Inverted Instruction - How the Impact Window Dictates What's Possible Via Stroke Mechanics

When Casio introduced High Speed Video (HSV) capability to the consumer camera market in 2008 with the introduction of its revolutionary Exilim EX-F1, a whole new world of instructional information and capabilities suddenly became accessible to everyone in tennis.

Previous to this, you had to invest at least $25K to have the same HSV capabilities (using industrial-grade Phantom camera systems, for example) as the Exilim HS family of cameras. Of particular usefulness was its capability of Shutter Speed control over the high-speed capture that eliminated blurring and gave clarity to key events in sports skill movements such as tennis strokes where none was possible before (well, for less than 25K, that is).

With the Casio, it became possible to clearly see the events in the 100-120 milliseconds around the ball impact event – the motion of the racket approaching the ball, the ball impact location on the string bed, the motion of the racket as the ball was in contact with the strings and the motion of both the ball and racket after the ball exited the string bed. All of these hugely important events were now revealed in full color and full clarity.

Given this revelation of the previously blurry impact event, it now became possible to ask concrete questions about what is going on in the most important motion of any tennis stroke – the racket motion in what sports science calls the "Impact Window" and perhaps some new information can be gained to help players increase stroke/shot performance.

Using the technological advance of a having a reasonably-priced HSV camera, we started looking at the events that happened in the Impact Window for the top players in the game, and what we saw was very, very interesting.

Among other things, we could begin to develop new concepts and perspectives about spin generation because we could now conveniently measure ball spin rates using HSV footage. Then we learned what type of racket motion is correlated with how much spin players could generate on any stroke.

So essentially for the first time, we could leverage information gathered about what is really happening inside the 100-120 milliseconds of the crucial Impact Window into developing a much more specific, detailed and refined way of coaching what movements are required both before and after players "interact" with the (racket and the) ball directly in the Impact Window.

Our knowledge of what's happening in the Impact Window for a top tennis competitor made a quantum leap in the Spring of 2012 when we obtained Impact Window information under match conditions by recording every impact made by 3 of the Top 4 ATP male players – Djokovic, Nadal, Federer and Murray. We have a fairly extensive video library of racket and ball motion actually deployed by these players in a live match with correlations to the ball spin rates of the shots emerging from their string beds.

The HawkEye people have the spin rate and speed data from every HawkEye court from every match where their system was operative across both tours, but we have footage of the racket motion that created those speed and spin values. This fact gives us a huge advantage in terms of translating these visual and quantitative data into practical, usable instructional information for any and all players.

We also collected the same information during this period between 2012 to 2014 for competitors at the National Junior level at Delray Beach (16/18 Clays) and Kalamazoo, as well as at the Orange Bowl (U16/18). We also have captured the same events at a local NTRP tournament for NTRP 3.5, 4.0 and 4.5-level competitors. So, we have a very clear idea how these events compare across a wide spectrum of tennis performance level and have learned a number of surprising trends between the NTRP 3.5 and NTRP 6.0-7.0 levels. Quite surprising!

Using this information we collected for a very large number of players across a wide range of performance level, we have re-organized almost entirely our instructional ideas and suggestions based on what we have observed in the Impact Window in the context of both racket and ball motion. We have expanded on these observations by capturing these events from different visual perspectives and used these to develop a 3D understanding of these movements.  Based on these concepts, we have revamped and reinvented how we understand and teach/coach stroke mechanics to all players. 

Essentially ,we have "inverted" the perspective from which we organize all movement information required to execute a tennis stroke.

For us, the beginning of the instructional information is based on what we have discovered about the formerly invisible or blurred events of the Impact Window. Then, we "organize" and base all instruction of the Pre-Impact and Post-Impact movements that "lead into" and "lead away" from those critical Impact Window movements.

So, we call this "Inverted Instruction" as we start by studying how you create Impact whereas all other instructional models or methods start with the Ready Position. Then, we work fluidly from the information we glean from your personal Impact Window in both "directions" and give you functional options to deliver whatever you want from your strokes  – more spin, more shape, more speed, less spin (sometimes), less shape, etc., etc.. All of which is achieved in a very specific, explicit and calculated way.

Therefore, when a player comes to us and asks us to increase their topspin levels, we will ask the player exactly what qualitative differences they want to achieve and then we can translate those desires into quantitative performance targets and stroke mechanical instructions. 

For example, if a player is hitting their transition FH consistently 6 inches long and wants to reverse this outcome so their FH lands 6 inches inside the line, this requires increasing the topspin rate on those transition FH by a minimum of 150-250 RPMs. 

We will then present the qualitative and quantitative difference in how their shots will be influenced in terms of shape and depth – the 2 most important characteristics of your shots, in our opinion – and then give them very specific instructional information - specific to the player's current FH stroke mechanics - to achieve the desired increase in topspin production (or decrease if that's what they really want or need) to the player.

Bottom line is this... We at TennisSpeed Research can "tune" any player's strokes in a manner that few can or will ever achieve.

Like the various Constructors of Formula 1 racing, we can deliver very precise and specific changes to your stroke mechanics, the shots coming off your strings, and therefore open up new tactical options to your game in a very rapid timeframe in a highly integrative way.

The quality of tennis technical coaching isn't the same across the industry on a global basis from the tour level to your local club or facility and especially compared to the ever-growing armada of online instructors and instruction sites.

Life just isn't fair… Fact of life.