Category Archives: Pain
In the words of Lord Kelvin (May 1883) “When you can measure what you are speaking about, and express it in numbers, you know something about it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts advanced to the stage of science.”
That is why every racquet we do has over fifty (50) numbers attached to the finished data. Most of these numbers will remain unknown to the client, but for us, it is imperative that we know them.
Which leads me, again, to this very important discussion.
Every day we see a statement from tennis string manufactures claiming, or suggesting, their string is the “softest ever tested” and other claims. What the heck is “soft” anyway? There is a lot more to it than meets the eye so we have done significant analysis on bunches of string and can now quantify “soft” as it relates to tennis string.
What is “soft”?
In 1994 I did a presentation for the USRSA in Atlanta. What was the topic?
It is now 2016, and we are still trying to understand string! Especially “soft” polyester based string.
In 1994 PolyStar was the only polyester based string I was familiar with. Since then there are dozens of offerings from anyone that can afford to purchase from manufacturers and market the string. If you have a desire to do it, I applaud you!
In 1989 I started testing string and calculating “power potential.” Why “power potential”? Because “modulus,” “elongation” and “elasticity” didn’t get to the bottom line of string performance quickly enough! The steps to arrive at power potential are many.
For the testing, several calculations take place including “stretching” the string as in a ball impact. The difference between the first calculation and the “stretched” calculation is the power potential!
I have calculated hundreds of power potentials but have not until now quantified “soft.”
I think now is the time!
Under the direction of Dr. Rich Zarda, we have done a tremendous amount of work on this issue so we can now distill this work into the following explanation.
So, what is a “soft” tennis string?
Strings in a tennis racquet carry the ball impact load in two ways:
1) Via the pre-load string tension placed in the strings caused by a stringing machine (and the racquet frame “holding” those tensions in place) and
2) Via additional tensions that develop in the same string caused by the elongation of the strings as they deflect with ball impact.
Both of these conditions occur simultaneously and contribute to the string bed stiffness (SBS, units of lbs./in). Racquet technicians measure SBS by applying a load to the center of a supported string bed and measuring the resulting deflection. Dividing the load by the deflection provides the SBS (lbs./in). The lower the SBS, the more power you have (power here is the ability of the ball to easily rebound from the string bed), but the less control (presumably); the higher the SBS, the less power you have but, the more control you have (presumably).
One more point about SBS: the lower the SBS, the less the load your body will feel for a given swing. But for an SBS too low (less than 50-80 lbs./in), balls will be flying off your racquet going over the fence; and for an SBS too high (greater than 200-240 lbs./in), the racquet will hit like a board with significantly less ball rebound. So the most common SBSs are between 100-200 lbs./in: a balance between control and power.
As already expressed, SBS is a function of the pulled string tension and the string elongation. Here is what is interesting: For large string elongations (for example, greater than 15%) and reasonably pulled string tensions (greater than 30-40 lbs.), SBS only depends on the pulled string tension, and it does not depend on string elongation. Additionally, for this condition, SBS, for these high elongation strings, does not change as a ball is hit with more impact.
But for a string bed with low elongation strings (less than 5%) under low pulled tensions (less than 20 lbs., or tensions that have been reduced due to racquet deformation and/or string tension relaxing with time), the SBS additionally depends on the string elongation and will significantly increase, in a nonlinear ever-increasing way, for harder ball impacts.
In order to achieve a repetitive feel for a player when hitting with a racquet, it is best to have an SBS that is independent of an increasing ball impact force. This will lead to a more consistent playability of the racquet, which includes a more repetitive feel. This desired “feel” implies using high elongation strings (greater than 10%). If low elongation strings are used (less than 4%), the SBS will significantly increase as the ball impact force increases, resulting in a racquet feeling “boardy” for higher impact loads. And low elongation strings will cause un-proportionally increasing load into the body.
As you can see by the graph, elongation contributes to SBS in a big way. The red line indicates a stiff string, about 4%, and the blue line indicates a “soft” string, about 15% elongation. You can see the loads increase dramatically as the impact increases. So the harder the hit the higher the loads on the body.
So to the question asked at the start “What is a soft tennis string?” In the context of the SBS discussed above, I would suggest that a soft tennis string is one whose elongation is 10-15%, and a stiff tennis string is 4-6%. And any string under 4% should be categorized as ultra-stiff.
String elongation (soft, stiff, ultra-stiff), stringing machine strung tension, and string pattern(s) all contribute to SBS and SBS is an important measure of how a racquet plays and should be adjusted for an individual player, stiff and ultra-stiff strings can lead to less-repeatable racquet performance and player injury.
Soft = 10 -15% Elongation Power Potential Range = 10.0 – 16.0
Stiff = 4 – 6% Elongation Power Potential Range = 4.0 – 7.0
Ultra Stiff = Less than 4% Power Potential Range = .65 – 3.96
You probably don’t think about it when you drop your racquet off for service but look what can happen!
That is a very “pointy” awl that has fallen onto my foot! The shoes are a “meshy” fabric that does not offer any protection from falling objects!
Then there is this…
It is no surprise that a tennis racquet, or even two, will not compete against the weight of a car
After a tough match it is easy to forget where you put your racquets, so, I suggest the first thing you do is put them in your giant bag that can not be missed!
The other thing to be careful of is the carbon fiber that is now exposed! If this gets into your skin it is not a pleasant experience!
The best thing to do is go directly to the dump and toss them in! Don’t mess with them!
Well, I made it to see 2016 arrive! I am not sure why I stayed up but it does commit me to pay attention to what may happen in the coming year.
I think the big story for 2016 is going to be more string related than racquet related. Why? Because manufacturers can “turn around” a string model much quicker than a racquet model, and, there are significant areas for improvement in selecting the correct string material for each player physicality and style.
String characteristics, materials, tensions, and applications are confusing to many and rightly so. This year I want to continue the “educational” effort and invite anyone with something to contribute to speak up.
My motto for 2016 is “Speak Up…Then String Up”
As most of you know I am a big fan of Ashaway Monogut ZX (16g) and ZX Pro (17G) string. These models are PEEK mono filament strings that resemble polyester strings but these contain no polyester!
Here is the latest PR from Ashaway for your review.
Please let me know if you have any questions, and of course if you want to try this string.
This has been an incredible year filled with challenges, great rewards, learning, and teaching!
One of the greatest challenges is making sure that tennis players of all ages can continue to play without injury. This is especially true of younger players that subject themselves to many hours of training and tournaments.
Along with all that hitting comes the risk of arm and shoulder injuries so this year has been filled with research, design, formatting, and experimenting with various string material combinations.
I would like to thank the folks at Acelon Racquet Sports for their tremendous support of our research, and, of course, continuing trial and error! There are many suppliers of tennis string that have contributed but Acelon has stepped up with an extraordinary array of string materials, and configurations. Thank you Dan!
Ashaway Line & Twine Manufacturing has also played a major role in our string research and our commitment to minimize injuries. The Ashaway Monogut ZX has proven to be an outstanding product in fulfilling our commitment. Thank you Steve!
Our commitment to “injury free” tennis will continue as long as I do this and I appreciate the contribution of many suppliers and players. Without the honest and clear feedback of the players it would be impossible to make as much progress as we did this year.
2015 is going to be a very good year! We will be challenged, rewarded, taught and will teach! I am looking forward to it!
Happy New Year!
Of all my clients a small percentage, maybe up to ten (10) percent, suffer from premature string failure.
If you are one of these ten (10) percent this post may shed some light on the reason(s) or at least offer some sympathy!
First, what is premature string failure?
In the case of the ten (10) percent it is “the string broke”. Period.
Players are experiencing failure in less than ten (10) hours and some in less than two (2) hours. Unless you are a touring professional this may be too often! I understand that so we try to accommodate your desired “cost per hour” threshold.
So, premature failure is less than ten (10) hours of playing time before breaking.
Here are some contributors to this failure…
String Gauge: the thinner (higher number) the more quickly it will break, typically.
String Tension: lower tensions, or SBS, String Bed Stiffness, the more the strings will move which creates friction which causes notching, which, well you know.
String Movement: See above. There is some belief that string moving will create more top spin.
String Pattern: the fewer number of strings the more open the pattern will be and allow more movement.
Racquet Stiffness: a very stiff racquet (RDC 70+) will put more of the impact load on the string, significantly, leading to decreased string life.
Spin: to generate spin you must swing from low to high with plenty of force (harder) causing the strings to move more.
Training: if you are hitting for two (2) hours in training it may be like playing several tournaments.
Mis-Hits: hitting the ball close to the racquet frame creates increased stress on the string and results in “shearing” the string.
As you know there are many more reasons a string may break prematurely and some of it has to do with the away the strings are installed in your racquet but that is another post.
What should you do about premature string breakage?
If your situation is chronic you should consider a more dense string pattern. A pattern of 18 x 20 is a good pattern for increased durability. The dense pattern does not allow the strings to move so freely.
Of course if you are currently using a very open pattern, typically fewer cross strings, in hopes of maximum top spin then you are in for frequent stringing! I hope you enjoy the “spin”!
You may consider a hybrid format with a monofilament main string and a different cross string. Monofilaments are typically polyester based and can be a contributor to arm pain. Monogut ZX by Ashaway is a monofilament made using PEEK (no polyester) and makes a really good hybrid format, and does not put extra stress on the arm.
Consider using a larger diameter (lower number) string. It makes sense that the thicker the string the longer it will take to “saw” through it. A sacrifice in “playability may occur!
Once you determine how much per hour you are willing to spend on string we can design a string setup for you that can contribute to your tennis enjoyment and still leave some money for other things!
Respond to this post with your “cost per hour” threshold and I will respond with a possible solution. How’s that?
By now all of us have seen various colors of “strapping” over the shoulders, elbows, and legs, of high value athletes, but what, exactly, is it?
It is “kinesiology tape” and has provided much needed therapy to many athletes for many years. But how?
“This taping method gently lifts the layer of skin and attached tissue covering a muscle so that blood and other body fluids can move more freely in and around that muscle.”
OK, that is how but why? From a tennis perspective I see a huge value as a means to mitigate elbow and shoulder pain without medicine, either OTC or prescribed. To me that is a good thing.
With more and more players, of every age, trying to generate the maximum amount of “spin” with power it is inevitable that discomfort, or worse, can occur.
A recent article that I posted by the ITPA, International Tennis Performance Association, confirms that most injuries affect the shoulder and back. After reading this article and having many conversations with clients I have decided to offer a kinesiology tape for my customers.
I have selected KT Tape as my primary supplier for reasons that I can’t cover adequately here. You can take a look at the details at their web site www.kttape.com
The KT Tape comes in plain “beige” or some really outrageous colors! Decorate and heal yourself at the same time!
I invite you to stop by and pick up a sample and try it yourself. I am using it for an upper arm pain and I like the result.