Soderling's Backhand; Video Available?

[airforce1]

USPTA, yes I definitely agree that contentiousness gets old, but when people are constantly attacking your ideas without showing any understanding of them or the principles they involve it becomes impossible to avoid.

so it's not beyond the realm of possibility that a handful of scientists studying an obscure aspect of recreational sport could be incorrect about something.

This site is a good idea, but insulting paying members simply because you're incapable of understanding what they have to say is really quite sad.

And I don't care if Rod Cross is the Dalai Lama, he's wrong. What I'm going to do now is explain why, but since you (John) are immune to reason and have already made up your mind about this issue based on what the guy you like more has said, you might as well stop reading. Even though I've already mentioned the factors involved here, I will mention them again for my own amusement. What the Right Honorable Mr. Cross has failed to take into account is the force that the racket exerts on the hand/s, which is then tranfered to the arm, shoulder, body, and feet. Mr. Cross would be correct if the two men both threw their rackets at the same speed. Since their rackets would no longer be anchored to anything, they would now have the same energy and impart the same amount of force on anything they struck, including a tennis ball.

But this is not the case. The rackets are attached to arms, bodies, etc. The amount of force that these arms are exerting on the racket is obviously significant, since you can imagine if they weren't there the rackets would not only begin to fall to the ground, but also go flying backwards or at least slow down dramatically when struck by a fast moving tennis ball. Tennis elbow is also a manifestation of how much force the elbow absorbs upon contact.

If the (arm and) racket decelerates less upon contact then it is going to impart more velocity upon the tennis ball while it is on the strings, which according to uspta is for about 4 milliseconds.

So each man's swing will be the same speed up to the point of contact, but at contact the heavier man's racket will decelerate less, sending the ball off at a higher velocity than the ball struck by the lighter man. And obviously the heavier man's follow through will also have more velocity than the lighter man's.

This decline in deceleration due to the weight transferred by the additional mass of the heavier man may seem insignificant, but this is the same phenomenon that leads to a heavyweight's punch being that much heavier than a middleweight's (with the same height and measurements), as oliensis mentioned.

excellent post.
This is one of the better threads we have had lately. I look forward to the day that all the factors are accounted for and the excuses about how why it was done a certain way in the past come out. Watch the history channel, as they update their findings weekly based on new understandings and better equipment.

Sorry for cutting the post down some to make it shorter and less contentious. Contrary to what some think, I do make efforts to avoid that type of discourse, just not to the point of backing down and giving up easily when someone is wrong. I'm afraid to ask what my recommendation was unless it was misunderstood that I suggested he should edit all posts.
That was just a suggestion about editing staffs insults towards members who care enough to post and share. No one has to read a post if they think the writer is not sharp.
Insulting your customers is about as crazy as things get.

[johnyandell]

Excellent. Obviously our policy is to repress idiocy and glad you understand and accept that.

[crass_lawner]

Like I said, please start your own blog somewhere else. Or you can create your own thread on Tennisplayer like Bottle, but you're done here other than that. You're not Galelio, sorry to break the news. Since you can't face facts and have nothing other than blather, I may have to break policy and take AF's suggestion.

Sorry I will never question your supreme authority again or express any of my opinions on this site since people who do so are clearly not welcome.

[johnyandell]

Like I said, please start your own blog somewhere else. Or you can create your own thread on Tennisplayer like Bottle, but you're done here other than that. You're not Galelio, sorry to break the news. Since you can't face facts and have nothing other than blather, I may have to break policy and take AF's suggestion.

[crass_lawner]

USPTA, yes I definitely agree that contentiousness gets old, but when people are constantly attacking your ideas without showing any understanding of them or the principles they involve it becomes impossible to avoid.

John's last post:

I'll tell you guys why I am tired of this thread. You have arguably the world's top biomechanist, agreeing with other established biomechanists, as well as some knowledgeable coaches and subscribers who seem to have the understanding of the math involved.

And on the other side, you have some people who are married to their opinions.

So once the debate has been settled it is a waste of my time to continue, because frankly I have a vision of continuing to add more and more to Tennisplayer, not rehashing debates that have been settled.

Just to put one more nail in the coffin here, I emailed my friend Rod Cross, the Australian physics professor, and if you don't know who he is or about his books or how heavy he is in the tennis science community, do some frickin' research.

Here's his quote:

"If a 100 lb male and a 200lb player both swing the same racquet at the
same speed and strike the ball at the same spot on the strings then
the ball speed will be the same. Whoever swings the racquet the
fastest will hit the ball the fastest. In fact a skinny guy might be able to swing a racquet faster than a heavy guy because his arm is much lighter."

If anyone in this thread wants to try to weasel around the facts, why not start on your own personal blog--on some other site please. And stop wasting time and energy here.

Sorry we don't all just simply echo everything that you and some people with degrees think. Maybe the forum would better suit your tastes if we all just typed little nodding emoticons in all our posts. It is possible for people without doctoral degrees to understand the basic laws of physics. There were once scientists who thought that the sun rotated around the earth, that Aryans were the master race, that the earth was cooling in the 1970's, that sick people should be bled, and that DDT and lead were harmless, so it's not beyond the realm of possibility that a handful of scientists studying an obscure aspect of recreational sport could be incorrect about something. If anyone were paying any attention they could tell from the following quote from Brian Gordon:

The torque will over time (angular impulse) causes the body's angular momentum to increase and it can then be transferred through the body to the racquet.

that what I'm saying is more in alignment with what the most knowledgeable person here has said than what you (John) or rosooki have said. I could explain why but it would obviously be a waste of characters. And as far as I know I agree with everything that Oliensis has said, and I don't think I have any problem with anything that uspta said, so who exactly comprises each of these camps you have identified? You and the guy who thinks that the weight of a ball machine has something to do with this discussion?

The problem is John, you don't like to or maybe aren't capable of thinking for yourself, all you do is defer to others. I am sure that this is why people who do think for themselves bother you so much. Not one thing you have said in any of your posts had any analytic content to it whatsoever. All you do is either say "well it appears to me that this is what happening, so obviously that's what's in fact happening" or "well some guy who went to college and read lots of books told me this so obviously that's what's true." This site is a good idea, but insulting paying members simply because you're incapable of understanding what they have to say is really quite sad.

And I don't care if Rod Cross is the Dalai Lama, he's wrong. What I'm going to do now is explain why, but since you (John) are immune to reason and have already made up your mind about this issue based on what the guy you like more has said, you might as well stop reading. Even though I've already mentioned the factors involved here, I will mention them again for my own amusement. What the Right Honorable Mr. Cross has failed to take into account is the force that the racket exerts on the hand/s, which is then tranfered to the arm, shoulder, body, and feet. Mr. Cross would be correct if the two men both threw their rackets at the same speed. Since their rackets would no longer be anchored to anything, they would now have the same energy and impart the same amount of force on anything they struck, including a tennis ball.

But this is not the case. The rackets are attached to arms, bodies, etc. The amount of force that these arms are exerting on the racket is obviously significant, since you can imagine if they weren't there the rackets would not only begin to fall to the ground, but also go flying backwards or at least slow down dramatically when struck by a fast moving tennis ball. Tennis elbow is also a manifestation of how much force the elbow absorbs upon contact.

So we have determined that the arm absorbs some force when the racket is hit by the ball. What does this have to do with body mass and the force with which the ball is struck? Well this goes back to the kinetic chain which Brian Gordon, the USTA site I linked to earlier, and everyone and their mother (excluding John and rosooki) knows about so I won't go into detail. But the end result is that the arm attached to the body with more mass is going to be able to absorb more force from the racket while decelerating less upon contact. If the (arm and) racket decelerates less upon contact then it is going to impart more velocity upon the tennis ball while it is on the strings, which according to uspta is for about 4 milliseconds.

So each man's swing will be the same speed up to the point of contact, but at contact the heavier man's racket will decelerate less, sending the ball off at a higher velocity than the ball struck by the lighter man. And obviously the heavier man's follow through will also have more velocity than the lighter man's.

This decline in deceleration due to the weight transferred by the additional mass of the heavier man may seem insignificant, but this is the same phenomenon that leads to a heavyweight's punch being that much heavier than a middleweight's (with the same height and measurements), as oliensis mentioned. I know many would say that the only reason the heavyweight's punch is harder is because he has more muscles, but although this is not the case, I'm not going to explain why, because I already have in earlier posts.

[johnyandell]

I'll tell you guys why I am tired of this thread. You have arguably the world's top biomechanist, agreeing with other established biomechanists, as well as some knowledgeable coaches and subscribers who seem to have the understanding of the math involved.

And on the other side, you have some people who are married to their opinions.

So once the debate has been settled it is a waste of my time to continue, because frankly I have a vision of continuing to add more and more to Tennisplayer, not rehashing debates that have been settled.

Just to put one more nail in the coffin here, I emailed my friend Rod Cross, the Australian physics professor, and if you don't know who he is or about his books or how heavy he is in the tennis science community, do some frickin' research.

Here's his quote:

"If a 100 lb male and a 200lb player both swing the same racquet at the
same speed and strike the ball at the same spot on the strings then
the ball speed will be the same. Whoever swings the racquet the
fastest will hit the ball the fastest. In fact a skinny guy might be able to swing a racquet faster than a heavy guy because his arm is much lighter."

If anyone in this thread wants to try to weasel around the facts, why not start on your own personal blog--on some other site please. And stop wasting time and energy here.

[oliensis]

After stepping away from the thread for a day or so and thinking about this subject, I wonder whether the concept of getting "weight" (mass) "into" the ball is closely related to how much the racquet decelerates when it strikes the ball.

A racquet on a string moving at a given rate of acceleration would likely decelerate more than a racquet that is firmly connected to a more substantial mass.

Clearly, as you move out on the hitting lever (away from the center around which it is rotating--in tennis, that is roughly the spine), the amount of mass becomes more significant in terms of how it affects the force delivered to the object that's being struck...but this is very tricky stuff.

How come heavyweight boxers can punch harder than middleweights (by and large)? Some of it is longer levers and stronger muscles. But there's more there.

[airforce1]

By the time Soderling is hitting Nadal's second serve (where this started) the 90 MPH second serve has bounced and dropped below 50 MPH, but that's still pretty quick. Just a wall will send the ball back at about 30 MPH. But Soderling was using that return to add about 50 MPH to that shot. Certainly, body weight makes a small contribution to that vector of momentum I was talking about, maybe accounting for even 10 MPH, but I can't imagine more. (I think that badmiton racket would just break. Don't know. But there are limits. I weight rackets with about 4 to 6 oz of lead wire so students can feel the racket head. The ball goes faster, but not 30 MPH. And there is a law of diminishing returns if I continued to take the weight higher because speed slows down.)

But perhaps your point is well taken about returns. On a blocked return, perhaps it is ALMOST a linear kind of body move that is applied to those shots taken on the rise. Incoming speed is a lot more than a normal groundstroke. It's so tough to time that you almost have to move a wall at the ball. But I don't really think that is the case.

Truthfully, I'm a little in over my head here. HELP!

I think we are roughly on the same page here.

[uspta990770809]

Addendum

I'm also overlooking the point I've tried to make in other posts before (but never got anyone interested in contesting), the way the body produces that force on the ball is with pulleys and levers and fulcrums. The fulcrum for the force the body applies is more stable and stronger if the weight is on the front foot and the force is at a 90 degree angle relative to impact (the ball is struck off the right hip/shoulder/foot on a righty THBH). But that's not "leaning into the court". That's just getting the weight forward for a more powerful and efficient transfer of power to the ball through the lever of the racket.

[uspta990770809]

Since the racket is so light, as well as the ball way lighter, we don't have to add much of our body wt to the wt of the racket, to get a pretty big addition (relative).

I know there are those who swing the racket like the post above yours, and there are times I do as well, but there are many shots where that is not the case. Taking the ball on the rise is a good example for me, where the racket becomes more of an extension of my arm and shoulders (like an Agassi 1st serve rtn). I think this is a good example of how this whole thread started on Soderling's ability to get his wt into shots. On charting his matches I was looking for those smoking backhands that were referenced in this thread. The best examples seemed to be serve rtns and taking low, hard shots on the rise; both with shorter, compact, stiffer swings IMO. I think I will look again in slo mo to confirm.

By the time Soderling is hitting Nadal's second serve (where this started) the 90 MPH second serve has bounced and dropped below 50 MPH, but that's still pretty quick. Just a wall will send the ball back at about 30 MPH. But Soderling was using that return to add about 50 MPH to that shot. Certainly, body weight makes a small contribution to that vector of momentum I was talking about, maybe accounting for even 10 MPH, but I can't imagine more. (I think that badmiton racket would just break. Don't know. But there are limits. I weight rackets with about 4 to 6 oz of lead wire so students can feel the racket head. The ball goes faster, but not 30 MPH. And there is a law of diminishing returns if I continued to take the weight higher because speed slows down.)

But perhaps your point is well taken about returns. On a blocked return, perhaps it is ALMOST a linear kind of body move that is applied to those shots taken on the rise. Incoming speed is a lot more than a normal groundstroke. It's so tough to time that you almost have to move a wall at the ball. But I don't really think that is the case.

Truthfully, I'm a little in over my head here. HELP!

[airforce1]

If that tractor is driving along at 5 MPH and the bucket catches something on the end of the bucket, because of the unforgiving nature of steel, the damage would be proportional in some way to the total weight of the tractor. But there is actually no acceleration. On the other hand as the side of the bucket causes the tractor to spin, let's say such that the actual speed of the outside end of the bucket is 3 MPH, the force applied to something that side of the bucket hits would be proportional to the velocity squared, but with a lot less of the mass and momentum of the entire tractor

By the way, there must be a reason I got out of the engineering field and became a tennis pro.

Since the racket is so light, as well as the ball way lighter, we don't have to add much of our body wt to the wt of the racket, to get a pretty big addition (relative).

I know there are those who swing the racket like the post above yours, and there are times I do as well, but there are many shots where that is not the case. Taking the ball on the rise is a good example for me, where the racket becomes more of an extension of my arm and shoulders (like an Agassi 1st serve rtn). I think this is a good example of how this whole thread started on Soderling's ability to get his wt into shots. On charting his matches I was looking for those smoking backhands that were referenced in this thread. The best examples seemed to be serve rtns and taking low, hard shots on the rise; both with shorter, compact, stiffer swings IMO. I think I will look again in slo mo to confirm.

[airforce1]

Contentiousness gets a little old,but this has been a great thread. It's almost as if we need an outside moderator to put each argument up on a board where we could see all the different arguments simultaneously. It seems as if answers are just slightly missing the questions presented, and yet a lot of information is getting laid out. I'm trying to follow along, but it's tough.

When I was in my first basic Dynamics class at Harvey Mudd with Dr. Alford back in 1967, the first thing you had to learn to do was to draw a force diagram. The trick was to include all the forces acting on the body you were concerned with, in this case, the ball. Those forces would be represented by vectors. We were still using slide rules (really!) in those days and now you probably just hit a couple of keys in the appropriate software and the diagram will appear including size and direction in whatever units you would chose.

The diagram of the ball would have a vector for gravity and perhaps one for wind. It would also have one that represented the force it carried from the momentum its movement gave it before impact. But at the moment of impact, the key outside force would be the force vector of the racket at the impact point. Also critical would be what portion of that force vector gave lift and what portion gave forward velocity. Except for gravity and initial up and down movement of the ball, the primary movement of the ball after impact will be in a direction perpendicular to the face of the racket in all three planes. The most powerful shots will be where the momentum vector of the racket head is the same as the directional vector of the string bed. I'm getting a little carried away, but that is it in simple terms. The ball doesn't know how heavy the hitter is or how big the racket is. It only knows, and for only about 4 milliseconds, that it has an incoming velocity and direction and is being influenced by gravity and the force at the little bit of the string bed that it is touching.

You all know what it feels like to hit a "sweet" shot where the ball just takes off effortlessly and you feel tremendous power with little effort. That happened because you lined up the vector of the racket face and the vector of the momentum of the racket head and they went where you wanted the ball to go (or rather a little above that because of gravity)!

I'm going to let someone else take it from there,
don

Don, if I'm understanding you correctly, you are saying that I just as well be using a badmitton stick at the same speed, on the sweetspot, for the same result. I don't think it will work.

If by momentum of the racket, you are taking the weight of the racket into account, then what is being said by some of us, is that some players can add some of their wt to the weight of that racket at that 4 millisecond impact.

[uspta990770809]

For Airforce

If that tractor is driving along at 5 MPH and the bucket catches something on the end of the bucket, because of the unforgiving nature of steel, the damage would be proportional in some way to the total weight of the tractor. But there is actually no acceleration. On the other hand as the side of the bucket causes the tractor to spin, let's say such that the actual speed of the outside end of the bucket is 3 MPH, the force applied to something that side of the bucket hits would be proportional to the velocity squared, but with a lot less of the mass and momentum of the entire tractor

By the way, there must be a reason I got out of the engineering field and became a tennis pro.

[uspta990770809]

More on dynamics and the wrecking ball

Didn't see the post about the wrecking ball before I wrote that, but I really like that.

Sometimes you are trying to teach a student a particular motion and you want them to make that motion in slow motion or at least slower. Usuallly, they end up producing a motion, but not a swing...they stiffen up a little too much. It's always a challenge to get the feeling of swinging the head of the racket head, not just making the motion. I don't have a definition of swing to back this up, but I think it is a lot like that wrecking ball that is on the end of a chain, not a stiff arm. That ball moves, no swings into the target in an arc at the end of the connecting chain, wire, whatever. And we know from math that the end of that string is accellerating as a function of the square of the velocity. This would be true even if the connecting medium was a beam if the beam was being rotated into the target. (of course, the beam would be destroyed along with the target, so that wouldn't be very good for a wrecking machine).

My point is, I want my student to imagine the weight at the center of the stringbed (swingweight??) being swung to and through the ball almost as if the racket was a piece of string; i.e. feel the acceleration through the ball to the target...don't muscle it.

Also, the point is, when the wrecking ball hits the target, it's not the weight of the chain. It's the speed and weight of the wrecking ball (which has a vector at impact by the way!)

[airforce1]

So far there has been the assumption that more mass in a player equals more strength, more backstop, more pop, etc. So we should actually be talking about those things instead of mass. We should be talking about the total quality of the machine instead of just the mass of the machine.

If we are talking only about mass, the only mass that matters is the amount delivered to the ball, not the total amount in the system. We can imagine a robotic tennis arm made of steel with a racket on the end. The arm currently hits the ball just fine at speed x. Doubling the weight of the arm without affecting the speed the robotic arm swings or any other variable will have a linear effect on the ball if the speed didn't slow down do to the heavier weight - the engine will have to be improved to move the heavier mass at the same speed as before.

The arm's mass doesn't matter that much once it has the minimum mass necessary to support the maximum performance of its engine. Increasing the mass after that will only slow it down, since the maximum performance of the engine has been reached. Raising the mass without improving the engine won't be helpful. Conversely, improving the engine without changing the mass will allow a faster swing.

We can imagine a wrecking ball on the end of a crane. The mass of the crane only matters in its effect on the wrecking ball – if any. It is the size and speed of the wrecking ball that actually brings down the building. A given wrecking ball imparts a certain amount of energy per hit on the building, and that's the force that matters. Doubling or tripling the size of the crane won't do anything - if you keep the same size engine in it. No one ever considers whether the crane should be as big as the building to more effectively knock it down. Instead they worry about whether the ball should be bigger or should be swung faster. It is the wrecking ball that matters – if I can swing that very fast with a crane the size of a tonka toy, I certainly will. I leave it to you to decide if swinging the wrecking ball faster or making it more massive will be more efficient in knocking the building down.

Looking at the specs of ball machines, I can’t see any relationship between the weight of the machine and the maximum advertised speed the ball machine serves the balls at. As technology improves, the machines will probably keep getting lighter until they reach the physical limit imposed by the weight of the tennis balls. At which point they would start to move backwards due to recoil.

I’m not suggesting anything is impossible. It may or may not be true that mass matters for a particular player, but it is not a rule. I doubt it is true for me - I'm 6'2" and full of muscles (although I've never smiled and gave anyone a vegemite sandwich), but I have no illusions that doubling my mass would allow me to hit the ball with more power. It would probably make me hit it more weakly. I'm also pretty sure Santoro could dominate me and blow me off the court. If the efficacy of mass depends on the system, it is not a given that more mass is better, and therefore the mass in the body can't be used in any physics calculations - we don't know the relationship of the mass of the body to the effect on the ball well enough to make any sort of equation.

Then there’s always the twilight zone – where Murray’s running shots come from.

Your wrecking ball example is perfect to show how this is "not" the same as in tennis. The ball is only connected by a cable and gets minimal input into the ball.

A over the top, but better example for tennis players who can get their wt into the shot would be a bull dozier that is moving forward, while doing a partial spin with it's skids, then hits something with it's lifting bucket. It's not just the wt of the bucket that is doing the hitting, but the wt of the tractor as well. The hand and arm have the ability to connect to the racket and become apart of it's mass to some extent.

I'm not really debating that it's better to be heavier, because the ball is so light it does not matter so much (which I believe is aligned with JY's point about little girls), but I do think your ability to transfer some of your wt to be part of the racket mass is a skill that helps those 90 lb girls knock the socks off.
I don't think a racket swung by connecting to my hand with a string at 15 mph will hit near as hard as a racket swung at the same speed held in my hand.