Category Archives: shoulder
It is raining today and it felt like a good time to talk about “string bed stiffness”…so let’s go!
This quick video will make a plea to you tennis players to demand more from your racquet technician so you are getting the most from your equipment.
Thank you for watching!
We were thrilled to have Dr. Brad Goodman visit the World Headquarters to produce a session for his Doc-Talk-Live program!
Dr. Goodman is a tennis player who wants to know more about equipment in an effort to protect his body and beat his opponents. You can catch this episode here: Doc Talk Live
In addition to the session Dr, Goodman was given the opportunity to “stretch” both a very stiff string and a very “stretchy” string, something that he, and many others, have not done. Needless to say he was amazed at the difference.
Dr, Goodman’s visit was a great opportunity to have a real conversation about tennis equipment. Please let me have your comments!
OK, here’s the deal. I have written about this several times and each time I decided that it was a waste of time, so it goes back into a file somewhere!
The time is now that we really need to understand more about stringing as a consumer and what we can do as racquet technicians to make the life of a player better, more fun, and safer.
This a quick story to set the premise of the rest.
Several weeks ago I received a freshly strung (24 hours) racquet to perhaps make a few modifications to the racquet. The racquet was strung by the player, a very good junior with a high ranking. The racquet was 18×20 with a full bed of polyester at 53 pounds. When I asked why the response was “I have always done it this way”. Fair enough!
The string bed stiffness (SBS) using the Beer’s ERT300 was 23, the SBS using the Babolat RDC was 29, and the SBS using the FlexFour was 50. If you are familiar with these data, you know the numbers are quite low.
The racquet had only one mis-weave and one crossover, but it was severely distorted, i.e., very wide.
For a quick comparison, a properly strung racquet would have numbers like 36, 58, and 67 respectively.
So, the “softness” of the string bed when improperly strung was something that may not transmit as much shock to the body as a racquet that was properly strung at the requested 53 pounds and has a higher SBS!
Therefore a poor stringing may save the life of polyester based string! It may not be good for performance or racquet integrity but it seems that very few players care!
So what do we do?
For years I have been advocating for the use of a finished SBS instead of a “reference tension”. Why? Because each stringer and stringing machine probably produce a different result.
If a player comes to us and requests an SBS of 37 (Beers ERT300 for example), we can adjust the stringing machine to produce that SBS number. Our machines may be set at 40 to achieve the requested 37, and another shop may have to set their machine to something different. The object is to arrive at the finished SBS, and it is up to the racquet technician to be able to do that! The result will be a better performing racquet that will last longer.
In dictionary terms it is:
“the amount of extension of an object under stress.”
In tennis terms, it means the same thing when talking about tennis racquet strings.
How much does a string stretch under the reference tension load or otherwise stretched (impact)? The proliferation of wrist, arm and shoulder injury has brought attention to the property of “stiffness.” The problem is that your stiffness may be different than my stiffness, so there needs to be an “index” associated with each string, in my opinion. I have that data on over 500 tennis strings, but that is just me.
The images show the results of high elongation (left) and low elongation (right) string upon breaking.
Several years ago a player asked me “where is the string that is missing?” Well, it is not missing. The ends you see should be connected!
If the string has little elongation when it breaks there is nothing “pulling” it apart like the high elongation string. So each time you hit the ball, the string either elongates a bunch or it doesn’t.
In the case of the high elongation string, on the left, it absorbs a good portion of the “shock” associated with a hard hit, whereas the low elongation string, on the right, lets your body do the absorbing to a great extent.
So, it is reasonable to use very low reference tensions for low elongation string (35 to 45 pounds; 16 to 20.5 Kg) and higher tensions (45 to 60 pounds; 20.5 to 27.2 Kg) for high elongation strings.
You may ask, “how do I know how stiff a string is?” If you see the word “polyester or co-polyester” it is likely that string wil be stiff compared to natural gut, most nylon based multi-filament construction, and PEEK (Zyex) material. In my opinion, there is no “bad” string just “bad” applications. If in doubt…ask!