Loose grip on ground strokes - what is the biomechanical science?

eah123

Professional
Often times, during warmup, I will attempt to hit a "big" forehand and the ball will sail long. What I noticed is that in that case, I need to consciously relax my grip from around 5 to 2 on a 10 point scale. When I do that, I can hit a very nice "big" forehand that stays in. Even though I am hitting a "flat" stroke (very little down to up), this stroke also results in a lot of top spin, which both cause the ball to "dive" in, and also kicks forward after the bounce.

Backhands with a looser grip are also better.

I was wondering, what is the "science" behind the looser grip with groundstrokes? Is it increased racquet head speed? Or something about hitting with softer hands allowing for longer dwell time (better feel?) on the strings and better control? I also saw a video that said the racquet naturally "covers" the ball (closes) at contact when it is struck with a loose grip, which makes more topspin.
 
Last edited:

Nollid

Semi-Pro
Often times, during warmup, I will attempt to hit a "big" forehand and the ball will sail long. What I noticed is that in that case, I need to consciously relax my grip from around 5 to 2 on a 10 point scale. When I do that, I can hit a very nice "big" forehand that stays in. Even though I am hit a "flat" ball (very little down to up), this stroke also results in a lot of top spin, which both cause the ball to "dive" in, and also kicks forward after the bounce.

Backhands with a looser grip are also better.

I was wondering, what is the "science" behind the looser grip with groundstrokes? Is it increased racquet head speed? Or something about hitting with softer hands allowing for longer dwell time (better feel?) on the strings and better control? I also saw a video that said the racquet naturally "covers" the ball (closes) at contact when it is struck with a loose grip, which makes more topspin.
So many things… It has taken a lot of time and reps to understand this. I can’t quote the science but I’ve learned that a looser grip translates into a looser wrist, improved racquet lag, improved whip and better spin through better pronation. All of that leads to a better hit ball.
 

cortado

Professional
What you perceive to be a 'loose grip' might not actually be that. It could be that when you think you are doing loose grip you might actually be doing something else, like swinging differently, or making contact in a slightly different way.
 

pencilcheck

Hall of Fame
Loose grip means you hit with less pace that’s why it goes in. But that wouldn’t make it better if you want to hit real big esp when you are moving about
 

eah123

Professional
This video is the one that talks about keeping a relaxed grip allows the racquet to close after contact.
 

RVT

Rookie
there is nothing you can to do increase dwell time on the racket except swing lower. You do not want this--it's just one of those myths that won't die.

A looser wrist is going to allow for more passive palmar and ulnar flexation--which results in greater racket speed. It's not a matter of keeping the grip loose AT contact, but when the forward swing starts. I think most experienced players naturally will tighten up right at contact--it's the part before that matters.
 

ballmachineguy

Hall of Fame
If you have a tight grip, your forearm muscles are tighter, shoulder muscles are tighter. A modern stroke with all the racquet movements via supination, pronation, lag etc happen to much greater effect when loose. To see the extreme, grab the handle like you are trying to crush it in your hand and swing.
It is like breathing/exhaling during the stroke. The muscles you are using to constrict breathing are not the only ones you are tightening/ contracting.
 

ballmachineguy

Hall of Fame
So he says to hit relaxed but also BELLOW THE SWEETSPOT( which he doesn't always do btw)?
Forty years of trying to hit on the sweet spot up in smoke. Too bad he didn’t elaborate on how to mishit serves, volleys and backhands so I get better results. Has wester European accent - advice must be legit.
 

socallefty

Legend
I think in terms of being relaxed and not trying to ‘muscle‘ the ball when I’m trying to hit hard. That definitely translates to a looser wrist and more racquet head speed (RHS). I have no idea if my grip is looser as I’m not ever focused on my grip when I‘m playing. After 40 years of tennis, it is too late and likely detrimental for me to be thinking of something as fundamental as how tight or loose my grip is when I’m playing.
 

Niwrad0

Rookie
it's about anatomy, though I might be biased due to my training - When your wrist is extended, i.e. bending wrist upwards like the "please don't shoot" pose, notice that your wrist cannot bend either left or right without making your forearm also rotate. Obviously it cannot be extended more once it's already extended, assuming you're not somehow hitting with the wrist in front of the racquet. This basically makes it so the bones in your wrist are supporting it instead of your muscles, avoiding tennis elbow which is damage to muscles or tendons that run to the wrist.

However every muscle has a 'resting' level of tension. Some people have it more and describe it as 'being tight'. Stretching directly resets the resting tension level, and using it more increases it. Therefore, one way to ensure the wrist remains fully extended through contact is to overpower the resting level of tension using the force of larger muscle groups. By swinging big, the inertia from the racquet combined with the force of your chest/abs more or less ensures the wrist goes into the lag part without needing to use the wrist muscles itself.
 

SystemicAnomaly

Bionic Poster
I was wondering, what is the "science" behind the looser grip with groundstrokes? Is it increased racquet head speed? Or something about hitting with softer hands allowing for longer dwell time (better feel?) on the strings and better control? I also saw a video that said the racquet naturally "covers" the ball (closes) at contact when it is struck with a loose grip, which makes more topspin.
There is little, possibly nothing, that we can do to increase dwell time. Except to string the racquet with a lower string tension. But that said, increasing dwell time is not usually a positive or desirable thing. Increased dwell time tends to make both depth control & directional control more challenging -- less forgiving.
 

SystemicAnomaly

Bionic Poster
@eah123

(I much prefer the phrase, relaxed grip, rather than loose grip)

I've not read anything comprehensive or definitive on why a relaxed grip produces optimal results but I have read enough to make an educated guess on why this is so.

For any physical action that we perform, some muscles need to be contracted while others need to be relaxed. For a given action, there may also be an optimal amount of tension (contraction) for a given muscle. Likewise, there may also be an optimal amount of stretch or relaxation for other muscles.

With a grip force that is too strong / tight, we tend to tighten too many muscles -- the ones that should be contracted as well as the ones that should be stretched or relaxed. This can the counterproductive for the particular action that we want to execute. Not only might we overtighten some muscles, we may have muscles fighting each other. Not good.

OTOH, if we maintain a relaxed grip most of the time, our brain (and nervous system) will figure out which muscles need to be contracted and which muscles need to be stretched or relaxed to produce a desired result. This happens largely on a subconscious level... we just need to stay out of the way of our brain's greater wisdom by having our grip relaxed most of the time

The following site also gets into some of the physics involved with a relaxed grip (soft hands) approach:

 
Last edited:

FatHead250

Professional
Loose grip allows for a more prolonged stroking motion. When the grip is tight, the motion is more abrupt. It's impossible to not have an abrupt motion when the grip is tight, because when the grip is tight you're trying to guide the racquet yourself through the motion, and it is impossible to do so. Instead, the ball should guide the racquet.
 

SystemicAnomaly

Bionic Poster
Loose grip allows for a more prolonged stroking motion. When the grip is tight, the motion is more abrupt. It's impossible to not have an abrupt motion when the grip is tight, because when the grip is tight you're trying to guide the racquet yourself through the motion, and it is impossible to do so. Instead, the ball should guide the racquet.
We've already dismissed the notion that we can change the dwell time very much at all with changing grip force or the way we stroke the ball. Short of actually catching the ball on the strings (not legal), about the only way to increase dwell time is by decreasing string tension (or, possibly, add mass to the frame). From TW University:


"Longer dwell time does not, contrary to popular opinion, allow you time to direct the ball. In 4-7 ms of impact, you are a totally helpless victim of the physics of impact. In fact, your hand and brain don't even get the message that an impact has occurred until the ball has almost left the racquet — certainly too late to do anything about it.".
 
Last edited:

SystemicAnomaly

Bionic Poster
He's wrong too!

J
The word that I've seen from physicists, Howard Brody and Rod Cross is that there is little variation in dwell time unless you significantly change the string tension. (Dwell time changes can possibly also be accomplished with different string types or by changing the hoop mass). Measurements from John Yandell at TennisPlayer appear to confirm that not much variation in dwell time occurs with a given setup.

Relatively minor changes in dwell time might be achievable with different swing speeds. But fairly small variation has been detected with swing speed changes. Contrary to what many expect, the fastest swing speeds (the hardest hits) will result in a slight increase in dwell time according to Howard Brody.
 
Last edited:

a12345

Professional
Just trying to read up about this. When you contract a muscle you basically create tension, and it looks like the grip muscles in the hand, which are located in the forearm also share muscles associated with the wrist:


"The gripping and wrist actions share several muscles; flexor digitorum profundis (FDP) and flexor pollicis longus (FPL) contribute to wrist flexion and grip force production, while extensor digitorum communis (EDC) contributes to wrist extension and grip relaxation.

The bellies of these muscles are located in the forearm, their tendons cross the wrist joint and insert at the base of the distal phalanges (Platzer 2004).

Additionally, there are dedicated muscles for wrist flexion/extension that do not directly affect grip force, whereas the intrinsic muscles of the hand have no direct effect on wrist action but can contribute to grip force via the extensor mechanism.

The presence of the multiple muscle groups with different actions on the wrist-grip system potentially allows for various muscle activation patterns compatible with any task; hence, the system is redundant at the muscle level."

To me this means that if you grip hard you create tension in the muscles that also create tension in the wrist as these tendons overlap, which is detrimental to your tennis stroke.

But it also says "there are dedicated muscles for wrist flexion/extension that do not directly affect grip force." Which to me suggest you can use muscles to move your wrist without affecting your grip strength.

So gripping hard will affect the tension on the wrist but yet this doesnt have to be the case the other way round as its possible to create tension/muscle movement in the wrist without affecting grip strength.
 
Last edited:

Niwrad0

Rookie
@a12345 Is pretty much correct

In fact, grip force can be generated entirely within the hand itself. The two pads of meat, one under the thumb and the other under the pinky, are the grip force muscles.

The muscles used for wrist flexion (palm turning towards the arm/body) are also connected to the fingers, which is why there is some confusion and overlap about grip vs wrist.

To "feel" for the muscles that exist entirely in the hand, do the fingertip to fingertip (including thumb) exercise. Also folding and unfolding the hand (like how people can grip a ball with the two aforementioned meat pads) are also entirely in the hand as well.

Random google picture of exercise
 

Dartagnan64

G.O.A.T.
The word that I've seen from physicists, Howard Brody and Rod Cross is that there is little variation in dwell time unless you significantly change the string tension. (Dwell time changes can possibly also be accomplished with different string types or by changing the hoop mass). Measurements from John Yandell at TennisPlayer appear to confirm that not much variation in dwell time occurs with a given setup.

Relatively minor changes in dwell time might be achievable with different swing speeds. But fairly small variation has been detected with swing speed changes. Contrary to what many expect, the fastest swing speeds (the hardest hits) will result in a slight increase in dwell time according to Howard Brody.
I don't think it's that contrary. If you swing faster the ball compresses more and takes longer to decompress before it comes off the racket face. But there will be a finite limit too how much the ball can compress and the variance from minimal compression to maximal is not going to be long and likely not appreciated by most folks.

Its quite probable what folks believe is "dwell time" is some other characteristic of the racket they are feeling and interpreting as the ball still on the strings.
 

SystemicAnomaly

Bionic Poster
@a12345 @Niwrad0

There are also some muscle in the palm at the base of the thumb used for adduction, abduction &, possibly, other actions of the thumb. The Adductor Pollicis is used for thumb adduction. The Abductor Pollicis Brevis is used for abduction. The Opponens Pollicis appears to be used for thumb opposition. Seems to me that this muscle and the adductor muscle probably assist in gripping with the thumb.

The Flexor Pollicis Longus starts in the forearm but attaches in the hand at the base of the thumb, I believe. It is responsible for flexion of the thumb.
 

a12345

Professional
This statement here fascinates me:

"Additionally, there are dedicated muscles for wrist flexion/extension that do not directly affect grip force, whereas the intrinsic muscles of the hand have no direct effect on wrist action but can contribute to grip force via the extensor mechanism."

The extensor mechanism, is basically the muscles connected to the fingers. But importantly they are on top of the fingers.

The extrinsic extensor muscles


"Extrinsic denotes their location outside the hand. Extensor denotes their action which is to extend, or open flat, joints in the hand."

So it looks like its possible to use these muscles to grip the racket, which are outside of the hand as they are on top of the fingers, and are connected to the top of the forearm vs hand gripping which uses the the muscles inside the hand, and share tendons with the wrist.

This maybe why we are told to grip with the fingers and let the racket "hang" off the finger tips, because you are using the extensor muscles located on the top of the fingers to hang, instead of the inner hand muscles which are shared by the wrist.
 

SystemicAnomaly

Bionic Poster
@a12345 Is pretty much correct

In fact, grip force can be generated entirely within the hand itself. The two pads of meat, one under the thumb and the other under the pinky, are the grip force muscles.

The muscles used for wrist flexion (palm turning towards the arm/body) are also connected to the fingers, which is why there is some confusion and overlap about grip vs wrist.

To "feel" for the muscles that exist entirely in the hand, do the fingertip to fingertip (including thumb) exercise. Also folding and unfolding the hand (like how people can grip a ball with the two aforementioned meat pads) are also entirely in the hand as well.

Random google picture of exercise
I was under the impression that the muscles in the palm for the pinky was used for abduction and adduction and not actually for gripping. Could be wrong about that tho.

I have issues in both hands with the muscles at the base of my thumbs. Also a bit of arthritis in the joints of both thumbs. I still have reasonable grip strength with the other fingers but find it difficult to open jars and bottles cuz of the thumb issue. Overall grip strength is limited because of the thumbs. But I can still grip a racket with only moderate discomfort (most of the time).
 

a12345

Professional
Basically a minimal use of the muscles in the fingertips, combined with an element of friction is probably likely to have the least amount of influence on the wrist muscles.

You can see how much here the finger tendons cross the wrist

 

Niwrad0

Rookie
@a12345 @Niwrad0

There are also some muscle in the palm at the base of the thumb used for adduction, abduction &, possibly, other actions of the thumb. The Adductor Pollicis is used for thumb adduction. The Abductor Pollicis Brevis is used for abduction. The Opponens Pollicis appears to be used for thumb opposition. Seems to me that this muscle and the adductor muscle probably assist in gripping with the thumb.

The Flexor Pollicis Longus starts in the forearm but attaches in the hand at the base of the thumb, I believe. It is responsible for flexion of the thumb.
Yes doctors like to use latin or expensive sounding words other than something like arm bender muscle.

Flexion and extension are originally based off the anatomical position of the fetus/embryo, which is why they don't seem standardized. But the rest of the latin converts over straightforwardly.

Standardized human position is lying flat, feet together, arms at sides, with palms facing anterior/forward.

Pollicis - Thumb
Hallux - Big Toe
Flexor - Bends
Extensor - straightens
Longus - Longer one
Brevis -Shorter one
Opponens - Opposite, i.e. Opponens Pollicis is opposite of Oppens minimi (Pair of muscles to pinch between thumb and pinky finger)
ADDuctor - Bend towards center of body
ABDuctor - bends away from center of body
interosseous - between bones
carpi - finger
ulnaris - pinky side
radialis - thumb side


Forgive my spelling, but google will know generally what you mean if you copy paste it
 
Last edited:

SystemicAnomaly

Bionic Poster
I don't think it's that contrary. If you swing faster the ball compresses more and takes longer to decompress before it comes off the racket face. But there will be a finite limit too how much the ball can compress and the variance from minimal compression to maximal is not going to be long and likely not appreciated by most folks.

Its quite probable what folks believe is "dwell time" is some other characteristic of the racket they are feeling and interpreting as the ball still on the strings.
There may be opposing factors that are in play here. For faster ball / racket speeds, there is, indeed, greater deformation of the ball & the stringbed. It could take slightly more time to compress and then recover from these actions.

OTOH, there is often a much greater entrance & exit speeds for hard hit balls. I believe that many, if not most, people probably consider this and, mistakenly, ignore the increased deformation of the ball & strings. This is why many people are tempted to think that the ball would spend less time on the strings rather than more time.

But, to my thinking, these 2 factors might partially cancel each other out. This would explain why there might not be much variation in dwell time for a standard frame / string (tension) setup. Typically that range is 4 to 5 ms. When we hear of dwell times in the 6-8 ms range, this is usually accomplished with much lower string tensions rather than diffs in swing speeds.
 
Last edited:

Niwrad0

Rookie
I was under the impression that the muscles in the palm for the pinky was used for abduction and adduction and not actually for gripping. Could be wrong about that tho.

I have issues in both hands with the muscles at the base of my thumbs. Also a bit of arthritis in the joints of both thumbs. I still have reasonable grip strength with the other fingers but find it difficult to open jars and bottles cuz of the thumb issue. Overall grip strength is limited because of the thumbs. But I can still grip a racket with only moderate discomfort (most of the time).
Quick test, if you place your thumb inside of your fingers and try to squeeze the thumb into your palm, does it hurt? If unsure, anything more than 0/10 would be positive unless it's also painful on the other thumb. If it is equally painful with same amount of squeezing, then is pain present when moving the thumb relaxed with your hand or only when trying to grip? If painful, how much range of movement can you get moving relaxed thumb with your other hand versus moving the thumb itself? Also if you bend both wrists downwards and push the top of your hands into each other, like an upside-down prayer, is there pain present within 90 seconds?
 
Last edited:

a12345

Professional
I was under the impression that the muscles in the palm for the pinky was used for abduction and adduction and not actually for gripping. Could be wrong about that tho.

I have issues in both hands with the muscles at the base of my thumbs. Also a bit of arthritis in the joints of both thumbs. I still have reasonable grip strength with the other fingers but find it difficult to open jars and bottles cuz of the thumb issue. Overall grip strength is limited because of the thumbs. But I can still grip a racket with only moderate discomfort (most of the time).
As I understand it we use the pinky finger to grip the most followed by the ring finger and index finger, for a bar type object. So for example you can hang off a monkey bar using just these three fingers, but it would be difficult to hang off your middle finger index finger and thumb.
 

Niwrad0

Rookie
As I understand it we use the pinky finger to grip the most followed by the ring finger and index finger, for a bar type object. So for example you can hang off a monkey bar using just these three fingers, but it would be difficult to hang off your middle finger index finger and thumb.
The undisputed strongest finger is the thumb.

The anatomy at this point will have some significant variation, some people will have fingers 2 (index), 3(middle), 4(ring), and 5(pinky) directly connected to the forearm muscles, whereas they may have only finger 2, and so on. Some people don't have the tendon at all, and can be see when flexing your wrist and the presence/absence of the thin cord like structure running from the arm into the center of the palm.
 

a12345

Professional
The undisputed strongest finger is the thumb.

The anatomy at this point will have some significant variation, some people will have fingers 2 (index), 3(middle), 4(ring), and 5(pinky) directly connected to the forearm muscles, whereas they may have only finger 2, and so on. Some people don't have the tendon at all, and can be see when flexing your wrist and the presence/absence of the thin cord like structure running from the arm into the center of the palm.
Probably but then it depends on how youre gripping something. Opening a bottle top probably needs more thumb strength , but grabbing a bar or handle is more the lower fingers. Like if you pick up a kettle with a sideways handle using the top 3 fingers its unstable but with bottom 3 its pretty strong.
 

Niwrad0

Rookie
Probably but then it depends on how youre gripping something. Opening a bottle top probably needs more thumb strength , but grabbing a bar or handle is more the lower fingers. Like if you pick up a kettle with a sideways handle using the top 3 fingers its unstable but with bottom 3 its pretty strong.
Yes, the thumb does move in the opposite direction, so I realize now that in the case of monkey bar, kettle, handle, you're referring to a slightly different action.

I guess there's not much to say in going further in this direction, so back to tennis - This reminded me of another tip I tried:

When looking into improving my toss I saw it was mentioned that the index and middle finger tend to 'roll' the ball and add in inconsistency. So I intentionally avoided it and used just the thumb and pinky to grip the ball during the toss and I had no spin or rolling of the ball as it went up. Worked great and don't need much grip strength
 

a12345

Professional
Another theory of optimal gripping is the idea of not gripping at all. And this maybe the way the pros do it.

Essentially we can also grip by using a stretch reflex.

What this means is that when the muscles are stretched there is a muscle contraction in response to the stretching.

So the loosest way to grip maybe to not actively grip at all and just let your bodys natural muscle response kick in.
 

J011yroger

Talk Tennis Guru
The word that I've seen from physicists, Howard Brody and Rod Cross is that there is little variation in dwell time unless you significantly change the string tension. (Dwell time changes can possibly also be accomplished with different string types or by changing the hoop mass). Measurements from John Yandell at TennisPlayer appear to confirm that not much variation in dwell time occurs with a given setup.

Relatively minor changes in dwell time might be achievable with different swing speeds. But fairly small variation has been detected with swing speed changes. Contrary to what many expect, the fastest swing speeds (the hardest hits) will result in a slight increase in dwell time according to Howard Brody.
Swing speed is far less relevant than acceleration w/r/t dwell time.

J
 

Niwrad0

Rookie
Essentially we can also grip by using a stretch reflex.

What this means is that when the muscles are stretched there is a muscle contraction in response to the stretching.
Yes, all muscles in the body do this. The classic one is hammer to just below the knee. Stretching a muscle very rapidly causes to rebound more strongly than a purely rubber band effect would predict
 

a12345

Professional
Something like this.


"It has been shown that subjects maintain grasp stability by automatically regulating grip force in response to loads applied tangentially to a manipulandum held using a precision grip. Signals from cutaneous mechanoreceptors convey the information necessary for both the initiation and scaling of responses. The central neural pathways that support these grip reactions are unknown. However, the latency of the increase in force is similar to that of ‘long-latency’ transcortical reflexes recorded from muscles following muscle stretch or electrical stimulation of digital nerves."

Very complicated but as a quick interpretation I think its something along the lines of, when a force occurs upon your grip your hand can naturally react to regulate your grip force as a reflex action.
 

SystemicAnomaly

Bionic Poster
Swing speed is far less relevant than acceleration w/r/t dwell time.

J
One of these days, I'll have to drive out to my storage facility to find &: retrieve my books on tennis physics -- I've got 2 of them with H. Brody & R. Cross along with Crawford Lindsey.

I really do not recall them addressing dwell time as a function of acceleration. There was, however, mention of racket speed or how hard the ball was hit. But it appeared to be a lesser factor than string type & racket mass distribution. And much less a factor than string tension / stiffness.

By far, most of what I've seen written about dwell time from these guys and others has to do with the latter factor --string tension / stiffness. Much less has been written about ball / racket velocity (or acceleration). It would appear that it is much less of a factor wrt dwell time

Even with the longer dwell times seen with flexible, low tension stringing (on the order of 7 ms compared to the usual 4-5 ms), the duration of contact is far too brief for us to really do anything about it. By the time we feel it, the ball is already leaving the stringbed.

"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."

Last point. There is a phrase that I've heard on the sports documentary show, Sport Science, numerous times:

"Feel & Real are not the same thing."

They have measured numerous times, distances, & other sports parameters on this show and have concluded that, often, what athletes feel or think is happening is not supported by the data / measurements.
 
Last edited:

SystemicAnomaly

Bionic Poster
@Niwrad0
Something like this.


"It has been shown that subjects maintain grasp stability by automatically regulating grip force in response to loads applied tangentially to a manipulandum held using a precision grip. Signals from cutaneous mechanoreceptors convey the information necessary for both the initiation and scaling of responses. The central neural pathways that support these grip reactions are unknown. However, the latency of the increase in force is similar to that of ‘long-latency’ transcortical reflexes recorded from muscles following muscle stretch or electrical stimulation of digital nerves."

Very complicated but as a quick interpretation I think its something along the lines of, when a force occurs upon your grip your hand can naturally react to regulate your grip force as a reflex action.
Interesting stuff but not an easy read. I really only skimmed through it. The fastest reflex times that I saw mentioned was 35 ms. Other mentions of 50-60 ms as I recall. These are quicker than auditory & tactile reaction times (which are quite a bit quicker than visual RT). These auditory / tactile RT are rarely quicker than 120 ms.

As Howard Brody & others have pointed out, the dwell time of the ball on the stringbed is significantly shorter than these reaction and reflex times. Dwell is typically 4-5 ms and rarely longer than 6-7 ms. Ball is long gone before we feel and can react to an impact.

Other studies have shown, however, that elite players & many non-elite players will execute an anticipatory squeeze (firming) of the fingers about 50 ms prior to contact. Apparently learned behavior from experiencing previous contacts.
 

a12345

Professional
Where I would consider this reflex action largely though is in the swing.

If you keep a loose grip, then apply a force to the object in your grip e.g racket being forced back, caused from you body rotation, the change in force from the racket to your hand will cause a reflex action in your hand to grip it without needing to consciously grip it.

This maybe a looser way to grip the racket.
 

Niwrad0

Rookie
Very complicated but as a quick interpretation I think its something along the lines of, when a force occurs upon your grip your hand can naturally react to regulate your grip force as a reflex action.
I read the article - it cannot be generalized to tennis. They use a precision grip, which is the grip for holding a pen or pencil. We use a power grip, which involves all the fingers but in the study only the index and thumb were used, and the forces used were very weak, on the order of 0.5 lbs, which again, cannot be generalized to tennis.

Also the article states that grip force is NOT a reflex action.

Prior to this article's publication, the authors state it was merely assumed to be so until they conducted this experiment on three individuals with a genetic disorder involving the brain itself (Kallmann's Syndrome). The reflexive pathway assumed is based on the "pain" or withdrawal reflex. The classic example is touching a hot stove - you pull back your hand before you realize it consciously. It is similar but not the same as the "stretch" reflex, but both types basically ignore the brain in order to act in the realm of <20ms.

However, in the case with people with this genetic disorder affecting the brain, signs are shown that the brain is required to modulate grip, which means it is not reflexive and accordingly takes more time to process than the classic withdrawal reflex.

Edit1: By muscle stretch, I mean the classic stretch, i.e. hammer below the knee. In this article they mention stretch but this is a central process they refer to, involving the brain. While the lower body can 'activate' the reflex, the brain can play a role in 'preparing' or modulating the point at which a reflex should occur.
 
Last edited:

Fintft

Legend
One of these days, I'll have to drive out to my storage facility to find &: retrieve my books on tennis physics -- I've got 2 of them with H. Brody & R. Cross along with Crawford Lindsey.

I really do not recall them addressing dwell time as a function of acceleration. There was, however, mention of racket speed or how hard the ball was hit. But it appeared to be a lesser factor than string type & racket mass distribution. And much less a factor than string tension / stiffness.

By far, most of what I've seen written about dwell time from these guys and others has to do with the latter factor --string tension / stiffness. Much less has been written about ball / racket velocity (or acceleration). It would appear that it is much less of a factor wrt dwell time

Even with the longer dwell times seen with flexible, low tension stringing (on the order of 7 ms compared to the usual 4-5 ms), the duration of contact is far too brief for us to really do anything about it. By the time we feel it, the ball is already leaving the stringbed.

"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."

Last point. There is a phrase that I've heard on the sports documentary show, Sport Science, numerous times:

"Feel & Real are not the same thing."

They have measured numerous times, distances, & other sports parameters on this show and have concluded that, often, what athletes feel or think is happening is not supported by the data / measurements.
Are you telling me that none of us feels the pocketing effect of natural gut?
 

Fintft

Legend
Forty years of trying to hit on the sweet spot up in smoke. Too bad he didn’t elaborate on how to mishit serves, volleys and backhands so I get better results. Has wester European accent - advice must be legit.
I tried just now to hit bellow the sweet spot a few times, with no good results.
 

a12345

Professional
I read the article - it cannot be generalized to tennis. They use a precision grip, which is the grip for holding a pen or pencil. We use a power grip, which involves all the fingers but in the study only the index and thumb were used, and the forces used were very weak, on the order of 0.5 lbs, which again, cannot be generalized to tennis.

Also the article states that grip force is NOT a reflex action.

Prior to this article's publication, the authors state it was merely assumed to be so until they conducted this experiment on three individuals with a genetic disorder involving the brain itself (Kallmann's Syndrome). The reflexive pathway assumed is based on the "pain" or withdrawal reflex. The classic example is touching a hot stove - you pull back your hand before you realize it consciously. It is similar but not the same as the "stretch" reflex, but both types basically ignore the brain in order to act in the realm of <20ms.

However, in the case with people with this genetic disorder affecting the brain, signs are shown that the brain is required to modulate grip, which means it is not reflexive and accordingly takes more time to process than the classic withdrawal reflex.

Edit1: By muscle stretch, I mean the classic stretch, i.e. hammer below the knee. In this article they mention stretch but this is a central process they refer to, involving the brain. While the lower body can 'activate' the reflex, the brain can play a role in 'preparing' or modulating the point at which a reflex should occur.
The paragraph I read looks like a summary of a previous study.

What im thinking is more along the lines of perhaps that we automatically change or modulate our grip pressure as a response to a sensory input. As the racket exerts a force in our hand our grip responds automatically to manage it.

So we are able to subconsciously apply a minimal grip to maintain the racket in our hand without actively gripping the racket.
 

J011yroger

Talk Tennis Guru
One of these days, I'll have to drive out to my storage facility to find &: retrieve my books on tennis physics -- I've got 2 of them with H. Brody & R. Cross along with Crawford Lindsey.

I really do not recall them addressing dwell time as a function of acceleration. There was, however, mention of racket speed or how hard the ball was hit. But it appeared to be a lesser factor than string type & racket mass distribution. And much less a factor than string tension / stiffness.

By far, most of what I've seen written about dwell time from these guys and others has to do with the latter factor --string tension / stiffness. Much less has been written about ball / racket velocity (or acceleration). It would appear that it is much less of a factor wrt dwell time

Even with the longer dwell times seen with flexible, low tension stringing (on the order of 7 ms compared to the usual 4-5 ms), the duration of contact is far too brief for us to really do anything about it. By the time we feel it, the ball is already leaving the stringbed.

"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."

Last point. There is a phrase that I've heard on the sports documentary show, Sport Science, numerous times:

"Feel & Real are not the same thing."

They have measured numerous times, distances, & other sports parameters on this show and have concluded that, often, what athletes feel or think is happening is not supported by the data / measurements.
Velocity and acceleration are two very different things.

J
 
Top