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Dynamics of skill acquisition: a constraints-led approach

The book Dynamics of Skill Acquisition: A Constraints-Led Approach has been a game-changer for me as a coach. I was introduced to it by Donnie Ecker, the now assistant hitting coach for the Cincinnati Reds. The results of his hitters are undeniable, so it was a pleasure learning from him and a no-brainer to invest in the book when he recommended it.

My time with him showed me how far behind the curve I was. In the book The Talent Code, Daniel Coyle writes about something he calls “primal cues.” A primal cue is something that tells us to “get busy” in a way that takes over your mind so completely that you become obsessed with improving.

One of the primal cues that Coyle writes about is the cue you receive when you are placed in an environment where you realize you are extremely behind. The environment I got to learn from Donnie in showed me how far behind I was. I needed to get better as a teacher.

One day, he told me, “it’s all about skill acquisition and using constraints.” This immediately made me remember a book I had seen on Twitter. That book was Dynamics of Skill Acquisition: A Constraints-Led Approach. Here is what I learned and how it changed the way I coached:

What is skill acquisition? For our purposes, a motor skill is essentially a learned behavior that accomplishes a goal within a sport that is constantly changing (has many variables constantly present). A skill is different from a habit. A habit is automatized within an athlete’s central nervous system. It happens unconsciously and automatically when triggered by a stimulus.

The way to think about a skill is as a motor pattern that is a collection of habits. It allows the athlete to be an athlete. A motor skill is a pattern that allows the athlete to be adaptable within a complex environment to accomplish the goal of the moment.

For a baseball example, let’s look at a shortstop on a relay throw from an outfielder to third base. The shortstop runs out to the outfield and awaits the throw from an outfielder. When the outfielder releases the ball, the shortstop must immediately judge the accuracy of the throw (variable). If the throw is high, the shortstop might backpedal to adjust to the throw. The shortstop might then jump to catch the ball while shuffling his feet so that when he lands his right foot will land followed quickly by his left foot to set up a quick catch and release to the third baseman.

If the shortstop does this well, it is because he learned and developed this skill. He may have practiced the quick exchange with his hands enough (through a consistently practiced catch-play routine) for it to be considered a habit. To get the baserunner out at third base in time, the shortstop must adjust that “habit” of a quick exchange to catch the high throw over his head. He must do it while backpedaling and jumping in a high pressure situation. These are all variables that make this action a skill the athlete had to acquire through a specific kind of practice.

In other words, the only way that shortstop can make that play effectively is if he has turned a few habits into a skill that can satisfy multiple variables in a complex environment.

So then skill acquisition is the process of developing adaptive behavior that allows athletes to interact with the environment of their sport to accomplish the goals of the given moment.

In the book Dynamics of Skill Acquisition: A Constraints-Led Approach, Keith Davids and colleagues write that skill acquisition “should result in coordination patterns that are adaptable to a range of varying performance characteristics.”

The writers continue, “adaptive behavior is important because conditions like the environment, task requirements, and our motivations can change every time we perform a motor skill.”

In our example of an outfield relay throw above, there are several “conditions” that the shortstop must adapt to.

The “environment” might force the player to adapt if it is hard to see against a white backdrop for example or if it is an important point in the game and the crowd is loud or the player’s nerves are affected.

The “task requirements” that dictate the shortstops actions include the score of the game, the time left in the game, the speed of the runner, etc. If the shortstop’s team is ahead by a lot of runs late in the game, he might decide not to throw the ball and take the risk of throwing it away. If the runner is faster, the throw might have to go to home plate rather than third base, in which case the shortstop would have to turn his feet harder to the left to make a good throw home. As the task requirements change, the athlete has to adapt.

The “motivations” of the player may make him adapt as well. For example, all of the above (the score, the situation in the game, runner speed, etc.) may affect the motivations of the athlete. If the hitter is faster and the shortstop knows that he doesn’t have a chance to get him out at third, he may not even try to make an exchange from glove to hand. He may just catch the ball and run it into the infield.

Another factor to consider under the motivations umbrella is the player’s mental toughness. If the player is playing poorly and pouting or overthinking, he might not execute the skill well. He might miss the ball because he is not focused or reacting too slowly because he is thinking too much.

So what kind of practice helps athletes acquire dynamic skills most effectively? That’s where the “constraints-led approach” comes in.

Constraints are manipulations the coach can make within a practice task that allows the athlete to build adaptive behaviors capable of accomplishing the goals of performance.

Maybe an analogy can help us…

Picture an ant crossing the floor of your kitchen. You want that ant to go out the kitchen door to the outside (goal). The ant is crawling along the floor aimlessly in different directions. To get the ant to go in the direction that you want, you start using your foot to block it’s path and re-direct it toward that doorway (constraint).

You could use a stool to re-direct the ant, or a spatula, or your foot, etc. You can get creative if you really want to, but the important thing is to effectively get the ant out the door. Now what would NOT work is to talk a lot to the ant until it changes direction. It would NOT work to yell at the ant. Maybe a sharp noise might shock the ant into moving when it gets tired or confused. But for the most part, you are going to be most effective as a passive observer, placing obstacles in the ant’s way to constrain it’s behavior so that it is taking the right action.


Let’s look at hitting through the lens of a constraints-led approach. Let’s simplify. Hitting is a goal-directed behavior. The goal is to score runs. To score runs, you have to get on base at a high rate. To get on base at a high-rate you have to hit the ball hard consistently. To hit the ball hard consistently, you have to swing the bat hard consistently. To swing the bat hard consistently, you have to generate and control forces from the ground. You also have to have the intent to do damage, and you have to swing at pitches you can do damage with on time. To do that, a hitter has to be capable of making quick and consistently accurate decisions based on information he sees within .04 seconds.

If consistently hitting the ball hard is the goal, then you have to put yourself in a mental and emotional place to consistently play the game hard pitch-by-pitch. This requires a certain kind of mental toughness.

Consistently hitting the ball hard also requires an environment of psychological safety that allows hitters to be unafraid of swinging and missing, and unafraid of looking stupid on occasion.

Those are the process goals of hitting. So to accomplish those goals efficiently, what constraints do you need to place in their way?

For example, to get a hitter’s rotation tighter and more efficient, we might place a high tee on the outside of the plate opposite of the hitter. The hitter will self-organize to avoid hitting the tee. This should result in the hitter cleaning up his rotation and getting rid of any long or inefficient movements.

I’m of the opinion that the coach needs to keep an eye on how the player is self-organizing to make sure that he is doing so in an optimal way. I have heard this called self-optimizing rather than self-organizing.

As another example, we might place a bucket behind the back foot of a hitter who is hanging back on his back side. If the hitter’s back foot spins and hits the bucket then he knows he is moving sub-optimally. Over time, the hitter will start getting off his back side and swinging more efficiently.

The above examples are examples of task constraints. A task constraint is a manipulation of the rules of a game or drill, thus changing the task into something that requires the right movements to successfully complete. The goal might originally have been to simply to hit the ball solidly off the tee. The task constraint was the rule change for the drill: don’t let your heel hit the bucket while you swing.

Another kind of constraint is an environmental constraint. An example of an environmental constraint would be something like changing the lighting or playing surface. There is a reason that some tennis players play better on clay and others play better on grass…the surfaces change the sport to a degree.

In baseball, a good example of an environmental constraint would be having a hitter swing with his feet in sand. This might allow him to feel how he is using the ground.

Another kind of environmental constraint that can be used to prepare a baseball player for the dynamic environment of a baseball game is noise or pressure. You can blare crowd noise over the speakers during scrimmages. You can also raise the stakes of a competition by letting teammates yell at each other to try to get under each other’s skin.

This will create the pressure of having other’s rely on the outcomes the player produces. Studies have found that replicating that kind of pressure has the most transfer on game performance in pressure situations. This changes the environment, thus it changes the environmental constraints placed on the players competing against each other.

We really have to understand that our jobs as coaches is not to develop players, it is to produce an environment that allows for players to develop themselves.

The other kind of constraint is a performer (or what most of the literature calls organismic) constraint. The above scenarios where an athlete is placed in an environment of high stress might create a performer constraint. Anxiety in an athlete would be considered a performer constraint.

Another performer constraint would be a device like a Libke trainer for an infielder that forces the athlete to cock back his wrist to fully present his glove properly. This would cause the infielder to change the way he fields a ground ball. It is a performer constraint that changes the player’s options so he is more likely to choose the right option to field the ground ball with better form. These options are called “affordances” in motor learning lingo.

Baseball is played in a dynamic and complex environment. A dynamic and complex system is like a storm system rather than a clock. Even the most complex-functioning clock can be broken down and put back together. There is a coherent structure that allows us to understand fully and completely how the clock works. We can understand it to the point that we could build a new clock if we wanted to.

If baseball were like this, it would function in a way that we could predict perfectly.

Coaches and managers would never be second-guessed because they would be able to know exactly what would happen with each decision they made. They would be able to know which relief pitcher could get them six outs to get the ball to their closer. They would be able to know exactly which guy on the bench would get a pinch hit against the pitcher in the game at that moment.

But the game doesn’t work like that. If it was, the same swing would have the same exact result on the same pitch in the same location every time. But the game is complex. Ball’s that are hit with a 95-percent hit probability get turned into outs sometimes. Perfectly manicured fields yield bad hops. Gold glove fielders make errors on routine plays.

The same mechanics for one player don’t work for another. The same changeup grip for one pitcher can cause the ball to tumble off the table so completely that hitters swing and miss at it while another pitch can only induce weak contact with that same grip. One player can drive pitches consistently thrown high in the strike zone while another can only drive pitches low in the strike zone.

A hitter’s swing and a pitcher’s delivery are themselves a complex system. One of the major discoveries in motor learning is Bernstein’s Degrees of Freedom Problem. With each complex movement (like a hitter’s swing or a pitcher’s delivery), there are hundreds of moving parts—joints, muscles, tendons, ligaments, etc.

So when performing movements, an athlete will never perform the same exact movement multiple times. There will always be slight differences in at least one degree of freedom within a movement.

Russian neurophysiologist Nikolai Bernsetein demonstrated this when he tracked his degrees of freedom as he swung a hammer. He found that he never did it with the exact same mechanics no matter how many times he did it. He called this “repetition without repetition.”

For a more detailed description of how baseball is an open, dynamic, and complex system, refer to my piece on the book Nonlinear Pedagogy in Skill Acquisition.

That post describes how an athlete works within constraints to interact with his perception of his environment. This book covers a lot of that, but with the overlap, I decided to cover that in my summary of Nonlinear Pedagogy in Skill Acquisition.

In that post, I will also cover the kind of practice that will best achieve skill acquisition.

The implication of Bernstein’s discoveries is that with complex movements within complex environments (like a hitter’s swing at a moving pitch in different locations at different speeds), the athlete will never repeat the same exact movement with all of his degrees of freedom.

So the art of skill acquisition is the ability to lock down enough degrees of freedom to achieve consistent positive results. I’ve learned that one of the best tools to achieving this is the constraints-led approach.

Another key aspect of the constraints-led approach is the emphasis it places on a hands-off and creative coach. If you were to watch a coach employing the constraints-led approach, he would not talk a lot. When he did talk, he would use questions. Questions are a kind of informational constraint. His athletes would be using all sorts of odd-looking tools or methods/drills to achieve certain movements.

In summary, the constraints-led approach limits the actions the athlete can choose from to the correct actions. Because there are many correct actions (as we learned from Bernstein), we want to afford the athlete with as many correct options as possible so that he can choose the ones that most fit his body.

The best way to do this is to provide the athlete with constraints that eliminate incorrect of inefficient action options. Like the ant crossing the kitchen floor, we are taking away all the wrong actions to let the athlete choose the right options for himself—options that his particular body can repeat most efficiently.

As a coach trying to implement the constraints-led approach, you should feel free to get creative. Most coaches have the correct mental models of what good baseball looks like. Trust yours. Get creative until you see what you know looks right.

A good first step is to start asking questions of your athletes. Be a therapist. The best hitting and pitching coaches I’ve ever known are essentially therapists. The goal of a therapist is to ask the right questions to lead their clients to a helpful solution. When a client comes up with the answer for themselves, it is much more powerful than the therapist just giving them the answer.

When the client gets to take ownership of the solution, he will be more likely to take action. When the therapist just gives him the solutions he needs, the client will not normally take the actions he needs to to take control of his life.

This is how it works with baseball players—especially baseball players. Baseball players have large egos, they usually have to to be good at a game that requires a high failure tax.

Asking questions constrains their thinking. It points them in the right direction toward the right answers. It then allows them to take ownership over the changes they make or don’t make.

One of the best examples of this that I can think of is that of one of the all-American college hitters I’ve worked with. He wanted to try something new. He was open to learning. In fact, he pretty much wanted me to tell him what to do. I refused.

He wanted to make a swing change in the middle of the season. I asked him a lot of questions about why he wanted to make the changes he wanted to make. My hope was that he would not make the changes he wanted to make.

But if I had simply told him not to make the swing change, it wouldn’t have ended well. He probably would have obeyed me, but at the first sight of a slump, he would have tried to make the change. Or it would have been a constant nag on his mind—enough of a nag that he would have not been able to fully commit to any sort of approach. That would have led to overthinking and a disaster on the stat sheet, or it would have led to him undermining both me and himself by making the swing change against my wishes.

The best thing I could do for him was ask pointed questions that would hopefully dissuade him from trying to make the swing change, but on his own terms. Or to ask him enough questions that he would make his own decision to make the swing change, go through the inevitable slump, then come out on the other side knowing for himself that the swing change was not the right change to make. This would then allow him to move forward with the conviction that his swing was more than fine the way it was.

That’s the route it ended up going. He decided to make the change of his own accord, he went through a slump for a few weeks, then went back to the swing that made him an all-American.

Ultimately, it allowed him to take ownership of his swing and led to the best swing for him. That is how the constraints-led approach works—it will take time and require the coach’s patience. You’ll want to step in when athlete’s are making the wrong decisions or moving the wrong way, but that will only hurt the athlete whether you are right or wrong.

I once was part of a lecture from a Harvard Business School professor who spent three hours in front of a group of about 200 students. In three hours, nothing came out of that professor’s mouth that wasn’t a question. It was one of the most impressive teaching experiences I’ve ever been a part of.

This is how the constraints-led approach works. He was constraining information so that the students could acquire the correct information on their own and take ownership of it.

I highly recommend this book for anyone trying to add to their toolbox as a coach. It gets really dense in some places but elevate yourself to the language if you need to. Your players deserve it.

Adding the constraints-led approach to your toolbox as a coach can change your world. You will see your athletes solving the right problems. You will see your athletes perform better in complex environments and situations. You will need to be patient and poised. But if you work at it and get creative, the results will come and so will your satisfaction.


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