jumpusle strokes?

philosoraptor · Jul 6, 2010

http://www.jumpulsetennis.com/
I recently came across this website which tries to teach a stroke where your racquet stays on the ball a tad bit longer....is this fake or is this actually the real deal?
edit: i spelled jumpulse wrong in the title

Memnoch · Jul 6, 2010

Those videos just show a regular ground stroke, the players are simply brushing up the ball for topspin.

ho · Jul 6, 2010

philosoraptor said:
http://www.jumpulsetennis.com/
I recently came across this website which tries to teach a stroke where your racquet stays on the ball a tad bit longer....is this fake or is this actually the real deal?
edit: i spelled jumpulse wrong in the title

keeping the ball on the string longer is not something new, not at all, it's been taught years and years ago, nothing is new to get exited and and call a new exotic name: jumpulse (?).
The author is just an educated man thought that he has something new. As for a tennis player, the author have showed that he has little understanding how to hit a ball that stay longer on the string bed, to start with and prolonged with experience over years and years of using like us.
There is alot of thread that the author need to read over and over on this site to know how to hit a ball which stay longer on the string bed.

SystemicAnomaly · Jul 6, 2010

It has been discussed quite a bit several years ago in this forum. Many were critical of the concept and the proponents' annoying "spamming". John Yandell and Bungallo Bill were highly critical of the concept. BB had his own name for the concept = Dum(b)pulse.

One poster even conducted a poll -- "Should Jumpulse threads be deleted?"

http://tt.tennis-warehouse.com/showthread.php?t=145739

ho said:
keeping the ball on the string longer is not something new, not at all, it's been taught years and years ago, nothing is new to get exited and and call a new exotic name: jumpulse (?)...

There is alot of thread that the author need to read over and over on this site to know how to hit a ball which stay longer on the string bed.

How much longer can you keep the ball on the strings? How is this accomplished?
.

trueba11er · Jul 6, 2010

its totally crap. dont waste your time!

JohnYandell · Jul 6, 2010

In the high speed video we have done over the years it's not debatable that the ball is on the strings around 4 milliseconds on the groundstrokes. It may be that there are microscopic differences based on strings, rackets, swing styles, or divine intervention.

Because this is such a universal factoid, "the duration" that the ball is on the strings does not in my opinion have much or anything to do with what makes a given stroke or shot effective.

ho · Jul 7, 2010

JohnYandell said:
"the duration" that the ball is on the strings does not in my opinion have much or anything to do with what makes a given stroke or shot effective.

dwell time of ball on string, not just dictate the power, but even for spin and directional control.
When ball hit the string, it will be deformed, when it is deformed, it will stay longer on the string bed, that will help greatly directional and spin, not mention that when it is deformed, it will pop out more, add to ball speed.

SystemicAnomaly · Jul 7, 2010

JohnYandell said:
In the high speed video we have done over the years it's not debatable that the ball is on the strings around 4 milliseconds on the groundstrokes. It may be that there are microscopic differences based on strings, rackets, swing styles, or divine intervention.

Because this is such a universal factoid, "the duration" that the ball is on the strings does not in my opinion have much or anything to do with what makes a given stroke or shot effective.

Thanks for confirming my suspicions, John. My thinking was that if there were any variations in the duration of ball/string contact, it would be very small fractions of a ms (hundredths of a ms, or tens of a ms at most). Short of catching the ball on the strings, I had a feeling that there was not going to be much variation on the duration of the contact. Did you perform any high speed study of drop volleys (or stop volleys) and see any differences in contact time?

I recall that physicist, Rod Cross, also spoke of the 4 ms duration. Don't know if he got that figure from his own testing, your high speed studies or from some other source. I'll have to get my hands of Rod's Technical Tennis (or The Physics and Technology of Tennis) to see if he had anything further to say about this duration.

As you have implied, it probably doesn't really make a whole lot of sense to dwell on the contact duration to improve one's effectiveness on a stroke. There are other aspects to work on that make more sense (or that would be more productive).

SystemicAnomaly · Jul 7, 2010

ho said:
dwell time of ball on string, not just dictate the power, but even for spin and directional control.
When ball hit the string, it will be deformed, when it is deformed, it will stay longer on the string bed, that will help greatly directional and spin, not mention that when it is deformed, it will pop out more, add to ball speed.

Nope, not buying this explanation. Consider this.

The ball, at a given pre-contact speed, would tend to compress more when hitting the ground or when contacting a tighter stringbed than when contacting a looser stringbed. With looser a stringbed, the strings would yield (deform) more resulting in somewhat less ball deformation. With a tight string bed, the ball compresses more and, as a result, comes off the strings slower that it would off strings that are somewhat looser. The ball actually loses more energy (and speed) in the form of heat of compression. This is actually the opposite of what you have suggested.

ho · Jul 7, 2010

JohnYandell said:
In the high speed video we have done over the years it's not debatable that the ball is on the strings around 4 milliseconds on the groundstrokes./QUOTE]
ball can stay longer or shorter depend how it is hitted:
1. Hit thru the ball: a head on collision will increase contact time
2. hit hard: it will compressed ball more, the more it is compressed, the more it stay longer on the string as long as we accelerate thru contact.
3. the solid, strong core which support the string play a great role in absorbe ball and keep it longer: stiff racket, stiff string, stiff heavy body (push stroke) will help keep ball stay longer

ho · Jul 7, 2010

SystemicAnomaly said:
With a tight string bed, the ball compresses more and, as a result, comes off the strings slower that it would off strings that are somewhat looser. The ball actually loses more energy (and speed) in the form of heat of compression. This is actually the opposite of what you have suggested.

humm... when ball compress more it will bounce out less?
a looser string will bounce out faster as trampoline effect, sure, and that is correct when you hit with slower speed (and that is not what you wanted) when you hit hard, the stiff string, stiff racket give you more power, due to the fact that the compression of ball by then is much more than and over shadow the trampoline effect.

JohnYandell · Jul 7, 2010

Ho,

Do you have any evidence?

SystemicAnomaly · Jul 7, 2010

ho said:
humm... when ball compress more it will bounce out less?
a looser string will bounce out faster as trampoline effect, sure, and that is correct when you hit with slower speed (and that is not what you wanted) when you hit hard, the stiff string, stiff racket give you more power, due to the fact that the compression of ball by then is much more than and over shadow the trampoline effect.

With looser strings (assuming they are not extremely loose), I believe that more of energy might be stored in the strings than with a tighter stringbed that does not yield as much. Assuming that the strings recover (or start to recover) from their deformation in the 4 ms that the ball is on the strings, (some of) the energy stored in the strings should be transferred back to the ball.

With ball deformation, some energy may be stored in the ball during its compression, but some is also lost in the form of heat, the heat of compression. More ball compression is expected with tighter strings since the stringbed is stiffer and does not yield as much.

We can see losses on other ball collisions as well. When a ball bounces on the court, it loses a significant amount of velocity. On the hard courts of the US Open this can easily be a 30-35% loss - the post bounce (exit) speed is this much slower that its pre-bounce speed.

http://wings.avkids.com/Tennis/Project/speed-03.html

If you are truly more interested in the research as well as the physics of tennis, refer to the 2 books I mentioned in post #8 as well as this page:

http://wings.avkids.com/Tennis/Project/index.html
.

ho · Jul 7, 2010

JohnYandell said:
Ho,

Do you have any evidence?

it's in your common senses.

ho · Jul 7, 2010

SystemicAnomaly said:
More ball compression is expected with tighter strings since the stringbed is stiffer and does not yield as much.

seem like you agree with me.
A luxilon string does not need to string tight, it still has power, because it is stiff. There is a different between tight and stiff.

SystemicAnomaly · Jul 7, 2010

ho said:
seem like you agree with me.
A luxilon string does not need to string tight, it still has power, because it is stiff. There is a different between tight and stiff.

Don't know if a stiff stringbed and a stiff string are exactly the same. Perhaps they are, perhaps not quite the same. I do not agree that greater ball compression results in more power (i.e., higher ball speeds). Just the opposite, it would appear.

ho said:
it's in your common senses.

Common sense is often wrong. The research done by Yandell and others had shown this. Check out the 1 or both of the 2 tennis physics books I've suggested and you will discover how often "common sense" and long-held assumptions have been proven wrong. Quite a few "common sense" myths have been busted by high-speed research and solid science.
.

ho · Jul 7, 2010

SystemicAnomaly said:
Common sense is often wrong.

if it does then it is not common sense.
i think we can rest our case here.
we have clearly understand each other, there is not much to discuss.

theZig · Jul 7, 2010

ho said:
if it does then it is not common sense.
i think we can rest our case here.
we have clearly understand each other, there is not much to discuss.

You have your opinions and we have ours.. Indeed, there is not much to discuss.

SystemicAnomaly · Jul 7, 2010

ho said:
if it does then it is not common sense.
i think we can rest our case here.
we have clearly understand each other, there is not much to discuss.

Often ideas that may be considered to be true by common sense are in fact false.

So you chose "common sense" over science? If that is the case, then perhaps we don't have much to discuss. Note, that the term "common sense" is somewhat vague (is that your intent?). It is often used as another term for intuition. As such, intuition is not always correct.

JohnYandell · Jul 7, 2010

Yes and when I look out over the horizon my common sense tells me the world is in fact flat.

supineAnimation · Jul 7, 2010

JohnYandell said:
Yes and when I look out over the horizon my common sense tells the world is in fact flat.

Don't bother with ho, John. I got into a similar argument with him on another topic and he is dead-set on his theories despite the fact that he doesn't have much in the way of evidence for them.

[d]ragon · Jul 7, 2010

JohnYandell said:
Yes and when I look out over the horizon my common sense tells the world is in fact flat.

Exactly! Surely this is common sense!

SystemicAnomaly · Jul 7, 2010

JohnYandell said:
Yes and when I look out over the horizon my common sense tells me the world is in fact flat.

Good one John.

. Come to think of it, common sense also tells me that the sun, moon and stars all revolve around the Earth.

.

SystemicAnomaly · Jul 8, 2010

"Common sense is neither"
~ unknown source

“Common sense is not so common.”
~ Voltaire

"Common sense breeds common results"
~ unknown source

"Common sense is the collection of prejudices acquired by age eighteen."
~ Albert Einstein

JohnYandell · Jul 8, 2010

The Einstein quote is frightening eh?

corners · Jul 8, 2010

Dwell time can vary by 2-3 milliseconds.

JohnYandell · Jul 8, 2010

Interesting. What is the basis for that statement?

SystemicAnomaly · Jul 8, 2010

corners said:
Dwell time can vary by 2-3 milliseconds.

I'm wondering if your decimal point might be misplaced. Might be more like 0.2-0.3 ms. But that's just a guess on my part. Yandell has hours and hours of high-speed video of string/ball contacts and he has already stated that dwell times don't vary much from 4ms on groundstrokes.

Now it might be possible to change dwell time somewhat with a significant change in string tension, but changing dwell time by altering your stroke while the ball is on the strings seems doubtful since dwell times are about 2 orders of magnitude shorter than human reaction times.

I do wonder how much dwell time can vary as a function of swing speed tho'. John?

.

SystemicAnomaly · Jul 9, 2010

corners said:
Dwell time can vary by 2-3 milliseconds.

I don't currently have access to Technical Tennis (or Rod Cross' other book on tennis physics) but I did poke around the www a bit to see if there was something on dwell time. Apparently, Rod does talk about dwell time in the book, The Physics and Technology of Tennis. He also has sections on string tension and dwell time in his Strings chapter (2) in Technical Tennis:

http://elib.tu-darmstadt.de/tocs/184953693.pdf

search.bn.com/Technical-Tennis/Rod-Cross/e/9780972275934/#TOC

http://www.racquettech.com/store/technical_contents.html

Upon inspection of the table of contents for this book, it would appear that there might be some variation of dwell as a function of string properties (string tension) and force applied. Without access to the actual contents of these books, it's difficult to determine how much variation is possible.

Still, I'll go out on a limb and say that for the very short duration that the ball is on the strings, the stroke cannot really be altered during this contact time to have any effect on dwell time.

.

JohnYandell · Jul 9, 2010

I think the original question was whether a player could somehow influence dwell time and "decide" to keep the ball on the racket strings. The dwell time is going to be a function of the type of swing and the set up of the racket. There isn't some last second thing that can influence this--it happens too fast. As for the racket speeding up to catch the ball after contact for a double hit, well, 3D studies show that the racket head decelerates radically after contact.

I've seen tons of groundstrokes at 4ms--250 frames/sec and the ball is on the frame for 1 frame. We now have a new 500 frame data base and the ball is on the strings for 2 frames. Same deal, 4ms. In the 500 frame footage, you don't see it for 1 frame and don't see it for 3 frames.

Could it be 2.5 occasionally? Possibly. At lower levels with slower speeds and different string tensions could it be something else? Possbily again.

One of the things we are interesting in is filming a lot faster to see what actually happens to the ball on the strings--deformation, any sliding etc.

corners · Jul 9, 2010

SystemicAnomaly said:
I don't currently have access to Technical Tennis (or Rod Cross' other book on tennis physics) but I did poke around the www a bit to see if there was something on dwell time. Apparently, Rod does talk about dwell time in the book, The Physics and Technology of Tennis. He also has sections on string tension and dwell time in his Strings chapter (2) in Technical Tennis:

http://elib.tu-darmstadt.de/tocs/184953693.pdf

search.bn.com/Technical-Tennis/Rod-Cross/e/9780972275934/#TOC

http://www.racquettech.com/store/technical_contents.html

Upon inspection of the table of contents for this book, it would appear that there might be some variation of dwell as a function of string properties (string tension) and force applied. Without access to the actual contents of these books, it's difficult to determine how much variation is possible.

Still, I'll go out on a limb and say that for the very short duration that the ball is on the strings, the stroke cannot really be altered during this contact time to have any effect on dwell time.

.

Yeah, sorry, I meant just that: that differences in racquet, string type, string tension, swing speed, angle, etc. can result in different dwell times. Some people seem to think that special techniques can be a factor as well, but that's not what I was talking about. Although, I really like the Jedi-factor that Jumpulse stirs in one's imagination.

SystemicAnomaly · Jul 10, 2010

corners said:
Yeah, sorry, I meant just that: that differences in racquet, string type, string tension, swing speed, angle, etc. can result in different dwell times. Some people seem to think that special techniques can be a factor as well, but that's not what I was talking about. Although, I really like the Jedi-factor that Jumpulse stirs in one's imagination.

The Jumpulse technique requires a very high level of midi-chlorians. Unfortunately, it is no longer possible to master these Jumpulse skills. At one time, it was a reality a long time ago in a galaxy far, far away. Sadly, the laws of physics have changed sufficiently enough in the modern-day Milky Way galaxy to render the Jumpulse technique unattainable.

sennoc · Jul 10, 2010

JohnYandell said:
Yes and when I look out over the horizon my common sense tells me the world is in fact flat.

Sorry for OT, but I could not resist...

People have serious problems to imagine the look of horizon on the infinite plane. Technically speaking, on the flat surface you should see any unhidden object, everywhere (NY from London as example). The only obstacle is the air transparency and it should significantly modify the look of objects closer to the line of horizon (the thickness of air layer would be practically infinite for "the farthest" objects). We do not observe that on Earth.

So, please be careful with "common sense", because if you look out over the horizon and think geometrically, common sense tells that Earth is not flat

SystemicAnomaly · Jul 10, 2010

^ You seriously believe that you came up with this insight all on your own? This is the way you were taught to think. It took "man" hundreds of thousands of years to reject the dominant "flat Earth" dogma in favor of the round Earth concept.

http://en.wikipedia.org/wiki/Flat_Earth
.

deluxe · Jul 10, 2010

Please delete this thread.

SystemicAnomaly · Jul 10, 2010

^ How about just deleting your post rather than the whole thread?

JohnYandell said:
I think the original question was whether a player could somehow influence dwell time and "decide" to keep the ball on the racket strings. The dwell time is going to be a function of the type of swing and the set up of the racket. There isn't some last second thing that can influence this--it happens too fast. As for the racket speeding up to catch the ball after contact for a double hit, well, 3D studies show that the racket head decelerates radically after contact.

I've seen tons of groundstrokes at 4ms--250 frames/sec and the ball is on the frame for 1 frame. We now have a new 500 frame data base and the ball is on the strings for 2 frames. Same deal, 4ms. In the 500 frame footage, you don't see it for 1 frame and don't see it for 3 frames.

Could it be 2.5 occasionally? Possibly. At lower levels with slower speeds and different string tensions could it be something else? Possbily again.

One of the things we are interesting in is filming a lot faster to see what actually happens to the ball on the strings--deformation, any sliding etc.

Excellent stuff here. The evidence that you've provided should tell us that the dwell times observed were in the 3-5 ms range. Anything less would be seen in only 1 frame at 500 fps while anything greater would be observed in 3 frames. Looking forward to hearing about results with faster film speeds.

I was able to dig up some of what Howard Brody and Rod Cross has to say about dwell times with reduced string tensions (and slower swing speeds). Some interesting excerpts:

http://tennis.quickfound.net/training/tennis_science.html

"These times are so much shorter than your reaction or reflex time that you cannot possibly do anything to change [the way you are hitting] the shot while the ball is on the strings"

"A longer dwell time also means that the shock of the ball being hit is spread over a longer time; the magnitude of the force at any given time is therefore reduced... If you wish to alleviate arm troubles such as tennis elbow, reducing the tension of your racket strings will not only lessen the initial shock transmitted to your arm... "

"All one need do is reduce the tension in the strings to ensure that the ball will spend more time on the racket. Yet... loose strings decrease rather than increase a player's ability to control the ball."
.

Mr_Shiver · Jul 10, 2010

Science? Who needs imperical facts when you can use voodoo. Add nose hair of Nadal, sweat of Sampras, foot fugus of Federer and saliva of Safin. Just mix and drink before match.

sennoc · Jul 10, 2010

SystemicAnomaly said:
^ You seriously believe that you came up with this insight all on your own? This is the way you were taught to think. It took "man" hundreds of thousands of years to reject the dominant "flat Earth" dogma in favor of the round Earth concept.

http://en.wikipedia.org/wiki/Flat_Earth
.

I do not have problems with euclidean geometry.

And yeah, it took hundreds of thousands of years to discover geometry, but then - only a few hundred or less to measure the radius of Earth (Eratosthenes, III century BC; just to remember: "Elements" by Euclid, IV century BC; first mention about spherical Earth - Parmenides, VI-V century BC; Pythagoras - VI century BC).

By the way: the bright horizon paradox (you can call it "sennoc's paradox"

) is a funny opposition of another famous paradox - this one.

Mike Cottrill · Jul 10, 2010

Video of ball on strings at 4000 frames per second

Here is a clip shot at 4k frames per second. Each frame is .00025 seconds or frame rate of 4000 frames per second. Ball on strings 16 frames +/- 1 frame. ~4msec on strings. Most likely a return of serve. . No jumpulse, no double hit
Unless you have bionics installed by Rudy Wells, even Fed cannot control his reflexes at 1 ms rate..

Mike Cottrill · Jul 10, 2010

prolonged contact?

I did not spend but about 10 seconds reading the front page of the jump pulse thing, but using the same video of Fed used by this site, you can see that Feds racket is not moving forward with more volicity after contact with the ball. Also, I do not see any prolonged contact.

JohnYandell · Jul 10, 2010

Gorgeous clip! Interesting stuff happens when the ball hits the strings for sure but this shows the duration quite definitively.

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