A picture can speak a thousand words—and many of us are familiar with the picture of a blacksmith swinging his hammer. The paradox of the picture is that we focus on the variations of paths the hammer takes, but I haven’t heard anyone talk about the blacksmith’s wrist, elbow, or shoulder.
Anyone familiar with the picture of should know that it comes from the “OG” of studying movement, Russian neurophysiologist Nikolai Bernstein. Bernstein was concerned with the number of muscles and joints that need to coordinate when we move (striking, throwing, running, and jumping). How many limbs, muscles, and joints are involved? How are they involved, and where are they involved?
There many ways in which humans can move to achieve a goal: this is known as the Degrees of Freedom Problem. However, from the start to the end of a movement, humans need to control and organize the body in one or more planes of motion, (i.e., solve the Degrees of Freedom Problem/motor abundance). When accomplished, we call this coordination.
The blacksmith picture and Bernstein’s work regarding the Degrees of Freedom Problem led to the understanding that there is movement variability in the normal variations that occur in motor performance across multiple repetitions of a task. If a person tries to repeat the same movement twice, the two actions will never be identical because each repetition involves a unique motor pattern. Bernstein termed this “repetition without repetition.”
Movement sciences and coaches studying movement are doing a great job trying to understand how various constraints (environment, task, and individual) help to form movement on the field and court. And that movement isn’t always as clean and straightforward as we would like, as the picture of the blacksmith depicts. In the context of athletics, this has led coaches to believe that there is no such thing as a perfect technique, and we should not worry about working on technique. Instead, we should spend time on physical outputs and teaching movement variations.
But from one sports movement to the next, there is always variability in speed, fatigue, opponents, task, etc. A world-renowned Olympic sprints coach once told me that “In chess, you don’t need the biomechanical part.”
My return argument is: there are mechanical rules by which chess pieces must move. The Bishop moves in a straight line diagonally on the board. It can move as many squares as wanted until it meets the end of the board or another piece. The Rook moves in a straight line horizontally or vertically through any number of unoccupied squares until it reaches the end of the board or another piece blocks the Rook—you get where I’m going with this.The velocities and ROM differ with each swing, but the joint actions appear to be the same. Click To Tweet
The path of the shoulder, elbow, and wrist are never fully the same, but that doesn’t mean the blacksmith doesn’t demonstrate shoulder rotation, elbow flexion and extension, and wrist supination. The velocities and ROM all differ with each swing, but the joint actions appear to be the same. My question to practitioners is this: Why are we only concerned with the path of the hammer and the variability it shows, rather than the joint actions and muscles that contribute to the hammer swing? In fact, this is something Bernstein contemplated, according to one of his former protégés.
Bernstein’s Concept of Key-Movements
Bernstein wrote that an improvement in motor skill comes from establishing the pathway for achieving the needed goal (or the motor pattern), which is resistant to possible fluctuations under the influence of environmental conditions. Establishing a motor pattern occurs through the assimilation of the motor task’s essential parameters (motor determinants) with the gradual adaption of its nonessential parameters to the environmental conditions. “The organism tries to realize the essential variables by completely overcoming any difficulties and influences from the environment; as for the parameters of nonessential variables, the organism, on the contrary, is yieldingly adaptable.”
So not only is there variability within the blacksmith’s motor pattern swinging his hammer, but there are also essential parameters which allow him to swing the hammer (perform the motor pattern) consistently well. His hammer’s path may differ from swing to swing, but his arm’s joint actions don’t completely differ.
Relate this to an athlete’s technical preparation: their motor pattern, which must be established to acquire the motor skill, is the correct technique used to execute the competition exercise. The essential parameters of a motor pattern are the most important key-movements of competition exercise, which determine its correct execution as a whole.
A little-known fact in the physical preparation world is that Dr. Vladimir Zatsiorsky and Dr. Yuri Verkhoshansky were protégés of Bernstein. Dr. Verkhoshansky is one of the first coach/scientists to use the idea of finding out and establishing these “essential variables” (key-movements) to develop athletes.
In a conversation I had with his daughter, Dr. Natalia Verkhoshansky, she told me: “I have to say that nobody has used this term key-movements. It was necessary for me to introduce this term because in the articles of Bernstein, there is no definition of this term, also because his articles/books are totally scientific. It’s necessary to deliberate this information…In every kind of exercise there are key-movements…and that these key-movements have two characteristics: 1) they improve the whole complex movement. They are very important in motor learning, so if a person tries to improve the sports technique, it is very important to improve their ability/capacity to execute the key-movements correctly; 2) key-movements are important in increasing the magnitude of force-effort (power) employed while also decreasing the time (speed) that it takes to employ.”
I reached out to one of the world’s experts on Nikolai Bernstein and Motor Control, Professor Mark Latash, to see if he knew of more information on this topic. He told me, “In his book, Dexterity and Its Development, Bernstein did use a term similar to that (Key-movements), although he used it in a very fuzzy way. He was one of those geniuses that had such a deep understanding that he could use a fuzzy word and could still make it sound ok.” Professor Latash was kind enough to put me in contact with Dr. Vladimir Zatsiorsky, who was also a student under Bernstein and was one of the top biomechanists in the former Soviet Union. Dr. Zatsiorsky discussed with me a study he did in 1981, which looked at determining the most vulnerable muscle groups in sprinting (key-movements).
Dr. Zatsiorsky wrote and gave an example of a key-movement in his book, Science and Practice of Sports Training. It was a practical example for coaches on how to strengthen this key-movement, which he called the Principle of Accentuation; it is training strength through the range of the main sport movement, where the demand for high-force production is maximal. “In natural movements, at least on land, muscles are active over a relatively narrow range of motion. Usually maximal muscle activity occurs near the extreme points of angular motion.”
One of the many things that Dr. Verkhoshansky is well known for is his Principle of Dynamic Correspondence. It became one of the first well-known criteria for selecting special strength exercises. Dr. Verkhoshansky proposed applying the Principle of Dynamic Correspondence in training exercises with resistance in the key-movements of competition exercises. According to this principle, these movements must have the same:
- muscle groups involved in the exercise
- ROM and direction of movement
- accentuate the part of the movement amplitude
- character of the force-effort applying (the magnitude of force-effort and time of its applying)
- regime of muscle contraction
More on the practical application aspect in a bit.
Context and Results Are King
With much discussion among coaches about variability, I find myself coming back to several things: What is good and what is bad variability? How much and how little should we allow? And where are the results?
I get it; it can be hard sometimes to quantify improvements in movement quality. But there should still be some videos of before and after to demonstrate what we see, need to change, address, and improve upon. Biomechanics, motor control, motor learning, are all very difficult subjects of study. But what good is all of the knowledge if we can’t apply it to an athlete and see a result?
One of my biggest issues with any discussion, article, book, or podcast on motor learning and control is that context is often missing in the discussion. Gary Vaynerchuk said, “Content is key, but context is King.” I argue that context and results are king. What good is the information without results to back it up?
Context means who, what, and why as to the type of motor control and learning strategy and what it should be used for. For instance, movement variability is thrown about in many different ways with athletes—athletes running up steps with weights on their backs, athletes tossing water bags around, and athletes performing different types of cutting. What seems to be missing, however, is coaches giving context and reasons for the variability. For example, they are important to the task, caused by fatigue, due to physical limitations, normal noise in the motor action, or improve performance. This is something that should be trained.A pitcher's key body actions of a weight shift and push off shouldn’t change from pitch to pitch. Click To Tweet
Looking at a track and field sprinter, for example, we know that variability happens based on fatigue or arousal. But the underlying motor pattern should not have so much variability that the arms and legs are swinging every which way. The same is true for a baseball pitcher. There can be some subtle variability between pitch types and pitch locations, with the pitcher making a slight change to their arm slot. However, the key body actions of their weight shift and push off shouldn’t change from pitch to pitch.
Help Make the Understanding of Movement Simple, Not Simpler
When it comes to looking at movement and motor learning, I try to take a more simplistic approach. That’s not to say that understanding movement is an easy task or that I have it all figured out. I believe that simplifying it allows us to understand better which motor learning and control strategies we can best optimize.Break down complex motor skills into hard and soft skills to identify which motor strategy to use. Click To Tweet
Within the context of sport technique, we can break down complex motor skills into two types of skills that we should consider when trying to help a practitioner identify which motor control and motor learning strategy to use: hard skills and soft skills.
Hard skills are the optimal mechanics in an ideal situation and the foundation of playing sports. For example, quarterbacks and baseball players have throwing mechanics with no perceptual stress in an ideal situation. Also consider a baseball player’s swing mechanics, a basketball player’s jump shot, a golfer’s swing mechanics, and an athlete’s linear running mechanics.
Hard skills are the general laws of physics and biomechanics as they pertain to the sporting action. These are where the key-movements are mastered within the motor skill. “Neurologists call this the ‘sled on a snowy hill’ phenomenon. The first repetitions are like the first sled tracks on fresh snow: On subsequent tries, your sled will tend to follow those grooves.”1Hard skills are the general laws of physics and biomechanics that pertain to a sporting action. Click To Tweet
We should build hard skills in a very precise and measured fashion, perfecting and repeating them before we move onto the next piece. Within the hard skill, two types of movements are important to understand, so a coach knows where to spend their time with the athlete: key-movements and secondary movements. As discussed above, key-movements are the force producing actions in the mechanics (for example, sprinting: paw back, ankle extension, knee drive).
The secondary movements help to transmit and stabilize the motor skill. They don’t contribute to the hard skill’s power production, but they can contribute to power and energy leaks. In sprinting, for example, the role of the shoulders and arms don’t necessarily contribute to the production of power, but if the shoulders aren’t moving in synchronization with the hips and legs and are swinging all over the place, they certainly can leak power.Developing hard skills is where most of us can have a major effect. Click To Tweet
I pay the most attention to hard skills, particularly with the key-movements, as this is where most of us in this industry can have a major effect. But if an athlete looks like garbage in an ideal situation, then throwing them in a blender (chaotic environment) is only going to make trash soup.
The difficult truth about building the hard skills is that it’s not very fun, as it takes deliberate practice to master them. Errors should not be allowed because hard skills are hard to break. If an error occurs in these hard skills—let’s say heel striking in sprinting—a top-down approach works best to correct the error as the athlete can only change this motor pattern if they are thinking about it. We can try to manipulate the environment or the task all we want, but I guarantee that if an athlete isn’t thinking about correcting the issue, they aren’t going to correct it. The error has to move from unconscious-incompetent to conscious-incompetent and then all the way to unconscious-competent. This is a daunting task, but it can be done.
Understanding the biomechanics and qualitative technique analysis of the hard skills is extremely important when determining where and what joint actions are effective. What are ineffective? Is the error due to poor technical learning? Is the error from poor technical application to a sport situation? Is the error due to physical limitations (strength, speed, mobility, stability, etc.)? Can the joint movement(s) involved in XYZ actions be improved with physical exercises or with technical exercises? Could the athlete’s actions lead to injury (technique plays a very large role in non-contact related injuries)?
On the other hand, soft skills are how the hard skills are incorporated into a task and environmental situations. Soft skills are where you create a breadth of movement to learn how to adapt to the various changing situations of practice and sport.
“Soft skills are built by playing and exploring inside challenging, ever-changing environments. These are places where you encounter different obstacles and respond to them over and over, building the network of sensitive wiring you need to read, recognize, and react.”1A baseball player uses soft skills when batting against live pitching. Click To Tweet
Soft skills are the quarterback’s ability to throw with defenders at their feet, or on the run, with or without a hitch step, over the top of a corner, or through two linebackers. The baseball player bats against live pitching. The basketball player’s ability to shoot coming off of a pick, or with a hand in their face. A golfer swings on a slight hill through the ruff. A running back runs away from defenders.
This is where this movement about movement is focused. Perception and action. Repetition without repetition. How an athlete sprints, jumps, and changes direction will vary each time based on arousal, speed of movement, fatigue, goals, and the task of the situation.
However, this is where variability within a motor skill’s key-movements should not vary much per movement. In a quarterback’s throwing mechanics, the lower-body key-movements are the weight shift with the hip rotation separated from the shoulder rotation. The variability depends on whether they are standing tall in the pocket—as opposed to on the run—or throwing a route to their right (as a right-handed thrower) or to the left. Or if they’re in the shotgun formation and throwing a quick crossing route or rolling out to their left.
Generally, there should always be these key-movements, but the ROM and velocity of their actions will vary. The variability will differ for a baseball pitcher, whose body actions should not change while their arm slot should—elbow and wrist actions are based on the type of pitch and the location they are trying to throw.
In the Central Virginia Sports Performance Manual Vol. 3, I go into details of the three key-movements of sprinting. One of these is knee drive, which may vary for a soccer player based on the speed of motion and the direction of movement. But the mechanical law of the knee drive (creating a short lever) should not vary far regardless of the situation. That leg has to fold up from behind to quickly move to the front of the body.
How to tear an ACL is pretty well documented—have your knee go in and forward and rotate with an extreme amount of force. Change of direction mechanics will vary depending on the task and the perceived situation. However, the key laws of where and how to stop and slow down should not vary.
If you Google change of direction, you will likely see more commonalities than not. The athlete should stop or slow down in the fewest amount of steps as possible. The plant leg (depending on which direction the athlete is coming from and going) should be outside the width of the athlete’s hips on the outside leg with as little or no weight on the inside leg. The variability of change of direction occurs when the athlete reacts to getting to an open space, following an opponent, with a ball, or running away from an opponent.
The paradox of the hammer is that we get caught like a bug staring at the light, watching the variation of the hammer. The Degrees of Freedom Problem has shown that human movement is not clean cut. Variability of movement is essential because we are not robots, and the human body is a complex system with many degrees of freedom, which it must try and coordinate with various constraints to perform motor skills. This is what allows us to adapt our movements; it serves a functional role.
On the other side of the coin, however, there are mechanical laws by which we are allowed to move. These mechanical laws are similar from person to person, although they may not all be identical and can vary in ranges of motion, velocities, effects of physical and mental stress, etc. Certain joint actions and sequences are better suited as power developers and force absorbers, while some are not. There are mechanical laws according to which athletes must move, but then there is bandwidth we can move within. A coach’s intuition for knowing which is which—and how one thing can affect the other—is where our industry is missing pieces to this puzzle.
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- Coyle, D. The Talent Code: Greatness Isn’t Born. It’s Grown. Here’s How. A Bantam Book 2009.