Strength, Swim Power and Swim Performance by Joel Stager, Ph.D. (2003)


Published


Our third grant recipient – Dr. Joel Stager. Dr. Stager represents Indiana University and has been involved with swimming in a number of capacities, is highly involved with masters swimming as well as USA Swimming and his research is on the issue of strength swim power and swim performance.

Hypothetically then, rather than make things complicated we will try to make things simple, _________ performances unlimited by the biochemical capacities produce a metabolic energy and again in terms of sprints we are talking about events that last in the neighborhood of 20 seconds. Performances are also limited by the skeletal muscle’s ability to generate mechanical power and we will talk about that in a little bit on one of the next slides and thirdly sprinting performances are limited by the ability to effectively apply the mechanical forces to the water.

So we have got the biochemistry involved, we have got the application in terms of stroke mechanics and we have got the actual movements taking place within the muscle so the big question is whether or not there are relationships between strength, power and swim performance. Now this would seem logical to most coaches. It seems to logical to me, but when you look at the literature most of the literature suggests otherwise, that there are no relationships between the three of those so I actually went into this with the idea that perhaps in the past people had not been measuring the right variables or perhaps they had other things that were affecting their ability to see the nature of these relationships.

The next step is to determine which is the most important in terms of sprint swimming performance – whether it would be strength or power, again we tend to use those terms interchangeably and we certainly should not is going to be one of the messages today. So, even though I am presenting a study there are actually about five parts to this study and the handouts that I gave you will show you about 1/10 of the data that we collected over the last half a dozen years or so.

The first question is how are determinants or correlists of sprint swimming best measured. That is a tough one and we spent four or five years working on that one, we will talk about that. Are there differences between boys and girls – again – that seems obvious, but a lot of the previous literature collapsed the data and combined the results and perhaps got some results that they shouldn’t have.

If power is improved, is swim performance and that is obviously the question that most of the coaches are interested in so lets look at strength first.

From a physiological perspective the strength of the muscle is related to the cross-sectional area of the muscle and everything else was held constant and that is a doubtful right there. Muscle mass and muscle cross-section area from my perspective is the bottom line in terms of force that can be generated. Now needless to say my neurophysiologist friends will say that there is a neural recruitment pattern. There are other things beyond just cross section there and I agree with that too, but ultimately at the, lets say micromolecular level there is a number of cross bridges that you can form which can determine how much force that muscle can generate so try to keep it simple. On the other hand, power is something completely different.

Power is the work done for unit time and these are sort of rigid definitions or the rate at which work is being done. It is related to the force and can be generated by the muscle and it is related to how quickly that force can be developed. So we have muscle mass being involved which is directly related to the forces being generated and the muscle shortening velocities and those are two important traits that will ultimately dictate power.

Now this is a standard curve in physiology – a graph that everybody has seen and basically what we have done is we take a muscle and we ask it to generate lets say, increases in force so we are going to increase the force across this way and we are going to measure the rate at which that muscle shortens. So we have a shortening velocity on the wide axis and we are going to increase the amount of force that muscle is required to generate and basically what you see is anything above zero essentially there is an immediate decline in the rate of shortening for that particular muscle. Until you get all the way out to the end and the muscle doesn’t shorten at all so to simplify things strength is actually measured out here. For instance, when we measure lets say a one repetition maximum there is not a whole lot of shortening taking place. So it is out at this end of the curve. On the other hand power which has that time element involved which is related to both the force being generated and the rate of shortening exist on a dotted line that goes across here and you will see on that curve the maximum power output of this particular muscle actually occurs relatively low down on that force axis.

So, power is over here and strength is over here and it turns out if you want to train a muscle you had better know which one you want to train for, whether you want to train it for maximum power or whether you want to train it for maximum strength because the stimulus is going to be different for those two characteristics. Now, again – starting at the end. Where did we wind up?

Well, in terms of the most significant or the most important to determine sprint swim velocity we wound up generating a number of these curves and if you are familiar with statistics and you look at this R square that’s – the R is the correlation coefficient and a perfect value is 1 so a perfect value for R square would be 1 as well. That value is very high. That means the R value is somewhere around .9 so that is a single measure relating these two things and this basically says swim velocity is highly determined by the maximum power any given swimmer can generate.

Dr. Daniels was talking about some of these lines before. This is not a straight line and we will talk again more about that later, but one of the earlier questions we had to ask was whether or not men and women were different.

Are women swimmers different than male swimmers and you are going to see that they all fit on the same line. From this perspective there is no difference. It is the same line they describe the same relationship so there is no point in separating them. The women don’t generate as much force and they don’t swim at the same velocity so the women tend to be down here in the green dots and the men tend to be up here in the blue dots. Now, this doesn’t have all 900 or so subjects on there because it just got too many points to actually see anything, but there are a number of things to look at on this particular curve. For instance, this guy up here is pretty much doing everything right and if you look at his values he is swimming in excess of 2 meters a second. So that is a pretty fast clip and it turns out on our scale here he is generating the most power. He is the most powerful guy that we have measured.

This guy on the other hand is doing a lot of things wrong. He is actually fairly high up on the power curve but in terms of his velocity he is not very fast – this is not a function of not being able to generate power. This is a function of the other things such as drag and perhaps application of that power.

We are going to go backwards here. One step above power is actually power per stroke. So in other words in the tests that we are going to use on these guys we actually know how many strokes they took during the test that we gave them and we can divide that out and actually even get a higher correlation. Now we are over .9 on that simple correlation and we actually have an equation that would allow us to go both ways if we know what someone’s maximum power per stroke is we can calculate what their maximum velocity should be.

Now we are going to go back to the beginning. The last graph is where we ended up. This is where we started. Basically what you do is you hypothesize – you talk to a lot of people, you do a lot of reading and try to determine what variables you think should be important as far as determinants of maximum velocity in swimming. Then what you do is step by step start throwing some of these variables out so you are going to see on the front two pages, there is a list of variables and that is about half way through this weeding out process. You assess a sample of some population, statistically evaluate the differences within it, look at the variables, determine which ones are important in terms of making predictions or descriptive equations, that don’t make any sense and move on.

Alright – mechanical power. You have seen one of these. There is one sitting down the hallway not too far, originally described I think in 1980 by Hopper – this is now known as the power rack. This is a different variation of that. It took us about three years to get it from here to here and we will talk about it and we will come back.

One of the things we had to do was increase the travel distance that the power rack actually allowed us as a result of Hopper’s original description which required us to have 10 meters of swimming distance and this was not including lets say push off the wall or anything like that so it had to be 10 meters of free swimming. The original rack didn’t do that so we had to figure out a way to get that distance and so we wanted something around 15 or 16 or 17 meters and while we were at it we decided, what the heck, why not go for 25 and that has turned out to be a little bit more difficult.

So, we will go back and we will see this – we have managed to do this but in doing this what happens is we had to change the mechanical advantage of the rack. So each plate wound up weighing or representing less resistance. So to counteract that we had to add more plates. So, instead of having 20 we wound up having 40 plates, but in doing that we wound up losing travel distance because the weight would move less and the swimmer therefore would move less so we had to change around the mechanics a little bit more and fortunately, one of the athletes on the team – his dad owned a machine shop in town and so we would toss these things back and forth about twenty times over the last 15 years.

Well, in this phase there is an athlete down here in the water and there is a mark on the deck right here and there is a mark 10 meters down there. We have the kids start without any buildup – just right into it. You can see how the stack here is measured and it actually has color coding according to the descriptive specifics that we generated over the years. The difference again is all up here in that there is an aluminum shaft that has a bearing in it that has two different sizes of drums on there and also a dead pulley on there and that allows us basically to do everything we want it to do.

The next step was we had to develop a protocol; we had to establish time goals for the workouts because eventually what we are going to try to do is answer that last question. Can you actually increase power in the water using something like this? What we came up with was actually fortuitous. It turns out that if you take an athlete and you measure their flag to flag time which in this case – a 25 yard pool is at 15 yards, it turns out that, that time is about 97% of their maximum velocity when you are measuring maximum power. So it turns out that, that allowed us to use this flag to flag as our goal times when we started setting these work loads and I will explain this further as we get down.

Alright, a second test that is sort of addresses less about the mechanical power and a little bit more about the biochemical limitations is something we call the swim gate. The swim gate is very much the same as what a wind gate test is. A wind gate test is done on a cycle odometer and basically it is a 30 second test that is all out and if you have ever done it, it is pretty miserable.

Alright, as my swimmers would say it has a cute factor of about 10 so what do you do? Well you establish a maximum force that they can generate using nothing more than an elastic tubing hooked up to a force transducer. Basically what they do is they swim away from the wall as far as they can go and we record what their maximum force is . So in this case it is going to be basically in this area. You let them rest for a few minutes and then basically what we do is we take them back out to that spot that generated that maximum force and we say – ready – go and they have to hold that for 30 seconds. This is the typical curve. In fact, it looks exactly like a wind gate curve where it takes them a certain amount of time to develop this maximum force. We are calling it force here because with a bungee cord there is no displacement. If there is a displacement it is generally negative. They are coming back towards the wall as they start to fatigue so rather than look at this as power it is really just force.

You can get three things out of this. You can get peak force, which occurs somewhere between 3, 5, and 7 seconds – depending upon the athlete. You get a minimum force which in this case occurred right abut here and you get a fatigue index which is just a percent drop between the max and the mid, and it turns out those are the three characteristics we are interested in. The fourth one is actually from the start to this peak value up here – that is the time to peak force. This part of the curve is probably related to the immediate energy sources available. This part of the curve we start talking about other sources such as glycolytic sources and then down here we are starting to phase in aerobic sources.

Alright, so we got four parts. We got a lot of things to look at. We are looking at the difference between men and women in terms of strength, power and determinants to sprint swim velocity. In other words, are we trying to compare apples with oranges and the bottom line is going to be sometimes we are and we have to be careful.

2. lets look at the ___ of the various measures of power to describe the relationship defined earlier, are they easy to perform? Are they useful for coaches and do they discriminate between athletes?. In a large competitive population of varying swim ability – describe these relationships and establish the base useful to coaches. Hopefully that is where we are going. Then follow a group of competitors through the swim season and evaluate whether or not you can actually generate more force and ——– have performance ramifications.

So, some of the things we looked at and we tried we kept some and we discarded some. We kept this one, this one, this one, this one because most of the other things were not very useful as far as taking them someplace and measuring a large group of swimmers. You know, it had to be easy. I don’t have time to go through all these things but we did some classic strength tests that were applicable to swimming. We measured a bunch of different ________ measures, in other words, we had to be able to say well how big are these people in order to control for size in terms of power output. We used a variety of power tests that are available in the literature and other coaches have been using and then we used some measures of performance there and some of these are actually measured and some of them were actually self reported.

Quick rundown without a lot of numbers: men and women are different sometimes. Dry land strength measures are related to power measures sometimes. Power is related to _______ most of the time and strength does not necessarily relate to swim velocity – again, most of the time. That is in a nut shell. Basically, here is what we are trying to do.

Theoretically if I can increase muscular mass I can increase the force it can generate, that will happen basically anywhere along the line here. At any given force I am going to wind up having a faster shortening velocity. So again, this is right out of the textbooks. I wind up drawing this other curve and then on top of that the power output at a new given force is faster, primarily as a result of the shortening velocity. So, the question is could we do that?

Well, we are going to fly through some of the data. Basically all this does is it says that men and women are different. So, vertical jump, medicine ball, one RN bench, lat pulls, triceps, peak forces, total forces and swim velocities and performances – they are all basically different, that group was a group of collegiate swimmers. We know they are different.

When we start looking at the correlations between some of those values we find out that the relationships are different in men –it is more a function of power in terms of swim performance. Women, non-power measures turn out to have a higher correlation to swim performance. Strength measures are only marginally related to swim performance in contrast to power, particularly in the women and again, the logic behind this would be that women have less ability lets say to increase muscle mass, power. Lets deal with power and performance from that side.

So what they do rely on are other things and some of these things are actually surprising and hopefully you will get a chance to look at it. down here – body composition. That was one of the things that we looked at from the standpoint of skin folds and it makes a lot of the people happy to find out that the correlation between the sum of skin folds and the swim performances and the power output is essentially zero. It explains almost – something like 4/10 of 1%. So, yes body composition is important – it is not fat mass – it is muscle mass.

Alright, so progressive tests on a power rack is something that we had to develop and work on. We had the swim gate. We have already talked about that. We looked a little closer at this medicine ball pass because again, it is a very nice field measure and then another one is the vertical jump which is very classic and fairly widely used.

So, when we apply all the data to the graphs it looks something like this. You can see as we go from this to this, to this, to this, we go from a recognizable curve similar to what we saw earlier on between actual swim power and velocity to something that is more or less a shot gun. So measures from the power rack, measures from the swim gate rather than power, again it is force, medicine ball and then finally we have this vertical jump. Surprisingly enough the vertical jump basically falls out as not a very particularly good measure of discriminating between athletes and swim velocity, the one we stuck with then was the one that used the power rack.

Power per stroke again is measured as using this progressive test is superior to the swim gate test and medicine ball, chest pass, the vertical jump as a means of assessing power in swimmers. The differences between men and women exist, but again – generally they all fit on the same line as we said earlier on and this med ball pass actually worked with significant correlations as compared to the vertical jump.

I am going to hop back here and look a little bit more at this progressive test. This is the test, pretty much as defined by Hopper in 1980 and I think again he described it in 1982. Basically what you do is you start with a number of ____ down here at the low end, an athlete swims 10 meters, you time them, you count the number of strokes and then you do it again only you add another plate or another two plates depending on the population that you are working on. Basically you keep going up and I think in this case these new modified racks each plate is worth about two newtons and we wind up coming up with some sort of a point there which winds up being the peak power being produced. We needed to know this because eventually we are going to apply that value in terms of identifying a training routine based on power and performance.

Alright? so that is the progressive test and this is how we measure this peak force so all these athletes went through this. Again, peak velocity came from this flag to flag swim so they are not measured at the same time. They are independent measures. Again, this is a variation of what you have in the first two pages. These are the measurements that we stuck with, age, height, sitting heights. Sitting heights allow us to calculate something we call a maturity index so we could look at maturity as a factor in terms of performance as these athletes got _______, as our population got older, because it is cross-sectional.

Weight span is this –arm span. We calculated some ratios there as well. This is mid upper arm circumference from which you can get muscular circumference. This is cross sectional muscle area, some are skin folds, vertical jump, med ball, this is power ___ power ___, watts per stroke, swim gate peak force, total force, percent decline, our maximum velocities, 15 yard swim time, 50 free, 100 free and this maturity off set.

Males and females again they are different. With that many variables I can throw numbers at you all day. This is basically where you start weeding things out and looking at what is important and what is not. We are going to look at it in a different way. This is what happens when you separate them as a function of age.

One of the questions in the back of my mind has always been where do we get these age categories for kids. Are they appropriate? When do they change? And this starts separating that out so what you basically see in this particular case. This is height and again if you are an age group coach you recognize this. There is not much difference between boys and girls up until age 13 or 14. Then boys and girls become different and the values separate. No kidding. The one thing we have to keep in mind again, is, this is not longitudinal, this is cross sectional. So what is going to happen.

You are going to see some things happen at the top end and we have a very select group at this end. These are now our remaining college athletes so they are not growing taller, but as a result of selection they are taller, this is going to be true virtually of everything we measure. Down here at this end boys and girls are the same. At this end they are very different.

Alright, so this is cross sectional muscle area and this is weight and this is vertical jump and again we start seeing some affects of selection up here on vertical jumps. Power rack power and again, very big differences between the men and the women. This value here we don’t want to look at because I think in that age group we had one athlete so we cant take much from that.

Alright, part 4 and I am going to fly through this. We are going to follow and evaluate a group of swimmers who are specifically trained to increase power using this in water program. Basically what it is is establishing 80% of that peak power, putting them on 10 reps on 45 seconds and then doing this two to three times per week. Following them – I think that we had a total of 16 weeks. Change in protocol, a little bit – six weeks out from championships, reassessing via this progressive test changing their reps and then starting dropping the reps and adding more resistance as long as their power outputs are improving.

During each bout we timed them, we measure their stroke and we keep track of tempo because athletes tend to want to change their stroke mechanics when they are resisted. We don’t want to do anything that will slow these people down because that is going to have a negative effect on power. As you can see, basically here is an example of the last four weeks .

We would do 8 reps on a minute 15 with 20 plates, three weeks out we are doing two or three bouts, six reps – minute 30, 22 plates and on and on as long as their power out put is increased. This is an example for one of the athletes over the course of the season here, you can see this is the resistance that we applied and then this is the power output. Basically what is happening is this is where we start and the second time we re-evaluate.

We add more weight and more resistance, power output goes up and levels off and comes back up, change the resistance so we just step wise through the season.

Well lets look at this from the biochemical perspective – did we change these graphs? Alright, so this is wind gate if you will, but done in the water with a bungee cord and in fact it does virtually everything we wanted it to do: the peak power went up, the time to reach peak power actually came back towards the origin so it took less time to ramp up ,if you will at any given moment along this test they are always generating more force. The one thing that this program doesn’t do and it was a question that Mike Bottom asked me six years ago, how do I change the fatigue index?

I don’t know. I don’t know because you will see this is one individual – it is like a fingerprint. The curve mirrors the previous curve and you can pick this out from a distance so very repeatable. Nevertheless, again, if we look at ten seconds down here, pre versus post, at any given point here, even though we haven’t changed the slope of that line, they are generating more force and actually creating more power so –it can be done.

Now here is one of our 12 year olds that was on this program, in water mechanical output, if we looked at the girls over the course of this season – they increased on the average of 28% – that is pretty darn good. The boys on the other hand increased 40% – that is really good. They decreased time to maximal power output, body composition – the question is did they change? Well they didn’t change weight but we saw huge changes in skin fold percent.

Overall comments and things you might have missed. I am running out of time, but there is no doubt if you look at correlations that the older swimmers are faster, not always because the correlation ____ is about .5. it turns out that height somatotype – taller swimmers and swimmers with longer arms are faster. We are specifically interested in the 50 freestyle, we are somewhat interested in the 100 and we really not interested in the 200. So these values are pretty high, .6 and .7 and again, much more so for men than women these values drop off to about .4 and .5 for women.

I am not saying that it is not as important , I am just saying the population that we looked at – that is what we are describing. Muscle mass is important – again – the correlation coefficient is .7, fat mass is not correlation coefficient of .04 – again more so for men than women – this again drops off to about .3 for women. Power per stroke is essential .9, this is huge for men, .5 for women and something we didn’t anticipate, but we think is pretty important for at least the sprint swimmers – correlation between their sprint kick velocity and their sprint time is .7, that is a lot higher than what has been recorded in the past.

Now again I go back to Mike Bottom. I was at a camp over at Kenyon this summer and I think the first thing he said is , if you want to be a better sprinter, learn to be a better kicker. I think this leads us to conclude that as well, be careful with the word strength training, dry land training and power training; three different things.

Strength training from my perspective may assist in terms of joint mobility, injury prevention and things like that – it will not necessarily show up in terms of improvement in performance. Power on the other hand is another thing. You can do it – we didn’t look at dry land power training – we looked at in the water power training and our conclusion is that it is effective and it works.

Conclusions – we just went through these things: there is strength and swim velocity, there is shoulder health and joint stability. Power per stroke is probably the critical factor in sprint swim velocity. Swimmers can be trained to increase power and power per stroke and reduce the time to peak force by paying attention to tempo and distance per stroke while you are training them on these things.

Age related differences such as ——— may be appropriate at age 14 in girls and age 15 for boys, otherwise I wouldn’t worry about it. Before that there is probably no basis for doing it. We started there and we are going to end there.

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