Degrees of Freedom

Written by: Kevin Cann

Understanding motor control is important for any coach.  I believe that all coaches will emphasize the importance of technique.  In order to help guide a lifter to better technique in the lifts, the coach must understand how the human body solves movement problems.  In order to do this, we must look into the Degrees of Freedom (DOF) problem.

The DOF problem was introduced by Nikolai Bernstein, a Russian neurophysiologist, in 1967.  Bernstein researched the repetitive strikes of blacksmiths.  He noticed that the repetitive strikes of the blacksmiths had the same outcomes, but that the movements varied.  

He concluded that movement kinematics are not the same, even when performing the same movement over and over again.  Variations occur in position, velocity, and acceleration.  He also concluded that there are multiple ways to perform a movement to get the same goal. 

There is not just one specific motor solution to a specific motor problem or task.  The choices that the body has to complete a task are nearly infinite.  These movement options are known as the DOF.

As I just mentioned, the body has infinite choices to perform a task.  This complexity can be overwhelming for the nervous system.  In order to handle the complexity, the nervous system will “freeze” some of those DOF.  This decreases the movement options available to complete a task and begins to allow the body to find a better solution to the problem.  

Over time, the body begins to explore more options and the nervous system will “unfreeze” some of the DOF and the movements seen will be more effective and appear more fluid.  Think of the first time that you attempted a specific task.  Your movements were probably very awkward looking and most likely not the most efficient.

Over time of practicing that task, you probably got much better at it.  The movements were probably more fluid and more efficient.  Chances are you got much better at the task as well.  Lifting is the same.  The first time you squat with a barbell was probably pretty awkward.  However, through practice you got much better.  

The variability in movement is how the body is constantly attempting to learn more efficient ways to complete a task.  It does not mean that once you get through the awkward beginning phase, that you are done learning and every movement is the same.  The body is always trying to learn a better way.  This is what Bernstein saw with the blacksmiths.

One of Bernstein’s more well-known quotes is “Repetition without repetition.”  This may seem very confusing at first, but it refers to that constant variation seen in movements.  The body is using all of those repetitions to continue to learn more efficient ways to perform a task.

This is also a quote from Bernstein, “Process of practice…consists in the gradual success of a search for optimal motor solutions to the appropriate problems.  Because of this, practice, when properly undertaken does not consist of repeating the means of the solution of a motor problem time after time, but in the process of solving this problem again and again by techniques which we have changed and perfected from repetition to repetition.”  

The coach’s job is to give the lifter a problem to solve.  The answer to that problem is movement.  The coach can put lifters into positions that will punish a technical inefficiency by disallowing the completion of a repetition.  The task can also be setup in a way that only allows for a more technically efficient way to execute the lift.  Over time from continuously giving lifters problems to solve we can enhance their abilities to complete the task.

It might sound like I am trying to force one solution onto the problem.  This could not be further from the truth.  I feel every coach should have some heuristics of technique within the lifts.  This can help them setup the tasks appropriately to improve that technical efficiency.

This also includes getting stronger at various joint angles.  Even though I like to teach a more “hips back” squat, we still do variations such as high bar close stance squats that will have a very forward knee position and an upright torso.

We will find the angles that the lifter struggles with, and we will focus on making those angles stronger.  An important component of this is the specific loads that the coach needs to utilize.  It is not just the movement that we put the lifter in that matters.  It is the position plus the load.  This is how we get that transference of skill for the specific task of heavy singles.  

The heavy load punishes the technical inefficiency in a specific joint angle.  Most lifters can get away with technical inefficiencies under lighter weights.  The mind also plays a critical role in motor control.  Psychological arousal changes motor behavior.  Heavier weights bring into play the psychological arousal. This makes the task more specific to competition, where emotions tend to run high.

We have all heard the phrase “Frozen from fear.”  That fear can actually lead to the nervous system “freezing” up DOF.  This can even happen to elite athletes.  The nervous system is extremely complex.  We do not which DOF the body decides to lock up.  It is different for everyone and different under varying circumstances.

The more problems that a lifter is forced to face in training, the greater solutions bank they will have to draw from.  This is how we build a large skillset within the sport.  If a lifter is only given a competition lift to practice with submaximal weights, they will not have a large movement solution bank to choose from.

If they get pain, they will most likely not have the skill to change foot position in a squat, grip width in a bench, or even stances in a deadlift.  Heavier loads tend to cause lifts to breakdown.  If a lifter is always using submaximal loads, when the weight gets heavier and technique deviates from the norm, will they be able to fight through those positions?  Oftentimes the answer to that question is no.

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