Psychophysics
I always wanted to learn to juggle. I hoped that once I had mastered juggling I could use it to entertain small children, impress girls or be the life of the party. I purchased a "Juggling for the Complete Klutz" kit and set to work. As a consummate klutz, I found step one, keeping one ball in the air, challenging. Step two was even uglier, but through pure force of will, I managed to keep two balls in the air for short periods (microseconds). I never got to step three. Though deeply frustrated, I found it easier to abandon my hopes for a career as a street performer than to figure out how to simulate the miracle that so many ordinary appearing people have mastered. Having devoted over half a century to improve my tennis game, I am not willing to accept the consequences of my lack of natural athletic ability. I am determined to discover the root differences between those who are "born to play," and those of us who are are not. Engineers solve seemingly insoluble problems by breaking them into smaller, solvable pieces. It is for that reason that I have chosen to begin by breaking down tennis performance into its two most fundamental components: psychology and physics. I fully intend to gloss, over, or completely ignore the value of fitness, strategy, tactics, endurance, strength of character, and how to psych your opponent into a nuclear meltdown. All of these are important components of victory to be sure, but if you can't hit two forehands in a row then fitness is pretty pointless.
So, if on a given day you are spraying the ball all over the place, is the problem in your head or your hands? Are you hitting repeatedly into the alley because your topspin is insufficient, or are you a victim of the alley-oops syndrome, i.e., your brain is desperately trying to deal with an annoying retriever who runs down every ball you hit? If your stroke physics is bad, the balls you hit are not going to find the court, but even if your strokes give you ultimate dominion over the ball, psychopathology can still prevent you from performing. Worse yet, physics and psychology can play off of one another: Bad stroking can cause bad mojo, and bad mojo can cause bad stroking, so teasing out the proximate cause can be challenging.
The Medical Model and Tennis
To help us untangle this diagnostic slip-knot, we are going to apply the medical model to tennis. In this model, each player is both doctor and patient. We start with a problem as reported by the player, the chief complaint (CC). A typical chief complaint would be, "I just generally suck at tennis!" We then collect data from the patient, mostly in the form of subjective information, the symptoms (Sx), and observations or physical examination, the signs (S). Spraying the ball all over the court is a typical Symptom, while a hollow sound made by the ball as it strikes the strings is a Sign. We then assemble a list of maladies that might be responsible for the problem, the differential diagnosis (DDx), and start whittling down the list with more questions or diagnostic tests (Tx) in hope of identifying a specific disease process or 'syndrome' (Sy) that we can effectively treat (Rx). This 'whittling down' process is important. In tennis, as in medicine, signs, and symptoms are often 'non-specific.' That means that a given constellation of signs and symptoms may result from several disparate syndromes, each of which may be responsive to different attempts at treatment. If your forehands are often just long, the problem may be insufficient topspin, absent control, tightness, overhitting, not watching the ball, etc. Each of these will respond to a different intervention. In the medical model, we identify a single cause and therefore choose an appropriate treatment by applying the scientific method. In short, this means starting with a differential diagnosis list and challenging each of the list items with provocative tests designed to disprove it and thereby eliminate it from the list. This game is called trying to prove the null hypothesis, and it goes something like this; "If poor footwork is the problem with your forehand, you should be feeling off-balance at times. Do you?" If the answer is 'yes,' we have FAILED to prove that poor footwork is NOT the problem. It does not, however, mean that poor footwork IS the problem. If the answer is 'no,' we have proved that footwork is likely not the answer - you have proved the null hypothesis, i.e., proved that poor footwork is likely NOT the cause of the problem. This process may sound tiresome, but it is way less tiresome than spending weeks or months trying to fix your forehand footwork with no improvement in your game. I have wasted half a century chasing such specters, so I can attest to the value of correctly identifying the correct diagnosis. After we have attacked each possible diagnosis on the differential list we are left with is a shorter list, preferably one diagnosis, which we then try to fix, therapy (Rx). If the therapy works, we were (probably) right! If not, it is back to the differential diagnosis, and we consider something else on the list.