Pat Cash on Serve: "Knee bend means an extra 90% chance of messing up your timing".

[Raul_SJ]

Knee bend is important for top servers at Wimbledon, as it gives an extra 15-20% of power, but as Pat Cash says it means an extra 90% chance of messing up your timing. Once we understand that the upper body gives 80-85% of power in the serve we understand that the lower body is primarily used to promote torsion and the shifting of body weight backwards, around, then forward and up to contact with the ball.

http://www.bbc.co.uk/guides/zgppfg8​

Surprised to hear Pat say this. Why would bending the knees greatly increase (90%) the chances of mishits? Is he mainly talking about lifting off the ground or even staying grounded while bending knees?

If this is true, it suggests that club players should consider staying grounded with zero to minimal lift off the ground. I find that I have better feel and accuracy when staying grounded.​

 

[coolschreiber]

Wow! ok .. But all the power in the serve is ideally derived from legs. I guess practice should fix those timing issues.

 

[BurnNotice]

I don't consciously bend my knees with I serve. More I focus on the push off from the bent knees during the upwards motion.

Your knees are forced to bend in the proper trophy position. otherwise standing straight up and bending that back is going to hurt!

 

[GuyClinch]

Pat is correct - alot of servers on the rec side of things would be better serving on balance (not even launching into the air) and taking the legs mostly out of the shot. By trying to mimic everything a pro does at once they get set back and their coordination is off. Most of your serve power does NOT come from the legs. However if you want to serve really big - 100+ you going to need to use the legs more..

 

[ARKustom93]

In case you'd like to know what a pro-level, no-knee-bend serve looks like, check out Sjeng Schalken ...

Oh, and re that "90% chance" thing, ... love Pat Cash, but he pulled that number straight out of his ass ...

 

[P = NP]

Top players are able to coordinate their body movements more effectively. It is true that adding elements to your strokes can complicate timing, but obviously we need these elements to generate more power. Not sure where Cash got the 90% statistic; pretty sure that's B.S.

 

[Raul_SJ]

In case you'd like to know what a pro-level, no-knee-bend serve looks like, check out Sjeng Schalken ...

Oh, and re that "90% chance" thing, ... love Pat Cash, but he pulled that number straight out of his ass ...

Okay I will check him out. Never seen him play. He looks like a very tall guy. Would not call it a "no knee-bend serve". Seems to have significant knee bend, but he never really lifts off more than an inch. Always has one foot on the ground...

 

[Alien]

Wawrinka doesnt flex much

 

[ARKustom93]

Okay I will check him out. Never seen him play. He looks like a very tall guy. Would not call it a "no knee-bend serve". Seems to have significant knee bend, but he never really lifts off more than an inch. Always has one foot on the ground...

Try to find some footage from earlier in his career ... trust me, 0 knee bend, and stiff as a board ... quite a sight. JMac used to actually make fun of him ...

 

[Raul_SJ]

Try to find some footage from earlier in his career ... trust me, 0 knee bend, and stiff as a board ... quite a sight.

Isn't knee flexion (followed by extension) critical in achieving ESR and proper racket drop position?

 

[Chotobaka]

Lack of extreme knee bend does not negate the upward transfer of energy. I regularly see rec players actually lose energy transfer with excessive and superfluous movement while badly parroting the pros.

 

[Sentinel]

Okay I will check him out. Never seen him play. He looks like a very tall guy. Would not call it a "no knee-bend serve". Seems to have significant knee bend, but he never really lifts off more than an inch. Always has one foot on the ground...

What was that exchange at the end between the two ???

 

[dominikk1985]

you Need some knee bend, but most of the power Comes from the "arch" and turn of the Body (and Arm/shoulder of course).

stan has very Little kneebend and he regularly serves 140+. of course a well timed knee bend can add a few extra mph (roddick had a very deep bend and strong leg drive) but that is maybe the final 5 mph or so and if you do it wrong it can cost a lot more.

more important is to have good high contact point, good pronation/ISR, and turn/Extension of the Body as well as having good lag. if you get those things right and hit the ball consistently in the sweetspot you can still think of adding a leg drive like roddick or Groth.

 

[ARKustom93]

Isn't knee flexion (followed by extension) critical in achieving ESR and proper racket drop position?

Okay I will check him out. Never seen him play. He looks like a very tall guy. Would not call it a "no knee-bend serve". Seems to have significant knee bend, but he never really lifts off more than an inch. Always has one foot on the ground...

Try to find some footage from earlier in his career ... trust me, 0 knee bend, and stiff as a board ... quite a sight. JMac used to actually make fun of him ...

Correction: checked out his career profile, and apparently the no-knee-bend phase would have been around 2005/06, after an Achilles tendon injury which likely forced him to temporarily alter his motion. Sorry for the confusion ...

 

[Omedunk]

What was that exchange at the end between the two ???

I was there. Roddick complained about the running. Tongue in cheeck: it was an exhibition match.

 

[Hollywood401k]

He talks about knee bend in the very beginning here.

 

[LakeSnake]

I wonder how much of the debate on this site is intermediate players thinking they are or can be doing what the pros do.

 

[ultradr]

Knee bend is important for top servers at Wimbledon, as it gives an extra 15-20% of power, but as Pat Cash says it means an extra 90% chance of messing up your timing. Once we understand that the upper body gives 80-85% of power in the serve we understand that the lower body is primarily used to promote torsion and the shifting of body weight backwards, around, then forward and up to contact with the ball.

http://www.bbc.co.uk/guides/zgppfg8​

Surprised to hear Pat say this. Why would bending the knees greatly increase (90%) the chances of mishits? Is he mainly talking about lifting off the ground or even staying grounded while bending knees?

If this is true, it suggests that club players should consider staying grounded with zero to minimal lift off the ground. I find that I have better feel and accuracy when staying grounded.​

I agree. In fact, most of head speed is generated by arms swing.
In fact, there is a research paper from Indiana University that knee bend contribute less than ~10% of final swing speed.

Actually, most of us amateurs fail to master swing path of most strokes in tennis (before we die).

 

[Moz]

In case you'd like to know what a pro-level, no-knee-bend serve looks like, check out Sjeng Schalken ...

Oh, and re that "90% chance" thing, ... love Pat Cash, but he pulled that number straight out of his ass ...

Which is a coincidence because 90% of what Cash says appears to come out of his ass.

 

[ultradr]

Which is a coincidence because 90% of what Cash says appears to come out of his ass.

You just need minimum, natural flex of knee to transfer energy from back to front. That is not a forceful, conscious knee bend/flex to add power/head speed.

 

[dominikk1985]

He talks about knee bend in the very beginning here.

yes, we all know that roddick had a huge kneebend. nobody is denying that a good leg drive might add 10 mph to your serve if done correctly but MOST Comes from other factors.

a well timed knee drive might increase your Speed from 118 to 128 but it won't turn a 75 mph pancake serve into a 120 mph heater and it might in fact mess your serve up if you time it wrong.

 

[Hollywood401k]

Well obviously if someone is fundamentally failing at swinging a racquet, they've got other things to worry about. But assuming it's a real serve and not a pancake, I think what Roddick says may hold some value.

That being said, I'm sure Cash is right as well about timing. But... isn't that why we practice?

 

[r2473]

you Need some knee bend, but most of the power Comes from the "arch" and turn of the Body (and Arm/shoulder of course).

stan has very Little kneebend and he regularly serves 140+. of course a well timed knee bend can add a few extra mph (roddick had a very deep bend and strong leg drive) but that is maybe the final 5 mph or so and if you do it wrong it can cost a lot more.

more important is to have good high contact point, good pronation/ISR, and turn/Extension of the Body as well as having good lag. if you get those things right and hit the ball consistently in the sweetspot you can still think of adding a leg drive like roddick or Groth.

As explained by Pat in his Sonic Serve

I have little knee bend and still serve 120 mph in a pretty controlled manner.

 

[dgold44]

Who the hell am I to argue with Wimbledon Champ Cash.
MAkes sense. Never thought of that.

 

[SystemicAnomaly]

Isn't knee flexion (followed by extension) critical in achieving ESR and proper racket drop position?

Perhaps not actually critical but the leg drive (from the knee bend followed extension) can definitely be very instrumental in achieving a decent shoulder loading (ESR) and racket drop. While it is not absolutely to jump off the ground, some measure of leg drive will facilitate the actions of the shoulder and arm.

Jumping 6" off the ground should result in a higher contact point (and a better serving angle) and can result in a much more effective serve. But this is not an absolute must for rec servers. Knee bend can provide some other benefits for the serve.

Employing some knee bend and leg drive can add some 10-20 mph to a serve. But its value is more than just this. It facilitates a more efficient & effective kinetic chain. The shoulder and arm do not have to generate as much of the RHS and total power for the serve. Instead, they can transfer some of that power or kinetic energy generated from the legs and other parts of the chain. This could mean less "muscling" of the serve for some players.

I do not believe that adding a modest amount of knee bend is that difficult for many,if not most, rec players. It can be achieved without the extra 90% chance of screwing up the serve timing as Cash claims. While a deep, Roddick-like knee bend might result in timing issues for some, I don't believe that a moderate knee bend is much of a problem at all.

 

[TennisCJC]

I don't work too much on bending my knees. I do try to push up and in when serving and I think my knees flex a few inches unconsciously to maintain balance and to get in position to swing the racket up to contact. There have been other TT threads discussing knee bend and these reference articles that attribute about 10-15% of service power from knee bend. For me, I work on getting good balance, and a feeling of swinging the racket head upward and outward to contact. I also work on using the body to swing the racket and using the body involves leg push (up and in) and shoulder rotation. I think your knees will bend naturally if you keep the legs relaxed, maintain good balance and work on swing up and in with your body.

 

[Raul_SJ]

Employing some knee bend and leg drive can add some 10-20 mph to a serve. But its value is more than just this. It facilitates a more efficient & effective kinetic chain.
.

I do agree with the 10%-15% increase in speed that is commonly attributed to knee bend.

The question becomes how much of the kinetic chain, if any, is lost when bending the knees but staying practically grounded, as in the case of Sjeng Schalken, who bends but then barely lifts 3 inches with his right foot. I think his left toe is always grounded. Federer lifts off much higher with both feet off the ground.

 

[GuyClinch]

Cash might have pulled the 90% out of his ass - but as Nick Bolleteri was teaching years ago - its not really about knee bend. Pat is going after the players that just bend their knees like they were squatting - thinking this helps their pancake serve. Most serving progressions take the knees out until the proper throwing motion is established - and then try to work the legs in - but in the Nick B way - sliding the hips forward and using knee bend depending on flexibility.

What I see on the rec level is people with pancake serves squatting down some then slowing their swing down before contact and dinking the ball in. .This is really just a bunch of wasted energy. It's actually amusing. It's like they psyching you out - pretending they are going to hit this big serve - and then dink..

Roddick gets it too. Sure he does have great knee bend - but he recognizes it makes it harder to get the basics right.

 

[ultradr]

For world class pros, they should try to squeeze out of every 1% variable they can do.

For amateurs like us, you better off investing most of attention to the 90% element of it.
which is the upper body element: swing path, shoulder, pronation( ISR and ESR to be exact).
Most of amateurs do not fully master basic swing path of solid 2nd serves before we die.

 

[Chas Tennis]

Sjeng Schalken in a 2002 US Open quarterfinal match against Fernando Gonzales:

2002 & 2003 US Opens
http://voodemar.com/uo/2003-2/

"......Schalken is seeded 24th and never reached a Grand Slam quarterfinal until he did it on his 29th try this year at Wimbledon, where he was the only player to take a set from champion Hewitt. Gonzalez, seeded 28th, was in his first Grand Slam quarterfinal and bidding to become the first player from Chile to reach the Open semifinals. “I didn’t expect this, to be in the semis,” Schalken said. “I’m now a little bit more relaxed than before the quarterfinals.” Schalken won the match on a breezy day when he finally held on to a big lead in a tiebreaker. He led the first tiebreaker 5:1 and the second 5:3 and lost them both. At 6:5* in the 1st set he wasted a double set point. In the 2nd set Gonzalez led 3:2* (15/30) when lost 14 consecutive points, and a little bit later found himself at *0:3 in the 3rd set. There was no break point in the decider, no ‘deuce’ even once – they served so well. “You have to win one, of course to win the match”, Schalken said. He went ahead 6:0 in the last one before Gonzalez got the next two points. On the next point, Gonzalez returned Schalken’s serve wide, making Schalken the first Dutchman to reach the Open semifinals since Tom Okker in 1971. “I said to myself, ‘Go for it. The first six points you’re with the wind,”‘ he said of the tiebreaker. Schalken won his fifth match in the tournament after winning a total of seven in his previous seven U.S. Opens. But he failed at critical times. He committed his only two double faults of the match in the 4th-set tiebreaker. He matched Gonzalez with 12 aces, but Gonzalez also had 12 double faults. Schalken’s fastest serve was just 110 mph, compared with 130 mpg for Gonzalez. “I don’t have the speed. I don’t have that in my arm,” the 6-foot-3 Schalken said. “I tried that many times, but I get injuries.” The Dutchman improved his poor five-set record to 6-13....."

Video with career highlights.

 

[Moz]

It's strange that the majority of discussion about the leg drive in the serve is related to power generation. That's not the only benefit.

 

[Chas Tennis]

Elliott, Reid and Crespo discuss leg thrust. My interpretation has been that if the legs don't provide some thrust then it has to be made up in other motions that may add stress to the shoulder and, I believe, some other body part. There has been research on this subject.

Here is a 2008 publication, there were some earlier publications also.
http://www.researchgate.net/profile...nnis_serve/links/53df74980cf27a7b83067663.pdf

 

[LeeD]

Chotobaka posted a rare gem, way back in the middle of the thread.
Ain't how much bend you put in your knees, it's how much extension you put in the effort of serving.

 

[Raul_SJ]

Sjeng Schalken in a 2002 US Open quarterfinal match against Fernando Gonzales:

. Schalken’s fastest serve was just 110 mph, compared with 130 mpg for Gonzalez. “I don’t have the speed. I don’t have that in my arm,” the 6-foot-3 Schalken said. “I tried that many times, but I get injuries.” The Dutchman improved his poor five-set record to 6-13....."

I believe Schalken's low serve speed can be attributed to his lack off leg drive, which is consistent with the ~15% leg power contribution.
Schalken could be averaging 120 instead of 105 with more lift off. But maybe he is more consistent staying relatively grounded (~3 inches off the ground).

He should be able to serve faster without straining the arm if he lifted off more.

 

[LeeD]

Some player's have live arms, some don't.
Roddick had a live arm.
Brad Gilbert and Miraslov Mecir didn't.
Serve speed is about 1/20th of your tennis skill ratings.

 

[ARKustom93]

Sjeng Schalken in a 2002 US Open quarterfinal match against Fernando Gonzales:

2002 & 2003 US Opens
http://voodemar.com/uo/2003-2/

"......Schalken is seeded 24th and never reached a Grand Slam quarterfinal until he did it on his 29th try this year at Wimbledon, where he was the only player to take a set from champion Hewitt. Gonzalez, seeded 28th, was in his first Grand Slam quarterfinal and bidding to become the first player from Chile to reach the Open semifinals. “I didn’t expect this, to be in the semis,” Schalken said. “I’m now a little bit more relaxed than before the quarterfinals.” Schalken won the match on a breezy day when he finally held on to a big lead in a tiebreaker. He led the first tiebreaker 5:1 and the second 5:3 and lost them both. At 6:5* in the 1st set he wasted a double set point. In the 2nd set Gonzalez led 3:2* (15/30) when lost 14 consecutive points, and a little bit later found himself at *0:3 in the 3rd set. There was no break point in the decider, no ‘deuce’ even once – they served so well. “You have to win one, of course to win the match”, Schalken said. He went ahead 6:0 in the last one before Gonzalez got the next two points. On the next point, Gonzalez returned Schalken’s serve wide, making Schalken the first Dutchman to reach the Open semifinals since Tom Okker in 1971. “I said to myself, ‘Go for it. The first six points you’re with the wind,”‘ he said of the tiebreaker. Schalken won his fifth match in the tournament after winning a total of seven in his previous seven U.S. Opens. But he failed at critical times. He committed his only two double faults of the match in the 4th-set tiebreaker. He matched Gonzalez with 12 aces, but Gonzalez also had 12 double faults. Schalken’s fastest serve was just 110 mph, compared with 130 mpg for Gonzalez. “I don’t have the speed. I don’t have that in my arm,” the 6-foot-3 Schalken said. “I tried that many times, but I get injuries.” The Dutchman improved his poor five-set record to 6-13....."

Video with career highlights.

Thx for the clip, and I did find what I was looking for at 6:20 in, which is that no-leg-bend serve, the only reason for bringing Schalken into the discussion in the first place ...

 

[GuyClinch]

I believe Schalken's low serve speed can be attributed to his lack off leg drive, which is consistent with the ~15% leg power contribution.
Schalken could be averaging 120 instead of 105 with more lift off. But maybe he is more consistent staying relatively grounded (~3 inches off the ground).

He should be able to serve faster without straining the arm if he lifted off more.

True but most players I have seen under 4.0 don't get the upper body part of the serve right. So you want to get that down and then add in your legs, IMHO. This is what Pat is saying - and while the 90% number is made up - there is truth to how adding in extra stuff can mess up your serve. One progression that Florian Meier recommends is you first serve on balance. Then you serve where you essentially step through. And then you serve where you launch off your front foot. I don't know if this is a perfect progression or whatever - but the idea that balance and not leg drive should be the start of your serve is a sound one..

 

[gmatheis]

In case you'd like to know what a pro-level, no-knee-bend serve looks like, check out Sjeng Schalken ...

Oh, and re that "90% chance" thing, ... love Pat Cash, but he pulled that number straight out of his ass ...

I think that 90% is an increase in your chance to mess up. So lets say you have a 10% total mess up rate with no knee bend you would then have a 19% total mess up rate with knee bend added (90% increase in your mess up rate).

 

[TennisCJC]

Wawrinka and Almagro are 2 current pros with little knee bend. They as well as Sjeng Schalken have a bit of bend as it is almost impossible to have dead straight legs if you are extended the toss arm up and getting the front shoulder up but they do have very little bend. Wawrinka and Almagro to get leg push even without deep knee bend. I think this concept of good balance but not necessary using a deep knee bend is good as you can still get leg drive with just a few inches of bend and it is much easier to maintain balance and coordination.

 

[TennisCJC]

I think that 90% is an increase in your chance to mess up. So lets say you have a 10% total mess up rate with no knee bend you would then have a 19% total mess up rate with knee bend added (90% increase in your mess up rate).

Yes, that's what Cash is saying - a lot of people mess up their serves by trying to use a deep knee bend which is makes the motion more difficult as balance and coordination are complicated.

 

[psv255]

IMO people often hear "knee bend adds speed" and start trying it right away, simply bending their knees, jumping, and expecting a better result. The key is to tie the knee bend with its closest neighbor, the hip/non hitting arm stretch up the side of the body. That way the explosive push from the legs can speed up the hips opening, which is a better way to incorporate legs than simply "sit and lift"..

 

[RetroSpin]

It's interesting that there is next to no definitive biomechanical data on this issue. You'd think it would have been studied to death, but in reality we have a couple of studies and a lot of anecdotal or subjective opinion.

Two of the most analogous arm/shoulder motions to serving are an outfielder's long throw and a javelin throw. Neither athlete utilizes much in the way of upward leg motion. The skip or run forward and cartwheel their shoulders over a planted front foot. Of course, tennis rules preclude such a motion for serving.

Servers are using their legs to do three basic things. One is to hop into the court, two is to get a higher contact point, and three is to provide the claimed 10-15% increase in pace. I find this last one difficult to envision, as a top level server remains sideways after he leaves the ground, ie the upward motion is not being converted through some sort of kinematic chain mechanism into shoulder cartwheeling. I question how much if any additional ESR is generated from jumping. Maybe Stan and almagro are on to something.

 

[Raul_SJ]

It's interesting that there is next to no definitive biomechanical data on this issue. You'd think it would have been studied to death, but in reality we have a couple of studies and a lot of anecdotal or subjective opinion.
...
I question how much if any additional ESR is generated from jumping. Maybe Stan and almagro are on to something.

I am not convinced that lifting off necessarily generates greater ESR -- only that the knee bend is necessary to generate optimal ESR.

An earlier post claimed that some servers served with little/no knee bend, but I've never seen a high level serve with a straight knee.
Schalken, while staying grounded, still bends his knees.

I think significant knee bend is necessary for ESR (even while staying grounded) as the knee extension facilitates a deeper racket drop position. I suspect lifting off generates more speed, but that might be a result of other factors (higher contact point?).

Pancho Gonzales had a dominant serve during the era when the server had to be grounded. And he also played after the rule change that allowed jumping.
Examining the radar data from that period, if available, would give an insight. My impression is that Gonzales serve was not significantly faster after the rule change.

 

[gino]

Knee bend is important for top servers at Wimbledon, as it gives an extra 15-20% of power, but as Pat Cash says it means an extra 90% chance of messing up your timing. Once we understand that the upper body gives 80-85% of power in the serve we understand that the lower body is primarily used to promote torsion and the shifting of body weight backwards, around, then forward and up to contact with the ball.

http://www.bbc.co.uk/guides/zgppfg8​

Surprised to hear Pat say this. Why would bending the knees greatly increase (90%) the chances of mishits? Is he mainly talking about lifting off the ground or even staying grounded while bending knees?

If this is true, it suggests that club players should consider staying grounded with zero to minimal lift off the ground. I find that I have better feel and accuracy when staying grounded.​

Bold statement from Pat.......... Id say that top bio-mechanics specialists would say around 30-40% of power is generated by the kinetic chain from your feet, through your knees/quads/hips, into your torso for a powerful serve.

See below, courtesy of US National Library of Medicine:

"Effective servers maximally utilize their entire kinetic chain via the synchronous use of selective muscle groups, segmental rotations, and coordinated lower extremity muscle activation (quadriceps, hamstrings, and hip rotators, internal and external). This lower body–core force production is then transferred up into the upper body and out through the racket into the ball. If any of the links in the chain are not synchronized effectively, the outcome of the serve will not be optimal"

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445225/

 

[Raul_SJ]

I think that 90% is an increase in your chance to mess up. So lets say you have a 10% total mess up rate with no knee bend you would then have a 19% total mess up rate with knee bend added (90% increase in your mess up rate).

That is possible and maybe that's what he meant... So maybe Pat is not just pulling numbers out of the air.

 

[ARKustom93]

That is possible and maybe that's what he meant... So maybe Pat is not just pulling numbers out of the air.

Umm, one "possible" and two "maybe's"?? .... Yeah, right!!

 

[LeeD]

Pat is giving us old farts who can't jump a chance at tennis in the future.
Who needs to jump, if we're more accurate from the ground?
Accuracy can make up for pure power, line of sight, and athletic youthfullness.

 

[comeback]

Plus as you get older, doing a half squat on every serve will just make you more fatigued during the match.