005 Stretch-shortening cycle

And then just give some uh general recommendations focusing on uh the development of the stretch shorting cycle or the improvement of the stretch shorting cycle in high velocity movements. So As you'll find out as we just talk through this, there are a number of mechanisms that underpin the straight shortening cycle.

Some of them are more applicable in slow, heavy uh kind of situations, high load situations, others are more applicable in the fast end of the spectrum. And because generally speaking, we talk about straight shorting cycle most

in the context of fast movements, that's what we're going to focus on today. So as always, I'll just whiz through the physiology and how this works, and then I'll pass the ball over to Rob and we can start going backwards and forwards about the training programs and implications.

So starting at the beginning, the stretch shortening cycle is the observation or the phenomenon whereby we see essentially an improvement in concentric phase performance as a result of having an eccentric phase directly before it. So we have this thing called the stretch shortening cycle effect. And that essentially is the improvement in performance that we get in a concentric phase.

as a result of bolting on an eccentric phase beforehand. So if you do a concentric movement, concentric only movement, and you'll find that you don't quite get the same bar speeds, you don't quite get the same, you know, kind of jump heights, you don't get the same kind of force production.

as you would do, or impulse production is probably a better uh kind of characterization, you don't quite get the same levels of performance as you would do if you had a full stretch shortening cycle with both eccentric and concentric phases. So it's an observation or a phenomenon, in the same way that fatigue is a is a kind of a phenomenon. Now underpinning that we can have any physiological mechanism that essentially enhances concentric phase performance.

whenever you've got an eccentric phase preceding it. Now, researchers have found five separate mechanisms. I'm just gonna uh kind of pause very briefly and add a comment in here and say often in the kind of uh less technical parts of the fitness industry you'll find people equating

the stretch reflex with the stretch shortening cycle. So they'll say, oh you know, the stretch shortening cycle or the stretch reflex. No, the stretch reflex is one of the five mechanisms that underpin or create the stretch shortening cycle. In other words, it is a mechanism, a physiological mechanism, that enhances concentric phase performance whenever you've got an eccentric phase directly preceding it.

So essentially we've got these five mechanisms. Stretch reflex is one of them, something called preactivation is another, we've got the residual force enhancement effect, and then we've got elastic energy storage in the tendon. And finally we've got an interaction between the muscle and the tendon that changes where on the force velocity

relationship, the muscle fibers are working. So we've got these five mechanisms. So just very, very quickly whiz through those, explain what they are and then explain two that we're going to focus on for the purposes of high velocity movements. So the stretch reflex essentially is whenever the muscle spindles detect That the muscle is stretching, they will send the signal to the spinal cord, get a bounce back effect, and the muscle increases its

level of motinic recruitment. Now, this is obviously a way to increase muscle force and by increasing muscle activation. And it's debatable though how much the effect actually adds to overall recruitment at high levels of effort. So what we tend to find if we look at the kind of increment that you get, the extra recruitment that you get, we tend to get a much bigger effect, much bigger increment on recruitment at lower levels of effort than at higher levels of effort.

So the stretch reflex is one of those things that probably enhances performance more so during life endurance running, that kind of activity, doesn't really tend to create much of a an impact in the kind of high velocity, high effort movements that we're interested in, like jumping, throwing, sprinting, that kind of thing. So even though it is a

a straight shortening cycle a mechanism, if you like. It's probably not one that we need to worry about in the context of the high performance physiology that we're, you know, kind of uh devoting this podcast to. The second uh mechanism is

Preactivation, that really just works all the time in the background, can't really change it very easily. Essentially it's just that whenever you have any eccentric phase preceding a concentric, you've already activated the muscle before time zero, which is the start of your concentric phase. So the muscle's already activated. It doesn't need to build any activation, build force production. It's already there doing that at time zero. So you get that extra benefit of impulse.

at the start of the commoncentric contraction. Again, I don't think this is particularly modifiable. Make it just kinda happens most of the time in most situations whenever you've got a stretch shortening cycle going on. Thirdly, residual force enhancement effect. This is essentially where we're stretching tight in

inside the muscle fibers, inactivated muscle fibers in an eccentric phase. If you stretch them in a uh passive stretch to get into a position where you're gonna do a concentric phase but without the eccentric activ phase beforehand, you don't get the same effect because titan works differently.

in a passive muscle fiber from an activated muscle fiber. And so the residual force enhanc the residual force enhancement effect essentially gives you a benefit to the extent that you've got a large number of activated muscle fibers all being stretched in that kind of essential phase. Now for reasons I'll explain in a moment, that works really, really well in heavy load situations like powerlifting.

not so much in the context of high velocity movements where we've got a lot of tendon movement backwards and forwards. So the fourth mechanism is elastic energy storage in the tendon.

This basically is the first one that now is going to be interesting to us in the context of high velocity movements. Essentially in this situation, the tendon is going to move around and stretch in the eccentric phase and then it's going to recoil and return that elastic energy to us in the form of kinetic energy to aid us.

in that concentric phase that we're gonna do. So the more the tendon stretches in that scenario, the more elastic energy we get and the more uh kind of uh kinetic energy we're gonna be able to return to ourselves in that concentric phase to be able to enhance

the movement that we're interested in doing. So you can see straight away there that if the tendon moves around a lot, i.e. it behaves in a compliant way, because basically if a tendon is stiff, it doesn't move around. I mean that's the definition of stiffness. Uh if you if you I mean it bears it bears repeating, but if you have a compliant then then obviously it will move around a lot and it'll store more energy.

Now, um the uh equation for the storage of elastic energy is a half kx squared, so k being the stiffness. So yes, if the tendon is stiff but you do manage to stret uh stretch it and move it around a lot, then you will store more elastic energy. But X squared, X refers to the displacement of the tendon and of course being a squared term, much more important. So

much more important to have a tendon that does actually move around when you want it to than have a really stiff tendon that doesn't move around a lot. Yes, the perfect scenario would be to have a stiff tendon that you can stretch a long way.

that will store much more energy than a compliant tendon that you can stretch a long way. But having a tendon that is stiff and therefore does not move around because you can't stretch it is not actually very good for storage and elastic energy in the context of

high velocity situations that we're going to be talking about. And then finally, this idea of muscle and tendon uh interactions, if you have a muscle that is essentially capable of keeping a short a short length and and allowing the tendon to or pulling the tendon to a long length and letting that tendon then recoil, the muscle itself will stay at a shorter length because it's essentially forcing the tendon to do the

lengthening and shortening instead of the muscle doing the lengthening and shortening in that kind of straight shortening cycle movement. And as a result, the muscle then works closer to uh you know, a constant length through and you actually in sprinting we actually talk about quasi isometrics because ambitious get to a point where they're really kind of just moving very slightly, and as a result, they're able to produce really high

forces because they're not essentially uh the fibers themselves are not shortening very quickly. Because if you can keep the muscle at a relatively short length so it doesn't really, you know, lengthen and then have to shorten again, then obviously the shortening velocity of those muscle fibers is much, much reduced relative to the angular velocity of the body or the joint segments that you're actually rotating.

So what we see there is the muscle is going to work much closer to the force under the force velocity relationship and as a result produce a much higher force. So both of these factors, essentially, just like elastic energy storage, are relying on the tendon Byddwn yn ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r

shorten more slowly and therefore produce a higher force. Now the reason I said that these two mechanisms are essentially the ones we're interested in from a high velocity movement point of view is because what we see is that tendons tend to behave more in a kind of stretch.

and recoil type way, they behave in a more compliant way in those faster movements, whereas in heavy strength training movements like powerlifting, they tend to behave much more stiffly and stay at a fairly constant length. So you don't get a lot of elastic energy storage in that. strength training exercise, you don't get a lot of keeping the muscle at constant length in the same in the same kind of exercise. In contrast, in like a high velocity drop jump,

you know, or a sprint, you will tend to see that the tendons are moving around a lot more and the muscle is moving around a lot less. And therefore you do get this uh these two sort of mechanisms operating whereby we're storing and releasing kinetic or elastic and then kinetic energy getting it back.

And in the case of the muscle we're allowing it to stay at a relatively short length. Now, that's how all these mechanisms are working. The final thing for me to say then, before I hand over to Rob, is just to explain exactly what it is that allows us to enhance the stretch shortening cycle with respect to these two final mechanisms. So again,

what I'm explaining here only relates to these two mechanisms in which we're seeing a relationship between the muscle and the tendon, and that's going to be much more applicable in high velocity situations. So what I'm not saying is this is how I would, you know, kind of see the

mechanisms of improvement for something like the straight shortening cycle in a powerlifting exercise because that would be relying on the residual force enhancement effect changing, not reli which would probably require something to do with titan. Whereas what we're describing here is much more to do with, you know, how do I make the tendon, you know, kind of stretch and recoil to a greater extent, how do I keep the muscle

you know, at a shorter length to a greater extent. That's kind of the the adaption we're trying to drive. Now, hopefully, if you've been following along with this, you'll be thinking to yourself, well, this isn't an adaption. This is actually a ratio of effect. It's a ratio of muscle strength in the eccentric phase to tendon stiffness.

Because essentially what I'm talking about here, if I want to make the tendon behave in a more compliant way in a stretch shortening cycle movement, what I need to do is make the eccentric strength of a muscle bigger than the tendon stiffness. That's that's my adaptation. It's not actually an adaptation, it's the interaction between two adaptions. And that does not mean that I have to make the tendon more compliant.

It does not mean that I have to make the tendon essentially change in any way. What I have to do is make the eccentric strength of the muscle go up faster than the tendon stiffness is going up. And this is really, really important because

Sometimes when I tell people that they've got things upside down and they don't want to increase tender stiffeness for the purposes of improving their polymetric performance, they say, Oh, so you're saying we need to reduce tender stiveness? And I'm like, No, I'm not saying that. I'm saying that you need to increase the strength of your eccentric strength of your muscle relative to your tendon stiffness.

the very best climometric studies we've got that illustrate this point actually have tendon stiffness increasing during the experimental period of time when the people are training. But the eccentric strength of the muscle increases faster and as a result, by the end of the training program, the muscle is pulling the tendon around to a greater extent than it was at the beginning.

Tendant actually got stiffer in those training programs, very slightly. But that's not what we're interested in. What we're interested in is the ratio of these two improvements. So is my eccentric muscle strength increasing faster than my tendon stiffness, or is it the other way around?

And of course that's in like, okay, well now we do now that we know that, what types of training are going to create those effects? And the most kind of well uh kind of described training method in the literature that we have that does that is the pliometric activity. So plymetric uh kind of uh training methods are really, really good at increasing eccentric muscle strength while leaving tender stiffness either largely the same or just increasing it very slightly.

And I realise this is going to be kind of counterintuitive to many people who think that plymetrics work by increasing tendon stiffness. They actually don't. You know, in all of the literature we've got, eight or nine studies in plyometric training methods, at least the last time I checked, probably more by now. And generally speaking the increases in tendon stiffness are either non significant in many cases or just significant and actually quite small.

And in the couple of studies that's been done comparing heavy strength training increases in tendon stiffness with polimetric increases in tendon stiffness, heavy strength training or isometric training just blows polimetrics out of the water in terms of increasing tendon stiffness. And again, we can go into

exactly why that is in a future episode, but just for the purposes of today, plymetrics are not having any uniquely hugely beneficial effect on tendon stiffness. They kinda leave it more or less the same, increase it very slightly. What they're really doing is kind of creating this eccentric uh strength increase of the muscle that is relative, you know, without really modifying tendon stiffness to the same extent.

So that's the magic. That's the kind of physiology underneath the surface. Ro, tell us a little bit about how you're using plymetrics in your train training programs at the moment.

And it's an idea that you'll see all the time. I see it on social media. So people will be doing lots of isometrics, long duration isometrics, I've seen, you know, some mid range split squat iso holds. calf isometrics, all kinds of things like that. And people will say they're using it to improve the stretch shortening cycle. And like Chris just said, that is not really going to be the case. And we did mention using isometrics for increases of recruitment in that.

in uh the prior episodes. So like we were just saying before we came on today, one of the things to clarify there would be programming wise, just making sure that you're not using too much of those. We mentioned very brief, like three to five second contractions, and really not using very many of them either.

So you don't have to do very many. You don't have to do them super often since the adaptations aren't really gonna dissipate very quickly either. Once you use them you get those recruitment increases, those are gonna hang around quite a while. So if you are using those in your programming for

hip flexors, extensors, uh whatever it may be. Um, yeah, just keep them brief and you don't have to do a ton of them, you know, just I usually just do one in a session, honestly, and then cap it there. Just one max effort and then that's all I'm gonna do.

Um but, you know, moving forward into like actual plymetrics that I tend to use, you know, I don't think it's gonna be anything revolutionary here. Um, I think a lot of people are looking for super special fancy exercises or like an even complicated sequences of exercises. But I'll just give some uh some basic ones that I use. You know, the the first example for improving punching power and things like that. So some upper body plios. I mean, you know, big one.

people have seen a million times gonna be plyout push-ups. Uh really like those. Um a little bit more of like a drop plyo push-up so you get like a little bit more speed and definitely some more force requirements when you're actually like getting into that bottom and rebounding out of the bottom there. So I like those quite a bit.

You can do the same thing with like a drop medball chest pass or a drop medball throw. Really like those. And again, you don't have to do a ton of them. Usually I'm doing like three or four sets of just a couple of reps. Um honestly it's usually like something like three reps. Not very many reps at all. So

keeping the volume on those pretty low. Um in terms of like some of the ones that I've liked, some uh single arm overhead, um, you know, med ball slams and things like that. If you're watching like fighters and especially people on like the ground, they're throwing, you know, sometimes

hammer fists and the round and pound, things like that. And they, you know, were terribly clunky and slow. I found those will help people be, you know, just a little bit faster and more powerful with things like that. Help them not use just their arms and actually, you know, get more body into it and get more speed and power there. Baseball guys I've worked with in the past, although honestly not haven't worked with a ton of baseball players, but just a few.

um, using things like, you know, m rotational met ball throws and I like kind of a skip into that so you get a little bit faster velocity, more rotation. And then just, you know, more output there. Um, with all those, it is useful to be able to measure them. Obviously, you know, you wanna be measuring them, see if people are improving. But

At the same time if you don't have a lot of equipment and stuff like that, as long as people are giving, you know, an absolute maximal effort and you can usually tell whether or not they are, um, you're still gonna get the improvements there. So really like all those. In terms of

lower body polymetric stuff. Again, you know, probably nothing revolutionary. You know, I stay away from the calf things we had mentioned with improving sprinting and all that stuff. Probably not a good idea to be doing like calf ISOs, things like that. So really everything for the calves is super, super fast. Again, like the calf hops we mentioned a bunch of times. Really like those. You know, not too many in a

Set just a few quality contractions, getting as much height as you can. Big fan of some like you know, a lot of the more reflexive stuff. So you always want like that random component. So something like a split squat, drop, drop, jump there. You know, you just

Take your feet off the ground, catch and rebound as quickly as you can, using very, very light loads. You know, with all these focus, I never focus on any kind of like weight. People were using very light dumbbells, very light med balls, things like that. You wouldn't mention drop jumps.

Um, do use drop jumps a bit. So, you know, various heights there. And I don't know if you just mentioned it, but before we came on, Chris had mentioned that the concentric phase generally is not so so important with these things all the time. So I'm

People literally look at me as if, you know, I've grown an extra head at this point when I say things like this. I was like, No, just think about what adaptation we're trying to stimulate here. You know, it's got nothing to do with the concentric phase. You know, so

Yeah, cool. If we do get a concentric phase happening, we can use that for another purpose, you know, for a speed development. And the cool thing is that the straight shortening cycle effect does give us an enhanced speed in that concentric phase. So

it will get you to a faster velocity. Well, that's fantastic. That's going to potentially trigger some speed related adaptations. But that isn't what we're chasing with the actual drill that we're doing. So it's like a side effect. It's a benefit that we can kind of

take advantage of, but it isn't necessarily the thing that we're actually training. So, you know, I think it's it's cool to to do those things, but just kind of like I'm always coming back to first principles and saying, what is it about this particular exercise that I'm trying to

derive, what what benefit am I deriving from this drill or this exercise? And if it's an improvement in eccentric strength of the muscle relative to the tendon, then nothing in the concentric phase that I can possibly do will change that. So it's kind of like but I do get the potential for that improvement in that in that speed related adaption. And that's really then what goes into then thinking about what if you are chasing those speed adaptations in that concentrate phase.

you know, does it make sense then to jump or throw or or whatever do the exercise for maximum performance? So Typically in biometric circles, people will say, Uh I'm either going to minimize ground contact time with this particular exercise or I'm going to maximise performance, jump height, or whatever it might be in this particular exercise. Well, if you're maximizing jump height or actual movement performance,

you're gonna get the speed related adaptions. If you're minimizing ground contact time, you're probably not because you're not gonna get as big a uh kind of impulse in your contact phase, so you're not gonna reach as high velocities, so you're not gonna trigger the adaptions in speed. And I'm not entirely sure what people think they are triggering by minimizing rail contact times, because every time I ask them, they give me this kind of reactive strength kind of lecture.

I might yeah, but what's the physiology? What's the physiology underpinning that? Tell me the physiological adaptation that creates that outcome. And I'm really not certain there is a clear answer to that. So while on the surface I can kind of see the benefits of a maximum speed kind of

drop jump or maximum speed kind of plymetric performance to try and trigger those speed related adaptations. We've got you know, we did did a podcast on exactly what those are. You know, I'm not convinced that there is a reactive strength index or reactive strength

you know, kind of outcome that you can kind of sort of underpin with a series of physiological adaptations that are unique to minimizing ground contact times. I don't see that that exists, but, you know, if someone wants to argue that case, I'm happy to listen to that.

I can't see it in the physiology of what it is, you know. And if they say to me, Oh, well, it's rate coding because you're moving fast, I'm like, Well, I can do that with a fast movement phase. I don't need to minimize our contact times to get And the interesting thing is rate of force development

and maximum speed physiologically are incredibly similar really because all you're trying to do is build force faster. Well that is a key component of maximum speed. So they're very, very difficult to disentangle in my opinion. And I think, you know, logically,

I know we've got a history of no, we like you said earlier, we've got a history of thinking that tendon stiffness is driving biometric forwards. We've got a history of all kinds of upside down ideas. I this is one of those upside down ideas. I'm not convinced that

you know, minimizing ground contact times is the best use of apply metric if you want to bolt on the maximum speed component of adaptions onto the actual stretch shortening cycle component of adaptions and get two things in one exercise. Anyway, that was that was uh s that was that was the s second or the third thing I noticed while you were talking.'Cause the first thing I noticed was

Uh, you were talking about the isometrics stuff because I know we've been pushing isometrics at a lot and saying to people you can use these to maximize gains in recruitment. Two things occurred to me while you were saying that. One was that absolutely, as you point out, you don't need to do lots of reps of these to get an increase in recruitment. And because the reps and the total volume is really what's going to drive the tenant stiffness adaption. If we just do one or two quality reps

I mean personally I can't do more than one max effort isometric, but my brain just shuts down. I'm just like I no, I can't do any more of these.

Um, really the only one that's gonna trigger recruit a recruitment gain is gonna be the one with the max level of recruitment, which in many people's cases I think is just gonna be the first rep. So, yeah, I know it sounds like not very much, but I think you're probably right. that just doing those single repetitions is probably, you know, the best outcome for minimizing tenant stiffness increases while gaining the recruitment improvements.

tons of playos, certainly not tons of volume, or even them use them for very, very long. You and I discussed before that like stretch shortening cycle tends to peak like pretty quickly in athletes with your abilities with it. So you don't need to be doing a ton of them all the time. I mean I much prefer to do more concentric based max speed stuff a lot of the time for more of the the training time, the training year and then, you know, do plios and that stuff to maximize

Stretch shortening cycle adaptations like for I guess more brief periods. Um, you can I tend to find at least people's tending to get beat up, stuff like that.

And then that damage potentially could lead to a tendinopathy. So obviously we've got this uh kind of conflict between wanting the athlete to be as you know, kind of capable as possible in terms of their performances, but also as resilient as possible. I think there's that kind of uh

conflict there that we've got to be aware of. And like you say, just having periods of the year when we kind of allow the tendon to become more compliant for the purposes of maximising performance for some competitions that are important. And then allowing it to kind of or just, you know, kind of doing more heavy strength training and avoiding or some isometrics or whatever and letting it drift back to a stiffer state to avoid those problems, you know, around that time.

I think it really just comes down to, you know, how you how you think tendinopathies develop and obviously I'm not an expert in that area, so don't really kind of claim to have a a model that describes it. But I think, you know, broadly speaking, from my understanding of the literature, it generally it looks like

you know, if tendons are moving around a lot like ligaments, if they move around a lot, they tend to get damaged and therefore that damage could then be a problem. So yeah, I think it's uh it's uh definitely a uh a balancing kind of effect. The thing that I was thinking of when you mentioned the i the isometrics, just going back to that for a quick

moment because I was suddenly realizing that when we look at periodisation and this is obviously something that we can talk about again in another episode, but when we look at periodisation, one of the things that is hugely helpful in periodization uh kind of programs. One of the reasons that people would argue for periodization over non periodization

is if you can do something early on in an athletic kind of cycle that benefits you later on. Um and one of the only adaptations that actually does that is an increasing recruitment. Because if you can trigger an increase in recruitment in your first couple of weeks of training then you're

kind of several weeks later, you're going to be reaping the rewards of that because you can now access more muscle fibers, you can produce more force, you can do more exciting you know, reach high velocities. There's all kinds of things you can do as a result of that adaptation that you triggered earlier on. So

That actually fits really well if you're thinking in terms of building a base of recruitment earlier on in a period periodized training programme. But simultaneously, it doesn't matter so much if your tendons are slightly stiffer as a result of doing those things. Because when you've kind of done it, like you mentioned, you do those things earlier on.

if you've done that, then you can then back off on them because the adaptation, the recruitment adaptation doesn't go away. No. Again, this is one of those brilliant illustrations of how if you think in terms of outcomes like strength and speed and power,

then none of this makes any sense because people will say to me, I was building strength in the off season. I'm like, No, you weren't. You were creating certain adaptions in the off season which may or may not stay with you if you stop doing those types of training. You know, I had some questions in my Instagram literally yesterday where people were saying, Well, we do heavy strength training for sprinters in the off season and then we stop in season. I'm like, Are you pulling my leg?

But the hypertrophy and the other peripheral stuff, you you're gonna lose that if if if you stop doing it. So it's like we can't build strength in the off season. We create increases in recruitment and hypertrophy and psychomogenesis and all that good stuff. And then like as I say repeatedly, if you turn your back on sarcomerodenesis for five minutes, it'll disappear. It's like you have to kinda keep that stuff going throughout the

kind of period of time in which it's supposed to benefit you. If you do like a whole chunk of three months off season training in you know, however long the period might be, in heavy strength training and then stop and a month later it's like, well, you might as well not have bothered really.

all the extended eccentrics, all these things in the off season, thinking that it's gonna build them more muscle, thinking it's gonna do all these these magical things. And then they don't move fast. at all. You know, they don't not only do they not do any like pile work or anything, they don't do any max speed work. And I think we said the same thing in the speed episode. So that if you do an off season full of five second eccentrics on your

a squat bench, deadlift and things like that or even machine stuff. And then you all of a sudden go and try to just start chucking in plyometrics out of nowhere. Like you've moved incredibly slow for a long time. And I see people do that a lot. And then they'll have an athlete go right into plyos'cause oh, all of a sudden now we're in

fight camp we're in going into the season for, you know, soccer for this, for that. And then all of a sudden everything starts hurting. They feel beat up. They chuck in a big volume of pilos and I'm like Hilariously slowly for six months and now you're you're funny to move as quick as you can.

uh, you know, kind of emphasis on players in the off season'cause you don't want the tender to be moving around enormously potentially. So you could kind of argue that that is a subtlety there that bears, you know, kind of emphasis. But realistically, we kind of say, Well, no off season you could kinda get away with a little bit more volume, maybe a little bit more frequency. But really the same stuff that is working in the off season will work

in in season. It's just you might need to dial it right back to depending on the commitments of the athlete and what else they're doing. You know, if the athlete's hugely committed to a number of events and the practices and what have you, you might have to dial the like I said on my Instagram stories yesterday,

I said, you could literally do a single set of hip thrusts twice a week, maybe a hi single set of hiplexa heavy hip flexor work twice a week, maybe a single rep of Nordics and a single rep of uh, you know, reverse Nordics twice a week. And that could be it. I mean and I'm like, that will keep everything that you did in the off season, you know, completely, you know, more or less intact throughout the in season without having to actually, you know, kind of create tons and tons of fatigue.

or whatever it might be. I'm so I think ultimately it's just about, you know, as I was saying, the two training programs in those two phases shouldn't be that different. It should just be that you're dialing back the kind of uh volumes and maybe the frequency slightly as well in that uh period where you've got more commitments uh athletically.

But there's something else I wanted to come back to that you said, just to finish on perhaps. You mentioned about tracking performances. And you also, in a separate comment, you mentioned about um the oh I missed it now, I've just forgotten what you said.

In there it connected the two things together because you're mentioning the the tracking of performances. I know what it was. You mentioned how the stretch warning cycle improves and plateaus relatively quickly. So you kinda get a period of improvement. And really what that represents physiologically, most likely in the context of high velocity movements, is just the amount of compliance you get until you reach quasi isometric.

Because when you get to a quasi asymmetric you can't go any further. There's no there's no outcome that you can kind of influence that will make the stretch shorting cycle better.

So if you think about it in those two terms, what you can do then, if you combine those two observations and say, Okay, well I can monitor concentric phase performance and it's it's okay as a kind of a metric of stretch shortening cycle, you know, to just use that. Um we can say, Okay, so Um, I'll measure the difference between my squat jump height and my drop jump height for for height, not for ground contact time minimization.

look at the differences between those two and I've got then a metric of what I would call my straight shortening cycle effect. So if my drop jump height is five percent greater than my squat jump height, very approximately

I know that that's an a metric of my straight shorting cycle effect. Now it's not perfect. There's a number of other things going on there, but you know, it's good enough. If that improves over time while I'm doing the program that I'm doing, then I know that my tendons are moving around a bit more and I'm becoming more

capable of generating those positive mechanisms that influence the stretch shorting cycle effect in high velocity movements. If it's getting worse, it means I'm kind of leaning heavier on the strength training stuff and the isometries and it's it's kind of you know, kind of

Now importantly, in both of those scenarios, jump heights could still be going up. You know, both jump hikes could still be going up. One could just be going up faster than the other. And that's the thing that I just keep going back to. It's like the stretch running cycle is a ratio of things. It's not actually

you know, a thing on its own. It's the ratio of these things happening. So you can get squat jump height going up and drop jump high going up. It's just one goes up faster than the other, then you'll have an improvement in the strict shorting cycle or a reduction in your stretch shorting cycle. It really just depends on

Which one is going up faster? And then literally you can just monitor that, as you were saying, just track. And when it gets better and then starts to plateau, it's like, okay, we're done here.

Because y again, most people who are thinking about this stuff are not starting from the physiology and working their way to the end practical implication. They're starting from kind of Well, this is how things have been done and this is how the outcomes work and we're building strength and getting and I'm like, No, you're not So Go back to physiology and start building up brick by brick and then you'll get to a point where you can see

what actually should be happening and then you come up with these observations like you were saying, track stuff over time and you should see that the improvements are or, you know, kind of it gets worse rather than improving, depending on what you're actually doing. Um And you end up in and it honestly it depends. I mean, like if you've just come off a period of competition, you actually might want it to get worse. So if you kind of Yeah, so like finished a competition.

Yeah, it finished competition season, you can carry on tracking stra tracking straight short in cycle and you should see that drop jump height relative to squat jump height gets worse because you cut down your on your plometrics, you improve at the increase the amount of heavy strength training and maybe isometrics you're doing, and you see a drop away from that really kind of effective stretch training cycle in favour of a tendon that doesn't move around so much.

Then you can then do other stuff and be a little bit more relaxed about the risks potentially involved in creating tendon damage. So, you know, actually when you think about it, having that block of isometrics and heavy strength training immediately post competition season is actually a really interesting idea because it simultaneously puts you in a state of being able to do a little bit more volume at the same time as actually priming you for recruitment.

uh you know, that will benefit you in subsequent phases. So in terms of periodization, there's actually an interesting physiological rationale going on.