Thursday, January 15, 2015

A Roadmap to a Hall-of-Fame Forehand: Part 11 - Review and Quiz Answer Key UPDATED

**I've added and image or two and corrected a few typos in the text. Will there be new posts in the (near) future? Let's wait and see, shall we?**

Another long hiatus since the last post has finally passed, so let's pick up where we left off from the now distant past. Sorry about the delay...

I recall that I wrote in the original text of this Review and Quiz that I would provide an answer key "sometime after the New Year arrives". 

Notice I didn't specify exactly which New Year! :-)

The answers to these quiz questions won't be overly detailed compared to the typical posts on this blog. However, the answers are more than "in depth" enough for anyone with the motivation and ability to think critically and "connect the dots" to (re-)construct or correct their own (unique) forehand mechanics.

Also for those who are thinking along with an open and critical mind, you probably realized that the images accompanying many of the questions posed often provide a visual "hint" about the answer.

So without further ado, the quiz answers are presented in Italics to distinguish them clearly from the questions themselves.

Q: Why is spin production on the topspin forehand so critical to the effectiveness of this stroke in today’s pro game? 

A. Topspin is the only practical means to control the increased distance a shot travels at high ball (and racquet) speeds. At the types of racquet speeds demonstrated by the today's top players, the ball would not consistently fall down inside the lines of the court without the accompanying increase in topspin production.

Q: What impact location on the string bed is correlated with higher (top-)spin production compared with a “central impact” on the string bed? 

A: Forehands struck below the equator of the string bed are correlated to increased topspin rates (up to 50%) compared to a "central impact" on the string bed.

Q: What impact location on the string bed is correlated with lower (top-)spin production compared with a “central impact” on the string bed? 

A: Forehands struck above the equator of the string bed are correlated with decreased topspin rates (up to 70% less) compared to a "central impact" on the string bed.

Q: What is the position of the racquet face in the topspin forehand of the majority of the current ATP Top 10 at the end of their respective backswings?  

A: The racquet face is closed (using Elbow Pronation) when the top players complete their backswing.

Q: What is the position of the racquet face in the topspin forehand of the majority of the current ATP Top 10 just before they initiate their forward swing to impact? 

A: Same as previous question.

Q: What is the position of the racquet face in the topspin forehand of the majority of the current ATP top 10 at the moment of impact? 

A: While the exact extent of racquet face closure - forward tilt of the racquet face - may vary slightly, the racquet face is closed at the moment of impact in a top player's topspin forehand.

Q: True or False? The positioning of the racquet face alone is the most critical factor in determining overall topspin forehand performance? If false, explain what factors are also involved. 

A: TRUE. The functionality of the topspin forehand today is rooted in the player's ability to maintain (and manipulate in many cases) a closed racquet face at the most critical moments of the forehand stroke - i.e. when the racquet is swing through the Impact Zone. Other racquet arm movements (e.g. Elbow Flexion, Wrist Extension and Flexion) can either enhance or interfere with the player's ability to execute this necessary closre in the crucial milliseconds before, at and after Impact. 

Q: What is the optimal position of the racquet face in the following two points in the follow-through phase of the topspin forehand:

1. When the racquet arm first reaches shoulder height? 

A:The racquet face should be closed - hitting face pointing toward the court - at this stage of the follow-through.

2. At the completion of the stroke? 

A: Same as previous question.

Q: What are the 2 fundamental changes in the overall racquet motion – swing path and racquet face position – in the topspin forehand mechanics employed by current Top Players compared with previous generations of tour-level players? 

A: The two fundamental changes are:

1) the extent of closure of the racquet face at nearly all stages of the stroke from the backswing to the follow-through - but especially at the stage when the racquet is swung forward to Impact (or "FFM" - the "first Forward Move" - as we've defined it in an earlier post in this series); and

2) the significant reduction in the steepness of the (upward or "low to high") racquet swing path angle to Impact.

Q: What is the position of the racquet face in the topspin forehand of the majority of the current ATP Top 10 in the “Impact Zone” – i.e. about 18 inches before and after ball impact on the string bed? 

A: Again, the position of the racquet face is closed - tilted forward in a range from about 5 degrees to 17-18 degrees from the perpendicular - depending on the specific arm movements used by the player to execute their forward swing to Impact.

Q: What is the difference (in percent) in the amount of (top-)spin produced at impact locations other than the center of the string bed?

A: The amount of topspin that is produced when the ball is struck either above or below the "central section" of the string bed can vary up to 70 percent.

Q: Which of the following characteristics of a Top Player’s topspin forehand has the greatest influence on topspin production?

Swing path of the racquet?
Arm Structure during the forward swing?
Racquet arm movement in the Impact Zone?
Position of the racquet hand just before the forward swing?
Position of the racquet hand at Impact? 

A: From what we've observed after analyzing hundreds of hours of super-slow motion videos is that (controlling) the racquet arm movement in the Impact Zone is the critical factor or skill in maximizing topspin production on a forehand. The grip used by the player is the least important factor in our view.

The remaining attributes" the swing path of the racquet; the racquet arm structure (elbow flexed or extended; wrist stable or moving towards flexion from extension); the racquet hand positioning just before Impact, at Impact and after Impact; all run together as a close second to the racquet arm movement in the Impact Zone.

These four (4) factors all influence how much pronation - commonly referred to as "covering" - the player can execute in the Impact Zone to increase forehand topspin production.

However, without first having or "forming" the specific intent (in your mind) to create/maximize (Elbow) Pronation in the Impact Zone, players will not maximize their shot control at high racquet speeds by maximizing topspin production.

Maintain a "stable" or "constant" racquet face angle in the Impact Zone by controlling your overall racquet arm actually restricts/limits topspin production - a fact that might prove to be a useful concept in developing the ability to vary topspin production during play.

Q: Which of the following characteristics of a Top Player’s topspin forehand has the least influence on topspin production? 

Swing path of the racquet"
Arm structure during the forward swing"
Position of the racquet hand just before the forward swing"
Position of the racquet hand at Impact? 

A: The grip used by the player appears to have the least influence on topspin production. The racquet motion of the forward swing to Impact and the factors that contribute to maintaining forward tilt or encourage making consistent contact below the equator of the string bed have far greater influence on topspin production.

Does it help to use a grip - i.e. an extreme Eastern (i.e. Lendl and Federer) or a Semi-Western (Nadal, Djokovic; et al.) - that promotes having a closed racquet face in the Impact Zone? Yes, we would agree with that statement.

However, as they say. "the devil is in the details", and for those players who haven't yet realized that how they move their racquet arm through the Impact Zone is the primary determinant of topspin production rather than their grip choice, the net result is that they end up reducing their ability to produce the necessary "extreme" topspin rates by executing non-optimal movements at the moment(s) of truth in the forehand stroke.

For those critical thinkers in our audience, this may be a good time, for learning purposes, to apply the "Costanza Principle" and consider this question:

What kinds of (racquet arm) movements promote decreased topspin production and why?

Again, while we have focused up until this point on why and how today's top players maximize topspin production at (ultra-) high racquet speeds, there is no denying that the ability to vary the amount of topspin (or underspin or sidespin, for that matter) has important strategic and tactical benefits for all competitive players. 


Q: Rank in descending order – from most important (“1”) to least important (“6”) – how important is each of the stroke characteristics listed above to topspin production in the forehand stroke? 

A: At this point in history, we would rank the listed characteristics in this order of importance:

1. Position of the racquet hand just before the forward swing (i.e. at FFM)

2. Racquet arm movement in the Impact Zone
3. Arm structure during the forward swing to Impact
4. Swing path of the racquet
5. Position of the racquet hand at Impact
6. Grip

Q: What are the four (4) key characteristics of the racquet swing path used in the forward swing to Impact in today's Hall-of-Fame topspin forehands? 

A: These are the four (4) key characteristics of the racquet swing path used in HOF forehand today:

1. Elbow Pronation at FFM

2. Tendency toward Elbow Extension (versus Elbow Flexion) through the Impact Zone
3. Shallow, upward overall swing path to Impact
4. Active, but controlled Elbow and Wrist Pronation (and Wrist Flexion) in the Impact Zone

Q: What is the average ball speed of a Top Player’s topspin forehand when rallying in a tour-level tennis match? 

A: Based on our own measurements and supported by HawkEye ball speed measurements as shown in broadcasts of ATP Tour matches, the average forehand rally speed in a tour match ranges from the low- to high 70s range in MPH (114 to 129 KHM).

Q: What is the average ball spin rate of a Top Player’s topspin forehand when rallying in a tour-level tennis match? 

A: Of course spin rates do vary according to the unique topspin forehand mechanics (and play style preferences) of individual players , but generally speaking, most of the the current top 10 players generates topspin rates, on average, somewhere between 2,000 to 3,200 RPM during hard court play.

A so-called "flatter" player like Juan Martin Del Potro was shown by HawkEye to generate between 1,900 to 2,200 RPM on average, while Rafael Nadal at the high end often averages from 3,700 to 4,300 RPM during hard court play.

Q: What are the key anatomical characteristics of the topspin forehand mechanics that have been used to win 32 of the past 40 Men’s Grand Slam singles championships?

A: The two key anatomical characteristics we are referring to are:

1. Elbow Pronation at FFM, and

2. Elbow Extension during the forward swing to Impact

Q: What specific anatomical characteristic is common to the topspin forehand mechanics of 39 of the same 40 male Grand Slam Singles Champions? Well, make that 41 or 42 male Grand Slam Singles Champions as Stan Wawrinka won the 2014 Australian Open and Marin Cilic won 2014 US Open...

A: The specific anatomical characteristic is the significant Elbow Pronation at FFM that's developed during the transition from the backswing to the forward swing - using the terminology we've established in this blog, we refer to this type of forehand backswing to forward swing transition as  FHT-2.

Technically speaking, all 42 players demonstrate Elbow Pronation - it's just that the 2009 US Open Singles Champion, Juan Martin Del Potro, demostrates less Elbow Pronation than the other 41 players. Del Potro uses a different movement in the transition of his backswing to the forward swing call FHT-3 that results in far less Elbow Pronation at FFM.

Q: What is the most effective and efficient technology/methodology to analyze, optimize and correct tennis stroke mechanics today?

A: Slow motion stroke video capture and subsequent qualitative, anatomical motion analysis remains the most direct and effective way to help you - player, coach, parent, etc. - help you understand and improve your stroke mechanics, especially with the growing access to high-speed capture (up to 240 frames per second) from today's smartphones (both the latest I-Phone and Galaxy devices have high-speed video capture built in).

Since we are on the subject of using technology to improve your tennis skills, this give us an opportunity to present some feedback the effectiveness of a few initially promising tech-y tools that claim to accurately measure racquet speed, ball spin, Impact location on the string bed, even swing geometry characteristics such as racquet path - such as the Babolat Play racquet and the portable, racquet-mounted and smartphone-connected Zepp and Sony racquet sensors; etc. - that don't quite deliver fully on all their promised capabilities.

These new toys deliver okay on some of what they claim to measure about your swing and shot - specifically in terms of measuring racquet and ball speed. What they all fail at is (accurately) measuring spin rates. Why? Well, this is because, to the best of our knowledge, these devices do not directly measure ball spin rates.

So, where does their spin "read-out" come from? These devices most likely estimate the ball spin rate based on their racquet speed and/or sometimes direct trajectory measurement (which is possible using today's miniaturized accelerometers and gyroscopes) and then they "calculate" or "estimate" the resultant ball spin rate. Or, rather in the case of the Play racquet, the spin rate is based on a correlation between the calculated spin rate against known, spin rate data loaded into the Play chip.

Bottom line is that these devices at best, can deliver only a spin rate estimate all told... Not a measurement, but a rough estimate.

Ok, so you might be thinking (hoping) that it's still a reasonably accurate estimate, right? 

Well, frankly it's not close to being even reasonably accurate because we are aware of some privately conducted research that clearly demonstrated that the instrument used to create the correlative ball speed and ball spin rate data for the Play racquet does not generate accurate ball spin measurements.

So, again, for all practical intents and purposes, we circle back to high-speed video capture as the "gold standard" for both athletic motion and ball spin analysis at this point in history, despite growing claims that new products are available to deliver such measurements  more conveniently.


Q: What do the following numbers mean?
In this exact order: 4, 40, -5, 4000, 80, 18, 12, 25, 7
Input these numbers in the empty fields on this webpage, record the result and explain what those results show and mean.

A: These are the numbers that we input into a so-called "shot trajectory calculator/analyzer" that's available for public use on a prominent online tennis equipment retailer's website (that seems to be intended to help their customers make a better racquet buying decision).

These numbers are "real" measurements of a Nadal rally forehand that were requested as inputs for this "shot analyzer" (software) program.

In turn, the analyzer returned a result that calculated that Nadal's forehand wouldn't even clear the net. The result returned by the analyzer differed greatly from the actual outcome of the stroke. In fact, this particular Nadal forehand cleared by the 3 feet and landed into play 4 feet from the baseline near the center mark.

We also entered the values for several other Hall-of-Fame forehands and got similar results - according to this analyzer/calculator, a Hall-of-Fame defies the laws of physics, as defined by its software code, when we witness them clear the net and then fall into play.

Now, don't take this too seriously as we aren't trying to go all "Ralph Nader" on you by "unveiling" the discrepancy between the shot analyzer/calculator results and what actually happens in reality.

The shortcomings of this online shot analyzer offers a clear example of how much we have to learn about what's actually happening during play. The conception, formulae and/or algorithms deployed in this online tool clearly needs some improvement before it can be used to accurately predict the actual shot characteristics in the real world. What those improvements are, I'm afraid, are just beyond my interest and expertise.

Interestingly, we also entered values we measured from non-Hall-of-Fame topspin forehands struck by non-professional players - specifically players who are rated between 4.0 and 5.0 NTRP - and found that the analyzer was able to reproduce the actual shot trajectory in a reasonable accurate manner (although there were still pretty significant differences (15-25%) in the analyzer's calculated ball spin rates compared to the measured ball spin rates.

Our speculation about why this analyzer could more accurately calculate the shot characteristics of the non-tour pros leads us to suspect that the creators of the analyzer most likely used actual speed, spin and trajectory measurements taken from actual shots struck by non-tour players (as its far easier to get access to non-pros to gather this information) as the basis for 1) formulating the equations used by the software program to calculate/estimate the resulting shot characteristics (launch angle, ball speed, spin rate, etc.), and then 2) they used the measured characteristics to confirm/verify the accuracy and quality of the program's output.

What should be of concern to the tennis-playing public is that the creators of this analyzer, to give them the benefit of the doubt, clearly overlooked the possibility that entering "shot parameter" values that are characteristics to better players, much less the best players, might result in miscalculations that do not accurately reproduce or reflect the actual characteristics of the real world output of a certain "type" of player - however few the number of these kinds of players there are at any time in history.

OK, the creators failed to "quality check" their analyzer in a very thorough way and, as a result, the users of this program are only getting information of limited quality and usefulness. You can defend the creators by rationalizing that Tour-level players are unlikely to buy their racquets from an online retailer, among other rationalizations to mitigate the fact that the average consumer may have placed total faith and credence in the accuracy of this tool simply may not be getting the right information because this tool is fundamentally flawed.

The bottom line is that the clear misfire of this shot analyzer/calculator tool is yet another example that these are still early days as far as understanding the scientific realities of tennis performance.

We hope that this Review and Quiz has helped you tie together the important concepts of the stroke mechanics of today's Hall-of-Fame topspin forehand. There will be a few more installments of this forehand series to go where we'll "tie off a few loose ends" that have been raised  in previous posts, but not yet addressed or explained since.

Until next time (which will likely be sooner than 13 months from now, Ha)...


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