Dr Arent is a Professor and Chair of the Department of Exercise Science Arnold School of Public Health at the University of South Carolina. His research focuses on the relationship between exercise, nutrition, and stress and the implications for health, performance, and recovery. Dr. Arent is a Certified Strength and Conditioning Specialist with Distinction with the National Strength & Conditioning Association (NSCA), and a Fellow in the American College of Sports Medicine (ACSM), the International Society of Sports Nutrition (ISSN), and the National Academy of Kinesiology (NAK). He is also a past president of the ISSN.
Dr Arent is a Professor and Chair of the Department of Exercise Science Arnold School of Public Health at the University of South Carolina. His research focuses on the relationship between exercise, nutrition, and stress and the implications for health, performance, and recovery. Dr. Arent is a Certified Strength and Conditioning Specialist with Distinction with the National Strength & Conditioning Association (NSCA), and a Fellow in the American College of Sports Medicine (ACSM), the International Society of Sports Nutrition (ISSN), and the National Academy of Kinesiology (NAK). He is also a past president of the ISSN.
Yeah, and that's the last title. The past present part is one of my favorite ones, so the ISSN is near and dear to my heart and appreciate all you tuning in today. So what I'm going to be talking about is how we use biomarkers both in our research and our application, to enhance really human optimization overall. And that includes the health side of this. And I should probably start by saying that I think there was probably a point early in my career where, I don't know that, I would say I considered health and performance sort of mutually exclusive, but there was definitely a notion that you could push through some health issues and really performance was a different story. But I've come to appreciate more and more and more how the best ability is availability right and the ability to keep an athlete healthy on the field. You're going to win a lot more games. So one of the things I'm going to talk about today is how we put this all together. I should probably start by saying that I will mention a couple of things we've done with the military on this, but I'm going to leave in the sake of time, I'm going to leave quite a bit of that out, but if you want to look into some of the best research, in my opinion, on true overtraining and overreaching. It's the military work that's been done with like the Army, rangers and things like that, because they are used and abused in that period of time and we can really see how some of these hormonal and biochemical changes occur.
Speaker 1:But I think, to start us out, when we look at biomarkers themselves, there's three kind of buckets that I tend to deal in. One is the endocrine side. So if we look purely at a hormonal response that allows us to look at acute and chronic stress, this is really where we can get at some of the core of adaptation and certainly repair and recovery, but also the ability to maintain homeostasis and even what contributes to fuel metabolism. When we look at some things like cortisol, both free and total, acth, total and free testosterone I should probably include sex hormone binding globulin in here though it's not a hormone, it certainly impacts how testosterone functions growth hormone, igf1 and on and on, including the thyroid hormones, the catecholamines and whatnot. From a biochemical standpoint, we can look at things that are indicative of muscle damage, often surrogates for muscle damage but useful nonetheless. When we look at, for example, creatin kinase, we can look at fuel metabolism and bioenergetics. We can look at hydration markers, which are incredibly important for performance as well, and even oxidative stress and inflammation. I think early in my career we did quite a bit in the oxidative stress area and I've tended to gravitate a bit more towards the inflammatory cascade because of its tie-in with growth hormone as a cytokine, but also what we've seen with overlap with the HPA axis and stress, and certainly from a recovery standpoint, this has been a pretty big one for us.
Speaker 1:With athletes. We're looking at amino acids, triglycerides, glucose, certainly hemoglobin and hematocrit We'll talk a little bit later about iron, which I'm also going to knock down here in a second with the nutritional markers and then looking at a lot of our cytokines. Il-6 is an interesting one for us because it also plays a role in glucose metabolism. Then, finally, nutritional markers, when we're looking at that health and status and it's funny because any of you that work in athletics know that if you ask an athlete they pretty much lie. They're not really great at recall, but they're okay. The nice thing about blood is it doesn't lie. When we look at nutritional deficiencies or shortcomings, being able to assess this as a biomarker or biomarkers is probably one of our greatest strengths, looking at things like hemoglobin A1C, certainly, from a health standpoint, but B12, iron, omega-3, vitamin D, for sure. We've even looked at SOD as the mother antioxidant, as an indicator of oxidative status within their antioxidant status within their diet.
Speaker 1:Now, when we start to assess these, though, you have to take a number of things into account, right, and this is where the challenge comes in, because I've seen a lot of people that just try to plug and play with biomarkers and, to be quite frank, they don't know what the hell they're doing. Right, and that's a problematic situation. This is not quite so simple as we might want to make it seem. There is a lot of nuance and certainly a lot of education that goes into this in terms of what these things really contribute to, but, really, one of the first things we have to ask ourselves is what's the scientific meaningfulness when it comes to performance? When you're looking at assessing a biomarker, there's a lot of things we can assess. It doesn't mean we should, right, and just because you can do something doesn't mean you should do something, and I think that's a common theme going through this.
Speaker 1:But the other thing we have to think about is the timing as well. You need to understand the time course of these metabolites, these hormones, in relation to training and, as they indicate, recovery, because if you assess at the wrong time and maybe not even the wrong time, but the wrong time for what the question is that you're asking you may come up with very faulty information. You also have to consider the proximity to training. When was the last time they trained and how does that allow you to move forward in terms of being able to apply this fairly rapidly to modify their training? Because really it needs to be assessed in a way that influences preparation. If we don't do this frequently enough, we really wind up with these big gaps in information and by the time the damage is done it's hard to come back from. So we want it to be frequent enough that we can use it to modify our training prior to important competitions, prior to tournament time or, in the military, prior to deployments. But at the same time, if we measure it too frequently, it becomes very burdensome, very expensive, very quickly and also very noisy, because some of these things do fluctuate fairly readily. So you've got to be understanding of what the patterns are you might be looking at, and that's where the acute and chronic issue comes in.
Speaker 1:Some markers have very different meanings in terms of acute and chronic elevation or change. Probably one of my best examples is cortisol. So if you look at cortisol, cortisol acutely for high intensity exercise is absolutely necessary. If I use dexamethasone to block cortisol, my performance is going to go in the toilet because that becomes a huge problem from metabolism of fuel standpoint. On the other hand, chronically, of course, it all stays elevated. That indicates something very different from a stress standpoint. So how we balance those things out really starts to matter, and so we need to understand that some are going to be more important acutely, others chronically, and so catecholamines may be more useful to us in some cases. Acutely, though, there's a chronic consideration from a stress standpoint and we consider systemic activation. But some of the dietary markers may take a while to really change, like if you have an athlete with low iron, just giving them an iron supplement. Their iron stores are not going to magically be higher the next day. So the chronic tracking of some of these becomes really important. On the other hand, something like lactate has very little meaning chronically, except for looking at chronic acute changes. But the acute influences really where we want to pay attention in that case.
Speaker 1:Now, one of the things that we're doing is, anytime we collect any type of information like this biomarkers, heart rate data, training load, things like that it's just data, right, it's numbers. What we're trying to do is we're trying to take those data and turn it into information. Now we're consolidating in a way that we can have a usable number, right? What is this telling us? In some way, because what we're doing is we're trying to build our knowledge base about what this is doing in order to, ultimately, what we would like to do in this continuum is develop wisdom, right? So you might ask what's the difference in these? All right, here's one way of looking at it. Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad, right? So that movement to that experience and what you do with it really becomes important.
Speaker 1:And this is why I think it's so critical in some of the current trends I've seen for sports scientists is we often have much more of what I would consider to be data analysts, right? They're not at the training, they're not interacting with the athletes, they provide no context and we'll talk about context in a minute. But what we're trying to do is when we understand the team, the athletes, the coaching, the schedule and all the things that go into it and what resources they have. We're putting all that together with the numbers, with the data, to try to build that wisdom in order to apply this the best way we can to help the athletes stay healthy, stay injury-free and win a lot of games right, and that's really what we're ultimately trying to do. And so one of the questions I often get is well, okay, so like, if you had to pick like two biomarkers, what would you do? I'd be like, pick like three or four.
Speaker 1:So the reality is it's difficult to boil it down to one thing. There's only a couple studies where we've only looked at one biomarker. We just wrapped something up and had a couple papers accepted on this recently with some work we were doing with the Marine Corps in their gender integration model and we were actually tracking cortisol through basic training, but we were also tracking changes in sleep and changes in heart rate. So we had multiple markers on them to try to compile these things and, to be honest, it was interesting because that stress applied very, very quickly and even once some of the physical stress came down in basic training. The stress itself was still very high, right, because of the psychological demands that go with this. So that tells us a lot, but the reality is well, there's a lot of markers that are associated with overreaching and over training. Funny enough, there's no one set group that everybody agrees on in terms of this reflects overreaching and overtraining. And often because studies have been very limited in their scope of what they can like probably monetarily, if nothing else too. So they might pick three or four things and this did or didn't change.
Speaker 1:We were very fortunate with the work we did very early in this area to have a panel of over 90 biomarkers that we were then able to whittle down to meaningful patterns, so that we're not now using 90 biomarkers, but we've been able to develop that. So some of the things you have to think about when considering this as individual variability different people respond different ways the degree of overtraining right, how far into this are we? Because sympathetic or parasympathetic responses are going to vary with that and that's going to play a role. And then, finally, dietary influences what is their supplement regimen? What's their dietary intake? Are they eating enough? What are they eating? What's their protein intake? Are they fueling before workouts.
Speaker 1:All of these things start to matter, and so we want a grouping of biomarkers that's comprehensive enough to give us the full picture, but not so broad that we dilute the crap out of this and lose interpretability. All of a sudden, it's like oh my God, I'm looking at 70 different things. What do these mean? What you're really looking for patterns and you start to also identify and this is where I go back to is it meaningful for performance? What's the science behind this? Because the other thing that we have to think about is, by the time some of these markers change, overtraining may have already occurred. So now you have to ask yourself are we using biomarkers for prediction, or are we using biomarkers for confirmation? Where you're like oh, I think my athlete is totally tanked, let's do some blood work. Oh yeah, they're totally tanked. Now what do I do? Right, we want this to occur early enough that we can still intervene, and that's going to be a common theme, you'll see, for how we've used this going forward.
Speaker 1:So what we need to do is for biomarkers to have context. They have to be tied to other measurables. Performance testing or outcomes are very key, just looking at the blood work itself. Here's the problem is you don't know where the intervention is. There was a majorly baseball team I was working with for a while and it started out they weren't doing a lot of other physiological tracking but they wanted to look at biomarkers. We get the first blood panel back. What does this mean? I don't know because I got nothing else to go on Like. I can tell you what this reflects, but in terms of what we would change from a baseball training, sleep nutrition standpoint got me. So they needed to start tracking some other things to complement this so that we have the whole story. And so I'm a big fan of load monitoring and physiologic responses and systematic performance testing throughout the year to give us an idea of how these biomarkers are linking with the things that we need to consider on the field and off the field for how we treat the athlete. And then we can account for supplements and dietary influences.
Speaker 1:But ultimately, the most important and useful biomarkers are going to be the ones that can be modified through training, diet and sleep. If they're really really really hard to change, how useful can they be from a practical standpoint One of the worst things you can do, both as a scientist, but certainly, relaying this information to an athlete or coach is when you go oh man, this is really high. Okay, what do we do about it? I have no idea, but it's not good, right Like you don't want that. So you need to be able to identify what can change these things. And often it's a modification in training or it's that the athlete's not sleeping enough or it's their nutritional intake. But now we've got a target of acquisition in order to try to modify these things, and now we can track this over time and ultimately improve health and performance on the field.
Speaker 1:So we ask two key questions in our lab all the time so what? And now, what do I do with it? Right? So if you see something change, so what? What does this mean? And if it's important enough, what do I do? And so we kind of follow this three-word mantra see, say, do, do I see it change? If you never see it change, it's probably not going to be of much feedback used to you, but if you see it change too easily, we got a problem because it's so noisy. So the first thing is what are you seeing for patterns? The second thing is what would you say about it? What is this? What does this mean? What is this different marker consider for human physiology, for performance? Because then ultimately, that leads us to if you can say something about it and you can qualify why it's important. The next question is okay, now what do I do about it? Right, so what is my intervention here? See, say, do, if we follow that, simply hopefully South Carolina's winning another national title this year.
Speaker 1:For anything to be appealing to athletes or operators, it has to have impact. Right, it needs to be a needle mover for them. Then this is where that health and performance aspect comes in. I will tell you right now, I still do with a lot of coaches where you can talk the health part, but the selling point for them is performance. But if you explain to them how the health translates to performance and what that means, you get a lot better buy-in. Right, because these things that we relay have to be easy enough to understand but important enough to impact.
Speaker 1:Preparation, all right, because this should guide what we do. It shouldn't determine it for us. We got other things we have to consider in terms of rosters, in terms of depth and all these other things, but it should influence our preparation. Work could and, in many cases. The thing you have to think about is that maybe the most critical influence on biomarkers is the one not under individual control for a lot of athletes, which is their training right, because the coach, the strength coach, they dictate that. So what this requires for this to work is buying at multiple levels across the team. We were fortunate. A lot of the data I'm gonna show you is what we derived.
Speaker 1:When I was at Rutgers, we worked very closely with women's soccer. Some of its additional work we've done at South Carolina, but I will say, especially with the women's soccer coach at Rutgers, we had such an amazing relationship with Mike O'Neill that we were able to have these conversations, that buy-in at that higher level, to the point where he was willing to change the training. He was willing to change how he rested and recovered players. That takes a lot of trust and that's a lot of conversation. I will say this to anybody in this field If you're working with a team and athlete coach and they don't understand what you're trying to tell them and you get frustrated, that's your fault. You haven't explained it well enough. Explain it again. And if they still don't understand it, explain it again, but explain it better, because the reality is, most of these coaches, and certainly the athletes, do not have a background in exercise science and sports science and kinesiology or even nutrition, so we're teaching them from a very basic level. It's your job to put it into understandable terms, right, and I think if you can do that and wrap your mind around what this means for us, we're going to be doing a lot of good. In that case, we're doing a lot of games.
Speaker 1:One of the things that we started out with was looking at changes over an entire season. Now, there's a lot you can't control in this, but I would argue there has not been a single well-controlled study in exercise science. That's truly an overreaching or over-training study. They bring them into the lab for three weeks, they jack up the training for them. They go oh look, they overreached. Oh, we didn't see anything change, right? That's not how this works. You take a two and a half, three month, four month cycle of intense two games a week throughout a season gearing up for NCAAs. There's a lot that goes on, and now you're incorporating travel and you're incorporating relationships and you're incorporating the social environment and heat stress in August with these fall sports. On and on and on.
Speaker 1:Now this is competitive stress, but what we saw was that over the course of a season, we had declines, especially early on, in some of our performance metrics VO2 max, vertical jump weight. Also a decrease in percent body fat, as they lost weight throughout the season, but no differences in fat free mass, which was a good thing. We were able to maintain that In future seasons, based on the lessons we learned here, we were able to actually enhance some of those performance variables because of what we learned about where stress was applied, because what we saw is that training load and exercise energy expenditure were by far the highest in preseason. Preseason for fall sports is brutal, but we saw this. So we saw significant increases in cortisol, both free and total, a lot of our inflammatory markers, as well as T3, reflecting the enhanced metabolism that was needed, and then decreases in a lot of our very important and nutritional biomarkers throughout the season. And so, when female athletes but from the high training load, high energy expenditure from preseason, they never fully recovered from it, it persisted throughout the year. Now, knowing this, we were able to start making some changes though, and so this is actually off of paper that we just recently were in first round of revisions with this it looks like it'll get accepted.
Speaker 1:But we looked at in season changes in males and females from a comparative standpoint, and what's important to note here is the patterns in K-Cal's expended, distance covered and load accumulated were remarkably similar between males and females. So that's not explaining any differences we see in biomarkers. On the other hand, though, there were very different responses physiologically. So when we looked at free cortisol, it was actually higher in females and it was significantly elevated from baseline at that right after about two weeks after preseason and then a month after that. So each of these time frames represents a 28 day phase for when we were doing blood draws, and we would do these about 24 hours after the last weekend match, so that we were getting a recovery phase with this. We saw this with both three and total cortisol. And then CK was actually higher in the males, but maybe not surprising given the higher body mass and they also play at a higher speed. So there is a difference at that top level of power output.
Speaker 1:On the other hand, with growth hormone, we really don't see much change with males. I found it a very fairly useless biomarker in most of our males, but it's actually very sensitive in females we see something very similar in terms of responses with IGF-1, though it's responsive in both males and females and I know I put this all on the same scale here so that to be fair. But one thing to note, and I know in the graph it doesn't look that important actually in males by the end of season they had a significant decline in testosterone and it went from about 675 down to about 550. And so notable percent change, whereas in the females we actually saw an increase in testosterone coming out of preseason. And then certainly there were estrogen changes.
Speaker 1:But what we thought was really interesting was the blood markers when we looked at iron right, so some of these hemodynamic issues. When we're looking at iron, percent saturation and ferritin, the changes in women were remarkably consistent and remarkably robust and these were pretty significant decreases in iron coming out of preseason and it took to the end of the year to get these back up to baseline levels. And that was with supplementation. And when we look at percent saturation and ferritin, a lot of these things really reflect what the strain on the system was and because of this, one of the common suggestions that we're now seeing is prophylactic iron supplementation in female athletes, especially going into a season because of what we saw with these biomarkers, one of the more interesting things. We're almost out of time so I'm gonna wrap up here with a couple last little thoughts.
Speaker 1:But we actually done a study in field hockey and thinking that fitness would be protective. But we were tracking biomarkers along with this, thinking okay, they're gonna be more resilient, more robust, and what we actually found was that the more fit players actually had more biochemical and intricate disruption coming out of preseason. And we went wait what, and till we realized what was happening is they were incurring higher training load because they were making up for the less fit players. So we call that the fit athlete paradox. That actually induced more damage. So the message isn't come in out of shape. The message is if all of your players come in ready, you're able to distribute these loads better and actually, based on these lessons, the coaches the following preseason changed and actually rested the more fit players a bit more. This relationship went away and what we're able to see is that the less fit players actually trained up into fitness and we were really coming into the season in a much better situation at that point. And so we do know that these biomarkers do correlate with body composition and performance changes and when you have less disruption in the anabolic hormones and a shift in the catabolic hormones, some of our outcomes are very favorable. But what was interesting is cortisol actually positively correlated VO2 max, because what we saw is they were doing more running the ones with higher cortisol, so of course their VO2 max goes up, but they also lost fat free mass right. So there's an important consideration in that for how we look at these overall. And so, beyond blood, we're not gonna get into this day, but I wanted to throw these up here for you to consider. If you don't have the ability to do biomarker work, it's not just blood, that's biomarkers.
Speaker 1:We can also look at heart rate variability, though most people abuse the crap out of this and don't know what they're doing with it, which is unfortunate. It's not always that high is better, low is bad. Patterns really, really matter. But also power. We've actually gotten to the habit where we're tracking force production and power throughout a season every week, and looking at neuromuscular changes. Looking at heart rate recovery After an intense workout. When you get up to at least 85% to 90% of your max heart rate, how quickly does your heart rate come down after a minute of rest. Ideally we're seeing 25, 30, 35 beats per minute. Would be fantastic, but the reality is, when you're looking at this, also make sure that they have the same rest position and process every time they do this, otherwise that's going to skew it. And then, certainly, even just looking at resting heart rate, how is this changing over time as we apply this stress to somebody? Because if you see resting heart rate continue to creep up, that's a warning flag for us.
Speaker 1:So again, another important biomarker. So what are we trying to do? We're identifying when the greatest stress is incurred. In most cases it's actually preseason. So why is this important? Well, the more you sweat and training, the less you bleed and battle. So if we can iron some of these things out early, that's going to help tremendously.
Speaker 1:But you also have to ask what the individual can control. Some of this may be diet, some of it they may need help with the nutritional intake. Some of it may be training, but a lot of that has to be done at the organizational level. So how you communicate these efforts really matters. And really what biomarkers allow us to do is account for overall stress.
Speaker 1:This was a missing piece of the puzzle for us. Just looking at training load tells you what's happening in training. It doesn't tell you what's happening in the rest of the day. Biomarkers do. It's the accumulated stress response that goes beyond the field, beyond the court, beyond the pool, because it's not just about what's happening in training and games, it's also about life. And then taking into account individual factors, their fitness over the course of the year, as well as what they're coming into preseason with, and certainly injury history, and biomarkers have provided us information to bring athletes back from injury much more beneficially, because we can actually track where they're being overloaded and do this in a smart way, and so actually our return to play is sped up. But we're much smarter about the progression at certain times.
Speaker 1:And with that I just want to thank first of all Joey and the ISSN Always very grateful of the organization. All of these individuals listed Bridget, al and Brittany, dave Harry they were all former doctoral students of mine that are now doing their own great work my wife Michelle, who's the director of Olympic Sport Nutrition here at South Carolina, who was with Rutgers Soccer when we were working with them, and Mark Russell in the UK for some of the collaborations that we've had, and certainly Rutgers men's and women's soccer, gamecock athletics, the Marine Corps for the funding with the basic training, study and quest diagnostics. We had a phenomenal research partnership with them when I was at Rutgers to be able to look at these things much more comprehensively. So with that I thank everybody for their attention and, joey, I think I came in right on time. Thank you, even 1990.