to predict:
- The start / onset of COVID-19 before a person develops symptoms
- How severe the illness is likely to become
- When it is safe to resume training
If HRV was able to predict COVID infection during the 5-7 days a person has the virus before they show symptoms, they could self-isolate much sooner. This would significantly reduce the spread of the disease, whilst also giving the individual better opportunity reduce their Total Load and give their body the best chance of fighting the infection (i.e. stop training, sleep & eat as well as possible).
We are very happy to say our project was selected for funding, the required resources are in place, and are now conducting the study via the following steps:
- An appeal to HRV users to send in their data from any app or system (not just ithlete)
- Sending a link to a professionally designed symptom questionnaire
- Anonymising the data in a GDPR compliant manner to ensure it cannot be personally identified
- Statistical analysis to test whether our ideas are supported by the data
- Writing up the findings into a report and making them public so that everyone can benefit
The key point here is that we need HRV users who have had (or think they may have had) COVID-19 to support the initiative and spend 10 mins to fill in the questionnaire and send in their data. This can be from any app or system, not only ithlete, for example, Bioforce and Elite HRV (who have kindly agreed to support the initiative), HRV4Training, Oura, Whoop, etc.
The benefits of doing this are that we might be able to detect the onset of COVID, reducing infection rates, saving healthcare costs, and importantly for athletes, reducing or eliminating long post-infection periods of ill health that can scupper not only race plans but general wellbeing!
For those who support and spend the few minutes needed to fill out the survey and send in the data, grateful thanks, not only from us, but from fellow athletes that may be able to avoid a severe illness for themselves and others around them!
If you have any questions about taking part, or would like to discuss your suitability, please don’t hesitate to contact us on firstname.lastname@example.org
An update for those sending in data from the ithlete app on Android. We have been made aware of a bug where the export file sometimes cannot be sent from the mobile app. If this applies to you, we can find another way to export it, so please contact us at email@example.com and we will help.
Are you still collecting data for this study?
We’ve completed the general study and are not collecting any more data for the time being, but we have since done a couple of case studies and potentially could analyse your data for another one of those.
Feel free to contact me simon[at]myithlete.com if you want to discuss it further.
Hope the Covid has not affected you too badly.
Hello. I had a severe case of covid. Almost died. I was in hospital for 6 weeks. Nearly had to be ventilated. They did many tests on my heart. The virus left me with a high heart rate and my HRV fluctuates continuously throughout the day. I do have some Vegas nerve symptoms as well. Before covid I was never sick. No medical records to speak of and now it’s been a yr and a half since I had covid I’ve not even a sniffle. I have good days and bad days when it comes to my lungs. They weee severely scared from the covid. I’m 53 yrs old and I’ve worked out with weights most my life. I’ve benched 385 and a body weight of 181. I also was a land scraper and swong a pick axe all day long. I had tremendous cardio at times. The drs were really wanting to know why I had such a bad case being healthy and in good shape for 53. I’ll be 54 in August. They put me on beta blockers for the heart rate but I took myself off of them. I’ve just recently started to workout with Weights and some cardio(walking,bike). I wear an Apple Watch and it tells me I’ve a low cardio fitness and my HRV fluctuates. I feel pretty good. I’ve lots of energy and I can do more than most 53 yr olds I know. Not sure why my watch says I’m so outta shape. I’ve really got lots to say about my experience with the virus and being somewhat of an athlete and having a bad time with the virus. If you’d like to hear what I went through I’d love to tell it all. I lost over 45lbs in the first 2 weeks of having the virus. I have before and after photos I took that shock everyone I show. Anyway. Let me know. Thanks!
Wow, you have been through an awful lot! I would be really interested in hearing more, and how your HRV has responded throughout. If you could please drop me an email firstname.lastname@example.org that would be great.
Hi Simon, I just came across this thread and wanted to check something with you please (I’ve heard you on various podcasts). I’m a 48 year old competitive age group triathlete and have monitored my HRV for over two years, and am totally bought into this metric. So I caught Delta CoVID in late November 2021, I was double vaxxed but it had been six months since my last jab. My HRV was good/slightly elevated for the first five or so days of infection but declined steadily throughout the following 2-3 weeks, effectively going from a baseline of ~65ms to ~40ms. I’ve also had an intermittent but persistent cough. So arguably a mild case of what might be medically termed Long CoVID if it continues.
It’s not really recovered much since then despite a lot of rest up to the Christmas period. I have started to exercise again gently (base mileage riding and gentle swimming) in the last week which hasn’t really had a positive or negative effect.
My question is whether there is any observed pattern you’ve seen in other athletes or if you think I should be doing anything differently to my current plan to gently build back into the training even if HRV settles at a new, lower baseline? I am hoping it the HRV baseline will come back up with time, and would hope you’ve seen this in your study and with other athletes
Thanks in advance
Hi Simon. Thanks for the comment, and sorry to hear your symptoms are persisting. We did have correspondence over a long period of time with an athlete of similar age to you, who almost certainly did have long Covid. He caught it before vaccination was widely available, and his symptoms lasted for many months. His HRV baseline also declined during the illness, but did eventually recover, along with his sleep quality & energy levels. I hope that, having been vaccinated, the time course of your symptoms will be much shorter. You need to look after yourself with good quality nutrition and sleep, and I think daily HRV can help you find lifestyle factors and moderate low intensity exercise that can help you recover as fast as possible.
Best wishes & get well soon!
Simon – could I see if things have improved with you????. I am in the same place describe above now. I track my HR with my oura ring. My HRV is down significantly 6 weeks in and 4 weeks post recovery. Plus my resting heart rate is consistently 25% up each night overnight. I tried running early in recovery and my HR was very high. I am now recovering from secondary chest infection so have not tried exercise again yet. But I was just wondering how you got on. Have things returned to normal? Are you training again? I was triple vaccinated prior to infection. Thank you
Thanks for the update. I can’t offer you too much consolation unfortunately, as it can take several weeks (or even months) to recover fully. The most important thing is to listen to your body, using HRV and resting HR as useful tools to help you do that, and don’t exercise harder or for longer than leaves you feeling comfortable afterwards. If your resting HR remains consistently high, and especially if you experience palpitations, it is probably worth contacting your Dr, just to rule out myocarditis, which is a known after effect of Covid-19 infection. You will get better, but it may take time. All the best!
It seems as if the effects of the vaccine itself are being overlooked here. The reported heart problems of many athletes around the world might be a clue?
At the time the study was performed, the vaccines had not yet been rolled out, so there was no opportunity to include that.
One thing I would say is that the incidence of post Covid myocarditis has been widely reported in medical journals, so personally I’d rather be vaccinated and reduce that risk.