HRV: Injuries, Plasma Volume & Sports Implementation – with Andrew Flatt

Nov 10, 2016 | Android, Blog, Data, Health, iOS, News, Podcast, Research, Science, Training

Episode Guest

Andrew Flatt, MS, CSCS

PhD Student in Exercise Physiology at the University of Alabama, Researcher, Professor

Website(s): HRVtraining

Social Media:

Episode Resources and Links

In This Episode

Andrew Flatt goes deep into the research and application of Heart Rate Variability monitoring for athletes and sports teams. Andrew works extensively with elite level athletes and is one of the emerging names in athlete monitoring research.


  • The pros and cons of a high HRV vs low HRV on competition day
  • Sympathetic activation for performance
  • Low CV and low HRV – what does it really mean?
  • Injury potential and HRV
  • Hydration, plasma volume and HRV
  • The 3 step process to effectively implement HRV for sports and training
  • When NOT to use HRV monitoring
  • The danger of hype around HRV or any metric
  • More breakdown of Coefficient of Variation and Weekly Mean HRV

Episode Transcript

Jason Moore:   Hey, folks, Jason Moore here, and we’re back with Round 2 of Andrew Flatt. Before we jump in, just a quick note about our sponsor, is the premier resource for online educational material on Heart Rate Variability, health and performance. Listeners of this show get 10% off with discount code: elitepodcast, all one word, elitepodcast. Head on over to to learn more about the science and mechanisms behind HRV. I’m one of the instructors. We’ve got other instructors there as well. There’s a ton of great info,

Now Round 2 with Andrew Flatt. The first episode was jam-packed with tons of information regarding HRV and sports performance, and this episode has even more, believe it or not. A quick list of a few things that we’re about to cover: One is the pros and cons of a high HRV versus a low HRV on competition day, sympathetic activation for performance, injury potential in HRV, hydration, plasma volume in HRV, the three-step process to effectively implementing HRV for sports and training, and also when not to use HRV. Andrew is very cut-and-dry when it comes to this stuff. He doesn’t make promises that he doesn’t believe in, and he also makes sure to do his research. There are time maybe when HRV doesn’t make the most sense, we dive into all these and more. So since Andrew has so much great info to share, let’s go ahead and dive right in.

A question that I often get is whether or not it is good to have a high HRV on the morning of a competition day. I think this is one of those situations where, unless there’s some major problem with the athlete’s system on the day of the competition, that their preparation and training will make the biggest difference in the outcome of the competition. My experience though is that strength and power sports seem to actually benefit from a slight decrease in HRV on the morning of a competition, possibly correlating with sympathetic activation, and endurance athletes or athletes that rely heavily on intra-competition recovery may benefit from slight increased HRV on the morning of the competition. Again, this is just observational, and it also doesn’t seem to hold true for everyone. What are your thoughts?

Andrew Flatt:   Okay, I’ll start off by saying that I don’t like trying to predict performance based on your HRV in the morning of competition. There are so many factors that can affect your HRV that are hard to control for it to really say conclusively, a decreased HRV was associated with better performance or an increased or higher HRV was associated with decrease performance. I think first, let’s try and talk about the mechanisms of high HRV and low HRV in terms of what is happening and why, in the first place, higher HRV might be associated with improved performance in some capacity. I think originally, this all had to do with endurance training and not events that require complex movements, explosiveness, high changes of direction, very high-skilled type movements but rather like running or cycling. The reason for that is, and there are probably multiple reason, but when you’re considering changes in HRV, that might have to do with fatigue and fluid balance and plasma volume shifts, you’re probably at a condition to perform endurance training better when HRV is at or above baseline.

Simply, if we’re talking about fluid balance, increases in plasma volume when they’re at baseline or they increase above baseline, it’s going to cause a transient increase in blood pressure just because there’s more volume in the blood. That activates the baroreceptor reflex which basically is sensing changes in pressure within, for example, the arterial aorta and so forth.               We have baroreceptors in different areas, but they detect this change in blood pressure and sends that information to the brain. The brain processes it and says blood pressure is a little bit too high, we’ve got to reduce blood pressure. So it sends efferent information basically through the vagus nerve to the heart to reduce heart rate and thus, increase variability.

The reason why you’re probably in a condition to perform better is because when your plasma volume or your overall blood volume is higher, you’re going to increase your venous return, and you’re going to have a greater stroke volume. You’re going to be more efficient basically. You’re pumping more blood per beat. You’re just, physiologically, in a better state to perform endurance training. That has nothing to do with a sprint necessarily that’s very short in duration or very complex movement patterns that are neuromuscular. We’re looking at cardiovascular autonomic control. We’re not looking at neuromuscular potential with HRV. It’s not what it’s measuring.

Now, why would we have a decrease in HRV? Well I would tell you, the majority of the time, if you see a decrease in HRV on the day of competition, it’s probably due to pre-competitive anxiety which is going to result in elevated plasma catecholamines, but also probably they slept poorly. There’s pretty good research to show that athletes, whether they’re in a hotel — they’re going to sleep worse when they’re not in their own bed, and they’re going to sleep worse the night before competition. That’s obviously going to vary a little bit on an individual basis in terms of how they perceive everything.

But there was a recent study in European Journal of Applied Physiology by an Italian group that was looking at performance in sprint swimmers and how it related to Heart Rate Variability. So the morning of competition, they acquired Heart Rate Variability, and they were looking at pNN50 which is a marker of parasympathetic activity and another time-domain index. What they found was that the lower the HRV, the faster they sprinted. Was it due to pre-competitive anxiety? Was it because they were stressed because they’ve slept poorly? You can control for those things a little bit, yeah. I mean, you do questionnaires. You can quantify sleep. If you have the right tools, you can –there has been validated questionnaires to determine anxiety. But in my experience, it can create more problems than it can solve because you can’t do anything about it. It’s the day of competition. What are you going to do? You know what I mean?

You’ve got to consider the psychological impact that it might have on the athlete that especially – and this is a criticism of mine against all apps, not one in particular, but when you’re giving a color, like a green or a red or a yellow to an HRV score and an athlete does it, depending on the personality of the athlete, they’re going to ask questions. It can bother some athletes too to the point that we actually – I think there was at least one athlete that we were involved with that the color system, they just couldn’t stand seeing it everyday because it was freaking them out. This is telling me I’m not recovered. Or why is this bad, this, that and the other?

We’ve gone to the point that we actually don’t even measure HRV on days of competition and we don’t even have them do it. I mean, there are benefits to doing it in terms of seeing how they respond to travel and this and that, but it’s certainly not worth any kind of psychological added stress to the athlete because they’re worried about seeing a number and a color indication. So we’ve just done away with that, again, depending on the athlete. Then we have some guys that are just so even-keel. It doesn’t bother them. They can handle it.

So, again, it has to be done on an individual basis but, yeah, trying to predict performance on the day of an event based on your HRV, I think is a task, a futile task. There are a lot of variables, and I’m not sure what kind of intervention you could make at that point to change anything. You know what I mean? I guess there are calming techniques that we could use and so forth or techniques we can use to excite them, but I don’t know.

Jason:   This corroborates reports of users getting a PR on a red day and getting confused about it. I then usually explain that the green, yellow, red recommendations are actually geared towards long-term improvement and not necessarily how well you will perform today. Longer-term trends are generally more useful for that. We actually added a setting in the app for the same reasons you were talking about where users or a coach can hide the daily readiness score from their reading. We call it the non-self-fulfilling prophecy setting. In the team platform, the coach or trainer can actually still see the reading for the day or the score for the day, but the athlete can’t see it on the day of the reading and part of the reason is because the athlete’s reaction to the score is an unknown.

Psychology is kind of interesting. Some athletes see a low score and think of it as a challenge to overcome. Others are depressed when they get an “unfavorable score.” So by hiding the readiness score on that day, a team can still gather data but they can also avoid those mental unknowns. As you mentioned previously, if a sport requires a high degree of teamwork, skill, neuromuscular efficiency or other dynamic factors then it becomes harder and harder to predict outcomes based solely off any one metric.

There is a component to parasympathetic and sympathetic activation though when it comes to performance. As mentioned, as you mentioned, there is a benefit to having healthy sympathetic activation for performance especially with strength and power sports. When I mentioned PRs, we’ve specifically seen people in the power lifting community hit PRs on days when their HRV is slightly depressed. There could be many factors of course to that but, anecdotally, I’ve seen it more in that community than others probably due to the strong sympathetic nervous system requirements of the sport.

Andrew:   I would lean towards that hypothesis that greater sympathetic activity is going to contribute to, at least for those type of events, power and strength that is probably an increase in sympathetic activities that’s contributing. That would be my guess.

Jason:   Okay, so the last type of combination we have to discuss for weekly mean HRV and weekly HRV CV is when both are low or dropping. Could you talk a little bit about what that might indicate?

Andrew:   Yeah, okay. Again, in my experience, with the type of athletes that I work with which again are mostly team sports or more recently, sprint swimmers, that is usually almost always indicative of accumulating fatigue, and the more severe fatigue, I would add because that’s indicating that HRV is going down, and it’s not returning back up the baseline. We see this in athletes that are, for example, a two-sport athlete, someone that was competing in two sports at the same time. Their HRV was low. It was not bouncing back up to baseline, and that was the problem. We did accommodate that by adjusting his involvement in both sports a little bit.

I would say that we’re first going to see an increase in the CV with maybe no change in the mean but that’s indicating probably stimulation. As the mean starts to go down and the CV remains elevated, I would say fatigue is accumulating a little bit because the scores are starting to drop a little bit lower there. They might not be climbing quite up as high back to baseline, but they’re still going up and down. Then at the point when the CV stops bouncing back up towards baseline but kind of remains suppressed, that would indicate a high level of fatigue for sure. I’ve got to add that, just assume that this goes without saying, but I would never recommend that anyone use HRV by itself to determine anything without some kind of insight as to how performance is evolving, just their psychological status in terms of a simple wellness questionnaire.

I don’t expect anyone to be drawing blood or taking salivary hormone marker that’s not necessarily feasible in the field. But simply taken with the performance metric, a fitness metric, wellness questionnaires and an HRV trend, you can really look into how they’re adapting and responding to training, and using the evolution of these markers to guide train — not necessarily use HRV on a single day-to-day basis. HRV is this, it’s that, and therefore I’m going to train like this or like that. You can do it like that but in order to do that, you need to be able to have the freedom to adjust your training accordingly. That’s not necessarily going to work well in a team environment. Rather, in a team environment, as you’re monitoring the trends, you could start to see – if we see a decrease in the HRV across the week, usually what we see is after one day of rest, like on a weekend or something, it’s going to come back up to baseline and then we start again.

So accumulating a little bit of fatigue over the week isn’t a problem. We’re not going to change anything unless we really start to see it in some performance or they’re reporting just really high perceived training loads. Again, if it’s a short period of time, I’m not overly concerned about it because they’re going to have a day off in a few days. They’ll recover then. They adapt. So you can use HRV in a lot of different ways. You could look at the numbers in a lot of different ways. But I like to use it collectively with these other markers, see how they’re evolving over time and then making adjustments if necessary based on more than one marker of, whether it’s performance fatigue, this and all that kind of stuff.

Jason:   It’s important to reiterate what you just said. Goals have their own measurable or observational progress, like are you increasing performance, are you getting faster, stronger, more fit, or whatever your goals are? HRV can be a tool and useful metric in helping you achieve your goals, but changing HRV itself is usually not the end goal. You need to be checking performance before and after a block of training to see if you’re actually making progress. Also the daily indicators or daily tailoring might be useful for beginners or those that are picking up a new sport because individual training sessions have a bigger systemic impact on the trainee, so the more experienced you become with a given training modality, the less any single session is going to affect you.

Similarly, as you previously mentioned, the more experienced you become with a type of training, the lower your weekly HRV CV will be, generally, during that training block which because, of course, CV is a measure of the day-to-day fluctuation. Once you’re more experienced, the daily readings are more useful for basically watching for injury potential. For example, if your HRV spikes up really high on a given day, that might indicate an increased parasympathetic activity and your wellness questionnaire may identify that your energy levels are abnormally low on that day, so that day might not be the best day to do very ballistic or high-risk movement patterns if it’s not absolutely necessary.

That’s just what I’ve seen from talking to people and from my own personal data, actually. I’ve sustained some minor injuries that occurred on days when I was in the red, so to speak, on a given day. I’ve also had lots of reports from users on that. Now that doesn’t necessarily mean it can apply to everybody. What are your thoughts on injury potential in relation to changes in HRV?

Andrew:   That’s an interesting topic and one that is entirely speculative in terms of it’s anecdotal, so based on whatever you’ve seen, you may have observed the relationship where changes in HRV have related to an increased occurrence of injury or something. Here’s my take on HRV and injury. First and foremost, the higher level you are, the more meaningful, big changes in HRV are. That comes back to, again, your higher level, more fit athletes have a small CV so when they show a big change, it’s usually pretty meaningful. Whereas your lower level athletes, less fit athletes, they’re going to see big changes on a day-to-day basis despite not much change in anything else. They’re just physiologically different in some regards.

I don’t want to say that you’re at an increased risk of injury just because of HRV. What I would say is this. You’re at an increased risk of injury when you’re fatigued or when training loads have been increased progressively. There’s obviously a big association between an increase in training load and injury occurrence. You just look at transitioning to any kind of pre-season training camp where you’re training two, sometimes three times a day, your exposure to training, and depending on the sport, it could be body contacts, it could be abrupt changes of direction, you’re just exposed to more chance of injury.

Where HRV comes into that is that when you — we see a pretty good relationship that when training loads are increased, HRV tends to go down, the CV tends to go up a little bit. Obviously, if it’s more severe, the HRV mean goes down and the CV stays down. So in that situation, they’re injured because training loads are high that there is a higher exposure in it. There’s an innate increased risk because they’re doing more physical activity, more changing of directions, so they just naturally have an increased risk of injury. It may be heightened because they’re experiencing fatigue, accumulated fatigue which is reflected in HRV. Whether we can say with any kind of confidence that an acute change may be associated with injury, just hasn’t been shown in any kind of research yet. It doesn’t mean it’s not there.

There was a recent paper and medical hypothesis by a doctoral student out of New Zealand, Gisselman. I think her dissertation is focused on looking at the association of HRV in injury occurrence in, whether it’s rugby players or soccer or whatnot. At this point in time, the way I would associate HRV and injury potential is HRV is going to respond to increases in training load and you’re more likely to get hurt when training loads increased due to exposure. That’s just because I’m being a little bit skeptical. I just haven’t seen enough injuries where I could say, yes, HRV was down and stayed, that’s when they got hurt. I haven’t seen that enough yet. That doesn’t mean other people haven’t. That’s just my personal take on it.

Jason:    That’s a great point. It’s important to not make blanket statements based on personal experience or undocumented anecdotal evidence. Anecdotal evidence is meaningful, of course, but having statistically significant and well-documented observational research will definitely add value to that discussion. Injury potential is such an important topic for athletes and teams, of course, since injuries can cost a lot for both the athlete and the team. So it will be interesting to see what comes out of her dissertation research.

Andrew:   Actually, I’d like to add – sorry to cut you off — one of my big motivators to really pursue increasing my understanding and even graduate studies and learning more about Heart Rate Variability was that a paper by a veterinarian who’s a friend of mine, Dr. Christine Ross, who looked at HRV in racehorses. This was published in EQUUS Magazine or something, and I remember looking for this article. I was asking people if they had access, and they’re like, “What? What are you looking that for?” You know what I mean? It was because I knew that there was this relationship that she found between HRV and injury and so I was like, “Well, that’s obviously very interesting and could be meaningful to coaches and athletes.”

What she found basically was, in a group of these high level racehorses, those that were showing Heart Rate Variability patterns that would be associated with fatigue, illness or very high stress, ended up being the horses that ended up experiencing some type of injury or restriction that required them to be removed from training. That was, I think, based on the LF to HF ratio, so they were looking at what some consider a measure of sympathovagal balance, which is debatable in terms of what it actually means. But obviously a reduced parasympathetic activity was associated with – which was observed in certain racehorses where the same horses that ended up having to get pulled out of training because they ended up experiencing an injury or got ill or something.

So that was actually one of my early motivators for really trying to look at this and relating it to injury and so forth. It just kind of confirms that, yeah, when you’re fatigued or under a lot of physiological stress, your HRV is going to be lower, for the most part. Because you’re fatigued, your immune system may be compromised, so you’re more likely to get sick. You’re fatigued so, neuromuscularly, your performance may be – your reaction time may be a little bit slower. I wouldn’t say, again, an acute decrease may or may not increase or decrease injure potential on any level, but if the trend is going down, there’s clear indications of high fatigue then, yes, hypothetically, you may be at an increased risk.

Jason:   So it comes back to the power of weekly and longer term trends being more definitive in decision-making than the daily indicators, especially for a high-fit and experienced athlete. It’s great to hear that Dr. Christine’s work was an inspiration to you. She and I have actually had a few discussions, and I’ve also reviewed some of her work with the horses. In fact, I hope she doesn’t mind my mentioning that she’s taking our HRV course over on She has been very, very encouraging to us as well in our work.

I want to come back around to something you mentioned briefly and that’s the relationship between hydration and Heart Rate Variability. Let’s dive a little deeper in to that. What is the relationship between hydration and Heart Rate Variability?

Andrew:   Yeah, that comes back to plasma volume and how that affects blood pressure. What people need to understand about the heart is that it’s an effector organ. The brain uses the heart as a means to respond to a stressor. That could be during exercise, we increase heart rate to deliver more oxygen and remove more waste products during exercise. So the heart is a means for which we can accomplish that. Likewise, during the recovery from exercise, again, circulation, removing byproducts, the heart is used to help with heat loss by — or I should say, just the entire cardiovascular system is used because we direct and divert blood to peripheral or to the surface of the skin to try and lose heat. We perspire, we sweat, an effort to lose heat through evaporation on the skin. So the heart is used either directly or indirectly to accomplish a lot of these tasks.

When fluid levels are out of normal, again, we can see a transient decrease on blood pressure because there’s lots of volume in our circulation and so blood pressure decreases. We like to maintain a relatively reasonable narrow range of what our resting blood pressure is. So in response to a drop in blood pressure due to decreases in fluid volume, we’re going to increase sympathetic activity which is going to increase heart rate, which increases blood pressure. We get more total peripheral resistance. We can also adjust arterial diameter to affect blood pressure as well through sympathetic activities.

When we’re rehydrating and we’re restoring or we’re experiencing plasma volume expansion — you’ve got to understand, one of the earliest adaptations to endurance training is an increase in plasma volume as a result of increased plasma proteins which create an osmotic gradient that draws more fluid into circulation. So that probably accounts for some of these early increases in HRV that we see after a couple of weeks of training, in addition to a lower resting heart rate. Because if there’s an increase in venous return to the heart and we’re able to pump more blood per heartbeat, then we don’t need to beat as frequently or it’s more efficient, so we get a decrease in heart rate. We also get an increase in parasympathetic activity because of the plasma volume expansion where it would increase blood pressure with more volume, but now we counteract that with a baroreflex by stimulating parasympathetic activity of the heart.

There are more chronic adaptions that have to do with morphological, intrinsic morphological changes such as increasing ventricle capacity. So we can get some eccentric cardiac hypertrophy as a result of volume overload because we’re constantly, with exercise, we’re filling it up with blood and we’re expanding the volume. There’s concentric cardiac hypertrophy as a result also of volume overload where the myocardium gets thicker and stronger with greater contractility. These are all beneficial adaptations to endurance training. Not to be confused with pathological cardiac hypertrophy that can be a result of chronic pressure overload where we could see similar changes that actually doesn’t improve cardiovascular performance but actually results in a smaller ejection fraction and conditions that are not good, obviously. So there’s a difference, obviously, between cardiac adaptations as a result of volume overload from exercise versus pressure overload from hypertension and maybe ischemia and so forth.

So, yeah, fluid, one of the fastest, easiest ways to stimulate parasympathetic reactivation after exercise is to have a nice, big glass of cold water because the cold water is going to help with bringing body temperature back down. We’re going to initiate fluid balance restoration which is important. There are thermal receptors that detect the cold water. There are changes in osmolality that can affect parasympathetic activity. So simply rehydrating after exercise is probably one of the best things you could do to activate the recovery process. I just kind of went off on a tangent. I don’t know, did that answer the original question?

Jason:   Definitely. That’s even better than I’d hoped. So how important, would you say, it is to drink cold water or rehydrate immediately after training?

Andrew:   It’s more important for, I would say, athletes that maybe are competing multiple times in a day. They have several events. Otherwise, we’re going to rehydrate, we’re going to have dinner at some point, at our next meal, so it’s not a huge issue. But, yeah, definitely, if you’re competing or training multiple times in a day, then you definitely want to be very mindful of your hydration status. Without being too technical, just looking at pre-imposed changes in body mass can give you a good indication of how much fluid you lost. But obviously make sure you’re controlling for how you’re weighing yourself in terms of, if you’re wearing clothing and your clothing gets wet then you weigh yourself after, well wet clothes are going to weigh more and so it may obscure your changes in body mass from a training session. Generally, you want to weight yourself either nude or in a pair of Spandex or whatever, just so you’re controlling for that.

Jason:   Great. I was going to ask more about plasma volume, but I think we covered it unless you have anything to add about that specifically.

Andrew:   My insight to add to whatever we already discussed is ask Daniel Plews because he’s — again, working with endurance athletes, the plasma volume is obviously going to be much more related to performance for endurance than it is – obviously, it impacts team sports players like soccer players that there’s a high aerobic demand, but he’ll be able to give you probably some better insight on that.

Jason:   Great, I’ll have him on the show and that will take care of that. There’s something that you have recommended to me in the past and something that we’ve discussed before and that’s your three-step process for implementing Heart Rate Variability. You recommend that teams or coaches or folks who are going to implement Heart Rate Variability, go through a period of observation and then a period of experimentation and then a period of implementation. It’s kind of observe, experiment, implement. I’ve definitely used that three-step process before. I’ve told many coaches, I’ve shared that with other people, but I always credit it back to you. Why is that your recommendation, and what is all that about?

Andrew:   Observation is you have to observe how either – if you’re using this on yourself, you want to observe how you are responding in terms of your Heart Rate Variability to training, changes in training, changes in different types of training, volumes, loads, aerobic. You want to see how you respond to that, how travel stress affects you, how life events – you just want to start to observe some kind of trend where you’re like, oh, I’m noticing that I’m handling this well. I’m not handling this well. It just gives some kind of validation for you to know how you would typically respond to something so that in the future, you can make a more educated interpretation because you’ve seen it before and this has happened before.

Perhaps what you’re seeing is something that was a major stressor before or you responded to a given type of training with a reduction in HRV and your CV increased, you’re all over the place with your numbers but then, over time, that changes. That’s reflecting improved adaptation usually. So the observation period is, I think, really important for yourself to understand how you respond but also in showing coaches – listen, we’re never trying to tell a coach how to do his job. They’re the coach because more often than not, they’re very good at what they do. They’ve had success. They know how to —

Jason:   Exactly.

Andrew:   Right? But what we could say is, listen, we may be able to help a little bit. For example, there is a new study I think in the British Journal Sports Medicine that Dr. Tim Gabbett is on. Essentially what they found was, the more training sessions that you participate in during the pre-season period was associated with less injury chance for those athletes. For example, for monitoring HRV, we may be able to use it to help guide subtle variations in train load to keep our athletes able to participate which, again, if they’re participating in more training sessions, they’re going to increase fitness more, they’re going to increase capacity.

Because here’s what happens at the beginning of training camp, some athletes are more in shape than others and some respond to the first couple of days, they handle it really well and some don’t. The smartest, the best thing you could do as an athlete is just report to camp in peak physical condition. Definitely don’t try and rely on training camp to get you in shape. That comes down to strength and conditioning over the summer usually in the collegiate setting. If your athletes aren’t, you need to be able to train them, getting their fitness up, their work capacity up as high as possible, it’s generally going to keep them healthy throughout camp.

Again, we’re certainly not trying to tell a coach what to do but we can say, “Listen, if we’re monitoring these things, we may be able to give some insight on our starting players that we definitely don’t want to miss any games for whatever reason. We might be able to give you some insight when they may need to pack things off a little bit.” How I’ve done this in the past is tell them what we’re going to monitor and let’s see what happens in terms of who responds well and who doesn’t. I’ll show them the trends. I’ll show them some numbers and the correlations.

What they love to see is just comparing a couple of different athletes. So if you have a couple of different athletes at the same position or that are similar in terms of build, fitness or whatever, and saying, “Listen, you know how this person has been performing versus this person and look at the difference in the trends here.” Not that I’m trying to sell it but I’m just trying to show them that it could be useful. So that’s your observation period, is just observing trends that are meaningful.

Experimentation is, all right, we understand what these changes and the trend mean when we can include factors like training load and wellness questionnaires. Now we want to make an intervention, see how they changed because of it. Again, you’re assessing. Was it successful? Did it work? At that point, you get down to your implementation. So you’re confident that responding to a trend by either reducing training loads — again, we always talk about reducing training loads. But I’ve seen a lot of instances where athletes were just handling training really well, and we should probably increase training well.

So it’s giving you more insight. It’s an objective physiological marker. It’s not magical. If you understand what it’s telling you, you can definitely use it to your advantage. If you’ve experienced tracking training volume, maybe a wellness questionnaire, and you want to add more insight with an objective physiological marker, I think it’s great. But start with an observation period. Start with a handful of athletes. Don’t overwhelm yourself because the last thing you want to do is add something that’s going to make things worse and so forth. So I wouldn’t recommend HRV to be your first monitoring parameter. I would definitely not start using it and making interventions based on numbers that you’ve not validated on yourself and your athletes in terms of, yes, they’re showing these kind of trends in these situations, therefore we should make these changes.

Here’s a little bit of a rant, and I’m not picking on anyone in particular. If your goal is to be evidence-based and you’re trying to adjust training based on science and you’re relying on an algorithm that you don’t know what it’s factoring in, how it’s doing it, but you’re doing this marker, you say, “Okay, I’m measuring HRV. It’s giving me this light. It’s telling me I’m good. It’s telling me I’m not good. I’m going to depend on that because it’s science-based, therefore I’m making a training.” In your situation, it’s not science-based because you have no idea. If you don’t understand the algorithm or if you don’t understand where it’s coming from, you’re not being evidence-based. You’re relying on a Magic 8 Ball. So understanding what the numbers actually mean and what they’re telling you and how they evolve — because, again, high and low HRV can be good or bad, It depends on the situation. I don’t even remember what the original question was but…

Jason:   We’re talking observe, experiment, implement.

Andrew:   Exactly. Again, I almost think if you’re a coach and you want to implement this with athletes, you should probably do it on yourself for a couple of weeks or a month or two. The more experience you have seeing numbers and changes, the better you’re going to be at implementing it. So, again, start on yourself. Start with a small group of athletes then for it to be really effective, across more players. Or if you’re just looking at your starters, you want to have that experience of seeing trend changes, making interventions and seeing that it worked or didn’t worked before it really becomes part of the program. You know what I’m saying?

Jason:   Yeah, that makes complete sense. When it comes to training, the first thing that you should measure are performance markers because in that discussion, that’s typically the end goal, increases in performance. Then folks start tracking things like body weight because all you need is a scale, or they implement wellness questionnaires with questions like, what was your RPE or Relative Perceived Exertion after training, or your perceived energy levels or your muscle soreness? Would you mind sharing a few questions that you like to include in your wellness questionnaires?

Andrew:   For a wellness questionnaire to be useful, you need to get them down relatively frequently. Would you agree with that?

Jason:   Yes.

Andrew:   And in order to get them down frequently, they can’t be long. In terms of the athlete, 20 to 30 seconds, they’re responding. That’s pretty much what we want to limit to. My experience, there are a lot of extensive questionnaires that you could use for research purposes that have been validated. No one in the real world with athletes is necessarily going to apply those though on a regular basis in terms of daily or three times a week or whatever. I’d love the sliding scale on a smart phone app where they can just go, based on your perceived muscle soreness, it’s higher, it’s lower. They can see the scale where it changes color or whatever as they go one way or the other way. It simplifies it for the athlete’s perspective.

In terms of running correlations with changes in Heart Rate Variability and changes in wellness parameters, perceived stress and perceived sleep quality have been very helpful. Perceived fatigue and soreness tend to correlate well with each other. So if you’re asking them about their perceived fatigue and they’re reporting really high fatigue, most of the time they’re also reporting really high soreness. They are two different things, technically, but in the mind of the athlete, they might report that they’re fatigued because they’re sore.    Still I think they’re both useful.

If you have it set up where they could just answer it, whether it’s a sliding scale or they type in a number or however you want to do it, as long as they can do it quickly, conveniently, with not much sweat off the athlete’s back, those typical ones I just mentioned, I think are all useful. Definitely, we could get into more specifics about perceived stress. We can ask them to rate academic stress. We can ask them to rate — at the end of the day, you’re just adding clutter in their mind, perceived stress. How are you feeling? They’ll sit, they’ll think and like, “Yeah, pretty good.” As you could see when they’re doing it, like I’ll be visually observing, they sit, they think for a second and then they make their response.

We also need to be mindful about longevity and compliance, and can we carry this out throughout an entire season? Usually, we can but with the HRV and wellness, I don’t measure it at times where we don’t have to. As much as I’d love to just because I’m curious and I want to see the data, but just to get it off the athlete’s minds so they don’t have to worry about it. If it’s not an important time of the year or there’s a situation we just don’t really need it, we’re not going to measure it just to get them out of the routine of having to do things. There’s a ton of things that they already have to do.

Jason:   Right. Correct me if I’m wrong but you are referring to large chunks of time like weeks, months or off-season in which the data won’t be used anyway by your team. But not necessarily, like, skipping days of measurements between workouts just because it’s a day-off. Yeah, there’s definitely a lot of psychology involved when it comes to effectively coaching and training athletes.

Andrew:   If I could add before we move on to the next one, if you’re involved with the team, you’re going to be able to observe body language, performance, how they respond to — just through talking or seeing them interacting with their friends, you can tell simply by how much chatter there is in the locker room before practice, if they’re loud, they’re talking, they’re joking around and dancing around, which I see a lot; they’re probably feeling pretty good. Their stress levels probably aren’t too bad or at least they’re handling it well. Then there are days, a couple of days in the camp, and it’s quiet. People are more withdrawn and reserved. You could pretty much almost guess what they’re going to rate.

I would never recommend, if you’re in charge of monitoring, whether you’re a physiologist or a sports scientist or just a strength coach, which is in probably the majority of situations where you have your strength coach doing this. You’re in a good situation because you’re involved with the athletes, and you’re interacting with them on a regular basis. If you’re sitting behind a computer screen trying to make sense and decisions just based on the numbers, there’s a disconnect where you’re missing that human element of interaction or at least observation. Again, being there and interacting is just as important as all these numbers. That was the most original way of monitoring your athletes was simply your intuition based on how they’re responding, how they look in the warm-up. Just because we’re not talking about them doesn’t mean that I don’t hold those in very high regard in terms of value. So I just wanted to add that in.

Jason:   That’s so important that you say that especially coming from you since people listening may be interested in what you have to say because of your expertise with the numbers. I definitely appreciate you saying that because it’s so important to have an understanding of the real life situations that are involved in training and competing. That comes back to what you said earlier which is that we aren’t trying to tell a coach what to do or replace the need for good coaching, not at all. We’re just adding a tool to the arsenal of a good coach.

A good example just came to mind of when I recommended to a team to use this observe-experiment-implement process when implementing HRV with their athletes. The coach of one of the top national teams in the sport of orienteering approached us to learn how to implement HRV with his team of orienteers. Orienteering, for people that don’t know – I didn’t know much about it when the coach reached out to me — orienteering is basically racing across uneven terrain with the requirement of navigating with a map and compass to various checkpoints. It’s an interesting sport, and these athletes are usually in extremely good shape.

The coach was essentially asking, “How can I tailor training with my athletes based on HRV?” My initial response was, “Well, I’ve heard of orienteering, but I don’t really know anything about it. So I can’t tell you anything specifically about tailoring the training, but I can tell you what patterns to look for in the data so if you do an observation period, you can look for some of these patterns.” He was very open-minded and selected a group of his top athletes that were dedicated and willing to learn more about themselves. In preparation actually for the Orienteering World Cup, they rolled HRV out and started monitoring their athletes and observing what the HRV data did in relation to their training.

Early on, they found that the daily indicators were not the most useful for their application of HRV, which wasn’t a surprise. They did find that the weekly coefficient of variation correlates really very strongly with their wellness questionnaires. It correlated with the training really well as well. So after a few months, they began actually tailoring their training based on the observations they made in those first few months, and HRV CV was one of the big parts of that. So it would be really interesting to see what they conclude from all these because they all have about a year’s worth of HRV data and their elite endurance athletes leading up to a World Cup competition, so it would really be neat data set.

Andrew:   That’s great to hear that they’re finding the CV useful because it’s just reaffirming that what I’m seeing isn’t something I’m completely making up and that other people are making similar observations. That’s great to hear. I’m glad that they’ve observed this. Now that they’re confident that they could use it to help drive somewhat better or more informed decision-making, that’s great.

Jason:   Definitely. I’d also add that, anecdotally, I’ve received feedback from many coaches in various sports that HRV CV has definitely been a very valuable metric for them in their decision-making.

Andrew:   When I talked about a criticism of a lot of apps using a color code, I just want to talk about that a little bit more. When you’re trying to develop an app and make an app that’s useful, it’s very hard to accommodate everyone for every situation. Doing a color coding system actually makes the most sense because it’s making interpretation a little bit more easy, but I think what the coach needs to take from a color indication is not that green means good always. In most cases it’s usually a good thing. Red in most cases is probably usually a bad thing. Not bad, it’s indicating something.

What you want to interpret colors as is changes. If it’s green, you’re probably within normal. If it’s amber or red or however the app chooses to use it, it’s telling you that it’s outside of normal. So don’t take it as certain colors mean good or bad. Interpret it as based on what the algorithm is using, is, if it’s not green, that means that the numbers have changed substantially enough to change the color, okay? Whether that’s good or bad, you have to interpret that based on who the athlete is, how they typically respond, what training loads, the acute training loads have been, how they’ve been responding over time. Interpretation has to be made based on the change, not on the color.

I think if we change the way we see the color a little bit, we can actually get more use out of it. The problem is we’re naturally trained to think of green as good to go, red is stop, and that’s why it’s used. But again, if we’re having our athletes do this in the field everyday and they’re seeing red and green, that’s when it starts playing with their mind. So the color code can be very good, it could also be a little bit of a problem, depending on the situation. So when I made that criticism, I should say that it’s with complete understanding that it’s difficult because what we’re trying to do with an app is simplify it for people, right?

To make HRV useful and applicable for coaches, they don’t necessarily need to or have to be experts in physiology. But I’ll be honest, if you don’t know why these numbers are changing or what you can possibly attribute it to, then I don’t know how much use you’re going to get out of it. So you do need to educate yourself and see beyond the color and try and just understand that it means there’s a difference, there’s a change. What is it related to? Is it fatigue-related? Is it stress-related? Is it training load-related? Therefore make your decision. We’re still in the early stages of all this. Smartphone apps haven’t been available for – it hasn’t even been a decade really.

Jason:   Right. It comes back to that observe-experiment-implement. I generally tell higher level athletes or athletes that have a coach, to pay more attention to the weekly trends. But if you’re interested in still using the daily indicators, you can use the weekly and longer term trends to help validate whether your daily tweaks are having a positive or negative impact. For example, if the indicator flag is a yellow day, you might actually choose to push through a yellow day and just train hard anyways. That’s, of course, if you’re not worried about health or something like that. So you can just do this as an experiment and see if the long term recovery is actually impacted because I’d actually just automatically eat more, sleep more and just recover more, compensate automatically and recover just fine. So, ask yourself, is HRV impacted over the longer term? Are performance markers increasing or decreasing? Also, an important thing that we’ve touched on is that coaches and trainers and teams don’t have to be the only ones that use this template of observe-experiment-implement. It’s just as applicable to individuals as well.

Andrew:   Yeah, and prepare yourself for another little bit of a rant.

Jason:   Sure.

Andrew:   We’re in a stage right now where HRV — there’s a lot of hype behind HRV right now and that has to do with the overall hype in terms of athlete monitoring which is a buzzword in — and I’m speaking within the context of strength and conditioning and performance and sports, right? If you look at all the trends in training and in sports science or fitness industry, there’s usually going to be a hyper reaction at first. Right now I think we’re accumulating and we’re approaching a hyper reaction phase where everyone is thinking we ought to all be measuring HRV, and this is coming from someone who is a big proponent of HRV. The problem is when black and white guidelines for HRV are given, people take them, they start using and it’s not making sense, then all of a sudden HRV is crap, it’s not useful, people don’t know what they’re talking about, right? Well, no, you’re misinterpreting the data because you were given bad information, or not bad information, you just maybe weren’t taking it in the right context.

Another reason why it’s expanding or growing is there’s a mystery to it in terms of what does it mean? If you were to do a Google Scholar or a PubMed search on HRV and you see that trend over time of how many hits you’re going to get, it increases every single year. There’s more and more research being done. We’re finding associations with the cholinergic anti-inflammatory pathway and how increased HRV is typically associated with lower inflammatory levels. We’re looking at how it affects performance, training loads. So there’s all these stuff going on, there’s all this hype, and because not a lot of people are trained or have the physiological background to really understand and interpret HRV, there’s a mystery to it, and that always make something cool.

What’s going to happen is when more research comes about and when we really start to see, okay, this is how we should interpret it and we’re able to explain it physiologically, that mystery is going to go away, the hype is going to come down and what you’re going to be left with is what HRV is what it really is. It’s a useful objective physiological marker that can be used to help guide training if you use it and apply it appropriately. It’s not a magic tool. No monitoring variable is magic and I wouldn’t say one is even more important than another, I mean, maybe depending on your sport, but you have to take them together with other markers. That always is going to have more meaning and better interpretation.

Like I said, the pendulum is going to – I think that we’re still on the upward phase of the overreaction. It’s going to come back down but rather than going to fall into the wayside as being useful, people are going to be like, okay, it is useful. We maybe overreacted a little bit in terms of trying to be too sensitive to these numbers. Now we understand what they mean. We understand the trend, and we use it as a guide looking at trends to help with training. At least at this current point in time, that’s how I see where things are and where they’re headed. What do you think?

Jason:   That definitely aligns with how most health and performance trends occur, whether it’s a biomarker or a specific exercise or a diet recommendation. Basically when hype builds and people who don’t truly understand a topic, they often will extrapolate it out and start making promises that they don’t really have the experience to substantiate. Then it becomes this magic bullet, or seemingly so, that can cure all issues. But oftentimes, when the pendulum starts swinging back the other way, the truly useful tools and techniques are recognized for what they are, which, like you said, are useful tools. Then the ones that weren’t really what they seemed, end up dying off and pretty much time will tell, as they say. In the meantime, basically we can do our best to educate people and just take the mystery out of it so that it doesn’t get overblown and so that people aren’t put off by the hype because they already understand it better.

It kind of mirrors my personal evolution with Heart Rate Variability, which when I first started learning about it, I was super excited about it, obviously, enough to create my own Heart Rate Variability platform. I’m still very, very excited about it but early on, I realized that it was so much powerful and so much more useful if you had other metrics to go along with it and that it wasn’t a magic bullet by itself. It needed context to be used effectively. That’s why we were one of the earliest platforms to include what we call metadata or wellness questionnaires so early directly into our app because all those metrics and subjective measures and objective measures work together to add a lot of value. And alone, none of them are magic bullet. The value of HRV greatly increases with context.

Andrew:   The phase I went through with HRV was I read that some coaches, for example, Landen Evans was using it with athletes that he was writing about, and I was intrigued, started using it on myself, got to grad school, started reading the research on it, and the research was really cool, some of the available studies. The problem was I wasn’t, at that time, as schooled in statistics as I probably should have been. I definitely went through the stage of, oh, my goodness, this is amazing because this was related to this. But if you look at statistics and the relationship was 0.5, it tells you only 25% of variants was explained by that parameter or whatever, or you see them as a significant change in HRV and a significant this and that and then you start to realize that these are based on means. The reality of the situation is some showed this response, some showed this and so forth.

So, understanding a little bit more about research methodology, how data is analyzed, it brings you back down to earth and okay, yes, this isn’t as magical as maybe I thought it was at first. But the more you use it, the more you see its value and the more you could use it to your advantage. Yes. You’re probably going to go through a few different phases with it in terms of you love it, you hate it, it’s useful, it’s not useful. You got to take it for what it is. And again, these markers are all complimentary. So, exactly like you said, you have to include these other markers because it strengthens each one of them in terms of what they can tell you and how you can make decisions with it, at least in my experience.

Jason:   Andrew, I really appreciate you taking the time to come on the show and share all this knowledge with me and our listeners. Is there anything that you’d like to say before we start wrapping up?

Andrew:   Well, first, thanks for having me. I always enjoy – it’s nice to have a discussion with someone who is also pretty familiar with HRV and has experience so that it’s more of a discussion and less of kind of just a Q&A which makes things a little bit more fun from my perspective. I want to add that I learn something new, literally, probably every day, looking at data and seeing trends. In three months from now, what I’m saying right now may or may not still hold through, so bear that in mind.

Also just like to let everyone know about a conference that’s coming up. My friend, Dr. Brian Oddi is putting on a conference, and it’s going to be hosted at California University of Pennsylvania. A lot of friends and colleagues of mine are going to be presenting there. Dr. Mike Young will be there, Dr. Tudor Bompa, who’s one of the figureheads of periodization and wrote a big textbook back in the day that has been revised a few times and updated. Carl Valle from Inside Tracker, another friend of mine is going to be speaking and then a few other coaches I worked with over the years, Brian Shrum who’s a soccer coach at Duquesne University and so forth. So, if you’re in the Pittsburgh area, anywhere, I think May 13th to 14th, check it out. It’s not expensive, and you’re going to see some great speakers and learn a lot about speed and strength and conditioning.

Jason:   FYI, the conference Andrew mentioned has already passed at the time that this episode is going up. Feel free to check it out anyways online or next year. Also, if you’ve got questions for Andrew or would like to hire him to consult with you or your organization, we’ve been able to arrange a deal with Andrew for consulting. Just send an email to with a few details about what you need and we’ll make it happen. That’s Also, since the discussion with Andrew went so well, we’ve pulled him in to write some content for the Elite HRV blog and definitely check out the blog for Andrew’s posts on of course HRV and performance, and we’ll have some other topics there as well.

We talked about the – in this episode — we talked about the hype surrounding HRV at the moment and how it is a powerful tool that can give you a competitive edge, but it’s not a magic bullet. If you want to understand it in greater depth and how to apply it, I definitely recommend heading over to and checking out the video courses and materials there. I’m one of the instructors. We’ve got some other instructors as well and there’s a lot of great content. But make sure to use discount code: elitepodcast, all one word, to grab your 10% discount for being a listener of this show.

Next up, we’ve got a whole slew of doctors on the show including Dr. Marco Altini, Dr. Dan Plews who we mentioned in this episode, Dr. Paul Laursen which is the prof in Plews and Prof, if you’ve ever heard of them, and Dr. Eldred Taylor who is president of the American Functional Medicine Association; really awesome info from all of these guys. We’ve got everything from data science to world champion endurance, functional medicine, like I mentioned. Definitely subscribe to the podcast on iTunes or your favorite podcast app to make sure you don’t miss any of that great information that they will be sharing with us.

Lastly, the best way to help out the show and to attract more experts is to leave a short review on iTunes. Even if you listen on a different app, one to two sentences on iTunes specifically helps tremendously. I read them all. It attracts more big names to the show to share their knowledge and it really just helps. A big thanks from everyone on the team at Elite HRV for your time. We’re really honored to have these guests and to have you listening. And with that, we’ll see you next time.

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