Aliquot #113: Is resistance training a type of aerobic exercise?

Aerobic exercise and resistance training are essential for optimal health, but finding the time to do both can be challenging. That raises a question: can resistance training be aerobic? In my recent interview with Dr. Martin Gibala, he shares a few salient points about using resistance exercise to achieve the higher and more vigorous heart rates we associate with high-intensity interval training, effectively optimizing your workout's time efficiency and providing the benefits of both aerobic and resistance training. There's a lot of ways to sort of modify the, you know, the HIIT program in general. What about this, the, is it high-intensity resistance training or resistance intensity training? Which way do you say it? It goes different ways.

You know, some people call it functional training, but certainly there's high-intensity resistance training. You know, I think it can still count, you know, for a lot of resistance training, Just because the intensities are so high. You know, we're talking about now very high force efforts that last less than a second sometimes. By its definition, it's interval training. We just never really think about that. But so I think certainly bodyweight style type interval training or what used to be traditional calisthenics and that, that can play a role here. So I think, again, using this generic term interval training. I think we can have more aerobic-style interval training or resistance-style interval training.

And again, bodyweight-style interval training would sort of be the classic one to me that is interval resistance training. And I think it can have tremendous benefit. You know, it's often a sort of a middle ground. You're not going to see the gains in strength that you would see with traditional heavy weightlifting exercise, and you're not necessarily going to see the gains in fitness that you would have with a traditional well-structured aerobic training program, but you can get a lot of both right in the middle, you know, especially if, you know, we're talking air squats, burpee sets, push-ups, where you also keep recovery periods relatively short. You know, you engage in that for 10 to 20 minutes.

You can keep your maximum— your heart rate up to about 80% of maximum, but you've done a lot of resistance-style training that's increasing functional strength as well. I think it's a tremendous way for people to train. It sounds like a lot of CrossFit kind of things. Yeah, absolutely. You know, now maybe not necessarily as intense as some of these programs that you see, but absolutely that style of functional training, whatever you want to call it or label it, can be extremely beneficial, I think. And in a time-efficient way, you get strength gains and some aerobic conditioning as well. In another interview, Dr. Brad Schoenfeld highlights some time-efficient strategies that emphasize a similar quality of keeping intensity high and breaks short. Let's hear what he has to say.

And then you can use various time-efficient strategies. So kind of these advanced training methods, such as a superset, Which is doing 2 different exercises. And there's different ways to structure these. There's something called a paired set, paired set, where you do agonist-antagonist movements, such as— so, the biceps and triceps are agonist-antagonist muscles, meaning that when one is contracting, one is shortening, the other is lengthening, per se. So, if you do a biceps curl, you can immediately do a triceps press-down after that, and really, you're working the muscles in a different fashion, you don't have to rest. Between the sets. You could do a leg exercise followed by an upper, so, lower body followed by an upper body exercise.

Again, you're working different muscle groups, so you get— it's more time efficient, you don't have to take the rest. If you're going to do, let's say, sets of chest press, so, let's say, I do the typical traditional way of doing sets is you do a set, then you rest, then you do another set for the same muscle group, you rest. That's going to take more time because you're going to have to rest between those sets. There is something called drop sets where you can do a set to failure, or certainly close to failure, then you drop the weight. I don't mean drop literally, but you reduce the amount of load. So, let's say, for instance, let's say you're using— you have a rack of dumbbells and you use 20-pound dumbbells for curls.

You can then, when you finish, you're getting really difficult on those last reps, You then go to the 15-pound dumbbells and you do more reps because you're lightening the load, you're able to do more weights. You can do triple drops. So, you go from 20 to 15 to 10 to 5 even, and just do them without any rest and then not do any more sets. So, rather than doing multiple sets, you just do this one drop set, long drop set. Now, is that as effective as doing multiple sets of the same muscle? We don't have enough evidence to show, but I do think we have enough where I would confidently say, for the gen pop, it will be just, or close to, as effective. I don't think, for the majority of the populations, it will make much difference. Again, for the high-level athlete bodybuilder, it might.

And that's where, again, context is important. In this last segment, Dr. Mark Mattson shares an interesting personal anecdote that influenced his opinion about the importance of incorporating resistance training. even for endurance athletes. One thing that's being found is it's important to maintain muscle mass as you age. So, I think people need to be a little bit careful, you know, to take in sufficient energy to maintain their muscle mass. My own personal case, so, I've always had a low BMI and I started doing daily time-restricted eating, like, 30 years ago, not eating breakfast. And I was kind of an endurance semi-athlete, trail running, mountain bike riding. Actually, when I was a kid, I used to race motocross. But anyway, I did a lot of running.

And so, my BMI is always Around, it's very low, like 18, 18.5, you know, somewhere there. And then, 2 years ago, I had a mountain bike accident. And not to be too gory, but essentially tore my rectus abdominis muscle off my pubic bone and had adductor partially coming off. I had to have 3 surgeries. Wow. And I've had other issues now. But, so, I've lost some muscle mass, particularly in my legs during this ordeal. And I'm having trouble building it back up. So, like, hindsight's always 20/20. And, like, you know, I couldn't have predicted I'd have a mountain bike accident and have all this going on. In hindsight, I probably would have been better off.

And I didn't really do any resistance training because when I was running, when I started running in the '70s, like, there was no such thing as cross-training. It was like the runners, the training is you run, you stretch, and you run. And somehow, I guess because I'm stupid, I didn't pick up on, hey, as, you know, people started doing cross-training stuff, I didn't pick up on, hey, I should be working my core and I should be, you know, keeping, you know, some muscle mass. You know, so all these years, I was mainly just doing the same thing. But anyway, so that's just like a personal anecdote. And, you know, so, I guess what I'm saying is having a low body weight can be good, but you have to be a little careful during aging to make sure that you have a good muscle mass as part of that.

Like the main— well, I guess I was mostly muscle mass anyway, but still, yeah, more muscle mass. It's important to note that endurance exercise and strength training affect the heart differently, highlighting the importance of engaging in both types of training for optimal performance and overall health. Some of these differences are due to what's called the exercise pressor reflex, a physiological response during physical activity that mediates communication between the muscles and the cardiovascular center in the brainstem. Listen as cardiologist Dr. Ben Levine explains.

Can you sort of differentiate between, so I've heard you talk about, I mean, you're talking about the adaptations to endurance type of aerobic exercise versus, I mean, Olympic athletes that are more strength training, right? So in terms of this adaptation of the heart getting bigger, how are the adaptations different? Well, so I'm gonna give you the traditional thought, And then I'm going to tell you that that's not probably 100% right. So the traditional thought, what has been called the Morgan-Roth hypothesis, is that strength training, which does not increase venous return, that is the blood returning to the heart, it doesn't increase stroke volume very much because it imparts a huge afterload, a rise in pressure. During a static strength contraction.

Any idea how much the blood pressure goes up during exercise? Do you know this? Which kind of exercise? Strength exercise. If I were to have you do— Definitely hypertension, I mean 180 systolic. All right, so if you're going to do— if I take a competitive athlete and I do a 90% one repetition max squat, what do you think the systolic blood pressure gets to? Oh, like a multi-joint squat, like 200? Higher? Keep going. 250? Keep going. 300? Keep going. 400? 400 millimeters of mercury. And John Sutton and his colleagues put arterial lines and showed that many years ago. So you generate that kind of pressure by intense muscle contraction, which contracts the blood vessels.

So now you're driving stroke volume into a very small, much smaller space, than you did before, there's massive sympathetic activation from something called the exercise pressor reflex, which is a function of both the relative intensity and the total maximal muscle contraction. And so that raises arterial pressure very high during the contraction, right? And so to adapt to that, in order to reduce the load on the heart, the heart has to thicken because the wall stress, the stress on the heart muscle, is increased by the bigger the heart is, but is decreased the thicker the heart is. So traditionally, purely strength-trained athletes tend to have thicker hearts, what we call concentric hypertrophy, as opposed to dilated hearts, which we call eccentric hypertrophy.

And athletes who do almost exclusively endurance training, runners, swimmers, cross-country skiers in the days before skating technique, they have massive increases in blood flow. So the adaptation of the heart is to get bigger to accommodate and then sustain those big stroke volumes. So that's the sort of traditional view. The endurance athlete has a bigger heart which is eccentrically remodeled. I mean, if I just stretched it without making the heart thicker, the walls would get smaller. That's not what happens, right? The heart adapts, gets bigger and more muscular, but the walls don't get thicker. A strength-trained athlete, the heart doesn't dilate, the walls just get bigger. And it's the eccentric hypertrophy that's important for stroke volume and thus cardiorespiratory fitness.

Exactly, that's correct. Now, it turns out that it's not, probably not so simple. And it's not so simple for a number of reasons, because even during dynamic exercise, when you contract your muscles and run, you're actually occluding blood flow during those too. And many sports like rowing, for example, are an intense combination of both static And dynamic or strength and endurance type activity. So rowers, every time they pull on the oars, they use a massive amount of skeletal muscle that's contracting. But they're also doing that in a rhythmic basis, like a runner or a swimmer. So they're doing both strength and endurance, and they have the biggest hearts of any athletes. The biggest hearts that you ever see. Are in the rowers. And now in some skiers.

So, you know, skating technique in skiing is a huge strength as well as an endurance component. You know, and in the— for, I guess, gosh, this is 1984, for 40 years we've been classifying sports Yeah. Into their static versus dynamic exercise. And we created a little matrix, you know, low, medium, and high endurance, low, medium, and high static. So a 9-box factor. And in the Bethesda Guidelines for Managing of Athletes with Heart Disease, we put sports in these different bins. We're revising those guidelines, right, those scientific statements right now, and we're going to change how we display that. Yeah.

We've eliminated the individual boxes and we say there are increasing amounts of endurance requirements in the sport and increasing amount of strength requirements in the sport, but it's not so simple. I can't just put them into little bins because, I mean, even golfers strength train, right? And even some strength-trained athletes will do aerobic exercise. Yeah. Most American football players don't do anything more than 10 seconds, never. I tend to recommend to the trainers that even the strength-trained, those athletes will be better off if we incorporate some higher intensity. They're the perfect people to do not just a 10-second effort, which is all they ever do, but do a 1-minute or a 2-minute. I mean, how long do multiple play?

Series, take a last in a football game, for example, American football game. I think they need to do 4x4s or 2x2s. And that's what's gonna allow them to sustain their fitness and not get tired when they're playing fast in the sport. So I think we realize that sport is not so simple. I mean, Even within a sport, you know, the goalies are different than the than the than the fullbacks. The you know in in American football, the defensive backs are different than the linemen. You know, it's it's just really different. And so we can't just just bin sports and all the sport people will train with strength and or even runners are training with. Weight training and doing strength training. Even runners are doing strength training these days.

You know, to not— I'm trying not to bin them, but I'm going to bin them. So let's say purely strength trainers. There does seem to be an argument then that they should definitely incorporate some endurance training, if not for the stroke volume increase and eccentric hypertrophy and the effects on cardiorespiratory fitness, So I think that for strength-trained athletes, it's a mistake not to do any endurance. We can argue about what endurance means, whether 2 minutes or 4 minutes or 40 minutes is endurance. And I think that there are different ways to skin the cat, so to speak. Certainly for long-term health, that becomes critically important.

Jonathan Kim and Atlantis worked very closely with the National Football League to help retired NFL players figure out how to change their training and their eating and their habits to preserve their health over their lifetimes, where football careers just aren't that long. So I think you're right that for performance, maybe not for Olympic weightlifting, You know, but for other strength sports, I think there's no question that endurance is important. And for sports that require repetitive bursts of strength activities, I think some type of endurance training of some degree, whether that be high-intensity 4x4s or something, is critical for performance and will enhance performance. When we talk about cardiovascular health, that's a little bit of a different story.

And I think that it is important for overall cardiovascular health, in fact essential, to include that over time. And again, I'll come back to the point that no good athlete does just one thing. You know, I think that's where our studies kind of are a little bit— Too isolated, because in order to do the research, you've got to focus on and ask one simple question, but training is not that simple in real life. Right. There are people that are much more focused on resistance training and strength training that are not athletes. They're just interested in health. And some people wonder, well, I'm getting my heart rate up to, sub, almost maximal heart rate when I'm doing my compound lifts, my deadlifts or my squats.

And how much of that counts towards, am I getting this improvement in eccentric hypertrophy and stroke volume, or do I need to then incorporate some other types of training as well? So I think— You're articulating the CrossFit concept basically, right? And so I think that I'll tell you that it kind of depends. So I think that if you ask what happens to the heart rate and cardiac output during a purely strength activity, there are things that drive the heart rate that are controlled differently in a strength activity and an endurance activity. Let me give you an example. I want to dig into that, if that's okay. There's a little bit of science here. Please, please do. All right, so let's first talk about something called the exercise pressor reflex.

So simply, it's easiest to study by doing just a hand grip exercise, okay? But it would be true for any— if I squeeze my hand, okay, that's the same as, you know, doing a short static exercise. Do a hand grip, and I do it At, let's say, 30% of a maximal contraction and I hold it, okay? Heart rate will steadily rise. Blood pressure will steadily rise. If I put a little needle in an efferent sympathetic nerve as it passes by the fibular head, that's called microneurography, I can actually record signals from the brain to the blood vessels, which cause vasoconstriction throughout the body. Okay. It's a brain-driven process which comes from feedback from skeletal muscle. How do I know that?

Let's say I do that until I can't do it anymore, and I take a blood pressure cuff and I blow it up on the arm, and I trap all the muscle, all the metabolites, you know, the things that are happening in the muscle that are causing fatigue, that are utilizing that energy And I trap them there, and then I stop exercise, I let go. Heart rate comes all the way back to baseline immediately, but blood pressure stays up and the sympathetic nervous system stays up. And that is the essence of the exercise pressor reflex. The heart rate is— now you can ask me, is the heart rate controlled by the brain then? Because I've stopped exercising, right? So the brain's no longer trying to make something happen. That's called central command.

Or is it happening because of muscle tension, nothing to do with metabolites, because I stopped exercising? Well, to address that, my— one of my mentors, Jerry Mitchell, went to Copenhagen and put some— Neil Seker injected some curare into the nerves, which paralyzes them. And they had them look at a screen and they said, I want you to try to squeeze as hard as you did before. But because the hand was paralyzed, they couldn't contract the muscle, but they could try really hard and heart rate went up even higher, even though the muscle was not contracting. So we know that this vagal withdrawal and sympathetic activation The heart rate in particular comes from the central command.

The sympathetic activity also is stimulated by what's called group 3 and group 4, large and smaller unmyelinated fibers, fibers that are not insulated, that carry signals from the muscle to the brain and say, something's wrong, let's alert, let's get that blood pressure up. Increased nerve activity constricting the blood vessels. So that's called the exercise pressure reflex. The harder you squeeze, the longer you do it for, okay, the more amount of muscle mass, the bigger the blood pressure response. So that's one component, okay. How is the heart rate regulated during dynamic exercise, during running, for example? Well, it turns out that it is almost certainly coming from an energetic signal in your skeletal muscle. How do I know that?

Well, some patients have diseases of the mitochondria. They're called metabolic or mitochondrial myopathies. And one of my colleagues at the Institute for Exercise and Environmental Medicine, Ron Haller, He was a neurologist that studied those patients. He's since retired. He's not dead, just retired. And what he found is when those patients started to exercise, their cardiac output went through the roof. Their venous blood looked red because they couldn't extract the oxygen. They had a problem in the muscle. But they would— you and I might increase the cardiac output by about 5 liters, 5 liters. for every liter of oxygen uptake, these people were increasing it by 10 or 20 liters. So even just walking down the hall is maximal exercise to them.

And what that tells us, it is a signal that we need energy, we need oxygen delivered and fuel that drives the heart rate response and the cardiac output response during endurance exercise. So those are 2 fundamentally different things. One increases the heart rate during a muscle contraction from central command. The other drives muscle contract— cardiac output to match venous return. The more compliant the heart, the more blood could come back, the more it can pump out. And those 2 things are happening to a greater or lesser degree with any combination of movements. That's why I mean it's no longer so simple to talk about just strength or just endurance. And then that gets me back to the question Yeah. So it comes back to the question we started with, why are you training?

What's the purpose? Some people tell me they want to look good, they want their muscles to be big, they want to have, you know, relatively little muscle fat, they want to be strong. I say, well, then you got to do a lot of strength exercise. You know, if what you want is to perform during a CrossFit competition, you got to do CrossFit work. I think CrossFit is very interesting to me because it's a combination of repetitive strength-type maneuvers, but they also include repetitive muscle contractions. So I think that kind of exercise does have both an endurance and a strength component. Mike Emery from Cleveland Clinic now is a huge fan. Of the CrossFit-type training and believes that it will get you a combination of eccentric and concentric-type hypertrophy.

And again, it's where, you know, this Morgan-Roth hypothesis kind of falls apart because it's not one thing or the other, it's kind of a combination of both. I don't think you can lift free weights and expect, you know, that Yeah, I slam down the weights on the floor, walk around in between my sets, that you're going to get an endurance-type trained heart. That requires a more sustained, repetitive contraction and more dynamic-type exercise to engage. I know that's a little complicated, but does that help? Wonderful, wonderful. I mean, I also love that you did bring up the CrossFit. I have been doing CrossFit for the last few months. And also there is an incorporation of a lot of high intensity. There's rowing, there's jumping rope, there's getting on the bike.

So it is, like you said, it's not, you can't just put strength training and resistance training in one bin and endurance in another, particularly with a lot of these programs now that are available, like CrossFit, Orange Theory is another one. They do, they have something very similar. But you're right, just like if you're just raising the dumbbells and doing, You know, there's not as much of the endurance kind of training there. So it's good to talk about the science there on that. Coming from a background as a runner, I have grown to appreciate the importance of resistance exercise in my own routine. There are many benefits, especially when we reflect on the sarcopenia effects of aging.

As we grow older, we lose bone mass and we lose muscle mass, 2 critical losses that must be counteracted if we want to enjoy A high quality of life in old age. On the other hand, high heart rate activities are crucial for brain function, preventing neurodegeneration, and possibly reducing metastatic cancer risk. To me, it's clear that resistance training can be performed in such a way that it produces a higher heart rate and thus incorporates some aspects of cardiovascular exercise. But even aside from that, it helps us get more done in less time.

On the other hand, If you're only doing resistance training, it seems clear to me that you are probably leaving something on the table and that you would generally be better off if you also could fit in some dedicated time to focus on aerobic exercise to support your cardiovascular health. For people leaning towards not taking the time to do that, high-intensity interval training or sprint interval training is a great option. Ultimately, in answer to this question of whether resistance training can be a type of aerobic exercise, I would like to emphasize my conclusion is do both. If you're leaning on the resistance exercise side and aren't a runner, be efficient and use drop sets and keep intensity high to keep heart rate high while lifting.

Consider adding sprinting or high-intensity interval training to your workout routine. It doesn't take much time and it does make sure you're covering the bases. If you're more on the runner side, make it a point to lift or do squats. I have now started working with a coach to work on this. It will benefit your bone density and protect you from the sarcopenic forces of aging that work to whittle our skeletal muscle down and make us frail. If you're older and have already lost muscle, the good news is that functional strength can come back quickly. You can regain capacity very quickly if you make the effort. I hope you enjoyed this aliquot and find ways to incorporate aerobic exercise and resistance training into your personal workouts. Thank you so much for listening, and I'll talk to you soon.