[00:00:00] Speaker A: Welcome to the heart rate variability podcast. Each week we talk about heart rate variability and how it can be used to improve your overall health and wellness. Please consider the information in this podcast. For your informational use and not medical advice, please see your medical provider to apply any of the strategies outlined in this episode. Heart rate variability. Podcast is a production of optimal LLC and optimal HRV. Check us
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Welcome friends to the heart rate variability. Podcast. I'm Matt. I'm here today with someone that I've had the pleasure to get to know in my Heart Rate Variability journey and really excited to have Dr. Saul Rosenthal on the show today to talk about both his work in Heart rate variability and a little bit. Maybe we'll have a lot of time to touch on it, but I'm really excited and I reached out not only to get Saul's expertise on the podcast, but also talk about his work with long haul COVID as well, because it's a topic I see popping up quite a bit. And Heart Rate Variability seems to be a good metric to use with this population. So excited to have Saul's expertise on the show to discuss that. So, Saul, before we get going, just a brief introduction of you to our audience.
[00:01:26] Speaker B: Oh, sure, Matt. Thanks so much for having me on the podcast. I listen to it and really get a lot out of it. I'm a health psychologist. I'm in the Boston area and been practicing over about two decades or so.
Started as a research psychologist and then retrained as a clinician up here in Boston. Really focused on health, what's now called health psychology. It was behavioral medicine back in the day, and I trained at the Cambridge Health Alliance, which is part of the Harvard Medical School, in their behavioral medicine. I eventually went back there. I actually worked there as their training director and biofeedback coordinator. So I've worked in a few different healthcare settings, both primary care and specialty care, veterans Administration medical centers, as well as primarily right now I'm doing private practice. I do some teaching and supervision, mentoring for people getting trained in biofeedback.
I do host a podcast as well. This is for the Northeast Region Biofeedback Society. I should put my plug in for that. Absolutely healthy brain happy body is what we call it. So that's in its second year now.
[00:02:50] Speaker A: Awesome. Congratulations for getting to year two too. As I would like to remind myself, most podcasts don't make it past episode eight. Exactly.
Well, I appreciate you being on here and I'd love to know, obviously, health psychology, a lot of ways heart Rate Variability might fit into there, but when did you sort of come across Heart Rate Variability and how have you really integrated it into your thinking? Obviously as a biofeedback practitioner, it's a big part of it now, but I'd love to just hear a little bit about your journey with discovering heart rate variability and then how it's sort of been integrated into your work on health psychology.
[00:03:33] Speaker B: Well, I was fortunate enough that as a postdoc at the Cambridge Health Alliance we were trained in biofeedback and this was 1999, 2000 ish. So at least in the US heart rate variability had kind of come to the US with Paul Air brought it in the early 90s, went to Russia where they were using it so it was part of RBCI training as a postdoc. So I've certainly been known about it and used it for many years and clearly it was very clearly a powerful approach.
And primarily, I think, for the same reasons. It still is one compared to the other modalities it is relatively easy to change because it's all respiration driven and it has such a powerful effect on lots of different conditions.
In fact, I think at least in my mind I hope within the larger healthcare field I think things like heart rate variability help us to think more about conditions well less about them diagnostically and more about what it means to be dysregulated. Yeah, I think that's been a really.
[00:04:54] Speaker A: Absolutely and so bringing us then to in a great workshop at Aapbi it was one of those that I got caught in the hallway and had to poke my head in and wished I could be two places at once. But I was so intrigued I really wanted to have you talk because long haul COVID with the interactions I have through optimal with people who are looking I would say the word desperation is not too strong for some of the folks that I come across.
Frustration would also be another word of why do I still feel like this?
And we're seeing this kind of devastating effect and obviously it hits everybody a little bit differently. The severity of symptoms. But just kind of love to say, see kind of your thinking around heart rate variability, heart rate variability, biofeedback and kind of our evolving understanding of this condition just kind of throw it out there generally is how do you conceptualize this and then where's the role heart rate, heart rate variability, biofeedback might play.
[00:06:19] Speaker B: Well, the long COVID issue is complex, of course complex medically, it's complex psychosocially since there are all sorts of thoughts and feelings about it. It's complex medically in part because there are over 200 potential documented symptoms even even sort of figuring out what it is is difficult.
What it primarily seems to affect is pulmonary functioning seems to be a major one.
Also cognitive functioning. Those are sort of the two of the biggies a large proportion of people who seem to have long COVID also show dysautonomia of some sort or other. That is, the autonomic nervous system is dysregulated and that often shows up as Pots I think about 80% the statistic may be right 80% of people with long COVID have postural tachycardia Pots.
[00:07:24] Speaker A: Can you describe that a little bit for those of us who might not be as familiar with that?
[00:07:29] Speaker B: Sure, sorry, it's a term, and I forget what the Pots stands for.
[00:07:34] Speaker A: I know this postural, no worries, tachycardia.
[00:07:38] Speaker B: Syndrome or something, but basically you stand up and your heart rate zooms, it goes into tachycardia, and symptoms of it are a lot of dizziness, a lot of fog, brain fog.
But it can be so bad that it's hard to stand up and walk around.
[00:07:56] Speaker A: Yeah.
[00:07:58] Speaker B: It'S a symptom or a condition itself that can be really problematic. So obviously there's an autonomic component to it. And anything that has an autonomic component, heart rate variability is a really nice intervention to try out there, and so we're starting to do that.
Sherry Johansson is probably the expert in using biofeedback and neurofeedback as well.
Jay Gunkelman has been talking about the neurofeedback side of things with long COVID and how to think about it. But clearly there is this autonomic dysregulation that is part of the syndrome, and there's some theories about why that is and what the virus does. But basically it seems to really upend people's autonomic functioning. So we see a lot of this tachycardia might see a certain amount of just general dizziness, hyperventilation, sorts of things. So there's a lot of symptoms that come in. And of course, heart rate variability is a really nice intervention to use.
I believe that there is some published research on this that people who have post COVID or long COVID do show reduced heart rate variability indices. So, like other conditions like this, it seems to affect it, and so it would make sense to try to train it back up.
[00:09:30] Speaker A: Let me ask maybe just a totally uninformed question, but I think it's one of those that I think a lot of us are kind of struggling with. So there's COVID in the words like cytokine and cortisol, especially cytokines, something we've talked a lot about on here, and the higher rates during stress, or obviously we see escalated rates during COVID and other disease states, and so is long haul COVID. And I'll just throw my ignorance on the table here is you have this residual effect of a disease, a virus, which I would assume is that long haul state is somehow still associated with the effects of the virus. And again, this is a master's in psychology talking healthcare, and then you do heart rate variability, biofeedback. Are we kind of looking to address one of these symptoms of long haul COVID?
Are we trying to help cure the condition?
Because the virus and the disease state I don't think would be cured strong word there by biopec, just kind of how are you conceptualizing this?
Because it's got to be better than my struggles too.
[00:11:02] Speaker B: Well, I think your struggles are shared by many people who know a lot more than either of us do about the condition. We're still not sure. There's still a lot of uncertainty and mystery if you will, to it. But it seems to be like you're saying the impact of the virus, the impact doesn't go away when the virus goes away and so how do we deal with that is really a huge question in healthcare. It's affecting millions of people and costing millions of dollars at least.
The answer to are we curing this or what are we doing about this?
One of the ways that I conceive or conceptualize biofeedback is we don't have to actually answer that question.
We can sidestep it because we're not even really treating things.
Technically speaking, we are training the nervous system and a better trained nervous system that is a nervous system that is better self regulating.
We should experience what we call symptoms. Less symptoms are to some extent the result or symptoms of this kind of a condition are to some extent the result of dysregulated physiological functioning. So if we can better regulate the physiology we should have fewer symptoms. So it's a bit of a cop out, perhaps a bit of a side step but it's probably technically accurate.
[00:12:31] Speaker A: Excellent. So one of the things that's fascinated me and please for the audience don't hear that I'm trying to make a big announcement of I figured this out. But one of the things that again let's call it fascination is an area of expertise that I could claim to hold unlike with the COVID arena is around long term kind of chronic burnout and I see so many similarities between a lot of the symptoms of long haul COVID, the brain fog for example, low energy. I mean I'm not going to say there's a direct correlation or even get close to causation but it seems like there's so many similarities that I'm just fascinated by how both maybe a work stressor or other psychological life stressor and COVID might be in some ways. I mean they're both dysregulating the autonomic nervous system measured with heart rate variability. But it just seems so interesting how those line up in such a way.
I'm just kind of wondering are we seeing maybe both of these hitting the same system in similar ways or just kind of no or kind of an open question mark of what we are really seeing with the long haul COVID?
[00:14:04] Speaker B: Well certainly would I be curious about what you think from your expertise in burnout but again I think that to some extent this is part of the power of biofeedback, heart rate variability, biofeedback and other types which is we don't have to get stuck in the diagnosis. We are really looking at what is going on. Whether you want to call it functional I know in some realms that's a good word, in some words that's not a good word.
If you want to just look at well what are we seeing overtly and if we are able to improve, if we're able to improve brain fog or dizziness at some level, the patient may not care what the diagnosis says.
[00:14:56] Speaker A: Yeah.
[00:14:58] Speaker B: My background as a research psychologist, I care about those things, but I also know that I may care about them differently than the person I'm working with. Yeah.
[00:15:06] Speaker A: They just want to feel better.
[00:15:07] Speaker B: Exactly. That's often the case.
[00:15:10] Speaker A: Yeah. So when you work with folks with long haul COVID, is the protocol for the biofeedback, are you adjusting anything you're doing? Let's say I come in for anxiety disorder.
Are you kind of working with the long haul folks in similar ways? Do you have a separate protocol for them? Sort of. What is your approach to that? Is there anything, I guess, different than what it might look like for someone coming in for maybe anxiety disorder or another condition?
[00:15:50] Speaker B: Yeah, I think that's a really important question because I think it's really important for us to look at differences among conditions and how they present and how they respond as well as the sort of individual differences from person to person.
Because I know it's easy with heart rate variability just to sort of say, okay, breathe at 4 seconds in, 6 seconds out, and all will be fine. And there's a lot of truth to that.
I don't really want to disparage that. I do that myself with folks. That said, I think that there are some conditions you need to be a little more careful about, and the long COVID is one of those.
[00:16:34] Speaker A: Yeah.
[00:16:35] Speaker B: The closest condition or the most similar condition is post concussive syndrome, and there are some similarities there. So when I work with these folks, I tend to do it a lot more slowly. I'm a lot more sensitive to change because the system is not just dysregulated, but it's a little bit I guess fragile is sort of the word. So you can easily push someone over to have a migraine or to go into dizziness or to attack a cardia. So you just want to really be careful and a little bit more gentle and just keep things a little bit more slowly.
So with these folks, I'm not just doing heart rate variability. I may be doing other types of biofeedback. I'm often doing neurofeedback as well because there are so many cognitive effects. But these things all work in conjunction or you want to use things that work in conjunction?
[00:17:29] Speaker A: Yeah, go ahead.
[00:17:30] Speaker B: Slowing it down. I was just going to say just slowing it down.
[00:17:33] Speaker A: So are you gaining any insight when you bring the neurofeedback piece into this?
Just any insight? Let me just put it that way. Again, for a disease state that we're still trying to figure out, are you seeing when you combine that with what you're getting about heart rate variability with biofeedback, does that add any insight to the brain fog and other things people are experiencing?
[00:18:03] Speaker B: I would argue it does.
I don't think there's data out there. I think there's some thinking about it, and again, sort of going with the idea that it's similar to concussion, in which there is issues with nutrition and blood flow within the brain, which may lead to the migraine. It may lead to some of the brain fog and cognitive dysregulation, but some of that is because of dysregulated autonomic functioning.
And so the way that we think that heart rate variability may be helpful is that it sort of sets the stage for the neural feedback in some ways in that it starts to calm to regulate that nervous system and so we may be able to be a little bit more efficient with the neural feedback. So as you probably know, there's more neurotracks going from the heart to the brain than from the brain to the heart. So there's a lot of information that the autonomic nervous system is sending upwards and that's important.
[00:19:06] Speaker A: Yeah, fascinating.
I just think I'm going to need like a week or two to process it before looking at long haul COVID and concussive symptoms and seeing very similar stuff on neurofeedback.
It's absolutely fascinating in so many ways and I think hopefully give some of the patients who are dealing with this some way to conceptualize something that I don't think the medical industry has given them. We don't have concrete answers yet but that similarity has got to at least give some because I think we all know what a concussion is, whether you've experienced it or not to be. So I just find that absolutely fascinating that a virus can lead to very similar symptoms of that and again the.
[00:20:02] Speaker B: Pathophysiology is probably different but for what we're doing I think it's a useful model to follow. And so I think when we use heart rate variability, thinking about it as stabilizing a nervous system that's a little shaky is really helpful. And I think that really helps the patients, because that's their experience is that life was fine, they got this virus, and now suddenly they can't walk out the door without falling over because of dizziness. And so it just has such a big impact on people's lives and we can offer this intervention which is relatively and emphasis on the word relatively easy to engage with and can have this really profound effect.
[00:20:50] Speaker A: Awesome. So this is a very in the weeds question but I'm just fascinated with it as we look at establishing folks residence frequency breathing, which I'm assuming you do when you bring them in and just for our audience that might not be familiar with that term. And Saul, jump in here as you have more expertise of this than I do, but really looking for what breathing rate really peaks their low frequency or their heart rate variability in layman's terms. So we're looking at that breathing rate that best increases their heart rate variability that they can use then in their own practice.
I'm curious and this may be a question without an answer. But if somebody with long haul COVID, might we get a different residence frequency, a different peak, because of that disease state, than they would be maybe before they had COVID, if that makes any sense.
I'll just leave it at that because I just feel like, does that change maybe where that breathing rate is, and would that adjust over time? Where normally, I believe we say with residence frequency, we don't see much of a change with adults typically.
Is that even a good question to ask?
[00:22:20] Speaker B: I guess I think it's a good question to ask. I don't think we have the answer to it. We don't have pre and post. I mean, I think what people like Paul Air would say is it doesn't really change much.
But that said, what I do find, and again, there's no data on this, it's just my clinical experience, for what it's worth, is that people who have long COVID find it harder to tolerate slower breathing. So I'm thinking of a patient I was working with in particular, the resonance frequency, that is, the respiration rate, that sort of optimizes heart rate variability, as you were saying, was about five and a half breaths a minute and sort of the rule of thumb is six. But they couldn't tolerate breathing that slowly.
[00:23:10] Speaker A: Yeah.
[00:23:11] Speaker B: So I'm not going to tell them to breathe more slowly than they could tolerate. I won't see them again. It won't be helpful.
[00:23:17] Speaker A: That is interesting that that was still even though they had trouble tolerating it right. That would probably support Paul's sort of thing, I think.
[00:23:27] Speaker B: So again, that sort of falls into my idea of you just need to be a little bit sensitive, a little bit more sensitive than you typically would be with these folks, that they just are having a harder time than even they understand until they start doing it.
[00:23:45] Speaker A: Yeah, absolutely. So maybe the most important question is what are some of the results that you're seeing from this? As you have people go through biofeedback, I'm very fascinated with what are you seeing as folks go through treatment?
[00:24:04] Speaker B: So what I'm often seeing with success is the dizziness starts to go away first. That's often the first thing that happens. And then you start to see how connected dizziness is to so many other things, including anxiety, which makes dizziness worse, so it becomes this feedback loop. So I'm often seeing improvements with dizziness. There'll be some improvements with sleep, with functioning in general, the sort of things you would expect to see with heart rate variability. Again, we're stabilizing the autonomic nervous system and they're starting to get a little bit more functional.
There's a lot of other things going on with long COVID that they may need more treatment for.
As I was saying, there's pulmonary issues, oftentimes there's brain issues that we're not entirely clear about. But again, I think of heart rate variability often as setting the stage for further intervention and treatment for these complex conditions. So there's obviously many things you just use heart rate variability for.
This may be one of them for some people, but I think for the majority, they're going to need other interventions.
[00:25:18] Speaker A: Okay.
I think that's really critical, too, because, again, regulating a dysregulated nervous system, whether that's by a psychological stress or trauma or a virus or an infection, I think that that is a key component to that healing for folks. And I would imagine I wondered if more of a question is you're giving people something to do that is at least helping, which my conversations with individuals who are struggling with this is again, frustration, hopelessness, despair.
Nothing I'm doing is helping. So at least helping to be part of that healing process has got to be a tremendous tool to help people with.
[00:26:07] Speaker B: I think that really hits the nail on the head.
These are folks that like you're saying, they don't really know what's going on, and the medical fields don't either.
You do have long COVID clinics, but most of them are really either just trying to treat specific symptoms as they are typically treated or trying to get people into research so we can understand better what's going on.
[00:26:34] Speaker A: Right.
[00:26:35] Speaker B: And so it's very frustrating and frightening. I work with people who've lost their jobs.
They're just in really dire straits, and they were totally functional before.
[00:26:46] Speaker A: Yeah.
If you just want to not touch this with a stick, I totally understand. But if you were to and please everybody, hear the word speculate. If you were to absolutely. We're not holding Saul to this in any way, shape or form, but as somebody who's worked with folks, do you have any just guesses, let's even call it that, of what might be happening here.
And again, if you don't want to touch that, I totally respect that, but I just like total guess of anything that might be causing this mysterious condition that we know so many people are struggling with.
[00:27:32] Speaker B: Well, again, in the spirit of speculation.
[00:27:36] Speaker A: And guessing speculation and guessing, that's what.
[00:27:38] Speaker B: This is, I suspect that the virus is going after parts of the brain that the sort of rhythmicity parts that drive the autonomic nervous system.
I suspect that's part of what's going on, whether that's directly going after those parts of the brain or secondarily to other problems. So again, reduced nutrition and blood flow to sort of the rhythmic origins of the autonomic nervous system. That would be my best guess. But it is a guess without a lot of not just data, but not also not a lot of expertise behind.
[00:28:21] Speaker A: It, which would somewhere, again, just as a speculation with a concussive that would at least make logical sense as a guess, which is all what we're talking about. This any other just insights that we might not have covered? I want to make sure I don't leave anything on the table with this?
[00:28:45] Speaker B: Well, about long COVID, I suppose.
It is a condition that is very complex and like so many of these other complex conditions, it can range from minor annoyance to really life altering.
As providers.
I think that it's an area that's very worth learning about, not just because it's interesting, but because there are probably hundreds of thousands of, if not more people who have this condition. They may not even entirely know it.
[00:29:17] Speaker A: Right.
[00:29:18] Speaker B: From the sort of client side of things, as frustrating as it is, and it is beyond frustrating to try to deal with applied psychophysiology has something to say that's worth saying and at the very least, the do no harm maxim is certainly followed. But there's a lot of at least anecdotal and more and more empirical evidence that heart rate variability and other sorts of bioinoral feedback interventions can really be useful for this condition.
[00:29:53] Speaker A: I love that. So I can't let you go here without asking my favorite question to folks like you who have been working in this field long before I even heard about the term heart rate variability. So such an honor to ask this question, is you've obviously seen the field develop for decades now, and I kind of wonder, and I think that what you're doing right now in this whole conversation is a great example of, okay, we have this tool.
Here's a condition. Let's try to apply that tool to this condition and getting some really good results from doing so. As somebody who's been a pioneer working in this field, has seen it evolve over the years, has been a teacher to so many of us, where do you see heart rate variability? Heart rate variability, biofeedback going in the next five to ten years as the world is coming into your realm and more and more people are hearing about this and getting excited about it, where do you see us going with this concept you've been working with for decades?
[00:31:07] Speaker B: I think, well, one of the obvious answers to that question is it's going home?
It's going right into the consumer's fingers, earlobes, things like that, which I think is actually fantastic. I mean, I think the system you have is really useful and I have a number of clients using it and so I get to follow along with their heart rate variability. And I think that's one of the main places that it's going and this is technology driven, primarily technology is getting better and less expensive so we can bring it home.
The place that I find some frustration with heart rate variability in general, and I would love the field to go this way, is that measures of HRV are not as good in the short term as they are for the longer term. Right. And of course, clinically we have to use it very short term measures. So I would love to see more development of reliable and valid short term measures of heart rate variability because right now it's really good. But there's always the sense that it could just show us so much more if we could just figure out how to better measure it, which I'm sure is always the case with everything we do. But I just think that the usefulness of heart rate variability or our understanding of the usefulness of it has just grown so much in the last even ten years that it would be really nice to put some attention into figuring out how better to measure it, particularly clinically, which is always hard.
[00:32:44] Speaker A: And I got to ask a follow up because you just hit on my current obsession with this is we're starting to get with AI, the ability to really analyze an amazing amount of data in an incredibly short period of time. So obviously I'm looking at this from right now in our app we do with the three minute morning readings or anytime readings, we do RMSD because we believe there's a lot of great research that as a short term and then as you get the baselines, obviously totally support that.
You get a seven day average. It's going to tell you way more than a three minute reading is looking at like, okay, and I know that I got to be careful here because I wish we had maybe more metrics than we do, but we also collect high frequency during that three minute reading, sdn, max, Min. And I don't think there's necessarily a framework of what do all those tell you when combined together. But I kind of wonder, as I have you here, that's where my thinking is going with that issue is we're getting so much data historically, I even think with the fancy equipment you have in your office, it's kind of hard to put all that data together in real time. I think the real time piece is maybe getting solved with technology.
I think the field doesn't necessarily give us a way to put those pieces together to say, okay, we're going to learn this algorithm tells us a little bit more about your sympathetic or your venture or whatever it might be. But that's where Mind is obsessed with right now, is if we could put these pieces together, do we really get anything more than RMSSD?
Do we? And I think the answer is probably. But is it worth the effort to get maybe? Is it only a 2% increase in insight or is it a 50% increase in insight?
[00:34:56] Speaker B: Well, part of the problem, of course, is we don't know until we try. But actually I wanted to highlight something you just said, which is another, I think, real advantage to bringing this stuff home and that it's so much easier now to do these longer baselines. So if you're doing a one week or a two week or a one month baseline, that's so much more reliable than if I'm just getting my two to five minutes. Once a week or once every other week in the office. So that's an incredible advantage and I think that there's a lot of insight into there, which I suspect that's one place you're looking, but that's where you can kind of put your not you, but we can put our attention into what can we tell from these longer baselines that might be useful.
But to go back a little bit more directly to your question, I think you're absolutely right. I think we need to figure out what components are most useful and it's tough to think of combining them, if only because in two minutes or five minutes I'm not getting a lot of very low frequency data. Yeah, and that's why you wear a harness for 24 to 48 hours.
[00:36:13] Speaker A: Right.
[00:36:14] Speaker B: So there's the question of well, what does the very low frequency mean? And that's hard to answer with what we're doing. But that said, I think that somehow combining, even in decision to figure out is it useful? I think makes a lot of sense.
I can increase somebody's RMSSD or Max minus Min when they're stressed. Yeah, right. In fact, that happens acutely, so it's hard to argue that higher RMSD always shows regulation. When I can dysregulate you, if I give you a sympathetic surge, your heart rate is going to zoom up and that increases variability in the short term.
[00:36:58] Speaker A: Yeah.
[00:36:59] Speaker B: So that's why again, we need to figure out how to bridge like you're asking me, you're asking a really good question. Is it worth bridging or do we have enough? We don't know.
But again, that's smarter minds than mine. Yours are looking at it.
[00:37:16] Speaker A: Well, I don't know about that, but I'll take the compliment. Well, it's been a pleasure because like I said, I've been really fascinated with how heart rate variability, biofeedback and just the tracking as well with long haul COVID I think our field is now really ideally positioned to really have a major impact. And I love the fact that folks like you see this opportunity of using your expertise, your knowledge, to really, hey, maybe we have a solution to part of this problem. Maybe again, cure is too strong of a word, but to give help to regulate that nervous system, I'm sure for folks can be like they get even if they get 2030, 40, 60% improvement in symptoms that can keep them employed. And it's such a huge, I think, very interesting piece. So, my friend, there is always an invitation to come back as your work progresses. I've been a fan of yours since we first met, so anytime you have any insight, please feel free to come back and I'm glad I'm in your journey and fellow passenger along with you on this.
[00:38:41] Speaker B: No, and I appreciate all the work you've been doing. I think your system is really good and there are a lot of systems for home use and that use smartphones technology. But I really like the model you've put together.
And if I could just put you one more plug. Yes, please do. And this is actually primarily to the clinicians and other healthcare professionals, although others may be interested, that is.
The association for Applied Psychophysiology and Biofeedback. AAPB.
We publish a book called The Evidence Based Practice in Biofeedback and Neurofeedback, and the new edition has just come out, so go to Aapb.org and order it.
And it's particularly useful for those of us who do the work.
It's sort of the closest book to my hand. I'm always grabbing it. But it's also, I think, really written. Each chapter is sort of a brief summary of the data and the evidence that biofeedback and neurofeedback may work with a certain condition. And the last decision was 2016.
The size of it has much more than doubled, and there's many more heart rate variability. There's a lot more heart rate variability research. So there's a lot more evidence showing the effectiveness of heart rate variability. So I would really urge anybody who's interested to go grab the newest edition.
Disclosure I am an editor. I've written a couple of chapters. There's no financial interest, but Ena Kazan is the lead editor in that.
[00:40:21] Speaker A: All. Before you came on, I was like, I was wondering, how could I get all the editors on a podcast episode? Well, talk about that.
[00:40:31] Speaker B: I had them on the Healthy Brain Happy Body podcast, so you at least listen to them.
[00:40:40] Speaker A: Maybe we can put a link to that in the Show Notes. Always nice to get folks there and promote that as well, because, hey, if you've already done it, let's just send them there.
[00:40:52] Speaker B: Well, it's always good to do it more than once, I say.
[00:40:57] Speaker A: Absolutely.
Well, Saul, we'll put some information in show notes. Like I said, we'll get that link to that specific podcast and other links and information about Saul. But I really appreciate your time, my friend. Absolutely. I know we've been trying to get this interview scheduled for a while, and I just appreciate you and your work in this topic, because one of the reasons, besides just your expertise, is I know I have a lot of conversations that include this issue, both from the professional and the people that are struggling with it. So I was so happy to get your voice on our podcast here.
And again, we'll get show Notes and
[email protected]. Saul, thank you so much for your time and just want to appreciate everybody for tuning in.
[00:41:51] Speaker B: Well, thank you all for inviting me.
