Wisconsin Public Television University Place  James Reardon, "The Physics of Yoga"  March 31, 2011 UP575    cc >> James Reardon: All right, good evening, everybody. Thanks a lot for coming here to Chamberlain Hall at the University of Wisconsin campus, Madison, Wisconsin. We are here tonight for a presentation on the Physics of Yoga. So, my name is Jim Reardon and in addition to being a physicist here at the UW, I am a student of yoga. I studied with Roger Eischens at Mound Street Yoga here in town. And he studied in India, and I learned quite a lot from studying with him. I'm not claiming to be a yoga teacher tonight, but I would like to try to unpack some mysteries of yoga that might not really be part of yoga. But merely problem with communication. I know that when I studied yoga, there were some words that yoga teachers tended to use that I didn't really know what they meant. And there are several of those that I would like to write down here. 

They would say things like balance.  They would insist that my yoga pose have integrity.  They would talk about in order to achieve integrity in the pose, they would ask that I do work within the pose.  And then finally, the most mysterious of all, they would ask me to get into a position which I was told was called side warrior, which would be something like this. Then I was told all right, now press your feet into the floor. I didn't know what they meant. I still am not quite sure that I know what they mean. But, what I have brought here today, the things I was standing on are called force plates and we will be able to measure the forces that the human body has exerted upon it by the ground, during the course of this lecture. We'll be able to measure, to quantify the forces involved in yoga poses. So hopefully we'll be able to give some meaning, some physics meaning to balance, integrity of the pose, work within the pose and the especially mysterious press your feet into the floor. 

 Now that's just my personal list. Now, if you have things that you've been told during yoga class that you haven't really had explained properly, maybe you can bring them up tonight and we can try to figure out what the yoga teacher must have meant by mysterious phrases that are used. All right. So here we are in Chamberlain Hall, we have a bunch of props. The first word that I'm going need to define here, the first physics word is force. It turns out that it's actually very hard to define that word force. So I'm lucky that everybody, I hope, already knows what a force feels like. If somebody comes up and exerts a force on you, you know that someone is exerting a force on you. Can I have a volunteer come down from the audience and we'll see? All right. Thanks a lot for coming down. 

So my name is Jim. What's your name? >> Chloe. >> Face the camera, Chloe, all right. So, we are going to do a test to see if Chloe knows when someone exerts a force on her. Are you ready? >> Uh-huh. >> Close your eyes and then if you feel someone exerting a force on you, if you feel a new force being exerted on you, raise your left hand, all right? We are going to start. At any time after now, a force could be exerted, but don't do anything until you feel a force and when you do, raise your left hand. All right. So a force is just a push. You can open your eyes. 

Everybody knows that, right? So a force is just like a push. Let's do that one more time, just to make sure, all right? Close your eyes, ok? All right. So here we go. Ready? All right. So, did you feel a force? Yeah, when I say push, I could mean pull. Push and pull are both types of forces. It doesn't matter the direction but you know automatically when someone exerts a force on you. Great. Thanks a lot, Chloe. Go back and sit down again. 

Physics of yoga. Yoga is all about forces but yoga teachers tend to use that word in a slightly unusual way. I'll draw your attention to this bowling ball here. So, what are the forces that are currently acting upon this bowling ball? Well, if you can see the bowling ball is hanging from this wire. We know, we who have gone bowling, bowling balls have some weight. So I'm going to represent the force of gravity by this arrow. Now the first thing that I want you to take away from this lecture is that whether or not you learn anything here tonight you are already experts in physics because physics is the study of motion, and everyone here already knows how to move. After all, you got here tonight. So, you are already an expert in motion. You already know how to manipulate forces, to get where you want to go. 

What I hope to teach you tonight is the language of arrows. Are there any other forces acting on this bowling ball? There's the force of gravity pointed downwards. Is there any other force acting on the bowling ball? Yeah. >> Tension. >> So, which direction does the tension force act? >> Upward. >> Upwards, that's the tension in the wire up here. That's exactly right. I'm going to represent the upward force of the wire with this arrow going up like this. And so the rule of physics is that if an object is not moving, then those arrows have to add up to nothing. And when I say add up arrows, I mean head to tail, so that means, let me take my arrows off, to add up these two arrows I would put them head to tail would be like this. 

So these two forces add up to zero. And that has to be the case for any object which is not moving. Now we could go further with this language of arrows. If you study yoga deeply enough you'll eventually want to learn a language called Sanskrit in which the most important yoga texts are written. If you want to really dive into physics you'll want to learn the language of math, in which the most important physics texts are written. Sanskrit is a language of great antiquity, being at least 5,000 years old. Math is a language of equal, and perhaps greater antiquity. I don't know if anyone has ever told you that math is a language, but it is. If you take the trouble to learn it just like you take the trouble to learn Sanskrit, you may find that it's a lot easier to understand, in this case, physics. So, there is our bowling ball. 

 Now let's go over here to our yoga master.  Here is a cut out of a person in --, also known as Side Warrior Pose. No, this is, I'm sorry, this is Extended Triangle Pose. Extended Triangle Pose, my mistake. So, you know how to do this. Has anyone ever done this particular pose before in yoga class? So, it's not a very hard pose. It does share with all the yoga poses the fact that you should get into it and stay there for a little while. And if you stay there for a little while, that means that the forces upon you have to add up to nothing. So what are the forces that act upon you when you are on this pose? Well, there's the force of gravity, just like the bowling ball that points downward. And then there's a force on one leg that points upwards, put this one over here. 

 And then you know you are bearing some weight on the other leg, too, so that has to have an arrow representing an upwards force on that. And then I need one more arrow because in this pose you are resting your hand lightly on the floor. So I need a fourth arrow to represent the force upwards that the floor is exerting on your hand. And so if you want to stay in this pose, those arrows all have to add up to zero. Now, do you have any control over this arrow? The mass arrow. Is there anything you can do about the length of that arrow? The length of this arrow is the force of gravity upon you. That's equal to your weight. So there's nothing you can do about that. But these arrows, maybe there is something. So what I would like to do, I would like to introduce you to our force plates here. 

I need a volunteer to come down and stand on these force plates. These force plates measure force, so they'll measure the arrows that are pushing upwards on your feet. So who can I get to come down to volunteer to stand on the force plates? All right. Yeah. You could come down from in back, I will set up the force plates so you can see their readout.  All right, great. What's your name? >> Phil. >> All right. Go ahead and face the audience Phil. Are you a student here at the university? >> Graduate student, yes. 

>> Have you ever studied yoga before? >> No. >> Great, here is your first lesson then. The first thing I want you to do is stand on this plate right here. This is plate number one. Stand on it, you might want to face the screen there. So, what I'm going to do, I'm going to start the force plate. Hop off it for a second so people can see. All right. Now go ahead and stand on the force plate. And if you watch the screen, you see there is this thing, and if you step off the force plate again then that line changes. 

So let's take a bigger look at that line. The first thing I'll do is get rid of the old data. And the second thing I'll do is blow up this scale here. So can you see that you stood on that scale at about three seconds, a little bit after, let me blow this up. A little bit after three seconds. You stood on the scale and it had been reading zero. Now, have you ever measured force in Newton's before? >> Yes. >> Where did you learn to do that? >> In physics class. >> I wonder if anybody else knows how to measure force in Newton's. I don't want to make this more confusing than it has to be. 

What I think I'll try, let me see if I can go here, and let's see if we can change the axis values to pounds. I know how to do that. I'll go here and I'll go over there and then I'll go over here. I'll do that. I'll go over here. Because I think we might want to measure things, not in the language of science, which is Newton's, but in the language of everyday people which is pounds. So, you don't mind if I show everybody your weight, do you? >> Go for it. >> What we see is there was a force of about zero pounds and then you stood on it and it was maybe a little bit more than 150 pounds and then you stepped off and it went back to zero, more or less again. So this thing is basically like a fancy bathroom scale. But, we've got two of them. 

So let me call up the other one here. And now what I want you to do in a moment is go ahead and when I give you the signal stand on the first one and step backwards and stand on the other one. So what I want to do is call up a force here. Ok. So, Phil, go ahead, when you are ready. Stand on there. Let me get the start line going. So we see from the graph here that's basically the same as before. Now go ahead, step backwards onto that other one. And we'll see what happens. 

The other one is scale number two. I'll stop now. And we'll get another graph going here. Normal force two, run three. All right. So here we have two graphs, I'm sorry it's a lot of clicking in different windows right now.  And the scale one, which is this one, normal force one--  And the red one is the data that we want to look at right now that shows that you are--  That got to be parallel force two. We want that to be one,  so we will try to tell it to be one again, so we want it to do that. All right. The front scale measured this, it measured your body weight until you took the big step backwards, and the other one which you are now standing on measured your body weight. 

Let's see what happens if you stand on both at once. Okay, go ahead and step off, and I'll start taking data now. Go ahead and stand on the back one. Now go ahead and take a step forward, and stand on both of them at the same time, and balance there. So now we have some serious wiggles going on. Push forward so you get onto the front one, stand there. And then stop again. And stop, step off again. All right. So let's try to figure out what those things on the screen mean. 

So, it started out, we need a laser pointer. I'm going to have to go back and get a laser pointer from back here.  All right. So, you were standing on one scale, which one are we looking at? Let me get the extraneous data off, we don't need that anymore.  All right. You were standing on scale two, which is the bottom one here. And then you took a step forward so that you landed on the front scale, this time in the middle your weight was equally on both, more or less. And then you took another step forward and ended up on the front scale up here. And all your weight was on that. All right. 

Does that make sense? >> Yes. >> All right. We'll try to do something-- You can do this at home with bathroom scales if you wanted. Let's see if your bathroom scales can do this! What we also have here is what we call the parallel force, so these scales measure not just the up and down force but also the side to side force. Let's see what that looks like. So if I took the side to side force from one, I'll put that here. And the side to side force from two and I'll put that down there and let's see if we can try to figure that out. So, they're in this part, at the beginning, when you are just standing on one scale, neither of the side to side forces is anything. And at the end when you are only standing on scale number one, the side to side forces are also zero. But in the middle they're not. 

So in the middle the force that you are exerting on, well, what leg is this, this is scale number one, this is your front leg, is in the opposite direction than the force on your rear leg. In other words, this line here is above zero, and this line here is below zero. And that turns out to be a very interesting thing for yoga. All right. So, do you want to try some yoga? >> Sure. >> Okay, so let's see what happens. Now I'm going to ask you to stand on both plates again. All right. We have a live recording going on of everything, let me remove some data so it's more clear.  All right. 

Looks like data studio has beaten me and stopped itself so we have to start over again. All right. So you are now standing on a plate more or less symmetrically. Face the audience perfectly symmetrically. You're not bending to the left, not bending to the right but you're standing straight up. The question is, which direction should we put the arrows that are coming upwards from the ground? So do you mind if we pin some arrows to you? You wouldn't mind. >> Go ahead. >> I do happen to have some arrows over here. Just take them off old BKS.  All right. 

So, here is one arrow that we are going to use to represent your weight. You mind if we see if this velcro sticks to your sweater? >> Sure. >> It doesn't. You'll have to hold that somewhere. A little bit lower down. We'll get into where the center of mass is momentarily, so that's the force of gravity. It has to be balanced by something, it's balanced by the force that the ground is pushing up on you with, so there have to be two arrows down here somewhere, so I'll start with this foot. So we know there's got to be an upward force to balance the downward force of gravity, and the force plate tells me there has to be a sideways force, which way does this arrow go? That's the sideways force that the ground is exerting on Phil. So how many people say the arrow should go this way? How many say the arrow should go that way? All right. Well, it looks like we have some good physicists in the audience, that's right. 

The arrow does, in fact, point inwards like this. Now, what would happen if it didn't? What would be an example of a surface that you can't have an arrow do anything other than go up? In other words, there's no friction because what we are talking about after all is the force of friction. Could you stand like this on ice? >> No. >> You couldn't? I think we still have some ice on the lake, you might want to go out and try. And that's the secret that we are going to get to over and over again here. You could stand like this on ice but you would have to do something with your muscles. It wouldn't change the shape that you have right now, but it would feel completely different because you can't rely on the force of friction to keep your leg from sliding out sideways the way it would on ice. However, you could, by tensing your abductors, by tensing some muscles in your legs, you could keep it from happening. Why don't you try? Let's see what happens? I'll go ahead and take this back. Let's see, now what would it feel like if you wanted to stand on ice? What would you have to do? >> Squeeze inward. 

>> Yeah, you personally would have to squeeze your legs together instead of relying on the ground to push you. Let's see if you can do that. So I'm going to start, we are still going with the data here. Go ahead and we're looking at this one here. We're looking at the one with the parallel forces which is, let me get rid of that, and let me get rid of this.  All right. We'll zoom out on there so we have a parallel force it looks like of about 18 pounds in each direction.  So we are still going, Phil, when you are ready. Try to squeeze, imagine you're standing on ice, squeeze your legs together, can you make the sideways component of the force go to zero? Now, if I allowed you to turn around and look, it would be easy. And in yoga, a lot of this is imagination. 

So can you just imagine that you are standing on ice? Can you imagine you are not squeezing your legs as tightly together as you could, but you are just imagining that you are standing on ice. So, now I think you'll be able to see here that he's doing a pretty good job, he's still got a little bit of force, but it's a lot smaller than it was. That's brilliant. So if you can see, I don't know if you can see, but that force is very close within a pound or two of zero. All right. You've slacked off a little bit. There you go. There you go. That's back really close to zero. So, you could stand on ice in that position. 

Is it tiring? >> Yeah. >> It is tiring. It works those muscles. You didn't pump any iron, you didn't go for a run or anything, you just stood there. But yet if you do the right things you can really get a good workout. Thank you, Phil, for staying up here for such a long time. Phil, a university student who now knows a little bit about yoga. Let's see what else we can do with these force plates. Let's see what happens if we get someone who is actually practiced in yoga to come up. So, do we have anyone here who has actually studied yoga before? All right. 

Chloe, you have, haven't you? >> A little bit. >> A little bit. Well, let's see what happens. So this time, are you familiar with that phrase work within the pose? >> Yes. >> So let's try that. So what's your favorite pose that you could do on two force plates? >> Probably what you were doing, like what he was doing. I can't think of it. >> It's one of the maybe front warriors or front lunges so you come down with the knee bent. Let's see what happens when you do that. So, let's see, we have there and you can-- >> This? >> Yep, so let me get-- Step off for a second. 

Wwhat I'm going to do is take this stuff off the screen. Let's see, I guess the easiest way for you to see what you're doing is stand the way that you are, yeah, so let's get run five off here.  And we're looking--  There's two questions that we want answer. What happens to the normal force, in other words, when you go into that pose, how is your weight distributed? Do you have more weight on your front leg or do you have more weight on your back leg. And then we'll see what happens if you go from just standing and sort of the right shape to standing in the correct yoga technique that you've been taught. We'll see what kind of difference that makes. All right. So, I'm fiddling around, trying to remove all of this old data from here and we'll put the normal force down there. Oh, look, it did something, interesting. And then we'll put the other normal force down there. 

 All right. So, when you are ready, go ahead and step on the scale. And just hang out there in a comfortable pose for a moment while I get rid of all this stuff so it's easier to see what's going on.  All right. So that's you right now. With a parallel force.  And this is statistics. How did that happen? Computers. Oh, that's what happened. All right. 

So get rid of that. I'll get rid of this. All right. And there we are with the normal force, and I didn't want that. I said normal. I told you normal force. Fascinating.  I'm sorry that physics, there is a certain amount of messing about with physics and this type, usually computers have something to do with it. I have to start all over again. You can stay on, I think I have managed to arm wrestle this computer into submission. 

 All right. So there is the parallel forces. And the thing doesn't like it when I take that one away. That's just too bad. All right. We'll have to make another graph. So we have the parallel forces going fine.  Okay, I think we've got it going there. So what we are seeing here on the graph number four, this one is, which weight do you have, which leg do you have more weight on? So you already know a lot about physics. Yes. 

So you know if you come down and lean like that, you get into the front warrior pose that you have more weight on the front leg and less weight on the back leg so we can see there is twice as much weight on the front leg, near 100 pounds as the back leg, down closer to 50. Meanwhile you see the parallel force on top, then on the front leg you've got about 20 pounds going backwards, and on the back leg, you have about 20 pounds going forwards. All right. Now, what happens when you work within the pose? >> Stabilize yourself. >> Exactly. That's exactly, uh-huh. Yep. So, I'm going to stop distracting you. Do what you have to do. You might find it interesting to look there. 

>> Okay.  So right now we learn a couple of things. You could not do what you are doing now on ice. >> No, I would do the splits. >> So you would do the splits, exactly. That's very important. I thought for a number of years when my yoga teacher was telling me to force my feet into the ground, to press my feet into the floor that what I ought to do is press them together like I would have to do in order to stand on ice and I now know, because I brought my yoga teacher in here to do it on the force plates, that that's not true.  Now, meanwhile, if you do that again, you come back into the neutral pose, and the weight goes-- That's the bottom graph. It shows you are almost equal weight on the front and on the back, there is no real front and back at this point. Now if you come down into the warrior pose, yeah, more weight goes into the front leg. 

What happens if you try to drive your back leg into the floor, to press down on it? So it looks like you can. Now, were you really pressing straight down on your back leg without moving anything else? Let's see you do it again. Or did you have to lean over a little bit backwards? Oh, ok. See what you can do without changing your shape. What work can you do within the pose? And yeah, feel free to watch.  >> I'm trying to dig my heel into it. >> Whatever you feel it takes to try to drive, only you cannot actually lean backwards or move backwards or put both arms backwards like this. Let's just make sure that everyone understands what happens if you do those things. If you are standing like that, and bring both arms like that backwards, you can actually-- It's slipping? Oh, no, okay. We better bring it a little bit closer. 

 >> Both arms back? >> Uh-huh.  All right. So we have, what is it? It's reversed, actually. So let's make sure we are clear which one is the front one. If you lean all the way forward onto the frong leg, so the orange is the front one. Are you capable of keeping that front leg bent at 90 degrees, say, like you are in warrior pose? Can you get an equal amount of weight onto the back leg by, say, moving your arms back or leaning backwards? It looks like you just about can. >> It's hard. >> It's hard to do that. Yeah. All right. 

So what did we learn? There is a point in the middle where you were bringing your legs together and able to make the parallel force go to zero, so you were able, you could do that pose on ice if you wanted to, but that's not part of your practice because when you are trying to do the practice properly, then the force was quite different. All right, splendid. Thanks a lot for helping us out with that. >> No problem.  >> All right. So, there is two words in physics that we have to use to talk about what one does in yoga. So I'll write those two words here.  I'm going to draw a line like this. So this is the yoga part.  And here I'm going to try to translate the yoga part into the physics language. 

 The first physics word that I need to use to explain what my yoga teachers are telling me is that one, equilibrium. And we have already covered that. That means that all the arrows--  Add up to zero.  What happens if all the arrows don't add up to zero? Well, what would be an example of an object that just had one force on it? Yeah, Phil? >> Falling bowling ball. >> A balling bowling ball. That's right. If I were to cut this wire, that would remove the tension force that is pulling up, and all that would be left is the gravitational force, the arrow pointing downwards. And since there's only one arrow, the resultant arrow would be pointing downwards and the resultant motion would be a downwards fall. So, if you don't want to fall down, you have to make sure all your arrows add up to zero and human beings are very good at that, as long as it's not bar time. You rarely see adults falling over and that means they are maintaining equilibrium. 

But the other word that we have to use if we want to say what is yoga, is stability.  That's a very important physics concept which is also a very important yoga concept. Let me quantify stability. I need another volunteer from the audience. All right, Phil. Thanks a lot for coming down. Do you have good balance? >> I think so, yes. >> All right. Let's find out. So, what I want you to do is to stand on, let's say, force plate number one. 

It doesn't matter, you can go ahead and stand right now. And what I'm going to do is put a graph on of the parallel force--  On that, which is actually not started yet. So, go ahead and start taking data right now. Parallel force run number ten, scale number one. All right. So you're standing around, not doing anything, but the parallel force still has some fluctuations in it. You can, I suppose, turn and face me and maybe see the fluctuations over there on the screen. All right. Let me zoom out a little bit, zoom in a little bit I mean so that you can see better. And I want to see what happens to those fluctuations if you now stand on one foot. 

So, go ahead and keep your balance as best you can. Ok. You notice that it's harder to keep your balance exactly and you have to wobble around, or you do wobble around a little bit more. All right. But you are pretty stable, you are pretty good, you are balancing successfully on one foot. It's been 15 or 20 seconds now, that's very good. Are you ready for another challenge to your balance? You are in front of a bunch of people, it could be tough, all right, because I'm going to ask you to close your eyes and it's now 75 seconds, all right? So close your eyes, that's it, come on, I know you can do it. You're doing great. It's been 10 seconds now. 75 to 85 seconds. 

For the last challenge, the most difficult balance trick of all, all right.  I want you to close your eyes and stand up on your tiptoes. Close your eyes. No, you have to do it on one foot, though. >> I have to get started, though. >> All right. It's now 100 seconds. You are doing great. Keep it as long as you can. All right. 

Excellent. From 100 to 110. Now let's see how you did. So this is the trace of your, of you standing on one foot, two feet, two feet then one foot then one foot eyes closed and then finally one foot eyes closed and on tiptoes.  So, this is, from 30 to 40, that is the time from 30 to 40 seconds when you were balanced on two feet. So let's see if we can get a standard deviation for that.  If you don't know what standard deviation means, then it's just the size of the fluctuations, it's the width of that line, the width of that hash, if you will. So, let's see if we can get a standard deviation out of this. It's one of these things, is it this one? No. Is it this one? I don't want that one. 

Is it this one? No. It's what? >> Go to the arrow on the side of the sum button. >> Standard deviation is what we want. So the standard deviation of that was .03 pounds. So that's a quantification of your balance. .03 pounds. So now for this part here--  All right. So, is this automatically tracking it when I move? 4 and 20, all right. Then we'll go over here to the last one. So for this part you are doing something really hard, you are trying to balance on one foot, on tip toe with your eyes closed, so the standard deviation is now a lot larger, 3.35. 

So how does that compare to .03? So that's about 100 times, yeah. So your balance is 100 times better when you are standing on two feet with your eyes open than when you are balancing on tiptoes with your eyes closed. We have some intermediate values from 75 to 85. So that would be about like here. So that was the, just one foot eyes closed. All right. So here for this part we have a standard deviation of 16, so how is that? That's five times worse than the first case, but it's a lot better than the second. That's about 20 times better than the second. All right. And then let's see, before that the one foot eyes open, I think that was here. 

And so it seems like you must have pretty good balance because there wasn't much difference between-- Let's make sure that's true. Let's do this over again. >> Ok. >> One more time. You know what I want to you do, so let's do it more quickly. Don't get on just yet.  So, we'll take data, all right? Go ahead and stand on it. >> Two feet? >> Uh-huh, two feet. Let me get the graph up. This is run 11, parallel force one. 

So there you are. Stand on one leg, now. That's at 20 seconds. We'll hold you there for 10 seconds until we'll say 31. Now when I give the signal, close your eyes. Ready, and now, at 35 seconds you close your eyes. That's fine. But we'll count it as a fluctuation. All right. And we'll see five seconds, go on the tip toe, right now. 

At 50 seconds. All right. So, let's see if we get the same answer for the statistics out of this. So, at the beginning, two feet, you stand on it that's here, we'll look at two feet from there, standard deviation, .03 again. That's the same as we got the first time. So maybe I should believe that. Then you stood on one leg, that happened at 21 seconds. So, we'll look at that from 21 to about 30. And we got the same answer. Look at that. 

Its .03 pounds again. So you really do have just as good balance, it looks like, on one leg as two. That's very rare. Do you practice? >> No. >> And then from 35 onwards, then that was the one, that was what? One leg with eyes closed, all right? So we had some fluctuation right there and obviously, big fluctuation, and we got .15 the first time, .12 the second time. And then at 50 or so, a little before 50, that's when you try to go on the tiptoes and that's really hard to do, not many people can do that at all, so we have a standard deviation that's about the same. So if I click on everything there, we get a little better that time, but 1.9, that's still a lot harder. Thanks a lot, Phil. You can go sit down again.  So what we can measure here in the physics lab that is important for yoga is, let me get an arrow here again. 

So if you are standing on a force plate, you have gravity going downwards. You have the force that the force plate exerts on you going upwards. But you, being a human being and not being a block of stone or something are not capable of exerting a constant force. So this arrow is constantly jiggling around. And what we were measuring there on the screen was the side to side motion of this arrow. So when anybody stands, no one, no one is capable of having a completely constant force. Everybody wobbles a little bit. And what we can measure and quantify is the amount of that wobble. So, someone who has good stability-- Where's my pen? It's over here.  So good stability. 

 I'm going to have to remove-- Anyone want a cheap bowling ball? So it's not real good for bowling, because it has this hook in it. Going once, going twice-- All right. I guess we get to keep our bowling ball then.  So good stability, let me write this slightly more neatly.  So in order to be stable you have to minimize the fluctuation of the ground forces. So that's what the yoga teacher, let's go back to our list here, so I can draw this talk to a close. The balance, when a yoga teacher talks about good balance, I think what they mean is they want you to minimize the fluctuations that are in your ground forces. Now, is it possible that you can do that? And the answer is it turns out to be yes. Now I don't claim to be a yoga teacher, but I think I know how to do that. Now, I'm not sure if we can actually do this live. 

You might not be able to do this live because I am not a yoga teacher. But let's see what happens. So, can we get someone up who wants to see if they can improve their balance in realtime by doing yoga work within the pose? All right. Chloe, thanks a lot for helping us out so much. All right. Now, go ahead and turn and face the cameras a bit. Is this the sort of thing that your yoga teacher says? >> Yeah. >> What sorts of thing does your yoga teacher say? >> She says just to stabilize yourself, and the breathing is so important. That helps the stability, too. >> Mm-hmm, breathing. 

>> Constant breath, constant kind of motion within your body. >> So you are emphasizing your breathing. >> Yep. >> All right. Well, do you mind if we see if that makes a difference? >> Sure. >> So I don't know if it will, and I realize it's an artificial environment for doing yoga, and it's not the most relaxing environment in which to do yoga, but let's go ahead and give it a try. I remember we had a little problem with the force plates being too far apart, we'll move them a little bit closer.  All right. So do you know what pose you want to do for us tonight to practice, to show off the breathing as a method of stabilizing? >> Yeah, I'll just do the same. >> Whatever your favorite is. 

>> Actually, I might do warrior 3, the forward one. >> Really, yeah. You're going to do Warrior 3. That's a one-legged pose. >> I'll try it. >> Wow, okay, great. This will be a great test, because it's not that easy to balance on one leg. >> The first time, really. >> I'm not going to put any data on the screen. So how long would be reasonable to ask you to just stand like that? And then how long would be reasonable to ask you to practice the yoga in that pose? Like 30 seconds for each? >> Sure. 

>> All right. >> Just standing? >> So, I'll ask you to stand for, let's cut it short so you don't get tired. 15 seconds starting right, now. 30 seconds.  So at this point, are you just standing? Or is that the yoga? >> I'm standing in a pose. >> But you are not doing the careful breathing stuff. Perfect, all right. I'm going to ask you to start the breathing stuff in five seconds. So, when you are ready, start it and just hold it as long as you want, at least 15 seconds. Start it now. 

 Okay, all right. So let's see what happened. Now how did you feel? Let me first ask you how you felt doing first, just standing in that position and then second, doing the actual yoga techniques of relaxation through breathing. How did you feel? >> When I was breathing I would focus on a spot in the ground and the breathing was keeping me more stable. >> Did you actually feel more stable? >> I did, yes. >> You did. So let's see. Well, what you feel is very important. And I don't want to claim that the machine is right and that you are not. So what you feel is very important. 

I'm trying to use machines as a way people can communicate with each other. Because I can take this computer and show it to someone else, and have somebody else stand and we can compare it. It's harder, I have found, to communicate feelings. All right. Let's look at what we had here. So you were run number 12, and on force plate number one. We'll look at the parallel force. We get this stuff, and so it was at about 30 seconds that I asked you to just stand there. Well, we don't know, we don't know. So I'm going to take from 30 to about 50. 

Take that 20-second period. And we'll look at the fluctuations, the technical name is the standard deviation. So this is like the wobble. It was .03 standing on one leg in that crazy pose, then your balance is still really good. All right. Now let's see how that compares with the next. Starting at 60, so this, let's see what yoga does. From 60 to, we'll say 80. And then we have the same. All right. 

So let's blow this up on the scale a little bit. So we can make sure that it looks the same to our eyes, too.  Is there any obvious change at 60 seconds, that's when you started doing the yoga. I didn't actually see any change at that point. All right. So, it's inconclusive. It doesn't show a change one way or the other. So, an inconclusive experiment doesn't mean it's a wrong experiment, but we didn't actually learn anything. >> The breathing might be a personal preference, a personal thing. >> So yeah, the only thing I know of that we might do is ask for you to try something more challenging. 

>> Okay. >> Well, I don't know. I don't want to challenge you too much. What would be-- >> I have trouble putting my arms up in that pose, I can try that. Compared to a different arm pose. >> Would you be willing to try that? Great. >> Should I do the first 30 this is what I'm comfortable in and then going up in the second 30? >> What I want to see is what yoga does. So if you can try and stand in a difficult pose without doing the yoga stuff and we'll take data on that, and then allow you to prepare the proper way, the way you are used to, the way that makes you feel more relaxed, and we'll see what that does. Tell me when you're ready. >> Okay, ready. 

>> All right. So that's the, that's the difficult challenge, that is quite a challenging pose.  I'm going to ask you to hold that for 10 more seconds.  Five more seconds. All right. You can go ahead and step off. All right. Now, are you ready to do what you need to do to get into that pose? The way that you are comfortable with? Using the breathing and then let me know when you are there. >> Okay.  All right. 

>> We are at 48 seconds now. Just keep breathing.  Okay, and that's 15 seconds through that. (inaudible) Well, I wonder why. So, we'll get rid of run 12, we don't need that anymore.  So here was the yoga stuff was from 48 to 1:03, that's about there. All right. Again, that's .03 standard deviation, it might be just a limit of resolution of this device. And then the first part was from 10 to about 25. All right, so I can't tell a difference. 

I cannot tell a difference in that pose. Well, we gave it the good scientific try and that's the sort of thing we do here at the yoga research labs we have here, we try to figure out what exactly is happening when people go into yoga, so we can communicate it, because it's difficult sometimes to communicate a feeling you get. All right. Chloe, thank you very much for helping us out. Well, I see that I have just about run out of time with what I wanted to say. Let me just finish by saying that people who have good balance or when the yoga teacher asks you to balance in the pose, you can think of that, you can measure it, if you had a force plate as minimizing the fluctuations in the ground forces. When a yoga teacher says maintain integrity of the pose, that also requires this to happen. I haven't had time to talk about integrity of the pose, but that means that you are not moving in the middle somewhere, that if you stand in that pose that you demonstrated for us, this outstretched pose, if someone were to press sideways on your hand then your whole body would swing around. That would mean that you have integrity, the whole thing is connected. And work within the pose, I think maybe Phil did that a little bit for us, when you are capable of standing in a pose and then tensing a lot of muscles but not actually moving. 

So you can't tell just by looking at someone whether they are standing with their legs relaxed as mine are now, or their legs tensed with all the muscles tensed as much as possible, which is what I'm doing now. The outside form doesn't change very much so you can work within the pose, maintaining your equilibrium without actually moving. By doing good work within the pose you improve your stability. Finally, the last one, press your feet into the floor, apparently that depends on the yoga teacher. I've had people come up on the force plates and when I tell them to do what your yoga teacher tells you to do, to press your feet into the floor, they make the sideways forces go to zero, as if they are standing on ice. Others don't. I conclude there is not one uniform standard among all yoga teachers for what they want you to accomplish in the pose. All right. Well that's all we have time for tonight. I'm Jim Reardon, this has been the physics of yoga. 

Thanks a lot for coming to Chamberlain Hall on this evening to try to do some laboratory work on yoga. Good luck in your practice, good luck in your physics classes.