Biomechanics by Ernie Maglischo (1998)


Published


George Block: It’s a great pleasure for me to welcome our first speaker; Dr. Ernie Maglischo. Ernie has just done everything in the sport of swimming. He’s coached age groups, he’s coached Club, he’s coached Division II, he’s coached Division I, he’s coached Internationally. And, even more remarkable is he’s had success at every level. He’s produced excellence at every level. And just like Doc Councilman, he is the practitioner researcher; by being the coach researcher. He has followed Doc’s shoes in writing great text books: Swimming Faster, Swimming Even Faster, after today he can write Swimming More Even Faster. And, Ernie has also followed Doc’s legacy in producing both cutting edge and controversial research and challenging our assumptions and our beliefs. And, making us reconsider what we’re seeing and what we’re thinking. Making us perhaps a little bit uncomfortable as we sit and listen to his new ideas and his new observations. He also comes to us with truth. And, it’s a great way to start a clinic to be challenged intellectually, to be put on the cutting edge of the sport. And, I welcome and thank Ernie for starting us off this year.

 

Ernie: Well, thanks for that introduction, George. I appreciate what George said. I.. I have size twelve and one half feet, your arches fall as you get older, and my feet have gone_ well, let’s see I’ve_ my height has dropped two inches, and my feet have gotten two inches longer. But, they don’t nearly fill Doc Councilman’s shoes.  Not at all. But, I appreciate what George said.

 

Today I want to talk about stroke mechanics. Three years ago, John Leonard asked me come to this convention and try to make some sense of the controversy that was going on about lift propulsion versus drag propulsion. Now, when I talk about drag propulsion, I’m talking about what we would call good drag. That is when you push back against the water, the resistance of the drag of the water pushes you forward. As opposed to the bad drag, the drag that holds you back. And, at the time I was very happy to do that. Because I had become disenchanted with the Bernoulli theorem. I just didn’t feel that the lift produced and where it had been described with Bernoulli was capable of .. of really propelling swimmers. I’m going to turn the lights down now so we can see a little better. For a quick review of the Bernoulli theorem: the idea is that as you move your hands through the water the water that’s passing underneath the hands gets slowed down and the pressure increases underneath the hand and the water that’s traveling over the top of the hand is sped up. And, so the pressure on the knuckle side becomes less and when you have the high pressure area moving towards the low pressure area, you get a propulsive thrust. And that propulsive thrust is due to the combination of the lift force and the drag force. The drag force is always opposite the direction that your limbs are moving. So, in this case the hands were moving back and in,  so the drag force is forward and out and the lift force is  always perpendicular to the drag force. And, then the combination of these two can produce a propulsive force. Well that all seemed reasonable, and it was supported by some things that we saw with stroke patterns. Where swimmers were making a lot of in and out and down and up movements with their arms. And, that the pattern had very little backward motion to it. And, I don’t think anybody jumped on that band wagon any harder than I did about lift propulsion. So, this talk today is going to be my mea culpa. And, I think I’ve been wrong, and I’ve provided you with a lot of misinformation over the years. And, I want to try and correct that today.  That’s why I asked John if I could do this talk.

 

Now, a little later on I came along and because I was disenchanted with the Bernoulli theorem, I tried to come up with another idea for propulsion. And, I want back to Newton’s third law of motion, that if your pushing water backward you’ll go forward. But, I still couldn’t let go of the sculling like motions that I thought swimmers were making. The in and out and down and up movements. And, so the way I described that was instead of being worried about Bernoulli and the water flowing the over the top and underneath the hand, just be concerned with the water flowing underneath the hand and that the hand is pitched as in this case, it’s pitched in, as the water flows from the thumb side toward the little finger side. It will be given a backward displacement. It would be pushed back for that short distance, and that would produce a reaction that would push the swimmer forward. And, so that was the way I was describing propulsion at that time.

 

It took an article by Brent Rushall and some others that maybe many of you have read. An article that was reprinted in the Journal of Swimming Research about lift versus drag dominated propulsion. It took that article to really shake me loose. Because I was still thinking lift, I couldn’t let go of lift. But, I now believe that propulsion is drag dominated. And, I want to show you how I came to that belief. And, that the sculling movements that I have been teaching, I think are incorrect. And, I want to apologize for that here and then go on and try to describe what I think some of the swimmers are doing. Now to take you through my thought process, we’ll start out with the roles of lift and drag in swimming propulsion. And, in this case we have a typical side view stroke pattern of the freestyle. And, it could be diagramed from this point where the hand is just finishing the stroke. Since the hand is pushing back and up at that point, the drag would be in the opposite direction which is down and forward the lift would be perpendicular and the combination would produce a propulsive force. Well, I don’t think there’s any doubt that when you swim through the water you are producing lift and drag forces. So, I want to make that clear, I’m not saying there is no lift. I’m just saying that lift probably plays a minor role in propulsion.

 

But, there is lift, there is drag when you are moving your hands through the water. Where I made the mistake was in drawing the length of these vectors. The direction of the vectors was always easy to determine. The drag was always opposite the direction the hand was moving. The lift was perpendicular. That was very easy. But, then the vectored length tells you the amount of force; the magnitude of the force. And, that’s where the problem was. Because, you could diagram these so that propulsion appeared to be lift dominated, or at least was due to equal proportions of lift and drag just by making the lines .. the length that would bring this propulsive vector out pointing directly forward. Now, there was support for that from work that Schleihauf had done. Which I’ll show you in a minute. Because, in Schleihau’s earlier work it appeared that lift forces were at least equal if not greater than drag forces during swimming.

 

But, before I get to that, let me show you what I mean about the vectors. Now, you can take this same stroke pattern and if I draw the lift vector longer, that and the drag vector shorter, I can still bring it out to propulsion. And, we’d have lift dominated propulsion. Because, the lift force is the greater of the two. And, the propulsive force is a combination of the two. On the other hand, if I draw the drag vector longer, I can come up with the same thing. Come up with propulsion, but in this case we would say it’s drag dominated. Now, that may not seem to be an important point to some of you, but it makes all the difference in the world. Because, if propulsion were lift dominated the sculling movements of the hands would be the propulsive motions. Because the lift force is perpendicular to the direction you are moving. And, so the diagonal movements of your hands and your legs would be the one that produced the propulsion, primarily. On the other hand, if propulsion is drag dominated then you would want the propulsive motions to be as close to backward directly backward as they possibly could be. And, so it does make all the difference in the world.  It’s the difference between paddling and sculling.

 

If propulsion is lift dominated or even if lift played a large role, then sculling motions would be your propulsive motions. If it were drag dominated then the major propulsive movements would be those which are primarily backward. Why I say primarily backward, because I’m going to show you a little bit later that you cannot make a direct backward motion through the water, because it will ruin the continuity of the stroke. But, that doesn’t change the fact that propulsion could be drag dominated.

 

Now, before I go on though, I want to show you some research to also illustrate how difficult this problem is. Now, this is the early research that Schleihauf did in the 1970’s that influenced us tremendously. He took a plaster cast of a swimmers hand and he put it in a water channel at different angels of attack, from zero to ninety degrees. Zero would be with the water flowing from the thumb to the little finger side, and no angel of attack what so ever. And, ninety degrees would be with the palm of the hand facing directing into the water flow. And, then he measured the lift and drag coefficients at each of these angels of attack. And, as you can see at angels twenty, thirty, and forty the lift force is in yellow and at twenty and thirty you’re much greater than the drag forces. And, at forty degrees the lift force is still greater than the drag force. And, at fifty degrees the lift force is almost as great as the drag force. Well, that’s significant because Schleihauf also indicated that the angle of attack swimmers used was generally between about twenty and fifty degrees to the direction of water flow. So, those angels were critical and if the lift forces were greater or at least as great as the drag forces then drawing those vectors the way I did, would be accurate.

 

But, Schleihauf never really tested what he had done. He just took it to be correct. A little later, Jane Cappaert at US Swimming tried to replicate Schleihauf’s study. And, she got very different results. These are printed in a 1992 US Swimming compilation of their research. And, as you can see at every angle of attack the drag force was considerably greater than the lift force. The drag force in brown. And, it was usually at least double if not triple or quadruple the lift forces. So, here you have two studies with very different results. I asked Jane how the results could be so different, and she couldn’t explain. But, if Schleihauf’s original was correct, then we would assume that swimmers were using equal amounts of lift and drag per propulsion. If Cappaert’s data is correct, we would have to assume that it is primarily the drag force that is the propulsive force. Because it’s the greater force available.

 

Now, here’s a comparison of the two, so you can see the difference. Here’s Schleihauf’s on your left, you can see how high the yellow bars are at angels of attack of twenty to fifty degrees. And, here’s Cappaert’s data on your right. Now, I looked through the literature and tried to see what other work had been done, and very little work had been done. It’s been difficult to do this kind of study, first of all nobody knew exactly the size of the hand that Schleihauf used. So, they’re always guessing when they tried to replicate the study with a plaster cast of the hand, they’re always guessing at the size of the hand. So, they felt that could have influenced their results. But, Berger and Hollander from the Netherlands, did a similar study. And, in their conclusions were that fifty percent of the total force resulted from lift. Lord, Troph, and Schleihauf did some work with actual swimmers and one of the conclusions was that the propulsive force was more determined by the drag then by the lift force. And, they did this about twenty years later. And, a fellow named Valiant from Canada, did a study with swimmers also. And, he determined that the drag force was predominate. And, by the way that’s one of the reasons we don’t like to read research, that’s really a mouth full, isn’t it? That last one? My GOD. You have to read that over about ten times to understand what he’s saying. But, essentially the drag force was greater than the lift force.  So, when we have these conflicting results  in the literature, as coaches we always have to either sit on the fence or take a position. And, if we sit on the fence we don’t get anywhere. And, so we have to do some work on our own and try to take a position.

 

Well, why could they get such different results? Well, first of all, you’re filming swimmers with at least two cameras and you have to match the frames. And, you’re taking video tape or earlier sixteen millimeter film, and you’re blowing it up on a screen and you have all this turbulence in the water, and you have very poor contrast. And, then you’re trying to measure something as precise as the angle of attack of the hand. Now, I’ve tried to do that. And, I even knew where I should be looking part of the time, and I still couldn’t find those landmarks on the hand. Generally, you’re trying to mark at least four places on the hand: the wrist, the fingertip, and either side of the hand. And, it’s very very difficult to see those. And, I can remember having some graduate students trying to digitize these. And, I walked in the lab and one of the graduate students was digitizing a knee, and he thought it was the hand. Because it was that difficult to see these films. So, it’s very very difficult to do this correct. In fact, there has been a study where they tried to determine the amount of air and the amount of air was plus or minus nearly twenty five percent. That’s almost fifty percent error you could get in attempting to digitize film. And, do something as precise as determine the angle of attack, which would make a tremendous difference on your calculations of lift and drag forces.  So, that could be one reason.

 

Another reason could be the testing procedure. If you test a plaster cast of a hand in a water channel, you’re going to have a lot more turbulence around the hand because it’s in a very confined space. If you test a plaster cast in a swimming pool, and just put it in swimming pool and move it through the water with some kind of a motor. You’re going to have less turbulence around the hand, because it’s in a larger space. And, that’s going to make a big difference in the lift and drag forces that you calculate. So, it becomes extremely difficult to do this. And, the digitizing process itself can drive you crazy. So, I think that’s probably why you see so many different results in the literature. And, simply because of the problems inherent in this very technical aspect of testing.

 

What I have relied on over the years is a device called a velocity meter. I was lucky enough to get one of these back in the late 1980’s. A friend of mine, David Costill from Ball State University actually put it together. And, then he gave me one. And,  the velocity meter is a device where you have a fishing line on a fishing reel and you attach one end of the reel to a swimmer and the swimmer goes down the pool pulling this fishing line over the reel. And, then mounted just in front of the reel is a generator, so the line’s going over a generator as well. The generator is connected to a computer, which can then determine by how fast the wheel of the generator is spinning, the actual velocity of the swimmer. At the same time, you video tape the swimmer, and you send that video image to the computer where it’s mixed with the output from the generator. And, what you get instantaneously on video is a tracing of the swimmers velocity together with the video of the swimmer. Now, in this case it’s a breast stroke swimmer. And, at any given point and time, this tracing for example, that swimmer is just about ready to start the kick, so actually the tracing would probably be stopped right here. And, this part wouldn’t exist. And, as soon as they started kicking, this line would go up and with each frame you would see the line go up. So, it’s possible then to see in what parts of the stroke the swimmer is propelling him or herself forward and at what part of the stroke they are decelerating. And, by looking at enough of these, then you get to know where you think somebody should be accelerating and where they should be decelerating. And, when they’re decelerating too much, when they’re decelerating too long, when they’re not accelerating enough, and such. And, it’s a quite a good device. And, then the velocity in meters per second is right there, on that axis.

 

The problem with using a velocity meter is that you’re actually measuring the linear velocity of a swimmer, for those of you who will probably jump me about this. You are measuring the linear velocity of the swimmer. Which is not perfectly accurate. The most accurate way of measuring velocity, is to measure the movement of the swimmers center of mass. What we use to call the center of gravity. Because the center of gravity is influenced by the position of the limbs. You raise your arms forward, bring your legs forward, the center of gravity shifts forward. It’s a balance point in your body, the center of your weight. Your arms are back, your legs are back, the center of gravity shifts back. But, when you’re on a velocity meter you just have one point, you either have a rope at the hips, or we put it on their neck. Which we find a little bit easier, and particularly good when you want to get rid of somebody that you’re not happy with. You just tighten up the reel on them. Just kidding.

 

So, knowing at first, when I saw some things I couldn’t explain on the velocity meter, I assumed the machine was at fault. So, what I did was do some measurements of center of mass and the velocity meter; simultaneously. And, this is an example of one of those. And, the center of mass is the red, and the output from the velocity meter is the blue. And, you can see that they match, very closely. They’re not exactly identical, sometimes the center of mass is not the acceleration is not as great as on the velocity meter. As you see right here. And, sometimes it’s greater. As you see here. And, sometimes they’re a little bit out of phase, as you see right here. But, the important thing is when the swimmer’s accelerating they are accelerating. When they are decelerating they are decelerating. And, I think the velocity meter is a reasonably good tool. And, when you consider how quick you can get your results, how quickly they come back to you instantaneously. Versus digitizing the center of mass, which can take all of several hours. It’s a very good tool. So, I came to trust it quite a bit. And, what concerned me, these are going to be difficult to see, was, that when swimmers were making these sculling motions that I was teaching them, they were decelerating. You can see the output from the velocity meter here. And, here’s a swimmer at the catch, and I’m sorry you can’t see this better. But, he’s making his catch and this output from the velocity meter you see right here, was the end of the push of the previous arm. So, he’s making the catch with his right arm, this output, this acceleration is due to his left arm. And, then he goes through the first part of the stroke, which I use to call the in-sweep. Where he brings his arm back and in under his body. And, you can see here that there’s a slight acceleration at the beginning of this, and then he decelerates. And, this is what I was seeing all the time. That when these swimmers were using this sculling motions that I was trying to teach them, that they were decelerating.

 

And, I at first assumed that the tool was not good. The velocity meter was in error. I checked that, it was not in error. I then assumed that maybe they weren’t doing the movements correctly. But, after a while many of them seemed to be doing the movements correctly, but they weren’t working. And, so I had to look for another explanation. Now, this top view shows this swimmer at the catch with his arm nearly straight. The angle at the elbow.. the elbow is flexed approximately forty degrees. There’s the elbow right there where the red arrow is. And it’s flexed approximately forty degrees. And, at the end of the end sweep that elbow is now flexed about seventy-eight degrees. So, what he did here was start out with a fairly straight arm, and establish his catch. And, then he gradually flexed his arm and he swung it across the water in under his body. As you can see right there. His arms moved across the water under his body. And, as a result of that motion, he decelerated. That’s what I use to call the end sweep. And, it caused a deceleration. Well, the reason it caused a deceleration is because he dropped his elbow. There was nothing else he could do. Here was the position of the elbow at the catch, and that’s represented here. And, by the time he completed the end sweep, his elbow had moved backward about that distance and downward slightly. And, this caused him to push down with his forearm as he brought his arm in, his hand in under his body. And, that’s why he was decelerating. Because he was actually pushing down with his forearm, or the classic dropped elbow.

 

You could assume, I think, that it would be possible to scull your hand in without dropping your elbow. And, I can do it up here. But, I’ve never seen anybody be able to do it in the water. The elbow drops. You bring that hand, you start sculling it in out in front of your body somewhere and the elbow will drop. There’s nothing else it can do. The forearm will push down in the water. And, the forearm is very effective in propelling swimmers. And, we’ve paid too much attention the hand, and not enough to the arm, I think. So, whenever I have seen the amount of inward or outward movement of the arm exceed or even be equal to the amount of backward motion, the swimmer decelerates.

 

The backward motion has to predominate. Or the swimmer decelerates. Now, this is exactly what happens with the dropped elbow. You start sliding your hand across and as you slide it across your elbow drops down, and your forearm has an orientation which is down on the water. And, you’re actually pushing down on the water with your forearm.

 

Now this is the same swimmer after we had changed his stroke. And, what he does now, is he makes his catch with his arm already flexed. His arm was flexed nearly ninety degrees when he made the catch. And, then instead of trying to bring his hand under his body out in front he simply brought his arm back to his ribs. And, you can see he got a tremendous propulsive thrust from that. And, that the elbow also moved upward. Not only backward but upward. And, that kept his forearm facing back better. And, made it a better paddle. And, that’s what I think swimmers are doing. I think they are using their hands and their arms as paddles, not propellers. So, I kept seeing this as I started teaching the strokes differently. The swimmers started getting these big accelerations at the places they should get accelerations. Their times improved. Not all of their times improved, because some of them only were able to do it when they were on the velocity meter. They never really got to where they could do it when they were swimming in races.

 

Now, here’s before and after. This is the same swimmer when he was sculling his hand in under his body, and the deceleration. And, when he was not sculling his hand in under his body, and the acceleration. But, you notice his hand is still under his body. And, I said he didn’t scull it in under his body. But, it’s still under his body. How did he do that. He did that by something called shoulder adduction. And, I’ll talk to you about that in a few minutes. But, right now, what I’d like to talk about is, probably the thing that provides the most evidence of sculling or lift propulsion being a dominate force. And, that is the stroke patterns. This is the thing that had me fooled for a long time. When I looked at stroke patterns, like these, where the hand actually came out  of the water ahead of where it went in. And, the pattern had a lot of downward motion, a lot of upward motion, very little backward movement. And, if you saw this pattern from the front you’d see a pattern that had a lot of in and out movement. And, that took me a while to figure out why swimmers would be making patterns like this and still using drag dominated propulsion.

 

Now, here’s a velocity pattern for Alexander Popov. Which is available, I can’t even remember where .. what publication I  got it from, it’s been so long ago. And, then I’ve super-imposed the typical stroke pattern on top here. Now, what I want you to notice is where the propulsion begins and where it finishes. The propulsion begins at the catch, which is about.. right about here. The catch always takes place about a third of the way through the pattern. And, when the pattern starts to become backward. As, long as the hand is moving down and forward, or even straight down, you never see the swimmer accelerating. But, once the pattern starts to become a little bit backward, they start to accelerate. And, the same kind of thing happens in the back here. They continue accelerating until this stroke pattern starts moving straight up and forward. And, it always does. As the swimmers hand passes their leg, the direction of the hand will.. will start moving forward and upward. And, that’s when they begin to decelerate. So, they begin to decelerate before the hand reaches the surface. And, they stop accelerating right at this point, where the hand stops moving backward. So, when you look at this pattern then, what you see is that the major propulsive thrust took place from here to there. During the backward portion of the pattern. That the swimmer decelerated when the hands were moving forward and downward, and they accelerate. Decelerated when the hand was moving forward and upward. But, it was only when it was moving backward as well as some other direction, that they actually accelerated in the stroke.

 

So, contrary to the impression I got when I first started looking at these stroke patterns, there is a considerable amount of backward motion to the pattern. Yeah, the hand comes out of the water ahead of where it went in. But, when the hand goes in the water, for example when the left hand goes in the water the right hand is usually mid-stroke. And, so you get your body moving forward quite a bit and your hand moves forward quite a long distance about this distance right here; simply on the push of the other hand. And, once you begin trying to propel yourself with that hand alone, it’s moving backward as well as in other directions. So, I think I misread these stroke patterns. That the backward motion was a significant propulsive aspect of this.

 

Now, how can you reconcile those kinds of patterns with drag dominated propulsion. Or, do swimmers really scull. And, when I have to define sculling. To me sculling is when you are moving your hands in and out with very little backward movement taking place. There has to be some, but very little backward motion. Or, you’re moving them down and up with very little backward motion taking place. With that definition, good swimmers do not scull. Can you propel yourself forward by sculling. Yes, you can. As long as you have a little bit of backward movement of the water. But, you have to move the water back to go forward. Ya got to move the water back. So, yes you can scull and propel yourself. But, I don’t think that’s the way swimmers do it. They only appear to be doing that because of these patterns.  Patterns that you see from the side and from underneath, with the out and the in movements and the down and the up. OK, now why does it look that way. Well, first of all, that’s the way I figured it out. The shoulder joint moves in a three dimensional circular path.  So, it dictates that your movements have to be circular,  in a three dimensional path. That means they have to be down and up and in and out. You cannot direct your hand to push the water backward in a straight line. Even if you could, it wouldn’t be effective. Because the arms have to go down in the water to make a catch. You gotta get your arm down deep enough to use the entire arm as a paddle. Not only the hand, but the forearm and perhaps even the upper arm, for part of the stroke. It’s got to get deep enough to do that. That accounts for the downward portion. Then it’s got to get up out of the water for the next stroke. And if you were to simply push your hand straight back from the catch, until it was extended, you’d finish with an extended arm a good foot and a half under water. And, then you’d have to drag it up through the water. So, instead, what the swimmer does, is try to finish the propulsive phase of the stroke, the underwater stroke, very near the surface of the water. And, in doing that they combine both backward and upward motion. So, they can have continuity of movement. That is as the arm finishes propulsive phase, it’s ready to come out of the water for the next. And, that is more effective. Now, you can argue that would be more effective to just push straight back, and you would have a good argument. But, then what do you do when you’re finished, with your arm a foot and a half under water. That’s where the problem comes. So, even if you could push directly backward, it would not be the smart thing to do.

 

Why do the hands move from side to side. Because once again, the shoulder joint moves in a three dimensional circular path. And in order to use the arm as an effective paddle, the arm has to move out in the beginning of the stroke, and in through the middle of the stroke, and then out again near the end of the stroke. It has to do that to become an effective paddle and to provide continuity of motion. In looking for an explanation, I went back to one of the old books by Charles Sylvia. And, I’m sure many of you know who he was. And, I remembered him talking about shoulder adduction and how important it was to swimming propulsion. And, I believe now he was right. That shoulder adduction is the preferred propulsive movement that swimmers use in all strokes, in the front half. And, the front half is the most important part of the stroke. Most of the swimmers I’ve coached could do the back half of the stroke fair to excellent. But, the ones who were not very good did the front half of the stroke poor. And, the ones who were pretty good would do the front half of the stroke good, and the ones who were really good could do the front half of the stroke well. So, the front half of the stroke seems to be where most swimmers make their mistakes. The rear half most do a pretty good job in that.

 

So, what is shoulder adduction? What is it exactly? Adduction is the process of moving the arm back in against the body. Adding the arm to the body. Now, in doing that your arm is going to go through an arc. And in the arc that it will go through the hand will move out and back and then in and back. And, it will travel through that arc. And, it has to travel through that arc. That’s  so you can make a good paddle of the entire arm. If you try to direct the arm right down the mid-line of the body, then  you’re going to drop your elbow as you pull. It’s the only way you can keep the arm moving under the mid-line of the body. And, that would be to drop your elbow here as you pull and push down on the water. But, if instead, and this is what you see swimmers doing, you move the arm.. now forget about my forearm and hand, just look at my upper arm from my armpit to my elbow. Move the arm this way, you can direct the water backwards for quite a long distance. And, you put the hand in that and what you get is a pattern where the arm moves out and back and then in and back. And, my hand really doesn’t come under my body until my arm is back near my side. And, that’s something else I noticed with the great swimmers. Most of the swimmers I was teaching sculling movements to wanted to initiated the sculling movement out in front. And, they wanted to get their arm under their body before it ever passed their shoulder. But, if you look at the videos of the great swimmers, the arm never comes in under the body until it passes the shoulder. And, that’s because you’re not sculling with your hand. You’re not moving your hand in and out like this. You’re using your entire arm as a paddle. And, in the first half of that, your arm is going to move out and back like this, where you see my hand is facing out a little bit. And, so if you measure the angle of attack, you’re going to get an angel of attack to the water of about forty or fifty degrees.

 

After the first half of the arc my arm starts to move in, see what happens to my hand. My hand is now facing in. Not because I turned my hand, and sculled it in, but simply because my arm is now moving in. And, so the hand is really just an extension of the arm, I think in swimming. And, you’re not moving it independently at the wrist. When you do, at least my experience is, is you decelerate. It just comes in like this. Now, that inward motion is probably not very propulsive from about here to the final part. So, why would the swimmer do that? To set themselves up for  a better push. So, that the push can be down the mid-line of the body and out toward the hip. There are many excellent world class swimmers who never finished this shoulder adduction motion. They pull to here, and then they push, and they reach world class. But, I think the best ones, finish the abduction and they get what we call a two peak stroke. They get a peak of propulsion here, they decelerate a little bit as their hand comes under their body, and then they get a huge peak again. Because they’re in a great position to finish the push.

 

Here’s a picture of a swimmer doing this shoulder adduction, and you’ll see a front view of this later. But, here he is at the catch position and now he’s mid-way through the pull. And, you can see his arm has not come under his body yet. And, if you tried to bring that hand in under your body, while your arm is moving out to the side you’ll drop your elbow and you’ll slip. And, then as he brings his arm back in toward his ribs, his hand comes in under the mid-line of his body and he’s ready for the push. That’s a shoulder adduction motion. And, I think it’s the primary propulsive movement in all strokes.

 

In the back stroke I think the swimmer starts with a bent arm and simply brings it like this. They don’t scull it up, flexing it. They start with the arm bent. And, if you study these velocity patterns, you see that. You see when the propulsion begins. It’s always when the arm is bent. Butterfly, I think the same thing happens. They catch, only in this case instead of going down for the catch they go out, and then they make their catch, and then they adduct. So, it’s the same adducting motion even in breast stroke. Although, they may not adduct all the way back. Now, by adducting the arm properly you can get the forearm and maybe even the upper arm adding to the propulsive thrust during the pull. At least during the first two thirds of that pull.

 

And, this is a velocity pattern for Fransisco Sanchez, who was short course world champion in the 50 and 100 free styles. Here is the point where his arm is, here was the catch, he’s just a little bit beyond the catch. And, you can see that he will get a peak of propulsion from this pull, which will end as his arm is coming back toward his side. And, then there’ll be a slight deceleration while he makes the transition, and then he’ll do the push. This is the kind of position you see generally with all the great swimmers. Where you can use that entire arm. Another thing that I’ve noticed in watching the videos, is that the swimmers don’t get propulsion until that entire arm is lined up. When the wrist is flexed, like this and it’s not lined up with the forearm, you don’t see good propulsion. I’ve got a video of Kieren Perkins, later, and I’m not sure you’re going to be able to see it. But, if we can see it, you’ll see him going into the water with his hand kind of like a claw. And, then as he’s ready to begin the stroke everything lines up, the hand, the forearm, the upper arm; they all line up. And, I think they make a very very effective paddle.

 

And, in another study by Cappaert, she determined that the forearm can more than double the force of the pull. And, this is by using plaster casts of the hand and forearm. Now, several people have tried to do this. Schleihauf initially tried to figure out who much the forearm added to propulsion, and he concluded that it didn’t add very much. But, later studies indicate that the forearm does add quite a bit to the propulsive force. Here it’s at least double, I suspect it’s even more than that. And, I also think the upper arm maybe contributing quite a bit to the propulsive force.

 

Now, I’m going to finish up by talking about the most common misconceptions that we have in swimming. And, I blame myself for, at least in part, for providing these misconceptions. One of these is that the arm flexes gradually during the pull. And, the second is that it extends gradually during the push. What I see with swimmers, is that the arm is flexed at the catch. It may go into the water straight, it may move toward the catch it may start moving toward the catch extended. But, when the catch is made, the arm is flexed. When the propulsive phase of the stroke begins, the arm is flexed. And, that’s one of the big mistakes swimmers make. They try to start the propulsive phase with a nearly extended arm, and then gradually flex it. And, as they gradually flex it or scull it, they lose propulsion. Here again, is Francisco Sanchez and I’ve tried to take some measurements of his elbow flexion. These are two dimensional measurements on video tape, so they are not accurate. To do it accurately I would have to do it for three dimensionally. But, I think you’ll agree that just by looking at it the elbow flexion does not change very much. When he makes his catch, his elbow’s flexed approximately eighty to ninety degrees. Mid way through the pull that has not changed. As he nears the end of the pull, the flexion increases a little bit. And, generally swimmers will, as they bring the arm in under the body, they will adjust a little bit. That is when they will flex a little bit more. And, I think that’s just for positioning for the push. I don’t think it’s adding to the propulsion, just positioning for the push. And, then as he begins the push, the arm is actually extending now. Since it’s only flexed eighty degrees, it actually is extended approximately twenty degrees. And, there is some extension of the arm during the push, but it’s not a great deal of extension, as you’ll see in a minute.

 

Now, during the push phase of the stroke, the swimmer wants to use not only the palm of their hand, but their forearm as a paddle. And, that’s why they don’t want to extend that arm too much. They want to keep that forearm facing back, until the hand is near the surface of the water. Again, we have Sanchez here, and right here as he’s about the middle of the push, his hand has come out from underneath his body and is pushing back and up and out to the side. You can see that the palm and the forearm are lined up beautifully. So, that they are both in position to push water back. As he nears the end of the push the forearm is going to start facing up. There’s no way to keep the forearm facing back. And, so it’s going to start facing up and start pushing water up. And, that’s why the swimmers release the water before their hand leaves the water. Most swimmers, if you look at their videos, you’ll see their fingers collapsing. You’ll see their fingers come apart, or their hand start to turn in sometime after it passes their suit. Sometime between the time it passes the waist band of a man’s suit or the waist of a woman, and back to where the suit ends on the thigh. That’s when they’ll release the water. And, they have to do that. Because if they push the arm completely straight, they push the water up with their forearm near the end of the stroke. And, they push it up. They probably lose more by pushing up with the forearm, then they would gain by pushing back with the hand. Yeah, the hand can be kept in backward facing position, but the forearm is probably causing more damage than the hand can help. So, somewhere at this point, the swimmers start releasing the water. And, when their arms leave the water they will usually still be flexed almost eighty degrees. And, that’s true in free style.

 

In butterfly the swimmer actually will release the water about the same place the freestyler releases, but then they’ll snap the arm straight. But, again if you look at the video carefully, you will see that their fingers have already come apart, and that their hands are turned on their side when they do that final snap straight. Which is really part of the recovery and not part of the push. In back stroke, yes you do push all the way to a straight arm, because you’re on your back, you have to. But, in free style the arm should come out of the water still flexed about the same degree it was flexed during most of the push. This is Kieren Perkins, these are taken from the 1992 Olympic Games, the actual finals of the 1500 meter free style. OK, I’m going to take that back. There’s the entry of the hand. You can see right there the kind of claw effect of the fingers. See how much trouble it is to digitize. See how hard that would be. There’s the arm starting to come together, the wrist is still a little bit flexed. Right there is about the catch, I’d say maybe just a little bit further. There’s the catch. Now, from this point he will simply swing that arm out and back and in against his side. And, the amount of flexion will not change very much at all. The entire arm will move back like one large paddle. And, the only time it will change in flexion will be as it’s coming in under his body. And, I think that is simply to position for the next part of the stroke. OK, there’s about half way. And, the arm is not under the body yet. It never is, until the upper arm passes the shoulder and the direction of the entire arm changes to inward. And, I can’t emphasis this too much, if you lead the stroke with your hand if you try moving, pushing your hand out then pushing your hand in, you’ll be doing it against the movement of the arm. The hand is just an extension of the arm. And, if the arm is moving out, the hand’s moving out. And, if the arm’s moving in the hand is moving in. That’s the way it should be. And, then there’s the push. And, there’s the release. You can see his arm is still flexed at the release.

 

Well, where do we go from here. If we want to resolve this, I’m not sure exactly how. We’re probably going to have to find more sophisticated ways to measure propulsion than we have thus far. We can continue to replicate studies until we’re satisfied what the roles of lift and drag are in propulsion. We’ve tried accelerometers. We’ve tried pressure transducers. They all have problems. They’re difficult to use.  We can’t be sure they’re accurate.

 

What I was going to try and show you with that last slide, which didn’t come out very well is, something that a fellow in Phoenix is doing. He’s trying to model the arm of a swimmer on a computer. Much the way people have done with ships and airplanes and automobiles. Where they try and measure the drag and the forces by simply computer modeling. And, he has this pretty well underway. And, programming in everything he knows about hydrodynamics and movement of fluids through tubes and such. He simply puts that model of the arm there, and he changes the position of it step wise. And, he can continue the lift and drag coefficients on any part of the hand and arm. And, this may help us quite a bit in really understanding propulsion. For example, he’s already told me that according to his calculations the boundary layer separates before the water ever passes over the upper side of the hand and arm. Now, what that means is the water breaks away from the hand before it ever passes over the upper side. And, the boundary layer would have to stay intact over the upper side of the hand and arm for Bernoulli’s theorem to be correct. And, so he doesn’t believe that there is a possibility that Bernoulli’s theorem is adding much to propulsion.

 

So, that might be a way to go in the future. And, I would recommend looking into that. But, otherwise I think you’re just going to have to take my ideas and ideas of other people and consider them. And, make up your own mind, as I have. So, I thank you for listening at such an early hour in the morning.

 

 

 

Answers to Audience Questions:

 

Ernie: What Tim has mentioned is that the ICAR data doesn’t show the standard error of measurement. Which is a serious problem.  But, then I don’t think Schleihauf’s did either.

 

Question:  What is happening in the breast stroke?

 

Ernie: I’m one who tends to believe that the principals of propulsions have to apply to all strokes. And, I concede that it’s possible that breast stroke could be lift dominated. Whereas the other strokes could be drag dominated. I concede that’s possible. But, I don’t think it’s probable. So, what I think the breaststroker is doing is catching the water like a butterflyer and simply pressing back like this and right up like that.

 

Ernie:  His question was how do you get swimmers to adapt  to using the whole arm. And, I’ve been playing around with a forearm paddle, trying to develop one. I think that would be a good idea. The other thing that we have done quite a bit is to use surgical tubing with Plexiglas paddles for the arms. And, then pull against surgical tubing with Plexiglas paddles. I finished coaching before I ever got this paddle developed. But, essentially, it’s a paddle with a hinge right here. Hand paddle forearm paddle with a hinge right here. I’ve got a guy working on it, and he just hasn’t finished it for me to where we can test it.

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