Dr. Rhonda Patrick: Okay, what about, I've heard you talk about recovery, and recovery days being as important as how much load you're putting on your heart, and so how much training, essentially. I'm curious what you mean by that.

Dr. Benjamin Levine: Right. So recovery is a essential part of training, and I think most athletes and coaches understand that. But it's a way that many athletes get into trouble, because if they're not performing as well as they want, they think, oh, I just need to train harder. And that ends up just getting them into a vicious cycle of increasing overtraining.

Dr. Benjamin Levine: In order to reap the benefits of a training stimulus, the body has to do something. The muscles have to produce protein, the blood vessels…there's a release of a variety of downstream metabolites from the oxygen sensing cascade, from hypoxia-inducible factor through VEGF, the vascular endothelial growth factor, the things that make the blood vessels that improve the lining, the endothelium, that add muscle fibers, that make them bigger. All these things have to happen. That's what, beneath the skin, those are the things that are happening after you do a training stimulus and if you don't allow those, their full expression, then you won't get the benefit of the workout that you do. And so most good coaches and trainers will always incorporate an easy session after a high intensity session.

Dr. Benjamin Levine: And always, I think, should always have a day off. Whether that day off is some, you know, strength training or technical training or things like that, that's okay by me. Watching film, doing some basic technical things, shooting free throws, if you're a basketball player, whatever, but it has to be something easy that's unstressed and that's what allows you to, to get the most benefit. And I think that people who are not coached or who have a coach that's perhaps a bit more inexperienced, they get driven to do more and more and more and they find that they're not getting better and that's probably because they're not having adequate recovery.

Dr. Benjamin Levine: One of the things we did in all our altitude training studies, we spent more than a decade studying the best way to do altitude training for, for USA track and field and the US Olympic Committee is to monitor early morning heart rate. That was our best indicator. So we'd have the athletes put their heart rate monitor on, you know, set an alarm, put their heart rate monitor on. If you've got a watch at rest, it's pretty accurate. During exercise, the watches that just use the PPG, the plethysmogram are not accurate. That's a whole 'nother discussion that we should talk about, but put it on at rest and track it for—you can go back to sleep and see what it was for those five minutes before you woke up again. And as you start to get overtrained, that resting heart rate starts to climb. And that's a signal that, okay, I need to reduce the frequency of my intensity sessions. I need to make them a little shorter, or I need to make sure that I'm adding adequate recovery and take a day off.

Dr. Rhonda Patrick: Inadequate recovery. If I'm just… I want to make sure I understand this. It includes, on a day you're training, doing something a little more light in terms of aerobic exercise.

Dr. Benjamin Levine: If you're used to doing stuff in zone three, in zone four or zone five, you might do in a zone one. Okay, so do you know what I mean by those five zones?

Dr. Rhonda Patrick: Go ahead. And it'd be great because it seems like definitions vary depending on what journal you're reading.

Dr. Benjamin Levine: And I think that that's true. Different coaches use different zones.

Dr. Benjamin Levine: And typically what that means is we would pick the, generally the second ventilatory threshold where ventilation starts to really increase out of proportion to oxygen uptake, where VE/VCO2 has gone down to its nadir, where lactate is between that two to four millimolar range. They all reflect what we call the maximal steady state. That's the highest level that you can sustain for a prolonged period of time. Most good marathon runners are running at the maximal steady state. And let's just say for argument's sake, that was at a heart rate of 155, because there's no magic to heart rate, and it changes on a day to day basis. We're not machines. We would bracket that and call it say, the maximal steady state or threshold, or zone three training would be 150 to 160. Okay.

Dr. Benjamin Levine: Then zone two training is about 20 beats below that. So 130 to 150. Okay. And then zone one or recovery is less than 130. So a recovery effort would be below the lower limits of zone two. Now, zone four is probably the hardest to quantify because in the physiology world, you need to bring people back and do multiple repeat testing to do that. Zone four is what we call critical power. That's the highest intensity you can sustain without failure, without a drift towards VO2 max. So when Kipchoge was trying to run the under-two-hour marathon, he worked with Andy Jones and Mike Joyner and trying to say what exactly is my critical power? And its amazing.

Dr. Benjamin Levine: If you look at Andy Jones from the UK's work, he does exercise in an MR magnet and looks at truly phosphocreatine ratios and hydrogen ions. One or two watt differences is the difference between sustainability and failure. Its extraordinary and its delicate and its hard to pick. It's my belief… I think Andy's also, is that the reason that some of these great runners from East Africa or some of the great swimmers spend so much time doing what they're doing is they want to feel what.. they got to figure out what the pace zone four is. They have to know what that is. And it's hard to prove that in a lab. Everybody, the good athletes know that. When can you push that pace and when do you have to back off? And so we know zone five because we're measuring maximum heart rate.

Dr. Benjamin Levine: And in the model that I gave you, let's say the max heart rate was 180. Okay, so the top of the zone three was 160. So often what I typically will do in the lab is I'll split the difference and we'll call zone four 160 to 170 and zone five 170 to 180. And so that gives you a nice broad heart rate, five zone, which reflects different kinds of events. So zone three typically is a marathon. And I'll calculate running economy. And so I know the speed at any given oxygen uptake for a runner, for example. And if I take zone three, heart rate and running economy, I can tell you what your marathon time is going to be. And if I figure out what zone four is, that's about a 10K pace or so. So you can't run that pace at an entire marathon, right. But you can run it for 45 minutes or an hour.

Dr. Benjamin Levine: Right. And then 5K in short, or 5K is run at VO2 max. So 5K is run at in zone five. And anything shorter than that, we know for sure that you can't run 10 meters a second for a marathon. You can't even run it for 5000 meters, but that's still going to be zone five. So anything that's pretty much 5K and shorter will be run at those higher heart rates and those higher training zones for endurance activity.

Dr. Rhonda Patrick: So you mentioned the importance of looking at your resting heart rate early morning for recovery and sort of a good….

Dr. Benjamin Levine: As a guide.

Dr. Rhonda Patrick: As a guide for training. Right. What about, you hear a lot about heart rate variability?

Dr. Benjamin Levine: Yeah. So, you know, we spent decades and I published probably 100 papers about cardiovascular variability. So first let's ask what is heart rate variability? So heart rate variability looks at the change in heart rate over time. And there are two, this is grossly simplifying it, but there are two main stimuli to heart rate variability. Number one is respiration and breathing. When you breathe, there are two things that happen. Your brain is sending signals to your diaphragm to breathe. The nerve that carries those signals also goes to the heart, that's the vagus nerve. There are also changes in blood pressure and stroke volume that occur as you breathe, because when you breathe in, you're decreasing intrathoracic pressure. Blood flows into the heart.

Dr. Benjamin Levine: When you breathe out, the blood comes out of the heart. You're changing stroke volume, you're stimulating the arterial baroreceptors, which are in the carotid arteries and in the arch of your aorta. There are a number of things that happen when you breathe that move blood in and out of the heart and also send neural activity from the brain to the pacemaker of the heart. That's the respiratory variability. That happens at the respiratory rate. Then there are other intrinsic rhythms within the circulation. They happen a little bit slower. If you think in terms of cycles per second, or Hertz, 0.1 Hz, or one cycle every 10 seconds, is the low frequency Mayer wave frequency. If I were to measure sympathetic nerves, the Mayer frequency is mostly sympathetically driven. Not entirely.

Dr. Benjamin Levine: It's sympathetic and vagally driven. So the problem is that all measures of heart rate variability when you use a heart rate monitor, do not take those into account. So if I told you to breathe at six breaths a minute, I would slam the high frequency on top of the low frequency rhythm and I would markedly increase your heart rate variability. If I had you breathe a little bit faster, I would separate those out. And most of the heart rate variability that's being measured by your heart rate devices, most of the heart rate variability that's being measured by your heart rate devices is mostly looking at the high frequency variability, but that is absolutely dependent on respiratory rate, and nobody controls that, right?

Dr. Benjamin Levine: You're not given a tone that tells you you breathe at this frequency and we'll measure your heart rate variability. No, it's not doing that. And then I'm going to add one more. That as you move around, very low frequency rhythms will alter heart rate. So when you stand up, heart rate goes up. When you lie down, heart rate goes down. When you pee, you have vagal withdrawal. It's the only way to pee. So your heart rate goes up when you pee. When you talk to somebody, your heart rate goes up. These are uncontrolled factors. In my laboratory, if I control every single factor, so, same time of day, same food in the body, same... I control how deep and how fast you breathe. I can't get better than a plus or minus 25 percent day to day variability.

Dr. Benjamin Levine: So I'm just telling you that even under the best of circumstances, these measurements are very technique dependent and very variable. So I don't think people should use them as an indicator of anything, because I think it's too. The science is not there. You can read lots of articles about heart rate variability. I was the thesis advisor and opponent for one of my good friend, Heikki Rusko from Finland, and his students tried a lot to look at heart rate variability as an indicator of training and overtraining, and it's just too hard to standardize and get right. So I think you. If you try to use that, except under extraordinarily controlled conditions, I think you'll find. Yeah, I think that you'll find you'll make more mistakes than benefit.

Dr. Rhonda Patrick: Well, that goes with what my gut was telling me, because with my training, I can see improvements in resting heart rate. I can see it in my heart rate. My maximal heart rate going even lower, like getting lower. But my heart rate variability, according to my Apple watch, nothing.