Un sito davvero serio su racchette

Per chi non lo conosce... lo trovo eccezionale:

http://racquetresearch.com/

ci sono una MAREA di info... veramente valide e NON condizionate dai comune pensiero e dal marketing.

In particolare, mi piace questo:


Is a Lightweight Racquet a Good Idea?


No, a lightweight racquet is a dumb idea, as pro customizers attest.  Weight is not bad.  You need weight to return a "heavy" ball (lots of pace and spin).  Wimpy racquets can't put much pace on the ball if you don't have time to develop a long stroke, such as when you are stretched wide.  Pete Sampras uses a racquet that is 14 oz. and evenly balanced, and when he is going for a putaway, he chokes down so the swingweight is even higher.  Andre Agassi uses one that is 13.2 ounces and 5/8 inch (5 points) head-light.  Mark Philippoussis uses one that is 13.5 ounces and is 3/4 inch head light.  Lest you think that these heroic sticks are as unwieldy as the sword of Goliath, remember that the lightest wood racquet was 13 ounces.  Ladies and children used them.  

Maybe, in the short space that you have to execute your stroke, you might swing the wimpy racquet a little faster -- but swing speed is not the key.  



Momentum, not energy, and not force, is what counts in a collision (Conservation of Momentum is the principle), and in computing momentum the racquet's mass is just as important as its velocity (momentum = mass times velocity).  Readers with baseball experience know what happens when you try to hit a hardball home run with a softball (i.e. lightweight) bat.  A softball bat cannot hit a hardball very far because it doesn't bring enough mass to the collision, and therefore its momentum on impact is low.

High Tip Speed is bad for accuracy because it is harder to time a violent swing precisely.  Even if you succeed in increasing the Tip Speed enough to offset the racquet's lack of mass, the shot will be hard to place.

Aside from the foregoing performance considerations, there is the even more important question of safety.  Light racquets are bad for tennis elbow.

Most racquet customers and their stringers know little, and care less, about the difference between weight, Moment, and swingweight.  "Pick up appeal" (how light the frame is when you pick it up in the pro shop) is the predominant criterion (after cosmetics) for the ignorant.  An epidemic of elbow and other arm injuries has been the result.  Tennis is losing players at an alarming rate, and slowly declining in popularity.  It's all because of the fundamental mistake of amateurs regarding racquet weight, a mistake that some racquet salesmen apparently have chosen to exploit for their short-term profit.  


The touring pros know better.  They add weight when they customize their racquets.  A more massive (heavier) racquet will crush majestically through the ball instead of bouncing off, which makes it more comfortable on impact and more accurate.  See the Official Rules of the ATP Tour regarding racquets.  This little secret vexes the sponsors that pay them lots of money to pretend to play with granny sticks, so you won't hear much about it.  See page 8 of the June 1996 issue of Stringer's Assistant (published by the US Racquet Stringer's Association) for some data on pro customized racquets.

What Causes Tennis Elbow?

Many professional researchers are still looking for an answer.  Damage to the tendon attaching the extensor carpi radialis brevis (ECRB) muscle to the elbow is the cause of the pain, but the cause of this cause is a mystery.  However, it is fairly certain that this type of damage is the result of repetitive stresses, such as hitting a tennis ball.

Producing causes of tennis elbow may include the following mechanisms, which are offered here for comment and further investigation:

   (1)    Elbow Crunch is a sudden shortening of the ECRB due to impact (explained at greater length above under Elbow Crunch).  This effectively is a muscle spasm that stresses the tendons.  

   (2)     On impact, the resultant Torque twists the racquet head back, while Moment is dragging the head down, and the hand is holding the racquet steady.  The resultant twist of the handle (Torsion, or Longitudinal Torque) is clockwise for a right-handed forehand.   This twist winds up a catapult.   When the ball leaves the racquet, the catapulting force is counterclockwise for the right-handed forehand.  The two opposite screwdriver twists in a short time give a severe stress cycle to the extensor carpi radialis brevis muscle that attaches the middle of the hand to the elbow, even for a dead-center hit.  

   (3)    The back-and-forth catapulting stress cycle of Torque from impact twisting the racquet back, followed by catapulting the racquet forward when the ball leaves, aggravates the handle twist cycle mechanism discussed above under (2).  The extensor carpi radialis brevis muscle is anchored at the elbow and at the metacarpal (hand) bone of the middle finger, on the index finger side.  The resultant Torque from impact is a twist backward that tends to yank this muscle as the middle finder is extended.  On impact, this muscle is either straining (on the backhand) or slack (on the forehand).  On the backhand, the first twist yanks this straining muscle, further stressing the tissues attaching it to the elbow.  Then the muscle suddenly loses resistance but continues to work against the combined stress, so it suddenly shortens after impact, giving an even more severe yank to the elbow (cf. the discussion below on Elbow Crunch).  For the forehand, the muscle is slack on impact, so the catapulting stress cycle cracks the muscle like a whip, stressing the points of attachment at the wrist and elbow.  Elbow straps help because they damp the whip effect.

   (4)     Shock becomes internal energy, which expresses itself as frame vibration, and this vibration is transmitted to the arm holding on to the racquet unless it is damped somehow.  (The correct term is damped, not "dampened.")  In the old wood racquets, vibration disappeared quickly because it was damped by the flex of the wood, but the new stiffer and lighter frames do a poor job of damping, so they efficiently transfer the subtle shaking to the arm.  Undamped high frequency frame vibration can stealthily sabotage the elbow, so the price of power may be pain.  Vibration of the frame shakes the extensor carpi radialis brevis muscle that attaches the middle of the hand to the elbow.  This causes cyclic stressing of the tendons at the lateral epicondyle, where the fat half of this long teardrop-shaped muscle attaches.  Cyclic stressing is how you break a coathanger by bending it back and forth.  Eventually, with enough stress cycles, fatigue can cause tissues to snap, even without any tremendous force.

What you don't want if you are concerned about the risk of tennis elbow is a stiff, high-Torque, high-Moment, high-Shock racquet.  That means a light, head-heavy racquet.

Poor stroking technique is frequently accused, conveniently diverting scrutiny from racquet design, but, as the calculations on this site prove, risk factors for tennis elbow include: (1) light racquet weight and (2) head-heavy balance.  Stiff frames are also bad.  What is good for minimizing elbow damage is low Shock, low Elbow Crunch, low Torque, and low Moment.

The Effect of Handle Size

Bigger is better for maintaining control.  A large handle size gives more area to apply friction and a wider radius to apply the frictional force in order to resist racquet twisting about its longitudinal axis (Torsion, or Longitudinal Torque) on off-center hits.  Handle size is the circumference (distance around).   It can be increased by adding an overgrip (e.g. Tournagrip ® or moleskin), or by building out the handle under the grip with tape or shims.  Bigger handles should also be better for preventing blisters.  

Big servers, however, prefer smaller handles.  The best thing would be a handle that for groundstrokes had a large circumference at the forefinger, and for serves, a small circumference at the forefinger when you choke down: i.e. a coke-bottle-shaped grip, or rounding off the bevels about 4 cm up the handle to give a tapering smaller circumference at that spot.  There is no reason but herd mentality why handles have remained uniformly octagonal for so long.   This smaller circumference on the serve allows the racquet to cock back farther on the backswing.

Una bella miniera di informazioni.... sempre interessante!
Leggetelo

pro-t-one ha scritto:Una bella miniera di informazioni.... sempre interessante!
Leggetelo

E se lo dice PRO-T-ONE...

E' una garanzia!

Sito bellissimo che mi avevi già girato.

Purtroppo il sito è cambiato, diventando un semplice blog, che dice cose ovvie.

Peccato.