Training Tendons & Sprint Interval Training Better Than Roadwork? w/ Dr. John Babraj (SSOF Ep 102)

James de Lacey2:50

That's pretty much covered, I think, my complete understanding of tendons just from that, and that's as far as I know in terms of maybe collagen fibers aligned, everything. So that's perfect. So now we can go a little deeper on that.

Okay. So you talked about tendons, we want those collagen fibers to be aligned, pretty much parallel to each other all the way across, based on the line of pull from the muscle. So for the patellar, if anyone's listening, for your knee, that will be straight up and down your leg.

Now I guess what happens, or what can happen to the tendon with exercise when you start maybe seeing pain or dysfunction? You obviously don't want collagen fibers to crisscross and things like that. Is there something that happens with exercise, or why does that happen? What kind of exercise causes that kind of change?

Dr. John Babraj3:52

So you can think about tendon like an elastic band almost, or a rubber band. It's got to stretch, it's got to return to its original structure. When you exercise, you put stretch on it. When you stop exercising, it releases.

When you then do exercise to the extreme, you overstretch the elastic band. It can't return to its original structure. It's been pulled too far apart, which then creates scar tissue, or in the worst case scenario, complete rupture of the tendon.

But even if it doesn't rupture, you can still get a break in the collagen fibril, which will then be infiltrated by scar tissue. Then it's not going to go back to its original conformation. So when you then try and create force again, transmit that force, it doesn't transmit in the same way.

So it's exceptionally important that we understand where the maximum point is in tendon property. So a lot of researchers will talk about Young's modulus, which is an engineering term about the integrity of a material under force, under strain. So we talk about tendon in the same way, about this ability to withstand strain. And if you overstretch it, essentially it's going to break.

James de Lacey4:58

So when we're talking overstretching, are we talking things like if someone's getting into plyometric training too early and they're not prepared for it, that could be an overstretching thing?

Dr. John Babraj5:38

Yep. So excessive plyometric work can lead to overstretching tendon. Excessive loading of bars when you're doing weight training can cause overstretching. Just generally pulling the tendon, sudden rapid change of direction where tendon is not wanting to go, can cause an excessive pull. So it's not just loading, it's not just plyometrics. It can happen in gameplay as well.

James de Lacey5:38

Gotcha. Okay. I was just going to say, okay, so overstretching tendon potentially if you're doing, essentially going above your means in a lot of ways, I guess, in terms of maybe weight training and plyometric-style training, or even not prepared for whatever the sport it is you're doing. It's probably more than that, it's probably more than...

Dr. John Babraj6:44

It's going back to that original statement that we have a muscle-skeletal unit. So the muscle can't provide more force than the tendon can transmit. But we know that when we do things like resistance training, it's highly anabolic to the muscle. You get a lot of muscle growth. The response of tendon protein synthesis isn't as high. So tendon remodeling is not as great as protein remodeling to that exercise stimulus.

So it's very easy to create an imbalance where the total muscle force that can be produced exceeds the stretch the tendon can transmit. So it's not just overloading or overtraining. It's training programming is maybe incorrect at times.

James de Lacey7:27

Okay. That's kind of why you see sometimes, I guess, juiced-up bodybuilders kind of rupture biceps tendons and stuff. That muscle force is really high and the tendons haven't adapted as quickly.

Dr. John Babraj7:27

There's two reasons why that happens. One's what you said. But the reason that tends to happen in bodybuilding, probably going to be steroids, which is still a big issue in bodybuilding. Tendons don't respond to anabolic steroids. Anabolic steroids create no change in tendon growth pattern. They create an exceptionally anabolic growth pattern in muscle. So with that, with the lifting and muscle growth from resistance training, you're just creating this perfect storm for essentially the whole extracellular sheath and framework to fail.

James de Lacey8:07

That makes sense. And again, there was that bodybuilder a long time ago whose bicep exploded. There's a few of them. Kellen Von Moger is probably one of the famous ones who tried to do that 180-kilo partner bicep curl or whatever, and then tore his bicep, and that was his career.

So we've got to balance. When we're trying to think about muscle growth for performance, we have to balance out with what the tendon's doing. So then, what is tendon training? Because I guess in the textbook version of it, they just say heavy strength training thickens the tendons. That's tendon training. Then, or even some people will talk about high-rep training because that pumps a lot of blood into the area, and that's tendon training. So what is tendon training to help prepare them for the rigors of sport?

Dr. John Babraj9:22

I think our understanding of how to train a tendon is poor, if I'm honest. Because there's no way to really non-invasively determine what's happening in the tendon. I think people make assumptions about what they're doing, and those assumptions may not be correct.

So we know if you load the tendon, you get a change in protein synthesis rate for roughly about two days post-exercise. But that's a remodeling event. It's not necessarily increasing cross-sectional area of a tendon.

So from MRI scans, you can see a small cross-sectional change in tendon area. But it's whether that's coming with a correct collagen fibril alignment or not. And I think at the moment we can't answer that. I don't think we can confidently say that any type of training is particularly targeting tendon in the correct way.

James de Lacey10:41

So we could potentially be making a tendon thicker but at the expense of maybe collagen fibers not being aligned correctly, et cetera?

Dr. John Babraj10:41

Yes. Or increased space between collagen fibers or something like that. So we might actually be... the structure of a tendon might not be improving as we think it is. And that means when we put high force on it, it's going to give.

James de Lacey10:41

Interesting. So is there a training method then to work on potentially the structure of the tendon or something that may be more beneficial for aligning collagen fibers that may not be aligned?

Dr. John Babraj11:17

I'm going to say that we have no clear scientific evidence that there is. What we know is we don't want to overload the tendon. So we want the training modality not to cause overstretch. So whatever we're doing, we have to do it with that in mind. It comes back to this: there's no right way to train.

You just need to know what you're changing. And I don't think we can say we know what we're changing with tendon. There's a lot of stuff done on biomechanics of movement that then gets taken back to tendon stiffness, tendon function, and how accurate that is, I'm not convinced by it, I'm honest.

There was a classic paper using MRI and ultrasound to try and look at in vivo, or within the body, tendon viscoelasticity—how stretchy and flexible the tendon is—but they were reporting errors in measurement of around about 15%. So we don't have a robust way to see what's happening.

The best way to see it is to biopsy it, which we have done, but that's exceptionally invasive and you're not going to do that with elite athletes. So that's what we did with the Karolinska Institute. Biopsies were taken under ultrasound guidance into the tendon. We took out probably about 7 milligrams of tendon. So it's exceptionally invasive, more invasive than a muscle biopsy.

And obviously repair of the tendon is slower because turnover of tendon is slow. So if you're trying to do that with an athlete there's potential you're going to create scar tissue and compromise performance, so that's never going to happen.

So I don't think we can say for definite we know a training type or we know how to change tendon structure at the moment, probably because it's too invasive to actually look at it. Because MRI is probably the most accurate imaging and papers that look at that are reporting 15% error in estimates, with a lot of ifs made in the marks and stuff of how tendon responds.

James de Lacey14:04

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So does that mean we also technically cannot say exercises like plyometric training improve tendon stiffness or the ability of the tendon to transfer elastic energy or store elastic energy or anything like that?

Dr. John Babraj15:26

Not really. People do say it and potentially it might be true, but I don't think we have a good measure of it doing that, if that makes sense. We know we can remodel the tendon with exercise, and the increase in protein turnover is about 100%. So post exercise you get a switch on.

But when you consider that post exercise the increase in muscle protein synthesis is about 250%, so we've got different things happening. And the other component that we've not talked about yet is the nutritional component to it.

James de Lacey15:59

Yeah, I was going to get to that too.

Dr. John Babraj15:59

And this is really important. Muscle is a protein-controlled tissue. So if you're looking to get a hypertrophy effect, get bigger, get jacked, go to the gym, lift heavy weights, take protein, probably about 20 grams of protein post-workout, and you'll create a really strong anabolic response because the protein will increase the protein synthesis rate and also switch off protein breakdown post-exercise to a certain degree. And that leaves us with a cross-sectional area growth of the muscle, so the muscle gets bigger quicker than if you just did exercise on its own.

The tendon, however, and bone are not protein-controlled tissues. So when you take in your whey protein post-exercise, it's not promoting an anabolic effect into your tendon and bones. And our tendons and bones, because these are fibroblast and osteoblast cells, these are fat-controlled. So protein metabolism in there is controlled by fat.

So then we start to get into, what do we not take in when we're trying to get jacked? Most people don't take in fats. So we're now into a situation where we're in a fat-deficient situation. So we're creating an anabolic effect in one and potentially a catabolic effect in a different tissue.

James de Lacey17:55

Interesting. So you would say if, to balance it out, you would want to take your protein with some kind of dietary fat directly after training to potentially improve, I guess, collagen protein synthesis within the tendon and bone?

Dr. John Babraj17:55

Yeah, so I would probably go with an omega-3 based, a fruit.

James de Lacey18:29

Interesting. Is there a general guideline of how much you would take in that instance?

Dr. John Babraj18:29

There isn't. Again, it's one of these areas that's, my understanding, it comes from cell culture. So from fibroblast and osteoblast cell culture, you get a big switch-on of collagen synthesis in cell culture when you expose them to omega-3s that you don't get when you expose them to proteins.

So you probably need—there's no upper limit for omega-3 intake. It's an essential fatty acid that we don't make particularly well, and it's an essential fatty acid but we tend to not take in from our diet very well because most people don't eat a lot of oily fish. Most diets that have high fish intake is probably Japan, and even there intake of omega-3 isn't sufficient.

So supplementation is normally the easiest way in that case without changing somebody's diet. We've got a very meat-based diet, not very fish-based diet. And then when people do eat fish these days, there's a lot of farmed fish, which is not a bad thing, but omega-3 levels in farmed fish is lower than in wild fish. So we change the makeup of the fish that we eat slightly.

James de Lacey19:52

So even just having a high omega-3 fatty, I guess, diet throughout the week, not just post-training, is likely beneficial then just for general tendon health?

Dr. John Babraj19:52

Yeah, yeah, health. So again, there's no point in the tendon being able to transmit the force if the bone can't withstand the force as well. All that's going to happen is the bone's going to fracture. You're going to get a stress fracture on the bone.

James de Lacey20:29

So on the same topic of, I guess, dietary and supplementation, obviously the collagen supplements are—I mean, they used to be cheap because they didn't do anything for muscle protein synthesis. Now obviously they've been rebranded and remarketed. Now they're charging like 60 bucks for a little bottle of it.

So from my general understanding of collagen, it's five main amino acids, and even if you get those five main amino acids anyway from any other source, you kind of have the structure of collagen. So that's pretty much, minus collagen, it's very basic. Don't we go into some details there. Is taking collagen going to do anything for someone's tendon structure?

Dr. John Babraj20:55

No, nothing. Nothing. Because it's a protein. So it's not going to go into the tendon unless there is essential fatty acids and fats available to activate the tendon.

James de Lacey20:55

Okay, so if you took collagen with omega-3 then, now possibly?

Dr. John Babraj20:55

Possibly, then it may have a benefit. Whether taking collagen with omega-3 is any different from taking collagen with protein, taking omega-3 with protein, it's debatable because essentially it's just a different protein.

Collagen has a triple helix. I don't know what the release rate of collagen when you take it in is, because it has to get broken down. So because it's triple helix, it probably takes longer to break down than something as simple as a whey protein, which is fairly quickly transmitted across a gut.

That could have—we talk about this one-hour window post-exercise that's highly anabolic. Potentially it could be the same in tendon, that if you get the right nutrition in in that early window when you've got a lot of cellular activity, you can enhance tendon structure and function.

James de Lacey22:05

What's your take on then some of the research around taking collagen before training with vitamin C?

Dr. John Babraj22:05

I haven't actually seen any of that, but vitamin C is—it doesn't really do—it's one of these vitamins that very rarely are we deficient in. That's why we don't have scurvy anymore. So taking excess—when we get into micronutrients, if you're deficient, bringing up to sufficiency will have a profound effect.

But taking sufficiency above tends to not have any additional benefit. So there's a finite ceiling to how much micronutrients your body's going to use. I think vitamin C is very much like that, and I don't think there's any real evidence that it does anything with excess.

James de Lacey23:34

Or if it does, the effect of it is very small, or it doesn't have any synergistic effect with collagen or anything like that?

Dr. John Babraj23:34

No, not I'm aware of. Yeah, I'm open to being shown evidence otherwise, but from what I've seen, the stuff I've seen, there's no synergistic effect.

James de Lacey23:34

Got it. If, I guess, if tendon collagen synthesis is only enhanced maybe less than half of what muscle protein synthesis after exercise would, that mean—

Dr. John Babraj24:11

Then if someone's trying to potentially improve tendon structure or function or maybe get out of injury or pain, training more often may be a better idea and shorter burst and less often. I always think I always feel shorter bursts of exercise are better than a prolonged session. So if you got 2-hour session, I tend to find intensity and stuff drops off and you don't get the performance benefits you're looking for. So I would always try and keep sessions shorter.

Obviously it's different if you're doing team sports and you're working with the technical components of it, the tactical components of it, that's different. But in terms of an overall fitness structure, I always think smaller sessions work better than long sessions. I think it's always better if you're running gym for 20 minutes than if you're in the gym for an hour and a half, for example.

James de Lacey24:51

And with I guess with tendon pain as well, there's a lot of that. I don't know if that's something you've covered in your research or you have more knowledge on, but just regarding the pain, is that typically coming down to a structural problem within those collagen fibers, like around the alignment, or is it more to that where it's like multifactorial?

Dr. John Babraj25:21

It's probably more multifactorial. There could be an inflammatory response in there causing swelling around the tendon tissue and the extracellular matrix around about the tendon as well. Our pain receptors and nerve endings tends to be in the myofascial around the muscle, and that is around the myofascial. So it's not actually in the muscle barely, it's in the collagen network.

So it could be a stretching of a collagen network due to fluid retention, which is then causing a stretch on the nerve endings which gives a pain stimulus. So it may be an inflammatory response or fluid influx rather than necessarily to do with the tendon, the collagen fibrils themselves, but rather an artificial swelling of the tissue.

James de Lacey25:59

Do you know the I guess the mechanisms why there's a few research papers showing, for example, isometrics or isometric work, for example like holding a leg extension, produces an analgesic or numbing effect on the tendons? Is there a mechanism around why that may happen? So you're putting the tendon into a stretch and then it would be like a mid-range holding of leg extension or even like a split squat position, and you're just holding that for like 40 to 45 seconds or even longer, and there's like a numbing effect on the tendon.

Dr. John Babraj26:37

I'm not sure. I mean, obviously when you're going into an isometric, you're changing the blood flow around the area. So it might be reduced blood flow which takes away a little bit of swelling around the tendon, so feels better. Maybe it's just something as simple as that rather than a complicated biochemical mechanism going on. It makes more sense that it's a blood flow change which is changing the fluid pressure around the tendon.

James de Lacey27:16

Interesting. And you talked about as well, was your research, differences between men and women regarding a lot of this? Do you want to maybe just go into that a bit?

Dr. John Babraj27:54

Yeah, so with resistance training, men have a bigger switch on of protein synthesis in tendon than in females. So again, there's no sex difference in terms of muscle that I'm aware of in the switch on protein synthesis, but there is in tendon. So collagen synthesis isn't getting activated as much in females.

And what we're seeing as female sport becomes more and more professional and there's a lot more S&C in it, we're getting a higher rate of tendon ligament injuries in female athletes. A lot of the injuries. And this may be that for female athletes we need to alter how we train them, so that we keep that muscle tendon unit firing as a whole rather than increasing muscle mass at the detriment of tendon adaptation.

James de Lacey28:31

So how does that training look then?

Dr. John Babraj28:31

I would say it looks like sprint interval. It's something we're seeing in our data as well in female boxers, when we look at Wingate performance and stuff and mitochondrial, what we think is mitochondrial activation. Mitochondrial activation in females isn't as high as it is in the males. They're not extracting oxygen as well.

So perhaps we need to refocus on how we train females. What's the best way to get the performance benefits? It's not going to over-increase the muscle in terms of mass and cross-sectional area so that the force that's getting produced. And that looks like doing things that don't create hypertrophy. So things like sprint interval training, enhancing endurance capacity of female, potentially trying to utilize fat oxidation better in females.

Because the female body tends to want to burn fat a lot more than the male body. Male body wants to burn carbohydrates. So potentially we need to sit down and think differently about females to males because biologically they're not responding the same to the stimulus.

James de Lacey30:01

Wouldn't trying to improve fat oxidization of females mean more lower intensity?

Dr. John Babraj30:01

Not necessarily. You get oxidation with sprinting, with high intensity as well. Again, it's about what's going to give you the biggest change in fat oxidation for the smallest amount of time for me. And that then comes down to a sprint or interval based approach rather than a continuous low intensity based approach.

James de Lacey30:42

I actually want to go down that road too. I know Andre's probably listening to this as well. We'll bring him back on too, once, well, once I guess maybe the PhD's defended, when he's less stressed about everything as well. But we can go down some of this anyway because I'm still interested in a lot of the stuff.

So I guess my number one question around this idea of doing the short sprint intervals, we see a lot of these I guess good adaptations regarding mitochondrial function being improving. Essentially we can just call it for the audience I guess resistance to fatigue with the muscle and be able to recover well. But then is there something that you would sustain, say, all year round, you would just do sprint intervals, say maybe once to three times a week and that would be enough to give you everything you need?

Or do you still need to do some kind of low intensity work or maybe stuff that's more volume based at some point within the training?

Dr. John Babraj31:44

That really comes down to engagement of the athlete, I would say. What they enjoy. What's going to keep them involved in the training. Because you've got, with the athlete, you've always got to have buy-in. They've got to buy into what you're asking them to do.

And telling them that all they need, they just need to do is short sprint intervals all year round, is almost like 180 degree flipping everything on its head, and they may not buy into that. They may buy for small bursts, but when you try and sell it for a year round, it becomes a harder sell.

You don't, you can do it year round, you don't need to do the low intensity stuff. You can produce adaptations and then look to maintain. So you could do it once a week rather than three times a week if you're into heavy game or load period. Can reduce the number of times that you train using high intensity.

So it's just like any other training modality and it's playing around with it. Well, not playing, it's thinking about what you're trying to do across the full year with it. There might be times where you put in a high block of it and then pull it down to a maintenance phase and take it back up again. It really depends on what you're trying to achieve.

James de Lacey33:30

Andrew actually commented on the YouTube saying, "Technical training is where we get the more steady state component. Sprint interval sets outside there, and probably where we're getting the bit of physiological adaptation. A big question seems around what we are doing, what adaptation are we trying to achieve? That seems to be the missing question in S&C."

Dr. John Babraj33:30

Yeah, I think that's a good point. Where S&C has got very prescriptive or can be very prescriptive. Part of that is with the accreditation process. So we've got in the U.S. it's NSCA, here over here it's the UKSCA. They have certain things they want you to do. So in order to increase power, you got to do this, that, and the other.

And I think that creates a very prescriptive S&C coach. So we don't think about what we're trying to change. What we think about is I need to, or we think loosely about what we're trying to change and we don't really think physiologically, what is it in the body I'm trying to change? Am I trying to be model 10? Am I trying to increased muscle cross-sectional area? What am I trying to achieve with the training modality that I'm using?

And that to me is a failing of either education or thinking, or both.

James de Lacey35:08

I'm going to try to play Devil's Advocate to some of the things that I see online, read, all that kind of stuff, to throw these questions at you. One of them will be the idea is that you need to have a base of I guess general fitness or base level of aerobic work so you can take advantage of these higher intensity intervals.

And if you don't have that base, and this is typically come from a lot of endurance, I guess endurance coaches, because that's kind of their sport, but if you don't have this base and going straight into high intensity, you can blow yourself up pretty good. Is there anything you've seen around this or anything against that statement?

Dr. John Babraj35:38

I've never seen anybody blow up with high intensity. And that's, we've done 80-year-old men, we've done 60-year-old women. I've read those papers. University students who are active, who are not active.

I've never seen anybody blow up with high intensity. And we've done 80-year-old men, we've done 60-year-old women, I've read those papers, university students who are active, who are not active. We've done elite athletes and we've never had anybody blow up.

I think there's a fallacy around what our endurance base is. If you don't have endurance, what will happen is your sprints will be really bad to start with because your recovery will be really poor. And then that becomes into how do you program sprints. So if somebody's struggling to recover, then you change the recovery period. You keep it hard, but you give them a longer period.

We know as long as we stay within that 1 to 8 down to 1 to 1 work to rest ratio, we're going to get endurance adaptations. So if somebody's really struggling in that first session, you can change it and expand the recovery window and then look, as you get used to it, to start to bring it down. So again, there's no point in taking somebody who's just started and putting them on a 1 to 1 work to rest issue because they're not going to be able to do it mentally.

They're not going to be in the right place to do it, and they're not going to give the adaptation. They're not going to do it again and again and again.

So you've got to program for your athlete coming in, not for what you believe or as a structure, not as a one-size-fits-all. You've got to pick on individual athlete. And I mean, we're working with one of the local university karate teams and they are not elite athletes. They are the opposite of elite athletes. But we've worked it slowly with them and they're now getting down towards that 1 to 3, 1 to 2 work to rest.

But at the start they were nowhere near that. We couldn't push them like that. So it's taking the athlete that you're working with or the group that you're working with and constructing the session around them.

James de Lacey38:06

And when we're talking about the work interval on these, we're talking about super maximal hard sprints, correct?

Dr. John Babraj38:06

Yeah, but everybody's super maximal is different. So what I view as super maximal or what my body views as super maximal will not be the same as what your body views as super maximum. It's not the same as what an 80-year-old's body will view as super maximum. So everyone is different, everyone will push differently.

I might hit 12 on a load bike, I might hit 1,200 watts. But one of our fighters coming in might only hit 700 watts. But in terms of our perception of how hard we went, it's the same. And the adaptations we'll get is the same. It's just I've had more experience of using the bike, so I can produce more power, blah blah blah.

James de Lacey39:17

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And I guess another one of the arguments often against a lot of, you say, just high-intensity training or sprint training is the idea that adaptations come very quickly and a lot of the studies are very short-term, you know, 3 to maybe 8 weeks of sprint intervals. I mean, you're doing them for long with athletes, so you're obviously seeing adaptations change. A lot of the time, do you just go into a little bit of that and I guess how you're continuing to keep getting those adaptations?

Dr. John Babraj40:44

So we know a study by Takaki Yamagishi a few years ago now looked at VO2 max across a 9-week block of the same sprint. So the programming didn't change, just it was constantly 4 times 15-second sprints. What we see is we get an early plateau in VO2 max around about 3 weeks in. VO2 max is at a new plateau. It's gone up, but it's now just steady.

But that time to get to max is continuing to extend. So each 3 weeks that we tested it, it took an extra minute, minute and a half to get to max. And that was showing no sign of plateauing. So while the VO2 max component of it was plateaued, the muscular endurance was still improving over the 9 weeks.

But how you change it is we do a lot of stuff on heart rate, not because heart rate is a good metric of anything particularly, but because it's an easy metric to get. And we can look at the shape. So we're not looking at numbers, we're looking at shapes. How's that heart rate going up? How's that heart rate coming down? What's the shape of it? And we'll adjust the sprints based on the shape of the heart rate.

If it's not going up quickly enough, we might go into a shorter sprint. So we'll drop from a 20-second sprint into a 6-second sprint, for example, and really concentrate on that takeoff component of it. Likewise, if it delays long at the end, we will play around. So if the heart rate is not starting to drop until about 20 seconds into a recovery period, we'll play around with it to get that recovery, that drop in heart rate happening earlier. And that tends to keep the adaptations coming across.

So again, it's a very individualized response. We're very much treating people like individuals and not one-size sprint fits all. So we don't take everybody, put them on the same sprint protocol. We individualize the sprints for a week, for a block, to what we want to change physiologically, not what we think has to happen.

James de Lacey43:37

I think that was one of the issues with the original Tabata study where it was the same thing for, was it 6 or 8 weeks? And you see this plateau of aerobic and anaerobic measures, but nothing changed. It was just the same thing every single week.

Dr. John Babraj43:37

Yeah, so there was nothing really to continue spurring the adaptation other than trying to mentally push through. Say somebody deadlift 20 kilos and they struggle week 1, week 2, and then we start getting in that 20 kilos becomes easy. If you don't change that 20-kilogram stimulus, we're not going to continue to adapt. It's exactly the same with sprint.

There's a point where you plateau where using the same sprint protocol. Where muscular endurance plateaus, we don't know, and that will probably depend on the athlete you're working with. So if somebody has a high endurance component already, they may get initial boost and plateau quickly, where somebody with a lower endurance component, you can probably keep them on the same sprints for longer and still keep getting endurance benefits week by week by week.

So I think we need to move away from our one-size-fits-all mentality in sport and really start to look at the athletes as individuals and train them as individuals.

James de Lacey44:43

I want to go into that practical a bit in a second. But before that, I guess the other argument against going all in on HIT training or interval training is the idea that people talk about maybe targeting peripheral adaptations or central adaptations at the heart. And yes, we can't just isolate whatever it is and there'll be some crossover to that. But I guess low-intensity zone 2, zone 1 kind of training, as mentioned to fill the heart chamber, stretch that heart chamber the most, how you're going to get the best adaptations for pumping or delivering oxygen from the heart.

Is there something to that? Maybe HIT training doesn't give you as much of that as you'd want? You still need to do something like that or the sport training takes care of that? Or what's going on there?

Dr. John Babraj45:47

For me, the central adaptation is not crucial. People can get to max. I could take an 80-year-old man and get his heart rate to max. It's not an issue. The issue is how quickly it gets there. So essentially, heart rate is just a measure of how often it beats. The heart's pumping the blood out. What's happening at the heart doesn't reflect microcirculation.

So that being like the blood being pumped around the body or the oxygen being pumped around the body, around the peripheral tissues, where oxygen's getting extracted from to get used, is very different. We can see when you look at exercise, heart rate will go up 3-fold from resting values. Estimate for microcirculation is a 100-fold increase in blood flow. There's a disconnect between microcirculation and central circulation, and I don't think we really have a good handle on the microcirculatory component.

I mean, it's only 2 years ago paper came out showing a new structure for capillary, a new model of capillary feeding into muscle. It's much more entwined in the fibers rather than a drip-in feed. And it makes more sense for the new model of how capillaries work. But that's only 2 years ago that came out in an animal study. So we're still at the stage that we...

We don't really know. And if you look at the techniques we have for measuring microcirculation, it's at the finger, and what's happening at the finger may not reflect what's happening at the muscle. So we don't have a good handle on how does central blood flow relate to microcirculatory blood flow. And that's a big problem.

But what we know is when you look at oxygen extraction from blood, it's always much higher after sprint interval training than by steady state training. So where it's getting used, sprint interval training produces a better adaptation. It may not create as big a myocardial effect, but it's producing a bigger microcirculatory effect, whatever that microcirculatory effect is.

James de Lacey48:15

Does that mean then that these sprint intervals—because they are, I guess, so peripherally dominant in terms of adaptations—that the exercise you choose should ideally prioritize the muscle groups used in the sport? So for example, maybe a kayaker would do upper body sprint intervals mainly versus, I don't know, a sprint cyclist doing lower body stuff, because those adaptations there? Or is the whole body kind of adapting to that?

Dr. John Babraj48:53

There's an argument that there's a whole body adaptation when you do sprints. How big that whole body adaptation is is debatable. What you need to think of is what's kinetic chain for force generation, what are the muscles involved. So once we think kinetic chain all upper body, there's a high isometric component to the lower body. So perhaps increasing lower body force production and isometric strength will lead to improved dynamics of the upper body.

So it's probably not as simple as what's the movement that's being done, but rather what's needing to be targeted. So somebody might—a kayaker probably from doing kayaking naturally has a higher upper body endurance, but they may not be targeting their legs effectively, and it's actually their legs that failure's happening. So what we need to do is focus on that component and not necessarily the upper body component.

James de Lacey49:35

Actually coming back to the male versus female as well, you mentioned obviously about females maybe focusing more on the endurance or sprint interval side versus maybe lifting weights and increasing muscle strength and potential and balancing with the tendons. So I guess from your point of view you would be doing far less or very little weight training, say, for most female athletes and focusing more on these sprint intervals? Or where does that balance fit for you?

Dr. John Babraj50:11

As you probably know, I'm not the biggest fan of resistance training. I think that's probably down to how it's been programmed rather than necessarily what it's trying to change. But yeah, for female athletes I would be doing very little resistance-based work with them, other than cycle-based sprinting. If they want to do some resistance work, that's fine, but I would keep it simple and very infrequently—so one session a week, something like that.

James de Lacey50:43

You mentioned how it's programmed as an issue. So, I mean, a traditional strength training program might be like three by six to five—just say three by six to five squat, three by six to five bench, whatever. How does that differ to how you see it should be programmed, maybe for—and I'm assuming this is for the female athlete?

Dr. John Babraj51:20

Correct. I mean, I think lifting heavy creates slow movement. So if lifting has to be done, then it should be done fast, with speed of movement as the core—good technique and speed of movement. So I would reduce the resistance and concentrate on speed. I think speed is a metric that's needed, not how much resistance you're lifting, but how fast are you moving that bar.

Because if you're moving fast, the muscles have to contract fast. If you're moving slow, you can recruit fibers and then recruit fibers and recruit fibers. So you're getting a different response to what you're going to be using in sport. Sport, you need to recruit fast and go. You don't need that time buildup of contraction.

James de Lacey51:59

Be like jumps, throws, throws, plyometrics, and things like that will kind of fit into your criteria there, potentially?

Dr. John Babraj51:59

I'm not a great fan of plyometrics. I think plyometrics is a good way to get injured, because people can't do the movements that are being asked to do.

James de Lacey52:36

Which ones in particular do you think?

Dr. John Babraj52:36

Things like when you're landing one-legged, you see people over-rotating on their ankle. That's a good way to damage tendon, ligament around the ankle. If you can land it and it's stable, yeah, by all means use it. But I think it's poor technique. Plyometrics has a heavy technique load. So with an athlete I think you need to take it back to basics and get the technique there before you start prescribing plyometrics.

James de Lacey53:10

Andrew actually says on the chat here about, "You guys see the upper body Wingate? Lower body has big oxygen utilization."

Dr. John Babraj53:10

Yeah, so there you go. We see huge recruitment of oxygen use in the lower position whilst doing upper body. Whether that's a stabilization or what, or whether it's using the lower body to try and create power on the upper body, I think it's probably you're trying to use the lower body to create upper body power.

James de Lacey53:46

Perfect. I want to finish with one last question with you, John, and I want to try and bring this as practical as possible around someone. So, I mean, I even bought a $100 spin bike on Facebook Marketplace because of all the stuff you guys are doing, so I can punish myself in the garage at some point.

But for someone who doesn't have access to someone who can read heart rate files with your fancy algorithms and everything else, how can someone go about building their own sprint training program and make changes to that program without having that kind of data—even if maybe they have a heart rate monitor, but they're not going to have that knowledge of slope, et cetera?

Dr. John Babraj54:12

Yeah, so if you don't have access to a bike, one of the easiest ways to do it is—we've done stuff on uphill sprints, which just increases the intensity of a straight line sprint. Again, you can break it into short and long: 20 meter, 30 meter, 40 meter. You can do lots of things.

A master's student this year at university looked at using the 5-10-5, the pro agility, as a training stimulus rather than a test. And what she found was that the shape of oxygen using the recovery was exactly the same as the bike when we did 15 seconds of pro agility and 15 seconds work.

So that accelerate-decelerate in the pro agility is what's driving the intensity. This ability to create force, remove force, create force, remove force.

James de Lacey55:13

More mechanical loading, right? Because you're changing direction often.

Dr. John Babraj55:13

Yeah. So again, you can replicate bike sprints by introducing change of direction.

James de Lacey55:13

Like a 10 meter—almost like, for someone at home, like a 10 meter shuttle back and forth for 15 seconds? And then your metric that you use is how many shuttles do they do in that 15 seconds, and then you look to beat that the next time?

And in terms of work to rest, when is someone looking to change rest times or even maybe change work, working periods?

Dr. John Babraj55:54

So if you do an interval session and by the time you start your next session you feel that you're completely recovered—so your breathing is normal, you think, "Yeah, I'm good to go, I'm just sitting here killing time"—that's the time you know yourself you need to change it. So it should be when you're going again, you shouldn't quite be ready to go. You should be thinking, "I could do with an extra 10 seconds recovery here." That's where you need to go.

So you've got to keep being uncomfortable in it. As soon as it's comfortable, that's when you might start to see power improvement, if that's what you're seeking, but you're not going to get the endurance benefits of it.

James de Lacey57:03

In terms of, I guess, being prescriptive here for people that they can apply, this would be looking at somewhere between like 6 to 30 second long work intervals—and this is regardless of 10 meter shuttles or spin bike or something like that. So 6 to 30 seconds of work, and you're looking at a 1 to 8 work to rest ratio within that. And then how many sets are you looking to do or something like this?

Dr. John Babraj57:33

So if I was doing 30 seconds, I would probably be doing two to four, depending on how cruel I was feeling. I did four when I did something for Andrew for his heart rate thing. I did it upstairs in the cardio room. I couldn't walk downstairs after the damn spin bike. So yeah, that's brutal.

Truthfully, a minute's work is all you need. And the reason why it's one minute is because—well, the reason why I think one minute is actually the crucial number—is that's the point where you've got maximum depletion of glycogen. All the glycogen that you're going to use has been used up. You're aerobic in your sprints by this time. So there's nothing happening. So more doesn't necessarily lead to better adaptation after you get past a minute's work. So it's roundabout a minute's work, roundabout it.

James de Lacey58:07

You could even give a range. I think some of your interval prescriptions could even be like one to two minutes of total work, potentially?

Dr. John Babraj58:44

Yeah, we've gone up to sort of three minutes of total work. But generally, when I'm starting somebody, I'll always be working in that one minute window, however I break it down—whether it's 6 seconds, 7 seconds, 10 seconds, 12 seconds. It's going to come out roundabout one minute of work.

James de Lacey58:44

Perfect, perfect. Now this was a great—

Great chat, John. Can people find you and follow you at all? Are you on social or anything?

Dr. John Babraj59:15

I am on social, but I don't post anything. I've reached that age where social media and me just like... Yeah. Best way to contact me is through my email address. I'll answer questions if people have questions. Email me is the best way to get me. I am on social media, on TikTok.

James de Lacey59:15

You're on TikTok?

Dr. John Babraj59:55

Not on TikTok doing dances. So yeah, contact me at University. I very rarely post on social media.

James de Lacey59:55

All right, perfect. I'll have that email address in the description anyway for anyone who needs it. But thanks for coming on, John. I appreciate it.

Dr. John Babraj59:55

Thanks, James. Thanks for having me. It's been good.