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pondus
01-11-2010, 08:36 PM
Help I'm confused. Can anyone explain the mechanics of the simple tennis stroke (forehand)

I basically don't "get" tennis because I can't find any place where the stroke is actually described in detail, like you would find in the golfing world. For example, a search on "leverage tennis" on Google found almost nothing, yet Pat Dougherty raves about this at http://www.youtube.com/watch?v=SZqhHdmqSPQ, so it must be important. (Why do so few instructors explain things as well as Pat).

Anyhow, an online dictionary defines leverage as :

1. (Engineering / Mechanical Engineering) the action of a lever
2. (Engineering / Mechanical Engineering) the mechanical advantage gained by employing a lever

Is this more important in generating power on the forehand than the concept of a large object colliding with a small object (body unit turn colliding with ball), or is it part of the same thing.

Is this more important than racquet head speed? While the speed of the racquet is important in generating spin on brushing up on the ball, surely a racquet weighing only 100 grams would not generate much power no matter how fast it's swung.

As Pat says, "cracking the whip", like Federer does his forehand, is not required to generate ball speed.

Your thoughts on what the physics of generating power is would be much appreciated. If you are just speculating, hold your thoughts, and let's save this thread for people who actually know (are you there BungalowBill?)

crash1929
01-11-2010, 09:51 PM
i think your on the right track. its a key word in tennis. keep looking you will like what you find. i think.

theZig
01-11-2010, 10:26 PM
Federer/Nadal/Verdasco/etc pronate through the ball, but what this video says not to do (and what many novices think the pros do) is wrist flexion. Notice the example he shows you when he talks about "cracking the whip". When have you ever seen the top pros doing that? Never! The "crack of the whip" is when the pros pronate through the ball with a loose wrist, giving a "snap" appearance, though most slow-mo cams do shot that their wrists are still laid back at contact.

phoenicks
01-12-2010, 12:38 AM
Your thoughts on what the physics of generating power is would be much appreciated. If you are just speculating, hold your thoughts, and let's save this thread for people who actually know (are you there BungalowBill?)

I think you should call out for BB in the title, that can reach him quicker, me thinks.

Sublime
01-12-2010, 05:59 AM
Is this more important than racquet head speed? While the speed of the racquet is important in generating spin on brushing up on the ball, surely a racquet weighing only 100 grams would not generate much power no matter how fast it's swung.

From a purely physics perspective, the only things that dictate how fast and with how much spin the ball leaves your racket with are the speed and mass of the racket (there are many components to speed and mass, but basically that's it). How tightly you're holding the racket or how much "weight you have behind the shot" does not effect the ball in the slightest.

Unfortunately, while physics clearly dictates everything, knowing the physics will only help you so much. Your knowledge of the physics must be communicated and put into action by your body, with direction from your mind. Since the muscles in your arm can't add 1+1, much less compute the effective mass of a contact point on a racket face, physics isn't the best language to get your body to do the right thing.

This is where terms like "leverage" and "getting your weight behind the ball" come in. They paint images your mind and body can follow, to produce the racket speed that the physics dictate will generate a fast / spinny ball. The key is to find the mental images that work best for you.

Don't throw out the physics knowledge though. It will keep you sane. When a ball leaves your racket at a 45 degree trajectory, you'll know its not some mystical force, but that the angle of your racket face was too open. Then you can find the mental images that will help you close the racket face.

LeeD
01-12-2010, 08:14 AM
Another scientist who's interested in tennis?
Hope you also play tennis.
Leverage? Long arms provide more leverage than short arms. Shots hit with arms extended more tend to have more leverage than shots hit with arms compact to body.
But when you add swing speed, body kinetics, force at the grip, then other factors come into play.
Maybe we should limit this to ONE factor at a time. Leverage.

TennisCoachFLA
01-12-2010, 08:59 AM
Yup, Bills your man for this one. I can teach people from age 4-74 how to hit a tennis ball much harder than they ever thought possible. Since I learned how from the best, I can probably do this as well as anyone.

But I could not write you 10000 words to explain leverage and how I teach them to hit so hard and accurately.

skiracer55
01-12-2010, 09:19 AM
...I'm not going to try to get into the physics, but here's a drill that will get you to feel the concept of leverage...really, of the power of angular momentum...on a forehand.

Basically, a forehand is like throwing a discus. You don't need to run out and buy a discus, however. Just go get a Frisbee, find a large, open area, as in a field next to a tennis court next to a park, and practice winging the Frisbee just as a discus thrower would. That's leverage on a forehand...

LeeD
01-12-2010, 09:21 AM
Me, I throw my frisbees with a backhand swing.... :):)

TennisCoachFLA
01-12-2010, 09:44 AM
...I'm not going to try to get into the physics, but here's a drill that will get you to feel the concept of leverage...really, of the power of angular momentum...on a forehand.

Basically, a forehand is like throwing a discus. You don't need to run out and buy a discus, however. Just go get a Frisbee, find a large, open area, as in a field next to a tennis court next to a park, and practice winging the Frisbee just as a discus thrower would. That's leverage on a forehand...

I think if he just reads and follows the slogan you put at the bottom of your posts he will be just fine.

smoothtennis
01-12-2010, 09:55 AM
How tightly you're holding the racket or how much "weight you have behind the shot" does not effect the ball in the slightest.



But the weight transfer and degree of grip DOES indeed affect the final racket head speed and transfer of energy transmitted through the racket. =====> which in turn does affect the ball.

LeeD
01-12-2010, 09:58 AM
Me, after playing tennis for well over 25 years, I find if I stick my racket out and barely hold it, the ball drops dead. If I stick the racket out and hold it firmly with both hands, the ball bounces back towards whence it came.

skiracer55
01-12-2010, 11:33 AM
Me, I throw my frisbees with a backhand swing.... :):)

...and that's the drill for getting leverage/angular momentum on the backhand! Now, for the serve, to get leverage, imagine you're trying to hang a towel over a shower curtain rod. And to perfect your service return, try a karate match in a phone booth! Just kidding!

skiracer55
01-12-2010, 11:34 AM
I think if he just reads and follows the slogan you put at the bottom of your posts he will be just fine.

...or as Edith Thys, one of my favorite ex-US Team skiers used to say about ski racing, "The dumber, the better."

pondus
01-12-2010, 09:12 PM
Yup, Bills your man for this one. I can teach people from age 4-74 how to hit a tennis ball much harder than they ever thought possible. Since I learned how from the best, I can probably do this as well as anyone.

But I could not write you 10000 words to explain leverage and how I teach them to hit so hard and accurately.

Too bad I'm in Ottawa and not Florida, otherwise I'd take a lesson with you tomorrow.

Thanks for all the great replies.... I love this forum.

pondus
01-12-2010, 09:16 PM
I think if he just reads and follows the slogan you put at the bottom of your posts he will be just fine.

I think this only works if you've already reached a certain level of understanding / feeling for the correct mechanics. If not, there must be a phase of relatively cerebral problem solving that must take place.

That's the way it works for playing the piano, trombone, learning to knit, and any other skill I think of, so why not tennis?

pondus
01-12-2010, 09:48 PM
i think your on the right track. its a key word in tennis. keep looking you will like what you find. i think.

You'd think Google would come up with lots of hits then with a search for "Tennis Leverage". It must be a key word that is not written much about then.

aimr75
01-12-2010, 10:02 PM
But the weight transfer and degree of grip DOES indeed affect the final racket head speed and transfer of energy transmitted through the racket. =====> which in turn does affect the ball.


yeah i agree.. try hitting a ball on the back foot with weight moving back, there is nothing on the ball compared to putting your weight into the shot.. it has to affect it

chico9166
01-13-2010, 04:56 AM
In my mind, leverage in tennis, is simply the relationship between you and the ball at impact. A positional advatage, is all that leverage really is.

Meeting your contact point requirement is an example of a leveraged position(on the groundstrokes for example), as is places the hand and hitting elbow in front of the midline, and allows for a more efficient release of kinetic energy.

IMO, leverage is an important concept in learning the game, and something I stress very early in development. An emphasis on meeting contact points, and "finding an advantages position on the ball" is one of the quickest ways to improvement, and building skill set.

Sublime
01-13-2010, 07:29 AM
yeah i agree.. try hitting a ball on the back foot with weight moving back, there is nothing on the ball compared to putting your weight into the shot.. it has to affect it

This is because when you push off your back foot (weight moving back) to invoke the kinetic chain, you cause your hips to rotate in the opposite direction from your swing path.

So your arm swings forward, your shoulders swing forward (using your back and abs), but your hips turn the opposite direction. This cause you to coil into your swing. Which slows the racket head speed and weakens the shot. It had nothing to do with the weight behind the racket.

Sublime
01-13-2010, 07:30 AM
Me, after playing tennis for well over 25 years, I find if I stick my racket out and barely hold it, the ball drops dead. If I stick the racket out and hold it firmly with both hands, the ball bounces back towards whence it came.

Good point! Volleys are different, because the ball has the mechanical advantage.

smoothtennis
01-13-2010, 09:15 AM
This is because when you push off your back foot (weight moving back) to invoke the kinetic chain, you cause your hips to rotate in the opposite direction from your swing path.

So your arm swings forward, your shoulders swing forward (using your back and abs), but your hips turn the opposite direction. This cause you to coil into your swing. Which slows the racket head speed and weakens the shot. It had nothing to do with the weight behind the racket.

On a normal forehand, your hips turn into the shot, ie, turns in the direction of the swing path. When he says "weight behind it" what he really means is his body weight is transfering through the kinetic chain forward into the racket which increases racket head speed.

However you want to expain it, it does make a HUGE difference when you transfer your body weight forward into a shot vs. leaning up and back. It is a night and day difference.

It is the same mass and force, but when the 'direction of force' is linearly into the ball the 'effect' on the ball is very different. Yes, weight and mass remain equal in both scenarios -but the plane and direction of force is where the effect on the ball means a weak or powerful shot. And that is what leverage is all about - applying force into a specific and advantageous area to allow a greater effect on the target object.

Zachol82
01-13-2010, 09:32 AM
However you want to expain it, it does make a HUGE difference when you transfer your body weight forward into a shot vs. leaning up and back. It is a night and day difference.

Someone posted in another thread that by stepping into your shot, you gain approximately 6mph on the ball. However, by stepping back on a shot, you lose approximately 4mph. This is with good form and all other things being equal. These may not look like big numbers, but if you consider that most rallies only reach 40mph, if even that, then +6mph is a pretty big chunk. Just think of standing in front of a car going at 6mph, I'm sure you'll feel it if it hits you (of course the car's mass is a lot more, but still 6mph is faster than most people think).

Also, a lot of the times, people will only miss reaching a ball by a couple milliseconds, therefore even a little bit more pace is important, especially if it's something as simple as stepping into your shots, which you can easily make a habit of doing.

papa
01-13-2010, 10:12 AM
The "leverage" pertains primarily to the "lift" aspect in the stroke. The arm is being used more like a lever in this process. However, it also used "somewhat" in the "push" aspect of the the stroke and that's one of the reasons for keeping the elbow tucked in produces consistency (FH side anyway).

Sublime
01-13-2010, 10:44 AM
When he says "weight behind it" what he really means is his body weight is transfering through the kinetic chain forward into the racket which increases racket head speed.

We agree. My point was that the physics dictate that only racket head speed matters. All the weight in the world behind a racket moving 20mph slower won't produce a faster shot.

But you're probably worse off performance wise knowing that, then just trusting the adage of "get your weight behind the racket". Because knowing that you need fast racket head speed is different than knowing how to get fast racket head speed.

pondus
01-13-2010, 05:01 PM
This is because when you push off your back foot (weight moving back) to invoke the kinetic chain, you cause your hips to rotate in the opposite direction from your swing path.

So your arm swings forward, your shoulders swing forward (using your back and abs), but your hips turn the opposite direction. This cause you to coil into your swing. Which slows the racket head speed and weakens the shot. It had nothing to do with the weight behind the racket.

Interesting stuff. What does it mean to coil into the swing? As opposed to what? Is this what folks mean when they speak of "hitting through the line of the incoming ball" (good) instead of "hitting out to the point of contact" (bad).

I'm trying to visualize the hips turning in the opposite direction, trying it in my living room etc. but I can't figure out how. Can you expand on it, or suggest an excercise to help understand this problem?

Many thanks! :)

pondus
01-13-2010, 05:19 PM
We agree. My point was that the physics dictate that only racket head speed matters. All the weight in the world behind a racket moving 20mph slower won't produce a faster shot.


Are you sure about this? I've been confused about this one for a long time!
Maybe it has something to do with the fact that less twisting upon impact means less power loss. Anyhow, check this out from the book "Technical Tennis" written by a couple of Ph.Ds who specialize in tennis physics (Rod Cross and Crawfor Lindsey:

Page 23: "[At any given racquet head speed] there is a 10 mph increase in outgoing ball speed when the racquet weight is increased from 200 to 400 grams. Alternatively, Joe could decide to swing the 400 gm racquet upwards at a steeper angle than the 200-gm racquet, in which case the outgoing ball off both racquets would be about the same, but the 400 gm racquet would generate more topspin."


But you're probably worse off performance wise knowing that, then just trusting the adage of "get your weight behind the racket". Because knowing that you need fast racket head speed is different than knowing how to get fast racket head speed.

pondus
01-13-2010, 05:25 PM
Good point! Volleys are different, because the ball has the mechanical advantage.

Are you saying that the racquet should be loose in your hand at impact.I believe the way pros get such devastating punch is by keeping their hand very loose and then tightening it just at the last second. This makes the racquet face snap into the ball a bit, but more importantly, creates a "wall" for the ball to bounce off without your arm and shoulders getting tight from squeezing the racquet throughout the stroke.

What do you mean by "the ball has the mechanical advantage".

pondus
01-13-2010, 05:30 PM
The "leverage" pertains primarily to the "lift" aspect in the stroke. The arm is being used more like a lever in this process. However, it also used "somewhat" in the "push" aspect of the the stroke and that's one of the reasons for keeping the elbow tucked in produces consistency (FH side anyway).

Verdasco, Federer, Henin, etc. all use a straight arm and keep their elbow far away from their body, yet they are consistent.

I thought having a long contact zone (18 inches) is what produces accuracy.

I think leverage refers to the fact that when you turn your entire body, arm, and racquet, which is well stabilized against your hand to prevent twisting, then this whole unit acts as a level that rotates on a fulcrum point located somewhere just inside the shoulder opposite to the hitting arm.

pondus
01-13-2010, 05:33 PM
In my mind, leverage in tennis, is simply the relationship between you and the ball at impact. A positional advatage, is all that leverage really is.

So why would they use the word "leverage" as opposed to another word that more accurately describes what you are talking about? (which does not sound like a "lever - like action".

papa
01-13-2010, 05:55 PM
Verdasco, Federer, Henin, etc. all use a straight arm and keep their elbow far away from their body, yet they are consistent.

I thought having a long contact zone (18 inches) is what produces accuracy.

I think leverage refers to the fact that when you turn your entire body, arm, and racquet, which is well stabilized against your hand to prevent twisting, then this whole unit acts as a level that rotates on a fulcrum point located somewhere just inside the shoulder opposite to the hitting arm.

NO, straight arm is much more difficult from a mechanics and consistency standpoint. Can it be done? - sure but were talking very gifted athletes here and I certainly would not suggest it to the average or even above average player.

Some of your second part is correct. I assume "level" was just a misprint and you meant "lever".

pondus
01-13-2010, 06:03 PM
NO, straight arm is much more difficult from a mechanics and consistency standpoint. Can it be done? - sure but were talking very gifted athletes here and I certainly would not suggest it to the average or even above average player.

Some of your second part is correct. I assume "level" was just a misprint and you meant "lever".

Yes, I meant "lever". What you say makes sense. My new instructor is a fan of snapping the wrist through the forehand like Federer does. Should I be suspicious of him? After all, it makes no sense for me to learn to hit like Federer when I started tennis at age 37 only a few years ago, and have only 5 hours pr. week to hit. I don't want to hit the ball hard, just consistently.

Hence my fascination with Pat Dougherty's explanation of the forehand because it seems so much more simple and elegant. I made a leverage band out of some bungee chord and an old tennis elbow brace, and when I hit against the well with it, I get more power than I've ever gotten with a wristy snap through the ball, even though it feels like the racquet head speed is substantially slower.

aimr75
01-13-2010, 06:15 PM
My new instructor is a fan of snapping the wrist through the forehand like Federer does. Should I be suspicious of him?

If he is telling you to actively use your wrist, then yeah, i would be dubious..

pondus
01-13-2010, 06:18 PM
If he is telling you to actively use your wrist, then yeah, i would be dubious..

Not actively, no. He say it happens automatically when you are relaxed, and that infact you should give no thought to what your arm is doing, and simply focus on the correct contact point, organizing your feet to establish a solid foundation, and then push against the ground to generate power. The other issues he claims are effects, not causes.

aimr75
01-13-2010, 06:24 PM
Not actively, no. He say it happens automatically when you are relaxed, and that infact you should give no thought to what your arm is doing, and simply focus on the correct contact point, organizing your feet to establish a solid foundation, and then push against the ground to generate power. The other issues he claims are effects, not causes.

yeah, the effect of keeping a wrist relaxed would create that hinge which makes it look like a whip.. theres been a number of threads on this however..

Federer seems to always be a focal point with how relaxed and flexible his wrist is, but there are so many pro's that do the same thing.. i only just recently saw a slo mo of robredo's forehand at the hopman cup.. his wrist looked very much like federers..

5263
01-13-2010, 07:19 PM
Not actively, no. He say it happens automatically when you are relaxed, and that infact you should give no thought to what your arm is doing, and simply focus on the correct contact point, organizing your feet to establish a solid foundation, and then push against the ground to generate power. The other issues he claims are effects, not causes.

When the wrist does move, it should be more of a radial deviation opposed to a flexion hinge type movement, and should largely take place after to contact has taken place.
IMO it is the flexion type movement that causes most of the problem on the Fh. Oscar agrees with this suggestion.

papa
01-14-2010, 06:09 AM
John Yandell and BB have studied this in painful detail. IMO, John is the best mind in the game today and his research, books, web site, etc. are absolutely top notch. If you haven't had the opportunity to see his material, your missing out. For a Yale graduate, he's does ok

BB has thousands of posts here and I can't think of one that isn't well thought and presented or that would steer anyone in the wrong direction - this Board is very fortunate to have him contribute on a ongoing basis.

From time to time we all see things a little different or perhaps are more passionate about certain aspects of the game than others - that's the strength of this Board where we have a variety of opinions, some good - some not so good, coming together.

Oh yeah, the wrist. I kinda agree with aimr75.

SystemicAnomaly
01-14-2010, 06:38 AM
3rd class lever:

http://www.worsleyschool.net/science/files/lever/third.gif

Check out the link below for my post on how the arm is a 3rd class lever.

http://tt.tennis-warehouse.com/showthread.php?p=4276401
.

chico9166
01-16-2010, 03:41 PM
So why would they use the word "leverage" as opposed to another word that more accurately describes what you are talking about? (which does not sound like a "lever - like action".

Yes, the double bend hitting structure is the lever. I would suggest that the the "proper" position of the lever relative to the body at impact, would increase the mechanical advantage of the lever. Which is why I stressed the importance of proper contact points.

BlewByU
01-16-2010, 08:22 PM
Congratulations, pondus.
You have just posted the most thought provoking question in tennis IMHO.
Namely ,, how to best hit our bread-and-butter forehand shots !!!
I have spent months & months trying to answer this simple question myself.

Yes, physics law does govern our tennis playing.
But its very hard to actually use physics equations to improve our strokes in my opinion.

My question was finally answered (as properly as i hoped) when i came across this humongously important thesis as analyzed by tennis guru Robert Lansdorp.

Its only 3 short pages. You should read them very very carefully.
Pay special attention to page#2 "downward finish forehand".

page#1 (out front finish forehand) ---> http://www.active.com/tennis/Articles/The_Three_Forehand_Finishes.htm
page#2 (downward finish forehand) ---> http://www.active.com/tennis/Articles/The_Downward_Finish.htm
page#3 (reverse forehand) ---> http://www.active.com/tennis/Articles/The_Reverse_Forehand_Finish.htm

Thanks to this article, my forehand is a carbon copy of Federer's !!!

Good luck & happy tennis to all.

sennoc
01-17-2010, 02:23 AM
But its very hard to actually use physics equations to improve our strokes in my opinion.

Yes, it's hard to do. But you do not need to use the equations. You can use your understanding of physical laws.

BlewByU
01-17-2010, 10:24 AM
Yes, it's hard to do. But you do not need to use the equations. You can use your understanding of physical laws.

Bingo, sennoc .. you are exactly correct.
We MUST UNDERSTAND physics laws that govern each phase of our strokes in order to become better at it.
What i meant was ,, if we memorize mathematical description of physics laws and try to apply them during shot making, it probably won't work.

That's why Lansdorp's "downward finish" thesis is spot-on.
Lansdorp includes all pertinent physics laws in his short analysis without even mentioning a single physics terminology.

Angular momentum, leverage effect, contact zone, alignment to ball, simple arithmetics of not wasting your energy trying to negate power of incoming shot, delicate process of creating top-spin without even thinking about it, how you can hit low error margin power forehand every time all day long without getting tired without having big muscles ..... ITS ALL THERE !!!!!

Since this is monumentally important topic, please allow me to take you step by step in showing how i attained Federer's forehand.
As i now will show you, the beauty of this process is that its all automatic (you can only do this in one way - and by doing it that one way, you are automatically following all principles of applicable physics laws to optimize our swing)

STEP 0 .. You should realize that Lansdorp's downward finish forehand might be the key to your success in tennis (hint: "it is"). So you should give it a try with open mind.

STEP 1 .. As the ball comes to you, start stepping into that ball using a few large steps (in crunch, open stance works too). This stepping-in-towards-the-ball really works great.

STEP 2 .. As you get near the ball, start your angular momentum path of forehand swing by raising your racquet above shoulder near head level. Gently move your non-dominant hand in the same direction as your right hand to amplify your angular momentum.

PLEASE DON'T START YOUR ANGULAR MOMENTUM SWING TOO EARLY!
If you start too early, then what happens is ,, you end up waiting for the ball at the bottom of swing path. All your previous momentum energy gets lost this way.
You must start your angular momentum swing just before you strike the ball so that all of momentum energy gets full usage. This is very important.

STEP 3 .. As you start striking the ball, you must try to "drive through" the ball. At least 1 foot. I always tell myself to drive through 2 feet (well, 2 feet is impossible, lol .. but by having this mentality I can drive thru near 1.5 feet)

STEP 4 .. When you drive thru the ball, you will find that your arm is stretched toward the net quite a bit. This stretch automatically locks your wrist, elbow and shoulder in an optimal position. You are already utilizing leverage effect whether you know it or not.

Since you are swinging with locked stretched position, there is very little room for error (another added bonus). All parts of your arm are moving without any loose play. Real solid robust swing this is!

STEP 5 .. As you drive thru the ball, i find it best to keep the drive thru at straight horizontal path. When i try to drive thru at upward horizontal path, i immediately encountered more errors.

STEP 6 .. By keeping your drive thru at straight horizontal path, you will find that you are getting automatic effortless top-spin.
You don't have make deliberate attempt to brush up the ball. You don't have to emulate so called windshield wiper motion.
Just finish your straight horizontal drive thru with natural downward follow-thru that wraps around your waist level. Your shot already has top-spin added onto it.

STEP 7 .. Finish your glorious forehand by performing natural downward follow-thru that wraps around your waist level. Just be natural about it.
I experimented with even lower downward finishes. They work great too.

STEP 8 .. Go look yourself in the mirror. You just performed Roger Federer's forehand !


Again, the beauty of this whole process is that its all automatic.
You are already incorporating all pertinent physics laws without even thinking about it.
Besides, this method has low margin of error.
It is as effortless as you will find.
It also guarantees optimal power generation regardless of your physical build.
You can literally hit forehands this way whole day without getting tired.

Thanks and good luck everyone.

5263
01-17-2010, 06:05 PM
Interesting to see Landsdorp try to explain modern strokes thru the perspective of his "hit out through the 5 balls" mentality. I prefer to study these strokes from the several instructors who have been teaching it
this way for over 40 years, while Landsdorp was warning against this style.