Power is the root of all that is good in tennis. Without power, there is no pace, spin, or control. Talented tennis players generate power then invest a significant portion of that power into control and spin. Spin and control are not the same things. Contrary to popular practice, you cant spray balls in all directions then pull them back into the court with spin. Topspin, for instance, will allow you to hit balls with pace that clear the net strap by a margin of six feet then dive at your opponent's baseline. That is not control. If you don't achieve sufficient revolutions-per-minute or aim the ball a few degrees higher, it will sail long. Too much top or a slightly lower trajectory and the ball will bury itself in the net.

Control is the ability to take a ball that is coming in at any angle with any amount of pace or spin and redirects it along the desired flight path. You can't achieve consistency by limiting pace or adding spin; you must learn control. Spin and control are means to the same end - improving consistency. Without consistency, tennis is a sick, black comedy of errors. To achieve control and spin you must understand and apply the techniques of lock, load, lag and explode.

The purpose of the lock, load, lag, and explode sequence is to convert power from the legs into ball control and spin and then inject them into the ball on contact. It all begins eons (actually milliseconds) of time before the racket makes contact with the ball. The goal is to store energy and force inside the arm muscles as your legs, hips, and shoulders accelerate the racket towards the ball. The forearm muscles store two distinct flavors of force:

1. A linear "force forward" that will use linear impulse to inject momentum directly into the ball at the moment of contact.
2. A rotational force that will inject spin into the ball without affecting its linear flight path.

These forces are delivered to the ball automagically. They represent forces, not motions, so they are invisible. You store the force in the muscles of the shoulder, arm, and forearm using a well-accepted process called the "stretch shortening cycle." The forces are stored and carried along with the hitting arm as it accelerates towards contact with the ball. The forces are finally released when the moving racket encounters the ball with an explosion that is not unlike a torpedo hitting the side of a ship. You know it is happening by the "ping" sound of the racket and the "pop" feeling of the ball flying off of the strings. If you do everything right, you should have sufficient spin and control on the ball to keep even the most powerful shot inbounds.

If you aren't snapping your volleys, you are probably watching a lot of them sail long or fizzle into the net.

This sequence of events, Lock, Load, Lag and Explode, applies to every stroke in tennis but is much more obvious when analyzing groundstrokes and the serve then it is when you look at the volley and other short-strokes. The more "swing" in a stroke, the more dramatic these processes appear, yet proper completion of each of these phases is as essential in the volleys and short strokes as it is in the topspin forehand. If you aren't snapping your volleys, you are probably watching a lot of them sail long or fizzle into the net.

You Must (not)Grip It by the Husk!

To ensure that the racket accelerates into the ball and impacts it firmly YOU MUST GRIP IT GENTLY!!! Doesn't make sense, does it!? Most of us "differently-talented" players prefer to put a death grip on the racket when we want to control it - our sinews rippling beneath tanned skin as we choke the life out of the racket's grip. The result is a ball that 'flutters and floats', and a sore arm. I will admit to being particularly guilty of this, but in my defense, this soft grip - hard ball thing is a pretty strange paradox. Sadly, you need to know some muscle physiology if you are ever going to accept this concept.

Muscles - are like springs. See, physiology is not so bad! Muscles don't just move things - they can also store energy and deliver it when needed like - well - like a spring. Unlike metal springs, they have adjustable tension - from a sloppy loose, mushy thing like a rubber band to a tight, firm thing like a bunch of rubber bands. When the lower body produces energy, the upper body's muscles can store the energy so they can deliver it to the ball at the proper moment. This delay is key because muscles are also something else - they are slow, slow, slow. It takes a muscle a long time (hundreds of milliseconds) to change tension. If you want your muscles to push on the ball at the exact moment of contact, you need to start contracting the muscles before the ball gets there. You can't just wait and "turn them on" the instant the ball hits the racket. You can try tensing all of the muscles and keeping them (and your teeth) clenched throughout the stroke; this is the "death grip" technique. The problem with this method is that the force of the muscles trying to push the racket forward will be balanced and canceled by the muscles that oppose them, so the net force on the racket is zero. The only solution is to get the pushing or "agonist" muscles to tense while the opposing or "antagonist" muscles are relaxed. The only way to achieve this is to start with all muscles completely relaxed then arrange to stretch only the agonist (pushing) muscles. When you have the pushing muscles pushing unopposed by the antagonist muscles at the exact moment that the racket meets the ball, you will have generated impulse, and the ball will fall under your control. The bottom line is this: You can't generate control over the tennis ball at the moment of contact. You must 'preload' control in the backswing portion of the stroke. You preload the force by 'locking' the arm into a certain position, then 'loading' control forces into the muscles for delivery when the arm and wrist 'explode' at the moment of contact.

Putting it All in Proper Order

This is where things start to get tricky. You need to store energy in the agonist muscles then deliver it to the ball at the moment of contact, not 50 milliseconds earlier or later. What's more, the force must be in the direction you want the ball to go. You can't be pulling up for added spin or pushing for more power at the moment of contact because those forces would add impulse in the wrong direction. You should rely on the speed of the racket head for most of the pace, and on the direction the racket head is traveling for half of the spin that you need. You should not pull up through the ball to get extra topspin or push forward through the ball to get more pace because both of those forces will changes the direction (vector) of force on the ball at the moment of contact. The upward "make more topspin" force will combine with the forward "make more pace" force and result in a net impulse that points up and out of play. Yanking up on the ball to get more topspin and to hold the ball in always has the opposite effect - making the ball tend to fly out. The same thing happens with hitting slice, but in reverse. Pulling down on the racket at the moment of contact is why your slice sometimes catches the net strap. Any pushing for pace or pulling for topspin has to be completed long before the racket gets to the ball. So, before you accelerate the racket head to produce pace and spin, you must first store a linear directional force for control and a rotational force for extra spin in the agonist muscles of the hitting arm.

Lock and Load

This is where "lock and load" come in; it is a very rapid sequence of events that begins after the initial shoulder turn of the stroke and ends as the racket begins moving forward in the acceleration (lag) phase of the stroke. The entire sequence is as follows:

Preparation - Unit Turn and Pose

As soon as we commit to a stroke, say a topspin forehand, we must complete the preliminaries that will allow us to execute lock and load. These preliminaries are all gross motor stuff, so you should execute them violently and quickly to give plenty of time for the fine motor stuff that follows. At the end of the unit turn, you should be in a "pose" that is appropriate for the shot you are hitting. The pose represents the proper stance of the feet and the needed upper body attitude going into the lock phase. You should also be in dynamic balance by this time to assure good ground purchase and because you are going to be moving the upper body through some pretty elaborate contortions, and you don't want them to throw you off balance.

The Lock Phase

The Pose puts your body at the threshold of the lock phase of the stroke. I like to call the Lock phase the "backswing proper" because there is a certain "backward" direction (or reverse-rotation) component to it and also to distinguish it from the unit turn, which represents the more obvious part of "bringing the racket back." The lock phase represents the most complex and mission-critical procedure of the stroke because it is how you harvest energy from the power wave and convert it into stored force for directional control and additional spin. A failure to lock means less spin and no control at all.

The goal is to put your hitting shoulder, elbow, forearm, and wrist into a state that will best absorb the energy coming up from the legs. That state includes the orientation of the racket face, position, and flexion of the elbow and shoulder, direction of motion, the position of the racket in space and time, and, most importantly, the degree of tone in the muscles of the forearm.

That last part is the hardest to accomplish. The key is to assure that when the peak of the power wave hits to start the load, the antagonist muscles of the forearm are completely relaxed and the agonist muscles are perfectly toned or shortened. It is at this critical point, setting the tone of the forearm, that the lock most often fails. If you tense the antagonist muscles, or if the agonist muscles are too tense or not tensed enough, the load will fail and with it the entire stroke. The key is the 'back' part of back and forth. The initial negative segment or 'trough' of the power wave pulls the racket back momentarily, sending the racket moving away from the ball. Your instinct is to 'catch' the racket to prevent it from flying into the back fence. It is no coincidence that the muscles of your forearm that you must use to stop the racket's backward movement are the 'forward' or agonist muscles, the very muscles you need to be stretch shortened to store force for control and spin.

If you produce just enough tension in the agonist muscles, the load will stretch-shorten the agonists and store those precious forces for you. Too much tension or tone and the forearm will not stretch, and the racket will not lag when the peak of the power wave hits. Too little tone and the arm goes all floppy when the peak hits and although the racket will lag and the agonist muscles will be stretched; they are not shortened so no useful forces will be stored. That means you have to hit the mark. Terrifying, I know. I believe that it is at this point in the stroke that even the great champions occasionally screw the pooch. The violence of the backswing proper must be neither too hot nor too cold - it must be just right.

Keeping the antagonist muscles relaxed is also critical. If the antagonist muscles of the forearm are tensed, their tone opposes and cancels any tone from the agonist muscles, erasing any beneficial stored forces. To keep the unused antagonist muscles of the forearm relaxed you must maintain a loose grip at all times and never forget that every stroke, no matter how short, must be back then forth, because the very act of catching the racket with the agonist muscles as it moves back will reflexively relax the antagonist muscles. You enhance the relaxation of unused muscles by relaxing completely in the early part of the load, allowing the racket and arm to fall out of the pose under gravity.

The Load phase

The load is so-called because it is the period during which the forces responsible for control and spin are "loaded" into the muscles of the upper arm and forearm. This phase begins as the peak of the power wave from the legs collides with the hitting arm just as the racket reaches is 'most 'back' position at the end of the lock. At this moment, you have just set the tone of your forearm, so the agonist muscles are appropriately shortened and ready for stretch-shortening. Suddenly the shoulders change direction and begin to accelerate forward towards contact with the ball. Petulantly, the racket head snaps back, dramatically in the long strokes (forehand, backhand, and serve), and quite subtly in the short strokes like the volley. It is inertia that keeps the racket head in place as the rest of the hitting unit advances on the ball. During this "flip," the racket changes its relationship to the hand and wrist, and the position in which it eventually finds itself determines nearly completely the success of the stroke. In the topspin forehand and backhand groundstrokes, for instance, if the racket head does not end up below the wrist at the end of the load phase, then topspin will not be generated. If racket face does not end up pointing at the side fence, then the control force will not be properly stored, and the ball will ultimately take a random path off of the racket face.

As important as the orientation of the racket is at the end of the load phase, you are not allowed to try to "make it happen" yourself. Any voluntary muscular intervention during the load would disrupt the critical and involuntary stretch-shortening cycle that is occurring at that moment. Instead, you should set the correct state of the hitting arm in the lock phase. At the end of the load phase, the racket is behind the wrist and is being pulled, butt first, towards the point of contact (POC) with the ball. The "pull" part is important because the wrist must continue to accelerate towards the POC to keep the racket head trapped by its inertia and keep the stored force imprisoned within the arm muscles until it is time for it to be released (during the explode phase).

The Lag Phase

The purpose of the lag phase is to keep the stored forces bottled up in the muscles of the arm and forearm just long enough (around .25 seconds) to achieve maximum racket head speed or velocity (about 35 meters per second for the forehand). The racket head is much "heavier" during this acceleration (about 10 pounds), and it is therefore much easier to pull the racket head along than to try to swing it into the ball. We define the beginning of the lag phase as the moment when the racket has flipped into the ideal orientation to accomplish these ends. In the serve and big groundstrokes, when the acceleration is greatest, the head will be behind the wrist with the butt end pointing more or less at the predicted point in space where the racket and ball will meet; the "point of contact" (POC). During the lag phase, the shoulders are rotating, and the racket is accelerating maximally. The abrupt end of shoulder rotation allows the arm and racket head to catch up to the wrist. The racket face squares up to the net, and the ball collides with the racket's sweet spot. You should, therefore, not aim the racket face at the ball; you should aim the heel of the racket at the ball! If you do that, the natural orbital path of the racket will bring the racket face into perfect contact with its target. Conversely, if you try to force the racket face to address the ball, constructing a mental straight-line path from where the racket face is in the backswing to where it has to be at the moment of contact, you will hit the ball with the frame (if you are lucky).

The Explode Phase

This is the shortest phase, but the one that makes it all happen (spin and control). Because it represents such a brief moment in time, we can't intellectually stretch out in it and contemplate it by itself. We need to look back in time to what preceded it and forward in time to what is coming next. At the end of the load phase, the racket head made 'heavy' by inertia, is lagging directly behind the wrist as it whips around the body. Although the racket is facing the right side fence, the relationship of the forearm and racket at this point is what it will be at the moment of contact. As the arm continues to orbit the body, the racket face comes around to the position it should be in if you were hitting an old-fashioned flat ball. Federer's arm position on his topspin forehand at the moment of contact looks like he is hitting a traditional, flat stroke. Immediately after contact, his arm seems to collapse and wrap around his left shoulder. His bizarre follow-through reflects occult control forces revealing themselves long after the ball has gone. Think of the stretch-shortened agonist muscles as helping to 'drive' the strings through the ball at the moment of impact injecting directional pace and control.

Now move forward in time from the Load phase to the few milliseconds just before impact. That is when one puts the brakes on the power wave that has been driving the arm and racket forward; this is the beginning of the explode phase. A sudden dip in the power wave cancels the peak and causes deceleration or even slight reversal of the hip and shoulder rotation, analogous to pulling back on the handle of a whip. There are many possible sources for this dip, including pushing back off of the front foot in a groundstroke, counter-rotation with the non-hittin arm in the volley and counter-kicking in the serve

Once forward momentum of the arm-wrist-racket complex begins to ebb, the stored force in the muscles of the arm are set free to inject control, spin and a little extra oomph directly into the ball. It is important to note that this explosion is invisible even on slow-motion video, but its effects can be heard, felt and seen in the effect it has on the ball and the arm in the follow-through. It is invisible because the actual change in position, velocity, and acceleration of the racket occur after the ball has left the strings. There is a lovely pop of ball on strings and a feeling of deep connection with the ball, but none of it shows up on video. It should also feel effortless at this point because it really is effortless. You have already invested your effort in earlier phases, and this is just the result of that effort delivered to the ball.

You should not feel like you are driving the racket through the ball. I call this grievous fault "hot shoulder" or Push syndrome. The lock, load, lag and explode are the trickiest components of any stroke and few of us mortals perform them naturally. Learning and practicing these techniques is time well spent because these are the quintessential components of consistent power and powerful consistency.

The Follow-Through

You can't turn back time, so the follow through is largely irrelevant to the task of adding spin and control to the ball. The ball is gone. The follow-through does give important clues to problems in the first three phases. A stiff follow-through may indicate tension that is not being properly dissipated in the lock phase or released in the explode phase. The racket face should close up after hitting a topspin shot, and if it doesn't, you probably aren't storing enough pronation force (in the forehand or supination force in the backhand). Bringin the arm down, i.e. recovering early in the follow through of the overhead and serve obliterates the explode phase in those over-the-head strokes robbing you of power and control. Unfortunately, you can't fix the underlying problem by forcing the follow-through to look pretty. You need to look backward in time into the guts of the stroke to find the culprit. The key is to recognize when something is missing from the follow through and seek its usual source.