The Future Of Combat Sports Training (Eccentrics, Flywheels & Wearables) w/ John Cronin (SSOF Ep 35)

John Cronin1:54

Mom had trouble getting us in at night, that sort of thing, breaking things all over the place. Mom's favorite was don't play with the ball inside the house type of thing.

But, you know, records, bats, balls, we had it all and we just played sports. I knew I wanted a life in sport. So at that time I decided to become a PE teacher back in Otago and did five years primary teaching, and then I went into secondary school teaching with PE and maths.

And thereafter, I decided that I wanted to give the top a little bit of a tickle and I headed over to Canada to do my postgrad study. I wanted to become the All Blacks' next All Black coach, but because my coaching was going quite well in my secondary school and I was really enjoying the coaching. But then I went across to UVic and to the National Coaching Institute there, and a little old lady by the name of Marian Alexander, and I think if she's still alive, but it's just one of those come to Jesus moments where she was teaching sports biomechanics.

And I hated sports biomechanics at Otago, and I actually got invited back to redo the course. So I think I even with the repeat I got a C minus. But this little old lady, she just, we just looked at videos all day and she would go, oh, why is that happening? Can you give us some sort of physics behind that? And I aced that course. I think I an A-plus. But she changed my life.

And I actually just from that little moment of that course got into the sports science side of things. And so my passions are in and around strength and conditioning and sports biomechanics. And so that's where I have gone. I've taught across all three age groups, primary, secondary, and tertiary, and by far the hardest was the primary and it got easier with secondary, and tertiary is much easier.

Most of my role now is supervising postgrad students, mainly PhDs and Masters. So I've got a really cool job. I actually love it. I still love it every day. I'm getting long in the tooth, but I actually, getting to deal with some very intelligent people, asking and answering some really great questions, creating new knowledge. And so yeah, I feel very blessed, that's for sure. So I think that's a quick five minute of it.

James de Lacey5:28

No, that was a great introduction there to start. But I know you've got a wealth of knowledge, I mean supervising a lot of these students with the different projects they have and your name on a lot of papers. But I want to jump down a few different topics for this podcast in relation, I guess, making them practical as well for the everyday fighter or everyday person. And one of them would be eccentric training.

And I guess, I guess you'd say eccentric training's kind of come back almost in vogue within the strength conditioning community. It's kind of like that almost that new thing again, along with isometrics. But do you want to maybe dive into maybe, let's just start with, you know, what eccentric training is and what you're trying to get out of it when you're doing it?

John Cronin5:54

I guess, you know, it depends what you, I always look at eccentrics, it's a funny term. And I always look at my perception of eccentric has been in around about three or four areas or three or four folds. So if you have it in your head that we've got a force velocity curve, and we know we have the eccentric portion of it, then we have the isometric, and super, zero velocity part of it, then we have the concentric part of it.

And some people will say, you know, true eccentric is that supramaximal part of it, with past isometric MVIC, past your concentric one RM, it's that supramaximal part, which is, you know, that's legitimate. And so there's a whole set of loading and training parameters for that part of the curve.

But also, you know, you also got to acknowledge, even when we've got the concentric force velocity curve, we still have eccentric contractions in them, but they're submaximal, okay? So again, I always think when I'm actually thinking about conditioning or teaching these type of things, well, there's high velocity, there's submaximal eccentrics, but there's high velocity, you know, low force eccentric, which are down that bottom end of that concentric force velocity curve. And then there's also that high force, low velocity eccentrics. They're very different.

And so that high velocity, I mean that high force, low velocity on the concentric curve is very much that hypertrophic type of response that we're looking for. Whereas if we go down to the other end of that curve where it's high velocity, low force eccentric, it's still, concentric is in there, but we've got that eccentric phase which is still submaximal, it's always dependent on that concentric strength. Then we've got that high velocity portion, which we know is that stretch-shortening cycle performance, where that eccentric type of training is really important. So that's two areas that I think, the submaximal eccentric.

Then that supramaximal eccentric, when we go past MVIC and concentric one RM, where we're putting 10%, 20%, 30% extra loads on, and that type of training is, you know, that type of eccentric training is just great for strength, it's great for hypertrophy, it's great for injury prevention, long as it's done in a safe and progressive.

Then the fourth type of eccentric that I always think about is that eccentric where we're trying to shift the optimum length of muscle, where we actually, you know, we're saying we want the muscles stronger at longer lengths. So that's where we actually, where the force-length relationship or the length-tension relationship becomes really important. And so that's that, where we're doing the eccentric training or putting stress into the muscle at long muscle lengths.

And so that's another form of eccentric training which we do for injury prevention, you know, the hamstring nordics, that sort of stuff that we really think about also. So I don't know, a roundabout answer to you, James, I just don't know if you want to dig.

James de Lacey9:46

That's good. Yeah, I think we'll go down maybe the stretch-shortening cycle part of this, because I think in terms of what people are maybe implementing, jumps, plyometrics, medicine ball throws and things like that, that are very common, I guess, within combat sports as well. So, but I think it's often a lot of that stuff's misapplied within training. It can be done in circuit conditioning formats under a lot of, or under a lot of fatigue, even though the goal might be to

Become more powerful or improve that stretch shortening cycle. Do you want to maybe dive into how the stretch shortening cycle works, what you're trying to do when you improve it and the outcomes from improving it, and then how you can go about doing that? A lot of questions in one, but we'll get down there.

John Cronin10:15

Absolutely. If I, you might have to come back, my memory is not okay. So a stretch shorten cycle or the eccentrics prior to a concentric contraction, as I guess much of the listeners understand, it actually potentiates and augments that concentric contraction. So that's, and it's the most common type of movement that we have in human movement.

So what we're trying to do therefore is actually with this type of eccentric training is to actually potentiate the concentric contraction by optimizing the eccentric portion of it. So how do we optimize the eccentric portion of it? Well there are, there's a number of researchers out there that will say that preactivation is a really important part of this enhancement. So just before ground contact or just for impact on something, and it could be a punch too, is that you actually preactivate the muscles.

Then the next most important part of it, and some people will say range of motion is really important because that determines the amount of elastic energy is stored. But I think, yeah it's a good point, but then the most important thing I think is this velocity of the eccentric contraction. So we've got to actually really work on that eccentric velocity and I think it's the most important part for a number of reasons.

One, I think you'll find that most the tissues, the contractile tissues, not necessarily the actin myosin filaments but also the cross bridges actually store elastic energy. But we also know Z-disc and Z alpha and also the titin filament that's within it, they store elastic energy. Then we've got all these connective tissues, the myofascial tissues, they all collect, store elastic energy. And I think that the higher the velocity in that eccentric phase, the more energy is stored in all these tissues, plus we've got this reflex thing happening, the stretch reflex which will add to it.

So a really high velocity contractions will actually store a lot of energy without a lot of energy loss and also will enhance the neuromuscular aspects of it via the stretch reflex. So out of those bits and pieces there, range of motion or velocity, I think the velocity of the eccentric phase is really important.

So going back to your sort of point before, if we're in a state of fatigue and we can't get that high velocity into the eccentric contraction, we're most probably dampening down the actual potentiating effects. Then the next part of it is that what we call the coupling phase, that transition between the eccentric and the concentric. And again, if we don't have a very quick coupling phase, again if that transition is not very quick, we're going to lose a little bit of that elastic potentiation or that stretch reflex enhancement. So those are some of the things that a lot of people really do concentrate on.

And then the practical parts of it, I can remember, and there's a lot to do with the mental side of it, that's called the mind muscle connect and having your athletes in the right state of mind to actually optimize that eccentric phase or just the quickness of everything to be to the point, I think is really important.

I can remember at times when, James, you develop an ear and that ear you can hear it on the ground, could be that foot contact, and you actually develop those and you can hear it. And sometimes said to my athletes, hey, just let's stop, let's go have a cup of tea because you're not, this is not happening. Or you've got to get your mind in the game here. I want to hear this, not slap slap slap. So those quick ground contact times are key to what we're talking about or again that velocity.

And the punch, but I guess you can actually tell me, there's not much what I understand in my reading is there's not much SSC in the punch, it's more of a concentric only. Or is it just a little shuffle in the punch?

James de Lacey15:07

Sure, I think it depends as well. If you're throwing combinations as well, I think Seth mentioned in his interview, obviously when you're pulling the punch back and throwing combinations you have some of the SSC component there as well. So but even within wrestling, grappling, if you're shooting double leg takedowns, you still got to drop your levels and that's going to be your eccentric before you shoot forward anyway.

So there's all sorts of it all around. And I mean depending on the sport as well, if you're an amateur boxer you're bouncing around the ring versus a professional boxer where you're not bouncing as much. So there's all sorts of different things going on there. But obviously with the Muay Thai boxing, it's a little more extensive in terms of the stretch shortening cycle in terms of what's being used.

John Cronin15:59

Yeah, yeah, true, true. But I want you, go kid. So that was more or less the little bit of the physiology of it. Where did you want to go to?

James de Lacey15:59

Yeah, I want to go to some examples. So you obviously mentioned you want to focus on the eccentric velocity, but I'm assuming you're not going to the fastest eccentric velocities from day one. So how are you getting to there and what, I guess how are you increasing the velocity through various exercises?

John Cronin16:26

One of the best ways is to keep an eye on this is obviously via force plates. And so we've got the freefall phase and then the eccentric braking phase on a force plate. So we can keep an eye on things straight away with that. So having some sort of feedback on this is good science. And so as a practitioner then start playing around with a whole lot of stuff.

Now obviously the first and easiest part of this is to actually verbal queuing. If we're doing that on a force plate they can see the signal, or we can actually cue them to actually drop faster or whatever and they get that feedback on a force plate. Or we keep our mouth shut, and then they actually see, get that live biofeedback on a signal and they can actually play with movement strategies that reinforce that quickness.

So having some of those tools available to us to actually give that explicit learning, give them the verbal cues or tactile cues, we grab them and put them in a position or teach them how to come back quicker or whatever and then see the outcome of that in terms of a number, I think is very powerful learning. But to actually them to work it out themselves is much more powerful, that's that implicit learning model.

Then you would just use different pieces of equipment from then on. And it doesn't have to be much, you can get them to jump off a 20 cm box versus a 30 cm box, or you can get them to jump vertically and horizontally onto a force platform, again giving them a feedback of what their absorption is or their breaking rate of force development. Or there's a ton of variables that we can actually report back on.

So we start using just gravity as the medium to improve it. So that can, you don't even have to drop off a box, you can just jump, that's what we call a reactive jump, and then they then actually monitor what's happening in terms of that and in terms of the feedback from various pieces of equipment.

Then there's other pieces of equipment. We can actually start putting wearable resistance on, wearable resistance with height. Then we can use machinery like the flywheel technology. And if you, I know you've played around with the flywheel technology, James, that motorized technology, that 10 to 20% boost that switch from concentric to eccentric is very quick. And so I think some of that flywheel technology is really good for that initial high velocity transition from concentric to eccentric.

Which I think there's no research on that at the moment and we most probably would be very interested in doing research in that area just to see what the outcomes would be from a dedicated intervention using that 10% boost technology.

James de Lacey19:28

Yeah, yeah, for sure. You actually touch on the two other topics I wanted to dive into on this podcast too. So let's go down them, but I want to start with the wearable resistance because I think both these things, the entry boost and the flywheel and the wearable resistance, is almost part of the future of strength conditioning. And especially wearable resistance with being able to integrate strength conditioning with skills training.

And obviously people like to talk about or share specific, I should say specific in quotation mark, strength exercises all over Instagram and whatever else of people doing whack that just doesn't make any sense. With wearable resistance you can, you

John Cronin20:31

For sure. Again, this is a bit of a passion area that we've been researching for around about eight years, and we've actually developed the science behind the wearable resistance. Wearable resistance is simply micro loads attached to the body in some manner, and it's been around for years.

I can remember, I think the first research came out with Bosco in 1986, so there was a lot of research in the early '80s and '90s, but then it died. And I think it died because the technology, the weighted vest and the weights in the shoes and the shoes, were just clumsy. The athletes knew that the wearable resistance on—I can remember designing my own vest there in the around about the 2000 and doing a study with Kai Hansen with comparing vests with resistance, sled towing.

And my vests, they were dangerous because they had fishing weights in them and up and down, and they just about knocked people out. So I can see why it stopped.

But then, around about 2010, 2011, a company called Leela came out with this very slick compression garments where they actually attached these micro loads—50, 100, 200 grams—to these compression garments. Now the compression garments had vests, arm sleeves and shorts and calf sleeves, and so that was a little bit of a game changer, to be sure, because you could actually train with these loads on and it became part of your training, not separate to your training. Okay, so that's a little bit of the history with it.

Now what you can do with it is amazing. It is a great piece of technology, and most people go, "100, 200 grams? That's not strength training." And I've got a great slide, and it shows the kinetic—there's a word, work-energy theorem, which says the amount of mechanical work equals the amount of energy that is associated with an exercise. Then that's the kinetic energy and the potential energy, et cetera, or the amount of energy associated with an exercise establishes the mechanical work, which establishes the muscular work, which establishes the metabolic work. So it's just a principle of physics.

And I go through, and I show people, "Well, here's a guy shifting a—lifting a 100 kg squat at 0.58 meters per second. That's what, 80% 1RM, I say." And I work out the kinetic energy associated with it. Then I put 500 grams on each thigh and get somebody to run very quickly with it. And again, that's 500—if we're looking at kinetic energy, it's half mv squared, half the mass. So it's 500 grams on, but you can actually move your thigh very quickly at around about 2,000 degrees per second in the elite sprinters, which is around about 6.1 meters per second linearly.

And so you square that, and suddenly when you have a look at the kinetic energies associated with both exercises—100 kg squat and moving 500 grams on each thigh very quickly—have similar kinetic energies and therefore muscular or mechanical work.

So the secret to the secret sauce here is moving lightweight—light loads—very quickly, and suddenly they become a very high velocity resistance training tool. And currently there's just loads of the top sprinters in the world are using this as a sprint training tool. And to a certain extent, we've been playing around with the UFC—we haven't been playing around, we've been doing some work with the UFC in this area in Shanghai. But it's on hold at the moment because they've had turnover, but Aaron might have talked about it a little bit.

And so we do see a lot of merit. It's hugely proven in the lower body. We can target train various things that—if you want to, we get into more detail about.

James de Lacey25:10

Yeah, so like—okay, so the beautiful thing about the wearable resistance is that we can vest load.

John Cronin25:10

Now, if you can imagine if you're wearing a vest and bouncing around the ring or running down a track, the vest load is a vertical overload. It tends to want to push you down because it's fixed to the core. Now, if you are bouncing around the ring or down the track running down the track, your center of mass height or displacement would be X with unloaded, okay? And that center of mass displacement determines your air time, which determines your stride length.

Now, if you put a vest on, what it's going to do is it's going to push your center of mass displacement down, so your air time is less or your bouncing time in the gym is less. It's going to provide more of an overload, a vertical overload, into your musculature. And as a result, if you're sprinting, your stride length will be less because you got less center of mass displacement.

But as your muscles get stronger, you actually return to your baseline center of mass displacement or the same air time. And if you actually take the weights off after a six-week training intervention, suddenly you actually can have more center of mass displacement if you so wish, and therefore you have more stride length.

Now, that's just intuitively makes sense. Where the wearable resistance is just so unique and it's such a great training tool is we can attach it to the thigh and the calf. And if you remember, if we attach it to those parts of the limbs, we've got a very different overload. It's not a vertical overload, it's a rotational overload. So linear movement is—we move in a linear fashion, but it's the product of angular motion at our joints. So suddenly we have a form of resistance that can actually overload angular or rotational motion.

So if we're looking at trying to change step frequency—remember, stride length and stride frequency are the two components that make people fast—if we want to overload step frequency, well, we just put wearable resistance on the lower limbs, and guess what? It does, it slows your lower limbs down because the limbs have become heavier. But as you become stronger, your limbs return to their baseline velocity.

And again, if we actually wanted to strip those off after a six-week intervention, hello, because they are much stronger, they can actually cycle through the airborne and stance phase much quicker, so your stride frequency is quicker. And so those are some of the things.

And one of the other unique things is—and it's one of those sort of things that I tell my students, what I tell you today can be very different tomorrow because I'm a lifelong learner. I'm learning things all the time. You guys are creating new knowledge and you're shaping me in different ways. And I used to think the most important thing was what you did on the ground.

Your air up in the air, does your leg up in the air does nothing. And so that one-tenth of a second that your foot is on the ground, you need to apply a hell of a lot of force and the right orientation, be fast.

However, Ken Clark came out with a paper in 2020, and what we do in the air is very important. And he named the paper "Whip from the Hip," and it makes a lot of sense. And that your thigh angular velocity correlates very highly to your linear speed. And that is again, how fast you can bring your leg through in the airborne phase and out the back door will determine speed.

So there's not many better resistance training tools to actually train that airborne phase. And so again, it's brilliant in that. And as you say, also, it's not that disruptive. It does not disrupt that technique. People think, "Well, I'm putting weight on my limbs, it's going to cause injury." We hardly see that at all. In fact, I don't know of a case that has received that—maybe one or two.

But so in terms of being safe, of course, because the resistances that you are putting on are not that great. And if you use the principles of overload and Progressive overload, frequency, and all those things that S&Cs know, you will be able to use wearable resistance in a very safe and effective manner.

James de Lacey30:14

I wanted to dive into the stuff with the UFC as well, because a lot of this is making me think, "Hey, applying it to your legs to improve kicking power." Obviously mentioned, I don't think you've done it too much with punching, but at least with kicking power, depending on where you put it, you're going to increase the angular resistance of the kick.

Obviously, if you have it on your thigh, it's not going to be as—you're not going to have as much resistance as if you have it down on your calf. So maybe dive into how you would apply that to kicking, to improve kicking power—how much weight, where you would put it, that kind of stuff.

John Cronin31:06

Yeah, it's a great question. And if you had a really good assessment system and you would say, "Okay, where's the weak link in the system? Is it around the muscles around the knee? Is it muscles around the hip? Or is it just a whole lower leg system?" Because if you had that granularity, you could actually—

Overload the leg very specifically. For example, if you found that the musculature around the hip was the weak link, well all you have to do is put the shorts on and load above the knee. So you could load heavily above the knee or behind the knee in the shorts. However, if you actually think that it's more of the whip at the end of the kick, and so therefore you would use the calf sleeves.

So as I say, you could get very granular in terms of is it above the knee or below the knee where I need the loading. And if you had that granularity you might go, okay, I can load here or there. However, most people would say okay, let's just be safe, we don't have that granularity, let's just load the whole leg.

Or if you were going to load one part, you most probably, if you did a lot of Muay Thai kicking, I don't know what it's called James, but how you lean and you just launch into them with your knee, well then obviously you'll be loading the thigh with your wearable resistance. But if you're actually doing some full kicks then you would load the whole leg. Okay, but if you had one area, if you only had a little bit of money and a little bit of kit, you would buy the calf sleeve.

Because as you just pointed out, putting a light load far away from the axis of rotation generates a lot of rotational inertia, which means it's very hard to get that limb going. It's very resistant to a change in motion with a load way out there at the end of the calf.

And so therefore the muscles at the hip and the knee have to work very hard with that loading at the calf. Be aware also that because it's so far out there, you most probably have got heightened likelihood, especially if you put substantial weight on, of causing a strain, a muscle strain.

So one of the things that we do is you can actually put a lightweight load on, and you most probably would make it a neutral load. You put a load on the anterior and posterior of the leg. And one of the ways of overloading is there's four ways of overloading with wearable resistance. One is just the magnitude of the load.

So we can make the limb heavier. So we can make the thigh heavier. And as they, we can actually get them to check in the next day: how did that feel, how did that session, we did 100 kicks or whatever? Yeah, I pulled up pretty good, coach. Okay, what we're going to do, we can put more load on.

All right, the second way that we can actually overload the musculature of the leg is actually start slipping that load down. Okay, so if we actually displace that load further away from the hip joint 10 cm, it will have a large effect on the rotational inertia because rotational inertia is mass times R squared. It has a larger effect than mass because it gets squared.

So that distance, that 10 cm, gets squared to 100. So if you think about that, so that's one of the ways that we actually start overloading. So you would just start bringing things down slowly. That's the principle of progressive overload with wearable resistance.

The third way that you most probably can think about it, that you would actually just monitor the velocity of the sessions. Just say, okay, we're going to do 30% maximal intensity kick, and we could build up the velocity of the movement. Okay. And then the fourth way we think about overloading the muscles or the leg is again, how we place it. The beautiful thing about the wearable resistance is that we can actually place the wearable resistance on the anterior or posterior. We can place it medial or lateral, or we can actually place it proximal or distal.

Yeah, so how we, where we place it, that orientation will have subtle effects on the kicking movement or the punching movement, whether we want a little bit of rotation in the limb or we want to actually correct rotation. That's the other beautiful thing about the wearable resistance. Lots of people use it as a coaching tool to correct faulty movement patterns.

James de Lacey36:26

Yeah, I think another interesting application is one you've, a case study I think you mentioned it must have been a while ago now, about there was a runner who was training for a race who, as he lost body weight, would add body weight with the wearable resistance as he continued training. And I'm thinking now, if someone who's doing Jiu-Jitsu, submission grappling, if you were maybe losing 5 kilos for an event and you were training and you just added that weight back on through the compression weight vest and continued to train with it and then took it off at training, that's another training effect right there as well.

John Cronin36:57

Brilliant. Yeah, that's just such a, you know, I've only thought about there that was a triathlete that just whooped his personal best by 12 minutes or something like that. That was an Ironman triathlete. And the last three months out he starts training and then keeps that same weight. He lost about seven or eight kilos over the three months, but he kept that vest weight on that you were talking about. And then one or two weeks out took it all off.

But then I'm thinking, yeah, what a great application for Combat Sports that have weight restrictions. Not only that enhanced metabolic cost of having it on, but also keeping the strength and the power there, also a strength and power overload. Yeah, great application of it.

James de Lacey37:58

Yeah. If someone wants to see the wearable resistance in action or learn more about it, where can they actually go to see it being used and things like that?

John Cronin37:58

If they go to the Leela Movement Technology website, they've got a lot of examples and videos and research on that website.

James de Lacey37:58

Okay, sweet. I'll link that up in the description too for anyone listening. But I wanted to take this towards the flywheels as well. We're talking about rotational inertia and I guess the high force side of eccentric training, and obviously flywheels can cover a huge spectrum. But in terms of flywheels, where does that fit within, I guess, someone's preparation for sport? And I guess how, I mean it's a very general question, but how is it used and what does it really do over just a traditional barbell squat? Why should I go on a flywheel instead of just going under the bar?

John Cronin38:25

Yeah, I think the first thing is for most people you got to get out there and feel it. Okay, and if you get an opportunity just get on a flywheel device and feel it yourself. And anybody that's got some movement history in the gym will suddenly understand what flywheel can give you.

And I always start off with, if I ask somebody to step on it and wheel it out, what do you notice mostly? And one of the things that they noticed I think is that it's pretty safe for a start. You can get in there and you can do an exercise, not the eccentric boost technology, okay, just the non-motorized technology. You can get on there and you can do one or two reps or four or five reps of an exercise, and you get in the groove pretty quickly.

And then after that you can start actually generating some high torques, high velocities with flywheel training pretty early in the piece, which you wouldn't get with traditional resistance training. So in terms of that, that is the first, you'll see people just get on and they're very tentative, the first couple of reps. What you put into the concentric phase, you get in the eccentric phase.

They start off very tentatively, but then they within four or five reps, they start amping it up. And then towards the end of it they're putting in some pretty solid contractions which are some concentric and eccentric forces or torques coming out of it.

So that's one of the big things that I think that you can get in there and train quite intensively very quickly. It's got a whole heap of other advantages in that it's a gravitationally independent type of training. What does that mean? Well, it was used in space basically because having a dumbbell or a barbell in space doesn't provide any overload. So the flywheel resistance provides that overload independent of the gravity.

So as a result, the technology does not need a lot of plates. You don't need hundreds or 200 kilos of dumbbells or plates or anything like that. You need maybe three, four plates that are very light that are easy to put on, that your granny could put on. It's a great form of resistance training. So in terms of that, you've got a lot of advantages in that flywheel can actually perform a lot of exercises with very little plates needed.

But one of the things that you'll notice straight away with the flywheels is that there's no gravitational dead spots. If you can actually imagine you were doing a front lateral raise, and down here with a...

Dumbbell, you're hardly getting any work. At 45 degrees gravity is starting to have effect. At 90 degrees, gravity is really starting to work hard on you. But then up here again there's hardly any work. Now if you were doing the same, we've got those gravitational dead—what I call gravitational dead spots—with free weight or constant resistance or traditional resistance training.

With flywheel training you don't get those gravitational dead spots. That's because it is gravitationally independent. So right from the get-go you can get overload, which is quite cool because down here, getting an overload at a long muscle length is pretty good for some sports. Whereas with traditional training you're going to have to play around with it. You know, lie down or try a cable or something like that. But you're getting a workout through the full range of motion, which is a little bit different to the traditional side of things.

There's a couple of things there. There's lots of other things. Flywheels is known for its eccentric overload, which we can talk about. But I think one of the stars of the piece is the concentric overload. I think there is stacks of research on flywheel resistance training. It's well researched for improving strength, power, speed, change of direction, hypertrophy.

One of the areas that I think it's really awesome—and you can think about this for your combat athletes that are returning to play or returning to sport—the rack mounts I think would be one of the best devices for punching power. And I'll talk about that a little bit later. But returning to play or returning to sport after injury, the flywheel technology is brilliant in that it's user-defined. And what I mean by that is that the user defines how much force or power or torque or whatever you want that you put into it.

So when you're injured your velocity and your range of motion could be small. And so the concentric phase doesn't generate a lot of angular force or angular momentum, and the eccentric phase corresponds to that. As you get stronger the concentric phase becomes longer range of motion, faster, and so therefore stores more energy. And as a result the eccentric phase is stronger and so on and so forth until you come back to full power where you're really driving very fast through a full range of motion and the eccentric phase as a result is a substantial overload.

So what the actual flywheel does very intuitively is matches your physiological status or your recovery status from injury. And so it's one of the most safest forms of training to actually bring athletes back, I think. And we don't see much research on that. Too often we could overload or underload somebody, whereas this one you say, "Okay athlete, just use it as such."

But the real star of the show though I think is the concentric only part of it. And a lot of critics criticize flywheel resistance training because you can't get ballistic with it. You can't get off the ground, so therefore it's not like plyometric activity, which I don't think is the problem that it's made out to be. Because if you actually—I got that flywheel behind me and I love it—but if you actually try the old concentric punch on the flywheel, okay?

If you were doing that with a traditional bench press on the ground or a barbell, what usually happens is that we've got to overcome the inertia of the dumbbell or the barbell. So we accelerate for a portion of time and then we spend the rest of the time decelerating. Now the advantage of plyometric or ballistic activity is that we actually get rid of the load, and so we can actually accelerate all the way through.

So that gives us superior forces and powers. And so the advantage of that ballistic profile, as I say, you accelerate all the way through, but you got to get rid of that whatever that implement or that medicine ball or whatever it is.

Come back to that flywheel in the background. You start back here and the beautiful thing about the flywheel is because it's got less inertia in it, less mass in it, you actually get it going quicker and you can accelerate all the way through. In essence it's like a ballistic contraction even though you don't get rid of the load. Because of the ability to accelerate it all the way through, you've generated more force and therefore more power, because force equals mass times acceleration. So if you're accelerating for a greater proportion of that movement, you're going to generate higher forces.

So in terms of punching power and that type of thing, I think it would be a great tool. And again, I don't know if we've actually seen much research in that area, but I'd hypothesize that it would actually have some great outcomes.

James de Lacey47:53

That's really interesting stuff. I remember you posting that graph of that force-time curve basically of flywheel versus traditional training. So I thought that was an interesting application of it being almost like a ballistic movement with high eccentric forces depending on how you use the flywheel. And yeah, it's so versatile, you can do almost anything and everything on it.

John Cronin48:24

And as you know, James, people—if you want to train your legs but your back is bugged or you got some sort of condition—well, you just put your waist harness on and you can actually get a massive leg workout. You can isolate muscles really easily. Like you say, there's a lot going for it. I think we've only just starting to unpack some of it, and that eccentric boost technology is a real game changer.

James de Lacey48:52

For sure. If anyone's interested, xfly, the ones who make the eccentric boost technology—essentially because the flywheel, you get back eccentrically what you produce concentrically. So if you do a maximal concentric squat and then you add the 10 or 20% boost, you get 10 or 20% more back on the eccentric, and it pulls you down hard.

John Cronin48:52

I love it. First time—I wish I had a video for every person that the first time that they use it they get a shock. But then they certainly started getting in, and by the end of it they're just smiling the dials off. It's just technology.

James de Lacey49:24

For sure. I wanted to finish this podcast on a—it's a graphic that I reference all the time from actually from your lecture when I was going through my postgrad. I still have all those files on my computer. And it was on the muscle spindles and golgi tendon organ, essentially exercises. You change your muscle length, you excite the muscle spindle essentially through whatever it is, and then you have the inhibition from the golgi tendon organ.

I think I got that right. And the graphic shows how you can enhance force through improving the excitability of the muscle spindles but also, I guess, desensitize the golgi tendon organ to keep forces high for that change in muscle length. Now from my understanding, if I can recall correctly, heavy strength training is something that can desensitize that golgi tendon organ, and plyometric training is something that can improve the excitability of that muscle spindle. Did I get that correct, or is there more to it than that?

John Cronin50:29

No, no, you're right on it. It's Comi's work way back from 1986, and exactly that. The muscle spindles are a length feedback mechanism, and so therefore we've actually got to play with the sensitivity of that length feedback mechanism so that the plyometric activities are one of the ways that we can enhance the force output.

But at the same time the golgi tendon organs, they want to disinhibit everything or inhibit everything. They're a force feedback mechanism. And so how can we actually reduce their influence on reduction of force output? So we just got to get them used to high force. And one of the ways to get them used to high forces is exactly what you said: just get them under load, get them under heavy loads.

James de Lacey51:29

Perfect. That cemented in my head then. I just wanted to make sure that I wasn't spewing or something. It's great that you remember it because it's one of my favorite—just a picture paints a thousand words. It's something that I still talk to a little bit.

John Cronin51:29

It's a great piece of work from Comi.

James de Lacey51:29

To me it's immense. The idea of why you need to do both high velocity and high resistance training, it literally just in one graph just tells you exactly why.

John Cronin51:59

And the old story: if in doubt, do both anyhow. Without anything.

James de Lacey51:59

Exactly. No, perfect. This was an awesome podcast, John. I guess if anyone wants to follow you and see what you're up to, where can they do that?

John Cronin51:59

I've got a website, www.professorjohncronin.com. That you remember stuff from lectures hundreds of years ago.

James de Lacey51:59

Not that long ago. What was it? What is it now? Must be, it's getting close. Actually it would be like 10 years ago now.

John Cronin51:59

A decade then, not quite a hundred.

James de Lacey52:58

I'm good.